201
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Cyclin-Dependent Kinase 4/6 Inhibition for the Treatment of Unresectable Mature Teratoma: Long-Term Follow-Up of a Phase II Study. Clin Genitourin Cancer 2016; 14:504-510. [DOI: 10.1016/j.clgc.2016.03.010] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/13/2016] [Revised: 03/02/2016] [Accepted: 03/07/2016] [Indexed: 11/18/2022]
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202
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Requejo-Aguilar R, Bolaños JP. Mitochondrial control of cell bioenergetics in Parkinson's disease. Free Radic Biol Med 2016; 100:123-137. [PMID: 27091692 PMCID: PMC5065935 DOI: 10.1016/j.freeradbiomed.2016.04.012] [Citation(s) in RCA: 51] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/05/2016] [Revised: 04/13/2016] [Accepted: 04/14/2016] [Indexed: 12/15/2022]
Abstract
Parkinson disease (PD) is a neurodegenerative disorder characterized by a selective loss of dopaminergic neurons in the substantia nigra. The earliest biochemical signs of the disease involve failure in mitochondrial-endoplasmic reticulum cross talk and lysosomal function, mitochondrial electron chain impairment, mitochondrial dynamics alterations, and calcium and iron homeostasis abnormalities. These changes are associated with increased mitochondrial reactive oxygen species (mROS) and energy deficiency. Recently, it has been reported that, as an attempt to compensate for the mitochondrial dysfunction, neurons invoke glycolysis as a low-efficient mode of energy production in models of PD. Here, we review how mitochondria orchestrate the maintenance of cellular energetic status in PD, with special focus on the switch from oxidative phosphorylation to glycolysis, as well as the implication of endoplasmic reticulum and lysosomes in the control of bioenergetics.
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Affiliation(s)
- Raquel Requejo-Aguilar
- Department of Biochemistry and Molecular Biology, University of Cordoba, Institute Maimonides of Biomedical Investigation of Cordoba (IMIBIC), Cordoba, Spain
| | - Juan P Bolaños
- Institute of Functional Biology and Genomics (IBFG), University of Salamanca-CSIC, Zacarias Gonzalez, 2, 37007 Salamanca, Spain.
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203
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Xu X, Wang JT, Li M, Liu Y. TIMELESS Suppresses the Accumulation of Aberrant CDC45·MCM2-7·GINS Replicative Helicase Complexes on Human Chromatin. J Biol Chem 2016; 291:22544-22558. [PMID: 27587400 PMCID: PMC5077192 DOI: 10.1074/jbc.m116.719963] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/05/2016] [Revised: 08/31/2016] [Indexed: 07/24/2023] Open
Abstract
The replication licensing factor CDC6 recruits the MCM2-7 replicative helicase to the replication origin, where MCM2-7 is activated to initiate DNA replication. MCM2-7 is activated by both the CDC7-Dbf4 kinase and cyclin-dependent kinase and via interactions with CDC45 and go-ichi-ni-san complex (GINS) to form the CDC45·MCM2-7·GINS (CMG) helicase complex. TIMELESS (TIM) is important for the subsequent coupling of CMG activity to DNA polymerases for efficient DNA synthesis. However, the mechanism by which TIM regulates CMG activity for proper replication fork progression remains unclear. Here we show that TIM interacts with MCM2-7 prior to the initiation of DNA replication. TIM depletion in various human cell lines results in the accumulation of aberrant CMG helicase complexes on chromatin. Importantly, the presence of these abnormal CMG helicase complexes is not restricted to cells undergoing DNA synthesis. Furthermore, even though these aberrant CMG complexes interact with the DNA polymerases on human chromatin, these complexes are not phosphorylated properly by cyclin-dependent kinase/CDC7-Dbf4 kinase and exhibit reduced DNA unwinding activity. This phenomenon coincides with a significant accumulation of the p27 and p21 replication inhibitors, reduced chromatin association of CDC6 and cyclin E, and a delay in S phase entry. Our results provide the first evidence that TIM is required for the correct chromatin association of the CMG complex to allow efficient DNA replication.
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Affiliation(s)
- Xiaohua Xu
- From the Department of Cancer Genetics and Epigenetics, Beckman Research Institute, City of Hope, Duarte, California 91010-3000
| | - Jiin-Tarng Wang
- From the Department of Cancer Genetics and Epigenetics, Beckman Research Institute, City of Hope, Duarte, California 91010-3000
| | - Min Li
- From the Department of Cancer Genetics and Epigenetics, Beckman Research Institute, City of Hope, Duarte, California 91010-3000
| | - Yilun Liu
- From the Department of Cancer Genetics and Epigenetics, Beckman Research Institute, City of Hope, Duarte, California 91010-3000
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204
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Roesley SNA, Suryadinata R, Morrish E, Tan AR, Issa SMA, Oakhill JS, Bernard O, Welch DR, Šarčević B. Cyclin-dependent kinase-mediated phosphorylation of breast cancer metastasis suppressor 1 (BRMS1) affects cell migration. Cell Cycle 2016; 15:137-51. [PMID: 26771717 DOI: 10.1080/15384101.2015.1121328] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023] Open
Abstract
Expression of Breast Cancer Metastasis Suppressor 1 (BRMS1) reduces the incidence of metastasis in many human cancers, without affecting tumorigenesis. BRMS1 carries out this function through several mechanisms, including regulation of gene expression by binding to the mSin3/histone deacetylase (HDAC) transcriptional repressor complex. In the present study, we show that BRMS1 is a novel substrate of Cyclin-Dependent Kinase 2 (CDK2) that is phosphorylated on serine 237 (S237). Although CDKs are known to regulate cell cycle progression, the mutation of BRMS1 on serine 237 did not affect cell cycle progression and proliferation of MDA-MB-231 breast cancer cells; however, their migration was affected. Phosphorylation of BRMS1 does not affect its association with the mSin3/HDAC transcriptional repressor complex or its transcriptional repressor activity. The serine 237 phosphorylation site is immediately proximal to a C-terminal nuclear localization sequence that plays an important role in BRMS1-mediated metastasis suppression but phosphorylation does not control BRMS1 subcellular localization. Our studies demonstrate that CDK-mediated phosphorylation of BRMS1 regulates the migration of tumor cells.
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Affiliation(s)
- Siti Nur Ain Roesley
- a Cell Cycle and Cancer Unit , St Vincent's Institute of Medical Research , Victoria , Australia.,b Department of Medicine , University of Melbourne , Victoria , Australia
| | | | - Emma Morrish
- a Cell Cycle and Cancer Unit , St Vincent's Institute of Medical Research , Victoria , Australia
| | | | - Samah M A Issa
- e Metabolic Signalling Laboratory, St Vincent's Institute of Medical Research , Victoria , Australia
| | - Jonathan S Oakhill
- e Metabolic Signalling Laboratory, St Vincent's Institute of Medical Research , Victoria , Australia
| | - Ora Bernard
- b Department of Medicine , University of Melbourne , Victoria , Australia
| | - Danny R Welch
- f Department of Cancer Biology and The University of Kansas Cancer Center , University of Kansas Medical Center , Kansas City , KS , USA
| | - Boris Šarčević
- a Cell Cycle and Cancer Unit , St Vincent's Institute of Medical Research , Victoria , Australia.,b Department of Medicine , University of Melbourne , Victoria , Australia
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205
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Aberrant modulation of the BRCA1 and G1/S cell cycle pathways in alcoholic hepatitis patients with Mallory Denk Bodies revealed by RNA sequencing. Oncotarget 2016; 6:42491-503. [PMID: 26623723 PMCID: PMC4767447 DOI: 10.18632/oncotarget.6382] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/19/2015] [Accepted: 11/15/2015] [Indexed: 01/01/2023] Open
Abstract
Mallory-Denk Bodies (MDBs) are prevalent in various liver diseases including alcoholic hepatitis (AH) and are formed in mice livers by feeding DDC. Liver injury from alcohol administration causes balloon hepatocytes and MDB formation impeding liver regeneration. By comparing AH livers where MDBs had formed with normal liver transcriptomes obtained by RNA sequencing (RNA-Seq), there was significant upregulation of BRCA1-mediated signaling and G1/S cell cycle checkpoint pathways. The transcriptional architecture of differentially expressed genes from AH livers reflected step-wise transcriptional changes progressing to AH. Key molecules such as BRCA1, p15 and p21 were significantly upregulated both in AH livers and in the livers of the DDC re-fed mice model where MDBs had formed. The increase of G1/S cell cycle checkpoint inhibitors p15 and p21 results in cell cycle arrest and inhibition of liver regeneration, implying that p15 and p21 could be exploited for the identification of specific targets for the treatment of liver disease. Provided here for the first time is the RNA-Seq data that represents the fully annotated catalogue of the expression of mRNAs. The most prominent alterations observed were the changes in BRCA1-mediated signaling and G1/S cell cycle checkpoint pathways. These new findings expand previous and related knowledge in the search for gene changes that might be critical in the understanding of the underlying progression to the development of AH.
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206
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Kim JA, Tan Y, Wang X, Cao X, Veeraraghavan J, Liang Y, Edwards DP, Huang S, Pan X, Li K, Schiff R, Wang XS. Comprehensive functional analysis of the tousled-like kinase 2 frequently amplified in aggressive luminal breast cancers. Nat Commun 2016; 7:12991. [PMID: 27694828 PMCID: PMC5064015 DOI: 10.1038/ncomms12991] [Citation(s) in RCA: 39] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/01/2016] [Accepted: 08/24/2016] [Indexed: 12/13/2022] Open
Abstract
More aggressive and therapy-resistant oestrogen receptor (ER)-positive breast cancers remain a great clinical challenge. Here our integrative genomic analysis identifies tousled-like kinase 2 (TLK2) as a candidate kinase target frequently amplified in ∼10.5% of ER-positive breast tumours. The resulting overexpression of TLK2 is more significant in aggressive and advanced tumours, and correlates with worse clinical outcome regardless of endocrine therapy. Ectopic expression of TLK2 leads to enhanced aggressiveness in breast cancer cells, which may involve the EGFR/SRC/FAK signalling. Conversely, TLK2 inhibition selectively inhibits the growth of TLK2-high breast cancer cells, downregulates ERα, BCL2 and SKP2, impairs G1/S cell cycle progression, induces apoptosis and significantly improves progression-free survival in vivo. We identify two potential TLK2 inhibitors that could serve as backbones for future drug development. Together, amplification of the cell cycle kinase TLK2 presents an attractive genomic target for aggressive ER-positive breast cancers. Luminal B oestrogen receptor positive breast cancers are generally aggressive tumors with poor outcomes. Here, the authors show that the kinase TLK2 is amplified and overexpressed in these tumors and correlates with reduced survival, TLK2 inhibition induces apoptosis in vitro and improves survival in mice.
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Affiliation(s)
- Jin-Ah Kim
- Lester &Sue Smith Breast Center, Baylor College of Medicine, Houston, Texas 77030, USA.,Dan L. Duncan Cancer Center, Baylor College of Medicine, Houston, Texas 77030, USA.,Department of Medicine, Baylor College of Medicine, Houston, Texas 77030, USA
| | - Ying Tan
- Lester &Sue Smith Breast Center, Baylor College of Medicine, Houston, Texas 77030, USA.,Dan L. Duncan Cancer Center, Baylor College of Medicine, Houston, Texas 77030, USA.,Department of Medicine, Baylor College of Medicine, Houston, Texas 77030, USA
| | - Xian Wang
- Lester &Sue Smith Breast Center, Baylor College of Medicine, Houston, Texas 77030, USA.,Dan L. Duncan Cancer Center, Baylor College of Medicine, Houston, Texas 77030, USA.,Department of Medicine, Baylor College of Medicine, Houston, Texas 77030, USA.,University of Pittsburgh Cancer Institute, University of Pittsburgh, Pittsburgh, Pennsylvania 15213, USA.,Department of Pathology, University of Pittsburgh, Pittsburgh, Pennsylvania 15213, USA
| | - Xixi Cao
- Lester &Sue Smith Breast Center, Baylor College of Medicine, Houston, Texas 77030, USA.,Dan L. Duncan Cancer Center, Baylor College of Medicine, Houston, Texas 77030, USA.,Department of Medicine, Baylor College of Medicine, Houston, Texas 77030, USA
| | - Jamunarani Veeraraghavan
- Lester &Sue Smith Breast Center, Baylor College of Medicine, Houston, Texas 77030, USA.,Dan L. Duncan Cancer Center, Baylor College of Medicine, Houston, Texas 77030, USA.,Department of Medicine, Baylor College of Medicine, Houston, Texas 77030, USA
| | - Yulong Liang
- Department of Surgery, Baylor College of Medicine, Houston, Texas 77030, USA
| | - Dean P Edwards
- Dan L. Duncan Cancer Center, Baylor College of Medicine, Houston, Texas 77030, USA.,Department of Pathology &Immunology, Baylor College of Medicine, Houston, Texas 77030, USA.,Department of Molecular and Cellular Biology, Baylor College of Medicine, Houston, Texas 77030, USA
| | - Shixia Huang
- Dan L. Duncan Cancer Center, Baylor College of Medicine, Houston, Texas 77030, USA.,Department of Molecular and Cellular Biology, Baylor College of Medicine, Houston, Texas 77030, USA
| | - Xuewen Pan
- Department of Biochemistry and Molecular Biology, Baylor College of Medicine, Houston, Texas 77030, USA
| | - Kaiyi Li
- Department of Surgery, Baylor College of Medicine, Houston, Texas 77030, USA
| | - Rachel Schiff
- Lester &Sue Smith Breast Center, Baylor College of Medicine, Houston, Texas 77030, USA.,Dan L. Duncan Cancer Center, Baylor College of Medicine, Houston, Texas 77030, USA.,Department of Medicine, Baylor College of Medicine, Houston, Texas 77030, USA.,Department of Molecular and Cellular Biology, Baylor College of Medicine, Houston, Texas 77030, USA
| | - Xiao-Song Wang
- Lester &Sue Smith Breast Center, Baylor College of Medicine, Houston, Texas 77030, USA.,Dan L. Duncan Cancer Center, Baylor College of Medicine, Houston, Texas 77030, USA.,Department of Medicine, Baylor College of Medicine, Houston, Texas 77030, USA.,University of Pittsburgh Cancer Institute, University of Pittsburgh, Pittsburgh, Pennsylvania 15213, USA.,Department of Pathology, University of Pittsburgh, Pittsburgh, Pennsylvania 15213, USA.,Department of Molecular and Cellular Biology, Baylor College of Medicine, Houston, Texas 77030, USA
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207
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Abstract
How and when eukaryotic cells make the irrevocable commitment to divide remain central questions in the cell-cycle field. Parallel studies in yeast and mammalian cells seemed to suggest analogous control mechanisms operating during the G1 phase—at Start or the restriction (R) point, respectively—to integrate nutritional and developmental signals and decide between distinct cell fates: cell-cycle arrest or exit versus irreversible commitment to a round of division. Recent work has revealed molecular mechanisms underlying this decision-making process in both yeast and mammalian cells but also cast doubt on the nature and timing of cell-cycle commitment in multicellular organisms. These studies suggest an expanded temporal window of mitogen sensing under certain growth conditions, illuminate unexpected obstacles and exit ramps on the path to full cell-cycle commitment, and raise new questions regarding the functions of cyclin-dependent kinases (CDKs) that drive G1 progression and S-phase entry.
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Affiliation(s)
- Robert P Fisher
- Department of Oncological Sciences, Icahn School of Medicine at Mount Sinai, New York, NY, USA
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208
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Abstract
microRNAs are a subclass of small non-coding RNAs that fine-tune the regulation of gene expression at the post-transcriptional level. The miR-302/367 cluster, generally consisting of five members, miR-367, miR-302d, miR-302a, miR-302c and miR-302b, is ubiquitously distributed in vertebrates and occupies an intragenic cluster located in the gene La-related protein 7 (LARP7). The cluster was demonstrated to play an important role in diverse biological processes, such as the pluripotency of human embryonic stem cells (hESCs), self-renewal and reprogramming. This paper provides an overview of the mir-302/367 cluster, discusses our current understanding of the cluster's evolutionary history and transcriptional regulation and reviews the literature surrounding the cluster's roles in cell cycle regulation, epigenetic regulation and different cellular signalling pathways.
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Affiliation(s)
- Zeqian Gao
- State Key Laboratory of Veterinary Etiological Biology, Key Laboratory of Veterinary Parasitology of Gansu Province, Lanzhou Veterinary Research Institute, Chinese Academy of Agricultural Sciences, 1 Xujiaping, Yanchangbu, Lanzhou, 730046 Gansu, China
| | - Xueliang Zhu
- State Key Laboratory of Veterinary Etiological Biology, Key Laboratory of Veterinary Parasitology of Gansu Province, Lanzhou Veterinary Research Institute, Chinese Academy of Agricultural Sciences, 1 Xujiaping, Yanchangbu, Lanzhou, 730046 Gansu, China
| | - Yongxi Dou
- State Key Laboratory of Veterinary Etiological Biology, Key Laboratory of Veterinary Parasitology of Gansu Province, Lanzhou Veterinary Research Institute, Chinese Academy of Agricultural Sciences, 1 Xujiaping, Yanchangbu, Lanzhou, 730046 Gansu, China
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209
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Human Cytomegalovirus Can Procure Deoxyribonucleotides for Viral DNA Replication in the Absence of Retinoblastoma Protein Phosphorylation. J Virol 2016; 90:8634-43. [PMID: 27440891 DOI: 10.1128/jvi.00731-16] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/18/2016] [Accepted: 07/13/2016] [Indexed: 01/31/2023] Open
Abstract
UNLABELLED Viral DNA replication requires deoxyribonucleotide triphosphates (dNTPs). These molecules, which are found at low levels in noncycling cells, are generated either by salvage pathways or through de novo synthesis. Nucleotide synthesis utilizes the activity of a series of nucleotide-biosynthetic enzymes (NBEs) whose expression is repressed in noncycling cells by complexes between the E2F transcription factors and the retinoblastoma (Rb) tumor suppressor. Rb-E2F complexes are dissociated and NBE expression is activated during cell cycle transit by cyclin-dependent kinase (Cdk)-mediated Rb phosphorylation. The DNA virus human cytomegalovirus (HCMV) encodes a viral Cdk (v-Cdk) (the UL97 protein) that phosphorylates Rb, induces the expression of cellular NBEs, and is required for efficient viral DNA synthesis. A long-held hypothesis proposed that viral proteins with Rb-inactivating activities functionally similar to those of UL97 facilitated viral DNA replication in part by inducing the de novo production of dNTPs. However, we found that dNTPs were limiting even in cells infected with wild-type HCMV in which UL97 is expressed and Rb is phosphorylated. Furthermore, we revealed that both de novo and salvage pathway enzymes contribute to viral DNA replication during HCMV infection and that Rb phosphorylation by cellular Cdks does not correct the viral DNA replication defect observed in cells infected with a UL97-deficient virus. We conclude that HCMV can obtain dNTPs in the absence of Rb phosphorylation and that UL97 can contribute to the efficiency of DNA replication in an Rb phosphorylation-independent manner. IMPORTANCE Transforming viral oncoproteins, such as adenovirus E1A and papillomavirus E7, inactivate Rb. The standard hypothesis for how Rb inactivation facilitates infection with these viruses is that it is through an increase in the enzymes required for DNA synthesis, which include nucleotide-biosynthetic enzymes. However, HCMV UL97, which functionally mimics these viral oncoproteins through phosphorylation of Rb, fails to induce the production of nonlimiting amounts of dNTPs. This finding challenges the paradigm of the role of Rb inactivation during DNA virus infection and uncovers the existence of an alternative mechanism by which UL97 contributes to HCMV DNA synthesis. The ineffectiveness of the UL97 inhibitor maribavir in clinical trials might be better explained with a fuller understanding of the role of UL97 during infection. Furthermore, as the nucleoside analog ganciclovir is the current drug of choice for treating HCMV, knowing the provenance of the dNTPs incorporated into viral DNA may help inform antiviral therapeutic regimens.
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210
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Beale G, Haagensen EJ, Thomas HD, Wang LZ, Revill CH, Payne SL, Golding BT, Hardcastle IR, Newell DR, Griffin RJ, Cano C. Combined PI3K and CDK2 inhibition induces cell death and enhances in vivo antitumour activity in colorectal cancer. Br J Cancer 2016; 115:682-90. [PMID: 27529512 PMCID: PMC5023777 DOI: 10.1038/bjc.2016.238] [Citation(s) in RCA: 33] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Revised: 05/31/2016] [Accepted: 07/14/2016] [Indexed: 02/06/2023] Open
Abstract
BACKGROUND The phosphatidylinositol-3-kinase/mammalian target of rapamycin (PI3K/mTOR) pathway is commonly deregulated in human cancer, hence many PI3K and mTOR inhibitors have been developed and have now reached clinical trials. Similarly, CDKs have been investigated as cancer drug targets. METHODS We have synthesised and characterised a series of 6-aminopyrimidines identified from a kinase screen that inhibit PI3K and/or mTOR and/or CDK2. Kinase inhibition, tumour cell growth, cell cycle distribution, cytotoxicity and signalling experiments were undertaken in HCT116 and HT29 colorectal cancer cell lines, and in vivo HT29 efficacy studies. RESULTS 2,6-Diaminopyrimidines with an O(4)-cyclohexylmethyl substituent and a C-5-nitroso or cyano group (1,2,5) induced cell cycle phase alterations and were growth inhibitory (GI50<20 μM). Compound 1, but not 2 or 5, potently inhibits CDK2 (IC50=0.1 nM) as well as PI3K, and was cytotoxic at growth inhibitory concentrations. Consistent with kinase inhibition data, compound 1 reduced phospho-Rb and phospho-rS6 at GI50 concentrations. Combination of NU6102 (CDK2 inhibitor) and pictilisib (GDC-0941; pan-PI3K inhibitor) resulted in synergistic growth inhibition, and enhanced cytotoxicity in HT29 cells in vitro and HT29 tumour growth inhibition in vivo. CONCLUSIONS These studies identified a novel series of mixed CDK2/PI3K inhibitors and demonstrate that dual targeting of CDK2 and PI3K can result in enhanced antitumour activity.
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Affiliation(s)
- Gary Beale
- Newcastle Cancer Centre, Northern Institute for Cancer Research, Paul O'Gorman Building, Medical School, Newcastle University, Framlington Place, Newcastle-upon-Tyne NE2 4HH, UK
| | - Emma J Haagensen
- Newcastle Cancer Centre, Northern Institute for Cancer Research, Paul O'Gorman Building, Medical School, Newcastle University, Framlington Place, Newcastle-upon-Tyne NE2 4HH, UK
| | - Huw D Thomas
- Newcastle Cancer Centre, Northern Institute for Cancer Research, Paul O'Gorman Building, Medical School, Newcastle University, Framlington Place, Newcastle-upon-Tyne NE2 4HH, UK
| | - Lan-Zhen Wang
- Newcastle Cancer Centre, Northern Institute for Cancer Research, Paul O'Gorman Building, Medical School, Newcastle University, Framlington Place, Newcastle-upon-Tyne NE2 4HH, UK
| | - Charlotte H Revill
- Newcastle Cancer Centre, Northern Institute for Cancer Research, School of Chemistry, Newcastle University, Bedson Building, Newcastle NE1 7RU, UK
| | - Sara L Payne
- Newcastle Cancer Centre, Northern Institute for Cancer Research, School of Chemistry, Newcastle University, Bedson Building, Newcastle NE1 7RU, UK
| | - Bernard T Golding
- Newcastle Cancer Centre, Northern Institute for Cancer Research, School of Chemistry, Newcastle University, Bedson Building, Newcastle NE1 7RU, UK
| | - Ian R Hardcastle
- Newcastle Cancer Centre, Northern Institute for Cancer Research, School of Chemistry, Newcastle University, Bedson Building, Newcastle NE1 7RU, UK
| | - David R Newell
- Newcastle Cancer Centre, Northern Institute for Cancer Research, Paul O'Gorman Building, Medical School, Newcastle University, Framlington Place, Newcastle-upon-Tyne NE2 4HH, UK
| | - Roger J Griffin
- Newcastle Cancer Centre, Northern Institute for Cancer Research, School of Chemistry, Newcastle University, Bedson Building, Newcastle NE1 7RU, UK
| | - Celine Cano
- Newcastle Cancer Centre, Northern Institute for Cancer Research, School of Chemistry, Newcastle University, Bedson Building, Newcastle NE1 7RU, UK
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211
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Tadesse S, Yu M, Kumarasiri M, Le BT, Wang S. Targeting CDK6 in cancer: State of the art and new insights. Cell Cycle 2016; 14:3220-30. [PMID: 26315616 DOI: 10.1080/15384101.2015.1084445] [Citation(s) in RCA: 94] [Impact Index Per Article: 11.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022] Open
Abstract
Cyclin-dependent kinase 6 (CDK6) plays a vital role in regulating the progression of the cell cycle. More recently, CDK6 has also been shown to have a transcriptional role in tumor angiogenesis. Up-regulated CDK6 activity is associated with the development of several types of cancers. While CDK6 is over-expressed in cancer cells, it has a low detectable level in non-cancerous cells and CDK6-null mice develop normally, suggesting a specific oncogenic role of CDK6, and that its inhibition may represent an ideal mechanism-based and low toxic therapeutic strategy in cancer treatment. Identification of selective small molecule inhibitors of CDK6 is thus needed for drug development. Herein, we review the latest understandings of the biological regulation and oncogenic roles of CDK6. The potential clinical relevance of CDK6 inhibition, the progress in the development of small-molecule CDK6 inhibitors and the rational design of potential selective CDK6 inhibitors are also discussed.
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Affiliation(s)
- Solomon Tadesse
- a Center for Drug Discovery and Development, Sansom Institute for Health Research, Center for Cancer Biology; and School of Pharmacy and Medical Sciences, University of South Australia ; Adelaide , Australia
| | - Mingfeng Yu
- a Center for Drug Discovery and Development, Sansom Institute for Health Research, Center for Cancer Biology; and School of Pharmacy and Medical Sciences, University of South Australia ; Adelaide , Australia
| | - Malika Kumarasiri
- a Center for Drug Discovery and Development, Sansom Institute for Health Research, Center for Cancer Biology; and School of Pharmacy and Medical Sciences, University of South Australia ; Adelaide , Australia
| | - Bich Thuy Le
- a Center for Drug Discovery and Development, Sansom Institute for Health Research, Center for Cancer Biology; and School of Pharmacy and Medical Sciences, University of South Australia ; Adelaide , Australia
| | - Shudong Wang
- a Center for Drug Discovery and Development, Sansom Institute for Health Research, Center for Cancer Biology; and School of Pharmacy and Medical Sciences, University of South Australia ; Adelaide , Australia
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212
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Yao M, Xie C, Kiang MY, Teng Y, Harman D, Tiffen J, Wang Q, Sved P, Bao S, Witting P, Holst J, Dong Q. Targeting of cytosolic phospholipase A2α impedes cell cycle re-entry of quiescent prostate cancer cells. Oncotarget 2016; 6:34458-74. [PMID: 26416244 PMCID: PMC4741466 DOI: 10.18632/oncotarget.5277] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/15/2015] [Accepted: 09/14/2015] [Indexed: 11/25/2022] Open
Abstract
Cell cycle re-entry of quiescent cancer cells has been proposed to be involved in cancer progression and recurrence. Cytosolic phospholipase A2α (cPLA2α) is an enzyme that hydrolyzes membrane glycerophospholipids to release arachidonic acid and lysophospholipids that are implicated in cancer cell proliferation. The aim of this study was to determine the role of cPLA2α in cell cycle re-entry of quiescent prostate cancer cells. When PC-3 and LNCaP cells were rendered to a quiescent state, the active form of cPLA2α with a phosphorylation at Ser505 was lower compared to their proliferating state. Conversely, the phospho-cPLA2α levels were resurgent during the induction of cell cycle re-entry. Pharmacological inhibition of cPLA2α with Efipladib upon induction of cell cycle re-entry inhibited the re-entry process, as manifested by refrained DNA synthesis, persistent high proportion of cells in G0/G1 and low percentage of cells in S and G2/M phases, together with a stagnant recovery of Ki-67 expression. Simultaneously, Efipladib prohibited the emergence of Skp2 while maintained p27 at a high level in the nuclear compartment during cell cycle re-entry. Inhibition of cPLA2α also prevented an accumulation of cyclin D1/CDK4, cyclin E/CDK2, phospho-pRb, pre-replicative complex proteins CDC6, MCM7, ORC6 and DNA synthesis-related protein PCNA during induction of cell cycle re-entry. Moreover, a pre-treatment of the prostate cancer cells with Efipladib during induction of cell cycle re-entry subsequently compromised their tumorigenic capacity in vivo. Hence, cPLA2α plays an important role in cell cycle re-entry by quiescent prostate cancer cells.
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Affiliation(s)
- Mu Yao
- Department of Endocrinology, Royal Prince Alfred Hospital, Camperdown, NSW 2050, Australia.,Central Clinical School and Bosch Institute, The University of Sydney, Sydney, NSW 2006, Australia
| | - Chanlu Xie
- Department of Endocrinology, Royal Prince Alfred Hospital, Camperdown, NSW 2050, Australia.,Central Clinical School and Bosch Institute, The University of Sydney, Sydney, NSW 2006, Australia.,School of Biomedical and Health Sciences, University of Western Sydney, Parramatta, NSW 2751, Australia
| | - Mei-Yee Kiang
- Department of Endocrinology, Royal Prince Alfred Hospital, Camperdown, NSW 2050, Australia.,Central Clinical School and Bosch Institute, The University of Sydney, Sydney, NSW 2006, Australia
| | - Ying Teng
- Department of Endocrinology, Royal Prince Alfred Hospital, Camperdown, NSW 2050, Australia.,Central Clinical School and Bosch Institute, The University of Sydney, Sydney, NSW 2006, Australia
| | - David Harman
- Molecular Medicine Research Group, University of Western Sydney, Parramatta, NSW 2751, Australia
| | - Jessamy Tiffen
- Origins of Cancer Laboratory, Centenary Institute, Camperdown, NSW 2050, Australia.,Sydney Medical School, The University of Sydney, Sydney, NSW 2006, Australia
| | - Qian Wang
- Origins of Cancer Laboratory, Centenary Institute, Camperdown, NSW 2050, Australia.,Sydney Medical School, The University of Sydney, Sydney, NSW 2006, Australia
| | - Paul Sved
- Department of Urology, Royal Prince Alfred Hospital, Camperdown, NSW 2050, Australia
| | - Shisan Bao
- Department of Pathology, The University of Sydney, Sydney, NSW 2006, Australia
| | - Paul Witting
- Department of Pathology, The University of Sydney, Sydney, NSW 2006, Australia
| | - Jeff Holst
- Origins of Cancer Laboratory, Centenary Institute, Camperdown, NSW 2050, Australia.,Sydney Medical School, The University of Sydney, Sydney, NSW 2006, Australia
| | - Qihan Dong
- Department of Endocrinology, Royal Prince Alfred Hospital, Camperdown, NSW 2050, Australia.,Central Clinical School and Bosch Institute, The University of Sydney, Sydney, NSW 2006, Australia.,School of Biomedical and Health Sciences, University of Western Sydney, Parramatta, NSW 2751, Australia
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213
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Yang X, Wang S, Mu Y, Zheng Y. Schisandrin B inhibits cell proliferation and induces apoptosis in human cholangiocarcinoma cells. Oncol Rep 2016; 36:1799-806. [PMID: 27499090 PMCID: PMC5022873 DOI: 10.3892/or.2016.4992] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/22/2016] [Accepted: 04/01/2016] [Indexed: 01/09/2023] Open
Abstract
Cholangiocarcinoma (CCA) is the second most common hepatic cancer with high resistance to current chemotherapies and extremely poor prognosis. The present study aimed to examine the effects of schisandrin B (Sch B) on CCA cells both in vitro and in vivo and to examine its underlying mechanism. We found that Sch B inhibited the viability and proliferation of CCA cells in a dose- and time-dependent manner as assessed by MTT and colony formation assays. The flow cytometric assay revealed G0/G1 phase arrest in the Sch B-treated HCCC-9810 and RBE cells. In addition, Sch B induced intrahepatic cholangiocarcinoma apoptosis as shown by the results of Annexin V/PI double staining. Rhodamine 123 staining revealed that Sch B decreased the mitochondrial membrane potential (ΔΨm) in a dose-dependent manner. Mechanistically, western blot analysis indicated that Sch B induced apoptosis by upregulating Bax, cleaved caspase-3, cleaved caspase-9 and cleaved PARP, and by downregulating cyclin D1, Bcl-2 and CDK-4. Moreover, Sch B significantly inhibited HCCC-9810 xenograft growth in athymic nude mice. In summary, these findings suggest that Sch B exhibited potent antitumor activities via the induction of CCA apoptosis and that Sch B may be a promising drug for the treatment of CCA.
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Affiliation(s)
- Xiaohui Yang
- The Fourth Affiliated Hospital, Zhejiang University School of Medicine, Yiwu, Zhejiang 322000, P.R. China
| | - Shuai Wang
- The Fourth Affiliated Hospital, Zhejiang University School of Medicine, Yiwu, Zhejiang 322000, P.R. China
| | - Yunchuan Mu
- The Fourth Affiliated Hospital, Zhejiang University School of Medicine, Yiwu, Zhejiang 322000, P.R. China
| | - Yixiong Zheng
- The Second Affiliated Hospital, Zhejiang University School of Medicine, Hangzhou, Zhejiang 310009, P.R. China
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214
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The TRAF-interacting protein (TRAIP) is a novel E2F target with peak expression in mitosis. Oncotarget 2016; 6:20933-45. [PMID: 26369285 PMCID: PMC4673240 DOI: 10.18632/oncotarget.3055] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/24/2014] [Accepted: 11/08/2014] [Indexed: 12/17/2022] Open
Abstract
The TRAF-interacting protein (TRAIP) is an E3 ubiquitin ligase required for cell proliferation. TRAIP mRNA is downregulated in human keratinocytes after inhibition of the PI3K/AKT/mTOR signaling. Since E2F transcription factors are downstream of PI3K/AKT/mTOR we investigated whether they regulate TRAIP expression. E2F1 expression significantly increased the TRAIP mRNA level in HeLa cells. Reporter assays with the 1400bp 5′-upstream promoter in HeLa cells and human keratinocytes showed that E2F1-, E2F2- and E2F4-induced upregulation of TRAIP expression is mediated by 168bp upstream of the translation start site. Mutating the E2F binding site within this fragment reduced the E2F1- and E2F2-dependent promoter activities and protein-DNA complex formation in gel shift assays. Abundance of TRAIP mRNA and protein was regulated by the cell cycle with a peak in G2/M. Expression of GFP and TRAIP-GFP demonstrated that TRAIP-GFP protein has a lower steady-state concentration than GFP despite similar mRNA levels. Cycloheximide inhibition experiments indicated that the TRAIP protein has a half-life of around four hours. Therefore, the combination of cell cycle-dependent transcription of the TRAIP gene by E2F and rapid protein degradation leads to cell cycle-dependent expression with a maximum in G2/M. These findings suggest that TRAIP has important functions in mitosis and tumorigenesis.
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215
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Premnath PN, Craig SN, Liu S, McInnes C. Benzamide capped peptidomimetics as non-ATP competitive inhibitors of CDK2 using the REPLACE strategy. Bioorg Med Chem Lett 2016; 26:3754-60. [PMID: 27297568 DOI: 10.1016/j.bmcl.2016.05.067] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/06/2016] [Revised: 05/20/2016] [Accepted: 05/21/2016] [Indexed: 11/25/2022]
Abstract
Inhibition of cyclin dependent kinase 2 (CDK2) in complex with cyclin A in G1/S phase of the cell cycle has been shown to promote selective apoptosis of cancer cells through the E2F1 pathway. An alternative approach to catalytic inhibition is to target the substrate recruitment site also known as the cyclin binding groove (CBG) to generate selective non-ATP competitive inhibitors. The REPLACE strategy has been applied to identify fragment alternatives and substituted benzoic acid derivatives were evaluated as a promising scaffold to present appropriate functionality to mimic key peptide determinants. Fragment Ligated Inhibitory Peptides (FLIPs) are described which potently inhibit both CDK2/cyclin A and CDK4/cyclin D1 and have preliminary anti-tumor activity. A structural rationale for binding was obtained through molecular modeling further demonstrating their potential for further development as next generation non ATP competitive CDK inhibitors.
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Affiliation(s)
- Padmavathy Nandha Premnath
- Drug Discovery and Biomedical Sciences, South Carolina College of Pharmacy, University of South Carolina, Columbia, SC 29208, USA.
| | - Sandra N Craig
- Drug Discovery and Biomedical Sciences, South Carolina College of Pharmacy, University of South Carolina, Columbia, SC 29208, USA
| | - Shu Liu
- Drug Discovery and Biomedical Sciences, South Carolina College of Pharmacy, University of South Carolina, Columbia, SC 29208, USA.
| | - Campbell McInnes
- Drug Discovery and Biomedical Sciences, South Carolina College of Pharmacy, University of South Carolina, Columbia, SC 29208, USA.
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216
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Hille S, Dierck F, Kühl C, Sosna J, Adam-Klages S, Adam D, Lüllmann-Rauch R, Frey N, Kuhn C. Dyrk1a regulates the cardiomyocyte cell cycle via D-cyclin-dependent Rb/E2f-signalling. Cardiovasc Res 2016; 110:381-94. [PMID: 27056896 DOI: 10.1093/cvr/cvw074] [Citation(s) in RCA: 44] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/17/2015] [Accepted: 04/01/2016] [Indexed: 11/14/2022] Open
Abstract
AIMS Down syndrome-associated dual-specificity tyrosine-(Y)-phosphorylation-regulated kinase 1A (DYRK1A) is a ubiquitously expressed protein kinase. Up to date a variety of targets have been identified, establishing a key role for Dyrk1a in selected signalling pathways. In cardiomyocytes, Dyrk1a acts as a negative regulator of hypertrophy by phosphorylating transcription factors of the NFAT family, but its mechanistic function in the heart remains poorly understood. This study was designed to investigate a potential protective role of Dyrk1a in cardiac hypertrophy in vivo. METHODS AND RESULTS We generated transgenic mice with cardiac-specific overexpression of Dyrk1a. Counterintuitively, these mice developed severe dilated cardiomyopathy associated with congestive heart failure and premature death. In search for the cause of this unexpected phenotype, we found that Dyrk1a interacts with all members of the D-cyclin family and represses their protein levels in vitro and in vivo. Particularly, forced expression of Dyrk1a leads to increased phosphorylation of Ccnd2 on Thr280 and promotes its subsequent proteasomal degradation. Accordingly, cardiomyocytes overexpressing Dyrk1a display hypo-phosphorylated Rb1, suppression of Rb/E2f-signalling, and reduced expression of E2f-target genes, which ultimately results in impaired cell cycle progression. CONCLUSIONS We identified Dyrk1a as a novel negative regulator of D-cyclin-mediated Rb/E2f-signalling. As dysregulation of this pathway with impaired cardiomyocyte proliferation leads to cardiomyopathy, dose-specific Dyrk1a expression and activity appears to be critical for the hyperplastic and hypertrophic growth of the developing heart.
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MESH Headings
- Animals
- Cardiomegaly/enzymology
- Cardiomegaly/genetics
- Cardiomegaly/pathology
- Cardiomegaly/physiopathology
- Cardiomyopathy, Dilated/enzymology
- Cardiomyopathy, Dilated/genetics
- Cardiomyopathy, Dilated/pathology
- Cardiomyopathy, Dilated/physiopathology
- Cell Cycle
- Cell Proliferation
- Cyclin D/genetics
- Cyclin D/metabolism
- Disease Models, Animal
- E2F Transcription Factors/metabolism
- Gene Expression Regulation
- HEK293 Cells
- Heart Failure/enzymology
- Heart Failure/genetics
- Heart Failure/pathology
- Heart Failure/physiopathology
- Humans
- Mice, Inbred C57BL
- Mice, Transgenic
- Myocytes, Cardiac/enzymology
- Myocytes, Cardiac/pathology
- Phosphorylation
- Protein Binding
- Protein Serine-Threonine Kinases/genetics
- Protein Serine-Threonine Kinases/metabolism
- Protein-Tyrosine Kinases/genetics
- Protein-Tyrosine Kinases/metabolism
- Rats, Wistar
- Retinoblastoma/metabolism
- Signal Transduction
- Time Factors
- Transfection
- Dyrk Kinases
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Affiliation(s)
- Susanne Hille
- Department of Internal Medicine III, University Medical Center of Schleswig-Holstein, Campus Kiel, Arnold-Heller-Str. 3 (Building 6), 24105 Kiel, Germany DZHK (German Centre for Cardiovascular Research), Partner Site Hamburg/Kiel/Lübeck, Kiel, Germany
| | - Franziska Dierck
- Department of Internal Medicine III, University Medical Center of Schleswig-Holstein, Campus Kiel, Arnold-Heller-Str. 3 (Building 6), 24105 Kiel, Germany DZHK (German Centre for Cardiovascular Research), Partner Site Hamburg/Kiel/Lübeck, Kiel, Germany
| | - Constantin Kühl
- Department of Internal Medicine III, University Medical Center of Schleswig-Holstein, Campus Kiel, Arnold-Heller-Str. 3 (Building 6), 24105 Kiel, Germany DZHK (German Centre for Cardiovascular Research), Partner Site Hamburg/Kiel/Lübeck, Kiel, Germany
| | - Justyna Sosna
- Institute of Immunology, Christian-Albrechts-University Kiel, UKSH Campus Kiel, 24105 Kiel, Germany
| | - Sabine Adam-Klages
- Institute of Immunology, Christian-Albrechts-University Kiel, UKSH Campus Kiel, 24105 Kiel, Germany
| | - Dieter Adam
- Institute of Immunology, Christian-Albrechts-University Kiel, UKSH Campus Kiel, 24105 Kiel, Germany
| | | | - Norbert Frey
- Department of Internal Medicine III, University Medical Center of Schleswig-Holstein, Campus Kiel, Arnold-Heller-Str. 3 (Building 6), 24105 Kiel, Germany DZHK (German Centre for Cardiovascular Research), Partner Site Hamburg/Kiel/Lübeck, Kiel, Germany
| | - Christian Kuhn
- Department of Internal Medicine III, University Medical Center of Schleswig-Holstein, Campus Kiel, Arnold-Heller-Str. 3 (Building 6), 24105 Kiel, Germany DZHK (German Centre for Cardiovascular Research), Partner Site Hamburg/Kiel/Lübeck, Kiel, Germany
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217
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Choudhary V, Gupta S. Comprehensive Gene Mutation Profiling of Breast Tumors: Is It Ready for Prime Time Use? CURRENT BREAST CANCER REPORTS 2016. [DOI: 10.1007/s12609-016-0213-8] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
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218
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β-catenin activation drives thymoma initiation and progression in mice. Oncotarget 2016; 6:13978-93. [PMID: 26101855 PMCID: PMC4546445 DOI: 10.18632/oncotarget.4368] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/23/2015] [Accepted: 06/01/2015] [Indexed: 11/25/2022] Open
Abstract
Thymoma is the most commonly identified cancer in the anterior mediastinum. To date, the causal mechanism that drives thymoma progression is not clear. Here, we generated K5-ΔN64Ctnnb1/ERT2 transgenic mice, which express an N-terminal deletion mutant of β-catenin fused to a mutated ligand-binding domain of estrogen receptor (ERT2) under the control of the bovine cytokeratin 5 (K5) promoter. The transgenic mouse lines named Tg1 and Tg4 were characterized. Forced expression of ΔN64Ctnnb1/ERT2 in the Tg1 and Tg4 mice developed small thymoma lesions in response to tamoxifen treatment. In the absence of tamoxifen, the Tg1 mice exhibited leaky activation of β-catenin, which activated the TOP-Gal transgene and Wnt/β-catenin-targeted genes. As the Tg1 mice aged in the absence of tamoxifen, manifest thymomas were found at 10-12 months. Interestingly, we detected loss of AIRE and increase of p63 in the thymomas of Tg1 mice, similar to that observed in human thymomas. Moreover, the β5t protease subunit, which was reported as a differential marker for human type B3 thymoma, was expressed in the Tg1 thymomas. Thus, the Tg1 mice generated in this study accurately mimic the characteristics of human thymomas and may serve as a model for understanding thymoma pathogenesis.
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219
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Meng F, Qian J, Yue H, Li X, Xue K. SUMOylation of Rb enhances its binding with CDK2 and phosphorylation at early G1 phase. Cell Cycle 2016; 15:1724-32. [PMID: 27163259 PMCID: PMC4957593 DOI: 10.1080/15384101.2016.1182267] [Citation(s) in RCA: 29] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022] Open
Abstract
Retinoblastoma protein (Rb) is a prototypical tumor suppressor that is vital to the negative regulation of the cell cycle and tumor progression. Hypo-phosphorylated Rb is associated with G0/G1 arrest by suppressing E2F transcription factor activity, whereas Rb hyper-phosphorylation allows E2F release and cell cycle progression from G0/G1 to S phase. However, the factors that regulate cyclin-dependent protein kinase (CDK)-dependent hyper-phosphorylation of Rb during the cell cycle remain obscure. In this study, we show that throughout the cell cycle, Rb is specifically small ubiquitin-like modifier (SUMO)ylated at early G1 phase. SUMOylation of Rb stimulates its phosphorylation level by recruiting a SUMO-interaction motif (SIM)-containing kinase CDK2, leading to Rb hyper-phosphorylation and E2F-1 release. In contrast, a SUMO-deficient Rb mutant results in reduced SUMOylation and phosphorylation, weakened CDK2 binding, and attenuated E2F-1 sequestration. Furthermore, we reveal that Rb SUMOylation is required for cell proliferation. Therefore, our study describes a novel mechanism that regulates Rb phosphorylation during cell cycle progression.
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Affiliation(s)
- Fengxi Meng
- a Department of Ophthalmology , Eye and ENT Hospital of Fudan University , Shanghai , China.,b Shanghai Key Laboratory of Visual Impairment and Restoration, Fudan University , Shanghai , China
| | - Jiang Qian
- a Department of Ophthalmology , Eye and ENT Hospital of Fudan University , Shanghai , China.,b Shanghai Key Laboratory of Visual Impairment and Restoration, Fudan University , Shanghai , China
| | - Han Yue
- a Department of Ophthalmology , Eye and ENT Hospital of Fudan University , Shanghai , China.,b Shanghai Key Laboratory of Visual Impairment and Restoration, Fudan University , Shanghai , China
| | - Xiaofeng Li
- a Department of Ophthalmology , Eye and ENT Hospital of Fudan University , Shanghai , China.,b Shanghai Key Laboratory of Visual Impairment and Restoration, Fudan University , Shanghai , China
| | - Kang Xue
- a Department of Ophthalmology , Eye and ENT Hospital of Fudan University , Shanghai , China.,b Shanghai Key Laboratory of Visual Impairment and Restoration, Fudan University , Shanghai , China
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220
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Nesset CK, Kong XY, Damme M, Schjalm C, Roos N, Løberg EM, Eskild W. Age-dependent development of liver fibrosis in Glmp (gt/gt) mice. FIBROGENESIS & TISSUE REPAIR 2016; 9:5. [PMID: 27141234 PMCID: PMC4852418 DOI: 10.1186/s13069-016-0042-4] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 03/09/2016] [Accepted: 04/20/2016] [Indexed: 02/08/2023]
Abstract
Background Mice lacking glycosylated lysosomal membrane protein (Glmpgt/gt mice) have liver fibrosis as the predominant phenotype due to chronic liver injury. The Glmpgt/gt mice grow and reproduce at the same rate as their wild-type siblings. Life expectancy is around 18 months. Methods Wild-type and Glmpgt/gt mice were studied between 1 week and 18 months of age. Livers were analyzed using histological, immunohistochemical, biochemical, and qPCR analyses. Results It was shown that Glmpgt/gt mice were not born with liver injury; however, it appeared shortly after birth as indicated by excess collagen expression, deposition of fibrous collagen in the periportal areas, and increased levels of hydroxyproline in Glmpgt/gt liver. Liver functional tests indicated a chronic, mild liver injury. Markers of inflammation, fibrosis, apoptosis, and modulation of extracellular matrix increased from an early age, peaking around 4 months of age and followed by attenuation of these signals. To compensate for loss of hepatocytes, the oval cell compartment was activated, with the highest activity of the oval cells detected at 3 months of age, suggesting insufficient hepatocyte proliferation in Glmpgt/gt mice around this age. Although constant proliferation of hepatocytes and oval cells maintained adequate hepatic function in Glmpgt/gt mice, it also resulted in a higher frequency of liver tumors in older animals. Conclusions The Glmpgt/gt mouse is proposed as a model for slowly progressing liver fibrosis and possibly as a model for a yet undescribed human lysosomal disorder. Electronic supplementary material The online version of this article (doi:10.1186/s13069-016-0042-4) contains supplementary material, which is available to authorized users.
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Affiliation(s)
| | - Xiang Yi Kong
- Department of Bioscience, University of Oslo, Oslo, Norway ; Research Institute for Internal Medicine, University of Oslo, Oslo, Norway ; Institute of Clinical Medicine, Faculty of Medicine, University of Oslo, Oslo, Norway ; K.G. Jebsen Inflammation Research Centre, University of Oslo, Oslo, Norway
| | - Markus Damme
- Institute of Biochemistry, Christian-Albrechts-Universität Kiel, Kiel, Germany
| | | | - Norbert Roos
- Department of Bioscience, University of Oslo, Oslo, Norway
| | - Else Marit Løberg
- Department of Pathology, Oslo University Hospital Ullevaal, Oslo, Norway
| | - Winnie Eskild
- Department of Bioscience, University of Oslo, Oslo, Norway
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221
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Abstract
Uncontrolled cellular proliferation, mediated by dysregulation of the cell-cycle machinery and activation of cyclin-dependent kinases (CDKs) to promote cell-cycle progression, lies at the heart of cancer as a pathological process. Clinical implementation of first-generation, nonselective CDK inhibitors, designed to inhibit this proliferation, was originally hampered by the high risk of toxicity and lack of efficacy noted with these agents. The emergence of a new generation of selective CDK4/6 inhibitors, including ribociclib, abemaciclib and palbociclib, has enabled tumour types in which CDK4/6 has a pivotal role in the G1-to-S-phase cell-cycle transition to be targeted with improved effectiveness, and fewer adverse effects. Results of pivotal phase III trials investigating palbociclib in patients with advanced-stage oestrogen receptor (ER)-positive breast cancer have demonstrated a substantial improvement in progression-free survival, with a well-tolerated toxicity profile. Mechanisms of acquired resistance to CDK4/6 inhibitors are beginning to emerge that, although unwelcome, might enable rational post-CDK4/6 inhibitor therapeutic strategies to be identified. Extending the use of CDK4/6 inhibitors beyond ER-positive breast cancer is challenging, and will likely require biomarkers that are predictive of a response, and the use of combination therapies in order to optimize CDK4/6 targeting.
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Affiliation(s)
- Ben O'Leary
- The Breakthrough Breast Cancer Research Centre, The Institute of Cancer Research, Fulham Road, London SW3 6JB, UK
| | - Richard S Finn
- Division of Haematology/Oncology, Geffen School of Medicine at UCLA, Los Angeles, California 90095, USA
| | - Nicholas C Turner
- The Breakthrough Breast Cancer Research Centre, The Institute of Cancer Research, Fulham Road, London SW3 6JB, UK.,Breast Unit, Royal Marsden Hospital, Fulham Road, London SW3 6JJ, UK
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222
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Oncogenes and tumor suppressor genes in squamous cell carcinoma of the tongue in young patients. Oncotarget 2016; 6:3443-51. [PMID: 25633809 PMCID: PMC4413665 DOI: 10.18632/oncotarget.2850] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/23/2014] [Accepted: 12/03/2014] [Indexed: 12/14/2022] Open
Abstract
Objectives The occurrence of squamous cell carcinoma of the tongue (SCCT) of young patients increased. There are still controversies about patient prognosis. The underlying molecular mechanisms remain unclear. Methods 276 patients (66 ≤45, 210 >45 years) with SCCT were included. Clinical parameters and survival data were assessed. Oncogenes and tumor suppressors were analyzed via immunohistochemistry (p53, CXCR4, p16, EGFR) and qPCR (CDK4, CDKN2A, TP53, MDM2, AKT1, PIK3CA, NRAS, HRAS, KRAS, HGF, MET, EGF, ATM, BRCA1, E2F1, FHIT, RUNX3, STK11, BCL2, CTNNB1). Results The median overall survival was 142 (≤45 years) and 34 months (>45 years) (p < 0.0001; HR [95%CI]: 0.37 [0.30–0.58]). Disease specific survival in patients ≤45 years was with 181 months significantly higher than in patients >45 years (p < 0.0001; HR [95%CI]: 0.33 [0.26–0.57]). Immunhistochemistry visualized a comparable expression of analyzed proteins. QPCR demonstrated in patients ≤45 years a higher expression of genes that are associated with carcinogenesis (CTNNB1, STK11, CDKN2A, HGF, MET) as well as tumor suppressors that constitute an enhanced radio-sensitivity (ATM, BRCA1E2F1, FHIT). Conclusion Derogation of the WNT-CTNNB1-STK11 and CDKN2A-HGF-MET pathway can constitute the carcinogenesis, while the higher expression of radio-sensitizers ATM, BRCA1E2F1 and FHIT can explain the better OS/DSS in young patients.
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223
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Osteosarcoma: prognosis plateau warrants retinoblastoma pathway targeted therapy. Signal Transduct Target Ther 2016; 1:16001. [PMID: 29263893 PMCID: PMC5657420 DOI: 10.1038/sigtrans.2016.1] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/18/2015] [Revised: 12/31/2015] [Accepted: 01/04/2016] [Indexed: 02/06/2023] Open
Abstract
Osteosarcoma (OS) is the most common primary bone cancer in children and adolescents, affecting ~560 young patients in the United States annually. The term OS describes a diverse array of subtypes with varying prognoses, but the majority of tumors are high grade and aggressive. Perhaps because the true etiology of these aggressive tumors remains unknown, advances in OS treatment have reached a discouraging plateau, with only incremental improvements over the past 40 years. Thus, research surrounding the pathogenesis of OS is essential, as it promises to unveil novel therapeutic targets that can attack tumor cells with greater specificity and lower toxicity. Among the candidate molecular targets in OS, the retinoblastoma (RB) pathway demonstrates the highest frequency of inactivation and thus represents a particularly promising avenue for molecular targeted therapy. This review examines the present thinking and practices in OS treatment and specifically highlights the relevance of the RB pathway in osteosarcomagenesis. Through further investigation into RB pathway-related novel therapeutic targets, we believe that a near-term breakthrough in improved OS prognosis is possible.
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224
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Wei H, Geng J, Shi B, Liu Z, Wang YH, Stevens AC, Sprout SL, Yao M, Wang H, Hu H. Cutting Edge: Foxp1 Controls Naive CD8+ T Cell Quiescence by Simultaneously Repressing Key Pathways in Cellular Metabolism and Cell Cycle Progression. THE JOURNAL OF IMMUNOLOGY 2016; 196:3537-41. [PMID: 27001958 DOI: 10.4049/jimmunol.1501896] [Citation(s) in RCA: 38] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Subscribe] [Scholar Register] [Received: 08/25/2015] [Accepted: 02/29/2016] [Indexed: 12/31/2022]
Abstract
Previously we have shown that transcription factor Foxp1 plays an essential role in maintaining naive T cell quiescence; in the absence of Foxp1, mature naive CD8(+) T cells proliferate in direct response to homeostatic cytokine IL-7. In this study, we report that the deletion of Foxp1 in naive CD8(+) T cells leads to enhanced activation of the PI3K/Akt/mammalian target of rapamycin signaling pathway and its downstream cell growth and metabolism targets in response to IL-7. We found that Foxp1 directly regulates PI3K interacting protein 1, a negative regulator of PI3K. Additionally, we found that deletion of Foxp1 in naive CD8(+) T cells results in increased expression levels of E2fs, the critical components for cell cycle progression and proliferation, in a manner that is not associated with increased phosphorylation of retinoblastoma protein. Taken together, our studies suggest that Foxp1 enforces naive CD8(+) T cell quiescence by simultaneously repressing key pathways in both cellular metabolism and cell cycle progression.
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Affiliation(s)
- Hairong Wei
- Department of Microbiology, School of Medicine, University of Alabama at Birmingham, Birmingham, AL 35205; and
| | - Jianlin Geng
- Department of Microbiology, School of Medicine, University of Alabama at Birmingham, Birmingham, AL 35205; and
| | - Bi Shi
- Department of Microbiology, School of Medicine, University of Alabama at Birmingham, Birmingham, AL 35205; and
| | - Zhenghui Liu
- Department of Microbiology, School of Medicine, University of Alabama at Birmingham, Birmingham, AL 35205; and
| | - Yin-Hu Wang
- Department of Microbiology, School of Medicine, University of Alabama at Birmingham, Birmingham, AL 35205; and
| | - Anna C Stevens
- Department of Microbiology, School of Medicine, University of Alabama at Birmingham, Birmingham, AL 35205; and
| | - Stephanie L Sprout
- Department of Microbiology, School of Medicine, University of Alabama at Birmingham, Birmingham, AL 35205; and
| | - Min Yao
- Key Laboratory of Molecular Virology and Immunology, Institut Pasteur of Shanghai, Chinese Academy of Sciences, Shanghai 200031, China
| | - Haikun Wang
- Key Laboratory of Molecular Virology and Immunology, Institut Pasteur of Shanghai, Chinese Academy of Sciences, Shanghai 200031, China
| | - Hui Hu
- Department of Microbiology, School of Medicine, University of Alabama at Birmingham, Birmingham, AL 35205; and
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Camarillo JM, Rose KL, Galligan JJ, Xu S, Marnett LJ. Covalent Modification of CDK2 by 4-Hydroxynonenal as a Mechanism of Inhibition of Cell Cycle Progression. Chem Res Toxicol 2016; 29:323-32. [PMID: 26910110 DOI: 10.1021/acs.chemrestox.5b00485] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
Oxidative stress is a contributing factor in a number of chronic diseases, including cancer, atherosclerosis, and neurodegenerative diseases. Lipid peroxidation that occurs during periods of oxidative stress results in the formation of lipid electrophiles, which can modify a multitude of proteins in the cell. 4-Hydroxy-2-nonenal (HNE) is one of the most well-studied lipid electrophiles and has previously been shown to arrest cells at the G1/S transition. Recently, proteomic data have shown that HNE is capable of covalently modifying CDK2, the kinase responsible for the G1/S transition. Here, we identify the sites adducted by HNE using recombinant CDK2 and show that HNE treatment suppresses the kinase activity of the enzyme. We further identify sites of adduction in HNE-treated intact human colorectal carcinoma cells (RKO) and show that HNE-dependent modification in cells is long-lived, disrupts CDK2 function, and correlates with a delay of progression of the cells into S-phase. We propose that adduction of CDK2 by HNE directly alters its activity, contributing to the cell cycle delay.
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Affiliation(s)
- Jeannie M Camarillo
- A.B. Hancock Jr. Memorial Laboratory for Cancer Research, Departments of Biochemistry, §Chemistry, and #Pharmacology, ‡Mass Spectrometry Research Center, ⊥Vanderbilt Institute of Chemical Biology, Center in Molecular Toxicology, Vanderbilt-Ingram Cancer Center, Vanderbilt University School of Medicine , Nashville, Tennessee 37232-0146, United States
| | - Kristie L Rose
- A.B. Hancock Jr. Memorial Laboratory for Cancer Research, Departments of Biochemistry, §Chemistry, and #Pharmacology, ‡Mass Spectrometry Research Center, ⊥Vanderbilt Institute of Chemical Biology, Center in Molecular Toxicology, Vanderbilt-Ingram Cancer Center, Vanderbilt University School of Medicine , Nashville, Tennessee 37232-0146, United States
| | - James J Galligan
- A.B. Hancock Jr. Memorial Laboratory for Cancer Research, Departments of Biochemistry, §Chemistry, and #Pharmacology, ‡Mass Spectrometry Research Center, ⊥Vanderbilt Institute of Chemical Biology, Center in Molecular Toxicology, Vanderbilt-Ingram Cancer Center, Vanderbilt University School of Medicine , Nashville, Tennessee 37232-0146, United States
| | - Shu Xu
- A.B. Hancock Jr. Memorial Laboratory for Cancer Research, Departments of Biochemistry, §Chemistry, and #Pharmacology, ‡Mass Spectrometry Research Center, ⊥Vanderbilt Institute of Chemical Biology, Center in Molecular Toxicology, Vanderbilt-Ingram Cancer Center, Vanderbilt University School of Medicine , Nashville, Tennessee 37232-0146, United States
| | - Lawrence J Marnett
- A.B. Hancock Jr. Memorial Laboratory for Cancer Research, Departments of Biochemistry, §Chemistry, and #Pharmacology, ‡Mass Spectrometry Research Center, ⊥Vanderbilt Institute of Chemical Biology, Center in Molecular Toxicology, Vanderbilt-Ingram Cancer Center, Vanderbilt University School of Medicine , Nashville, Tennessee 37232-0146, United States
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226
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Ouzounoglou E, Dionysiou D, Stamatakos GS. Differentiation resistance through altered retinoblastoma protein function in acute lymphoblastic leukemia: in silico modeling of the deregulations in the G1/S restriction point pathway. BMC SYSTEMS BIOLOGY 2016; 10:23. [PMID: 26932523 PMCID: PMC4774111 DOI: 10.1186/s12918-016-0264-5] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 05/06/2015] [Accepted: 01/31/2016] [Indexed: 12/13/2022]
Abstract
BACKGROUND As in many cancer types, the G1/S restriction point (RP) is deregulated in Acute Lymphoblastic Leukemia (ALL). Hyper-phosphorylated retinoblastoma protein (hyper-pRb) is found in high levels in ALL cells. Nevertheless, the ALL lymphocyte proliferation rate for the average patient is surprisingly low compared to its normal counterpart of the same maturation level. Additionally, as stated in literature, ALL cells possibly reside at or beyond the RP which is located in the late-G1 phase. This state may favor their differentiation resistant phenotype. A major phenomenon contributing to this fact is thought to be the observed limited redundancy in the phosphorylation of retinoblastoma protein (pRb) by the various Cyclin Dependent Kinases (Cdks). The latter may result in partial loss of pRb functions despite hyper-phosphorylation. RESULTS To test this hypothesis, an in silico model aiming at simulating the biochemical regulation of the RP in ALL is introduced. By exploiting experimental findings derived from leukemic cells and following a semi-quantitative calibration procedure, the model has been shown to satisfactorily reproduce such a behavior for the RP pathway. At the same time, the calibrated model has been proved to be in agreement with the observed variation in the ALL cell cycle duration. CONCLUSIONS The proposed model aims to contribute to a better understanding of the complex phenomena governing the leukemic cell cycle. At the same time it constitutes a significant first step in the creation of a personalized proliferation rate predictor that can be used in the context of multiscale cancer modeling. Such an approach is expected to play an important role in the refinement and the advancement of mechanistic modeling of ALL in the context of the emergent and promising scientific domains of In Silico Oncology and more generally In Silico Medicine.
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Affiliation(s)
- Eleftherios Ouzounoglou
- In Silico Oncology and In Silico Medicine Group, Laboratory of Microwaves and Fiber Optics, Institute of Communication and Computer Systems, School of Electrical and Computer Engineering, National Technical University of Athens, 9 Iroon Polytechniou, Zografou, 15780, Athens, Greece.
| | - Dimitra Dionysiou
- In Silico Oncology and In Silico Medicine Group, Laboratory of Microwaves and Fiber Optics, Institute of Communication and Computer Systems, School of Electrical and Computer Engineering, National Technical University of Athens, 9 Iroon Polytechniou, Zografou, 15780, Athens, Greece.
| | - Georgios S Stamatakos
- In Silico Oncology and In Silico Medicine Group, Laboratory of Microwaves and Fiber Optics, Institute of Communication and Computer Systems, School of Electrical and Computer Engineering, National Technical University of Athens, 9 Iroon Polytechniou, Zografou, 15780, Athens, Greece.
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227
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Greenshields AL, Shepherd TG, Hoskin DW. Contribution of reactive oxygen species to ovarian cancer cell growth arrest and killing by the anti-malarial drug artesunate. Mol Carcinog 2016; 56:75-93. [PMID: 26878598 DOI: 10.1002/mc.22474] [Citation(s) in RCA: 125] [Impact Index Per Article: 15.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/06/2015] [Revised: 01/07/2016] [Accepted: 01/28/2016] [Indexed: 12/14/2022]
Abstract
Ovarian cancer is a leading cause of cancer-related death in women and the most lethal gynecological malignancy in the developed world. The morbidity and mortality of ovarian cancer underscore the need for novel treatment options. Artesunate (ART) is a well-tolerated anti-malarial drug that also has anti-cancer activity. In this study, we show that ART inhibited the in vitro growth of a panel of ovarian cancer cell lines, as well as the growth of ovarian cancer cells isolated from patients. Moreover, ART decreased tumor growth in vivo in a mouse model of ovarian cancer. ART-treated ovarian cancer cells showed a strong induction of reactive oxygen species (ROS) and reduced proliferation. ROS-dependent cell cycle arrest occurred in the G2/M phase whereas ROS-independent cell cycle arrest occurred in the G1 phase, depending on the concentration of ART to which ovarian cancer cells were exposed. The anti-proliferative effect of ART was associated with altered expression of several key cell cycle regulatory proteins, including cyclin D3, E2F-1, and p21, as well as inhibition of mechanistic target of rapamycin signaling. Exposure of ovarian cancer cells to higher concentrations of ART resulted in ROS-dependent DNA damage and cell death. Pretreatment of ovarian cancer cells with a pan-caspase inhibitor or ferroptosis inhibitor decreased but did not completely eliminate ART-mediated cytotoxicity, suggesting the involvement of both caspase-dependent and caspase-independent pathways of killing. These data show that ART has potent anti-proliferative and cytotoxic effects on ovarian cancer cells, and may therefore be useful in the treatment of ovarian cancer. © 2016 Wiley Periodicals, Inc.
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Affiliation(s)
| | - Trevor G Shepherd
- Department of Obstetrics and Gynecology, University of Western Ontario, London, Ontario, Canada.,Department of Oncology, University of Western Ontario, London, Ontario, Canada.,Department of Anatomy and Cell Biology, University of Western Ontario, London, Ontario, Canada
| | - David W Hoskin
- Department of Pathology, Dalhousie University, Halifax, Nova Scotia, Canada.,Department of Microbiology and Immunology, Dalhousie University, Halifax, Nova Scotia, Canada.,Department of Surgery, Dalhousie University, Halifax, Nova Scotia, Canada
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228
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Brookes S, Gagrica S, Sanij E, Rowe J, Gregory FJ, Hara E, Peters G. Evidence for a CDK4-dependent checkpoint in a conditional model of cellular senescence. Cell Cycle 2016; 14:1164-73. [PMID: 25695870 PMCID: PMC4613988 DOI: 10.1080/15384101.2015.1010866] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/02/2022] Open
Abstract
Cellular senescence, the stable cell cycle arrest elicited by various forms of stress, is an important facet of tumor suppression. Although much is known about the key players in the implementation of senescence, including the pRb and p53 axes and the cyclin dependent kinase inhibitors p16INK4a and p21CIP1, many details remain unresolved. In studying conditional senescence in human fibroblasts that express a temperature sensitive SV40 large T-antigen (T-Ag), we uncovered an unexpected role for CDK4. At the permissive temperature, where pRb and p53 are functionally compromised by T-Ag, cyclin D-CDK4 complexes are disrupted by the high p16INK4a levels and reduced expression of p21CIP1. In cells arrested at the non-permissive temperature, p21CIP1 promotes reassembly of cyclin D-CDK4 yet pRb is in a hypo-phosphorylated state, consistent with cell cycle arrest. In exploring whether the reassembled cyclin D-CDK4-p21 complexes are functional, we found that shRNA-mediated knockdown or chemical inhibition of CDK4 prevented the increase in cell size associated with the senescent phenotype by allowing the cells to arrest in G1 rather than G2/M. The data point to a role for CDK4 kinase activity in a G2 checkpoint that contributes to senescence.
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Key Words
- BrdU, bromodeoxyuridine
- CDK, cyclin dependent kinase
- CDK4
- FACS, fluorescence actvated cell sorting
- HFs, human fibroblasts
- PI, propidium iodide
- SA-βgal, senescence-associated β-galactosidase activity
- SV40 T-antigen
- SV40, simian virus 40
- TERT, telomerase reverse transcriptase
- human fibroblasts
- p16INK4a
- p21CIP1
- p53
- pRb, retinoblastoma protein
- retinoblastoma protein
- senescence
- shRNA, short-hairpin RNA
- ts, temperature sensitive
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Affiliation(s)
- Sharon Brookes
- a Cancer Research-UK London Research Institute ; London , UK
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229
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E2F1: a promising regulator in ovarian carcinoma. Tumour Biol 2016; 37:2823-31. [PMID: 26749284 DOI: 10.1007/s13277-015-4770-7] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/20/2015] [Accepted: 12/29/2015] [Indexed: 10/22/2022] Open
Abstract
E2F is a family of transcription factors that recognized to regulate the expression of genes essential for a wide range of cellular functions, including cell cycle progression, DNA repair, DNA replication, differentiation, proliferation, and apoptosis. E2F1, the most classic member of the E2F family, exhibits a complex role in tumor development regulation. In recent years, a growing body of data suggested an intimate relationship between E2F1 and ovarian carcinoma. And E2F1 was well identified to play dual functions and serve as a useful prognostic indicator in ovarian carcinoma. However, the mechanism underlying E2F1 associated with ovarian carcinoma remains elusive. It is necessary to clarify the fundamental role of E2F1 in ovarian carcinoma. In this review, we tried to sum up the knowledge of E2F1, including its structure and related mechanism. We also attempt to absorb the research achievements and collect the mechanism of E2F1 in ovarian carcinoma.
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230
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Risal S, Adhikari D, Liu K. Animal Models for Studying the In Vivo Functions of Cell Cycle CDKs. Methods Mol Biol 2016; 1336:155-66. [PMID: 26231715 DOI: 10.1007/978-1-4939-2926-9_13] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
Multiple Cdks (Cdk4, Cdk6, and Cdk2) and a mitotic Cdk (Cdk1) are involved in cell cycle progression in mammals. Cyclins, Cdk inhibitors, and phosphorylations (both activating and inhibitory) at different cellular levels tightly modulate the activities of these kinases. Based on the results of biochemical studies, it was long believed that different Cdks functioned at specific stages during cell cycle progression. However, deletion of all three interphase Cdks in mice affected cell cycle entry and progression only in certain specialized cells such as hematopoietic cells, beta cells of the pancreas, pituitary lactotrophs, and cardiomyocytes. These genetic experiments challenged the prevailing biochemical model and established that Cdks function in a cell-specific, but not a stage-specific, manner during cell cycle entry and the progression of mitosis. Recent in vivo studies have further established that Cdk1 is the only Cdk that is both essential and sufficient for driving the resumption of meiosis during mouse oocyte maturation. These genetic studies suggest a minimal-essential cell cycle model in which Cdk1 is the central regulator of cell cycle progression. Cdk1 can compensate for the loss of the interphase Cdks by forming active complexes with A-, B-, E-, and D-type Cyclins in a stepwise manner. Thus, Cdk1 plays an essential role in both mitosis and meiosis in mammals, whereas interphase Cdks are dispensable.
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Affiliation(s)
- Sanjiv Risal
- Department of Chemistry and Molecular Biology, University of Gothenburg, 462, 405 30, Gothenburg, Sweden,
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231
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Peek GW, Tollefsbol TO. Combinatorial PX-866 and Raloxifene Decrease Rb Phosphorylation, Cyclin E2 Transcription, and Proliferation of MCF-7 Breast Cancer Cells. J Cell Biochem 2015; 117:1688-96. [PMID: 26660119 DOI: 10.1002/jcb.25462] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/24/2015] [Accepted: 12/10/2015] [Indexed: 01/03/2023]
Abstract
As a potential means to reduce proliferation of breast cancer cells, a multiple-pathway approach with no effect on control cells was explored. The human interactome being constructed by the Center for Cancer Systems Biology will prove indispensable to understanding composite effects of multiple pathways, but its discovered protein-protein interactions require characterization. Accordingly, we explored the effects of regulators of one protein on downstream targets of the other protein. MCF-7 estrogen receptor-positive (ER+) breast cancer cells were treated with raloxifene to upregulate the TGF-β pathway and PX-866 to down-regulate the PI3K/Akt pathway. This resulted in highly significant downstream reduction of cell cycle proliferation in breast cancer cells with no significant proliferation reduction following similar treatment of noncancerous MCF10A breast epithelial cells. Reduced phosphorylation of p107 and substantial reduction of Rb phosphorylation were observed in response. The effects of reduced Rb and p107 phosphorylation were reflected in significant decline in E2F-1 transcriptional activity, which is dependent on pocket protein phosphorylation status. The reduced proliferation was related to decreased expression of cyclins, including E2F-1-regulated Cyclin E2, which was also in response to raloxifene and PX-866. All combinations of raloxifene and PX-866 produced significant or highly significant results for reduced MCF-7 cell proliferation, reduced Cyclin E2 transcription, and reduced Rb phosphorylation. These studies demonstrated that uncontrolled proliferation of ER+ breast cancer cells can be significantly reduced by combinational targeting of two relevant pathways. J. Cell. Biochem. 117: 1688-1696, 2016. © 2015 Wiley Periodicals, Inc.
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Affiliation(s)
- Gregory W Peek
- Department of Biology, University of Alabama, Birmingham, Alabama
| | - Trygve O Tollefsbol
- Department of Biology, University of Alabama, Birmingham, Alabama.,Comprehensive Cancer Center, University of Alabama, Birmingham, Alabama.,Comprehensive Center for Healthy Aging, University of Alabama, Birmingham, Alabama.,Comprehensive Diabetes Center, University of Alabama, Birmingham, Alabama.,Nutrition Obesity Research Center, University of Alabama, Birmingham, Alabama
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232
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Chae M, Jung JY, Bae IH, Kim HJ, Lee TR, Shin DW. Lipin-1 expression is critical for keratinocyte differentiation. J Lipid Res 2015; 57:563-73. [PMID: 26658689 DOI: 10.1194/jlr.m062588] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/08/2015] [Indexed: 12/19/2022] Open
Abstract
Lipin-1 is an Mg(2+)-dependent phosphatidate phosphatase that facilitates the dephosphorylation of phosphatidic acid to generate diacylglycerol. Little is known about the expression and function of lipin-1 in normal human epidermal keratinocytes (NHEKs). Here, we demonstrate that lipin-1 is present in basal and spinous layers of the normal human epidermis, and lipin-1 expression is gradually downregulated during NHEK differentiation. Interestingly, lipin-1 knockdown (KD) inhibited keratinocyte differentiation and caused G1 arrest by upregulating p21 expression. Cell cycle arrest by p21 is required for commitment of keratinocytes to differentiation, but must be downregulated for the progress of keratinocyte differentiation. Therefore, reduced keratinocyte differentiation results from sustained upregulation of p21 by lipin-1 KD. Lipin-1 KD also decreased the phosphorylation/activation of protein kinase C (PKC)α, whereas lipin-1 overexpression increased PKCα phosphorylation. Treatment with PKCα inhibitors, like lipin-1 KD, stimulated p21 expression, while lipin-1 overexpression reduced p21 expression, implicating PKCα in lipin-1-induced regulation of p21 expression. Taken together, these results suggest that lipin-1-mediated downregulation of p21 is critical for the progress of keratinocyte differentiation after the initial commitment of keratinocytes to differentiation induced by p21, and that PKCα is involved in p21 expression regulation by lipin-1.
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Affiliation(s)
- Minjung Chae
- Bioscience Research Institute, Amorepacific Corporation R&D Center, Yongin-si, Gyeonggi-do, Republic of Korea
| | - Ji-Yong Jung
- Bioscience Research Institute, Amorepacific Corporation R&D Center, Yongin-si, Gyeonggi-do, Republic of Korea
| | - Il-Hong Bae
- Bioscience Research Institute, Amorepacific Corporation R&D Center, Yongin-si, Gyeonggi-do, Republic of Korea
| | - Hyoung-June Kim
- Bioscience Research Institute, Amorepacific Corporation R&D Center, Yongin-si, Gyeonggi-do, Republic of Korea
| | - Tae Ryong Lee
- Bioscience Research Institute, Amorepacific Corporation R&D Center, Yongin-si, Gyeonggi-do, Republic of Korea
| | - Dong Wook Shin
- Bioscience Research Institute, Amorepacific Corporation R&D Center, Yongin-si, Gyeonggi-do, Republic of Korea
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233
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Mao H, Lockyer P, Townley-Tilson WHD, Xie L, Pi X. LRP1 Regulates Retinal Angiogenesis by Inhibiting PARP-1 Activity and Endothelial Cell Proliferation. Arterioscler Thromb Vasc Biol 2015; 36:350-60. [PMID: 26634655 DOI: 10.1161/atvbaha.115.306713] [Citation(s) in RCA: 31] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/20/2015] [Accepted: 11/15/2015] [Indexed: 02/07/2023]
Abstract
OBJECTIVE We recently demonstrated that low-density lipoprotein receptor-related protein 1 (LRP1) is required for cardiovascular development in zebrafish. However, what role LRP1 plays in angiogenesis remains to be determined. To better understand the role of LRP1 in endothelial cell function, we investigated how LRP1 regulates mouse retinal angiogenesis. APPROACH AND RESULTS Depletion of LRP1 in endothelial cells results in increased retinal neovascularization in a mouse model of oxygen-induced retinopathy. Specifically, retinas in mice lacking endothelial LRP1 have more branching points and angiogenic sprouts at the leading edge of the newly formed vasculature. Increased endothelial proliferation as detected by Ki67 staining was observed in LRP1-deleted retinal endothelium in response to hypoxia. Using an array of biochemical and cell biology approaches, we demonstrate that poly(ADP-ribose) polymerase-1 (PARP-1) directly interacts with LRP1 in human retinal microvascular endothelial cells. This interaction between LRP1 and PARP-1 decreases under hypoxic condition. Moreover, LRP1 knockdown results in increased PARP-1 activity and subsequent phosphorylation of both retinoblastoma protein and cyclin-dependent kinase 2, which function to promote cell cycle progression and angiogenesis. CONCLUSIONS Together, these data reveal a pivotal role for LRP1 in endothelial cell proliferation and retinal neovascularization induced by hypoxia. In addition, we demonstrate for the first time the interaction between LRP1 and PARP-1 and the LRP1-dependent regulation of PARP-1-signaling pathways. These data bring forth the possibility of novel therapeutic approaches for pathological angiogenesis.
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Affiliation(s)
- Hua Mao
- From the Department of Medicine, Cardiovascular Research Institute, Baylor College of Medicine, Houston, TX (H.M., W.H.D.T.-T., L.X., X.P.); and Department of Pathology and Laboratory Medicine, University of North Carolina at Chapel Hill (P.L.)
| | - Pamela Lockyer
- From the Department of Medicine, Cardiovascular Research Institute, Baylor College of Medicine, Houston, TX (H.M., W.H.D.T.-T., L.X., X.P.); and Department of Pathology and Laboratory Medicine, University of North Carolina at Chapel Hill (P.L.)
| | - W H Davin Townley-Tilson
- From the Department of Medicine, Cardiovascular Research Institute, Baylor College of Medicine, Houston, TX (H.M., W.H.D.T.-T., L.X., X.P.); and Department of Pathology and Laboratory Medicine, University of North Carolina at Chapel Hill (P.L.)
| | - Liang Xie
- From the Department of Medicine, Cardiovascular Research Institute, Baylor College of Medicine, Houston, TX (H.M., W.H.D.T.-T., L.X., X.P.); and Department of Pathology and Laboratory Medicine, University of North Carolina at Chapel Hill (P.L.)
| | - Xinchun Pi
- From the Department of Medicine, Cardiovascular Research Institute, Baylor College of Medicine, Houston, TX (H.M., W.H.D.T.-T., L.X., X.P.); and Department of Pathology and Laboratory Medicine, University of North Carolina at Chapel Hill (P.L.).
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234
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Abstract
Senescence was classically defined as an irreversible cell cycle arrest in G1 phase (G1 exit) triggered by eroded telomeres in aged primary cells. The molecular basis of this G1 arrest is thought to be due to a DNA damage response, resulting in accumulation of the cyclin dependent kinase (Cdk) inhibitors p21 and p16 that block the inactivating phosphorylation of the retinoblastoma tumor suppressor pRb, thereby preventing DNA replication. More than a decade ago, several studies showed that p21 also mediates permanent DNA damage-induced cell cycle arrest in G2 (G2 exit) by inhibiting mitotic Cdk complexes and pRb phosphorylation. The idea that the senescence program can also be launched after G2 arrest has gained support from several recent publications, including evidence for its existence in vivo.
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Affiliation(s)
- Véronique Gire
- a Centre de Recherche en Biologie Macromoléculaire (CRBM) ; CNRS UMR5237; Montpellier , France
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235
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Schröder LBW, McDonald KL. CDK4/6 Inhibitor PD0332991 in Glioblastoma Treatment: Does It Have a Future? Front Oncol 2015; 5:259. [PMID: 26649278 PMCID: PMC4663246 DOI: 10.3389/fonc.2015.00259] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/14/2015] [Accepted: 11/06/2015] [Indexed: 11/13/2022] Open
Abstract
Glioblastoma is aggressive, highly infiltrating, and the most frequent malignant form of brain cancer. With a median survival time of only 14.6 months, when treated with the standard of care, it is essential to find new therapeutic options. A specific CDK4/6 inhibitor, PD0332991, obtained accelerated approval from the Food and Drug Administration for the treatment of patients with advanced estrogen receptor-positive and HER2-negative breast cancer. Common alterations in the cyclin D1-cyclin-dependent kinase 4/6-retinoblastoma 1 pathway in glioblastoma make PD0332991 also an interesting drug for the treatment of glioblastoma. Promising results in in vitro studies, where patient derived glioblastoma cell lines showed sensitivity to PD0332991, gave motive to start in vivo studies. Outcomes of these studies have been contrasting in terms of PD0332991 efficacy within the brain: more research is necessary to conclude whether CDK4/6 inhibitor can be beneficial in the treatment of glioblastoma.
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Affiliation(s)
| | - Kerrie L McDonald
- Cure Brain Cancer Foundation Biomarkers and Translational Research Laboratory, Prince of Wales Clinical School, University of New South Wales , Kensington, NSW , Australia
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236
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Niu Z, Wang M, Zhou L, Yao L, Liao Q, Zhao Y. Elevated GRP78 expression is associated with poor prognosis in patients with pancreatic cancer. Sci Rep 2015; 5:16067. [PMID: 26530532 PMCID: PMC4632002 DOI: 10.1038/srep16067] [Citation(s) in RCA: 73] [Impact Index Per Article: 8.1] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/10/2014] [Accepted: 10/06/2015] [Indexed: 01/05/2023] Open
Abstract
Glucose-regulated protein 78 (GRP78) is a member of the heat-shock protein 70 family. We evaluated the expression of GRP78 using tissue microarray-based immunohistochemistry in tumor tissues and adjacent nontumor tissues from 180 pancreatic ductal adenocarcinoma (PDAC) patients. The associations between the expression levels of GRP78, clinicopathological factors, and overall survival were evaluated. The results showed that the expression of GRP78 was significantly higher in PDAC cells than in normal pancreatic duct cells within adjacent nontumor tissues (p < 0.05). The increased expression of GRP78 in the tumor tissues was significantly correlated with a higher T-stage (p < 0.05) and a shorter overall survival (OS, p < 0.05). In an in vitro study, the regulation of GRP78 in the PDAC cell lines affected the proliferation, migration, and invasion of PDAC cells through the regulation of CyclinD1, cyclin-dependent kinase (CDK) 4, CDK6, phospho-signal transducer, activator of transcription 3 (p-STAT3), janus kinase 2 (JAK2), ras homolog gene family member A (RhoA), Rho-associated kinase 1 (ROCK1), and sterile alpha motif domain containing protein 4 (Smad4). The present data suggest that GRP78 plays a crucial role in the proliferation, migration, and invasion of pancreatic cancer cells and may be a suitable prognostic marker in PDAC.
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Affiliation(s)
- Zheyu Niu
- Department of General Surgery, Peking Union Medical College Hospital, Chinese Academy of Medical Science &Peking Union Medical College, Beijing 100730, China
| | - Mengyi Wang
- Department of General Surgery, Peking Union Medical College Hospital, Chinese Academy of Medical Science &Peking Union Medical College, Beijing 100730, China
| | - Li Zhou
- Department of General Surgery, Peking Union Medical College Hospital, Chinese Academy of Medical Science &Peking Union Medical College, Beijing 100730, China
| | - Lutian Yao
- Department of General Surgery, Peking Union Medical College Hospital, Chinese Academy of Medical Science &Peking Union Medical College, Beijing 100730, China
| | - Quan Liao
- Department of General Surgery, Peking Union Medical College Hospital, Chinese Academy of Medical Science &Peking Union Medical College, Beijing 100730, China
| | - Yupei Zhao
- Department of General Surgery, Peking Union Medical College Hospital, Chinese Academy of Medical Science &Peking Union Medical College, Beijing 100730, China
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237
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CDK6-a review of the past and a glimpse into the future: from cell-cycle control to transcriptional regulation. Oncogene 2015; 35:3083-91. [PMID: 26500059 DOI: 10.1038/onc.2015.407] [Citation(s) in RCA: 115] [Impact Index Per Article: 12.8] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/27/2015] [Revised: 09/22/2015] [Accepted: 09/22/2015] [Indexed: 12/19/2022]
Abstract
The G1 cell-cycle kinase CDK6 has long been thought of as a redundant homolog of CDK4. Although the two kinases have very similar roles in cell-cycle progression, it has recently become apparent that they differ in tissue-specific functions and contribute differently to tumor development. CDK6 is directly involved in transcription in tumor cells and in hematopoietic stem cells. These functions point to a role of CDK6 in tissue homeostasis and differentiation that is partially independent of CDK6's kinase activity and is not shared with CDK4. We review the literature on the contribution of CDK6 to transcription in an attempt to link the new findings on CDK6's transcriptional activity to cell-cycle progression. Finally, we note that anticancer therapies based on the inhibition of CDK6 kinase activity fail to take into account its kinase-independent role in tumor development.
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238
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Feng DD, Cai W, Chen X. The associations between Parkinson's disease and cancer: the plot thickens. Transl Neurodegener 2015; 4:20. [PMID: 26504519 PMCID: PMC4620601 DOI: 10.1186/s40035-015-0043-z] [Citation(s) in RCA: 72] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/12/2015] [Accepted: 10/07/2015] [Indexed: 01/10/2023] Open
Abstract
Epidemiological studies support a general inverse association between the risk of cancer development and Parkinson’s disease (PD). In recent years however, increasing amount of eclectic evidence points to a positive association between PD and cancers through different temporal analyses and ethnic groups. This positive association has been supported by several common genetic mutations in SNCA, PARK2, PARK8, ATM, p53, PTEN, and MC1R resulting in cellular changes such as mitochondrial dysfunction, aberrant protein aggregation, and cell cycle dysregulation. Here, we review the epidemiological and biological advances of the past decade in the association between PD and cancers to offer insight on the recent and sometimes contradictory findings.
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Affiliation(s)
- Danielle D Feng
- MassGeneral Institute for Neurodegenerative Disease, Department of Neurology, Massachusetts General Hospital, Harvard Medical School, Boston, MA USA.,Department of Epidemiology, Harvard T.H. Chan School of Public Health, Boston, MA USA
| | - Waijiao Cai
- MassGeneral Institute for Neurodegenerative Disease, Department of Neurology, Massachusetts General Hospital, Harvard Medical School, Boston, MA USA.,Key Laboratory of Cellular and Molecular Biology, Huashan Hospital, Fudan University, Shanghai, 200040 China
| | - Xiqun Chen
- MassGeneral Institute for Neurodegenerative Disease, Department of Neurology, Massachusetts General Hospital, Harvard Medical School, Boston, MA USA
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239
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Tang J, Chen Y, Cui R, Li D, Xiao L, Lin P, Du Y, Sun H, Yu X, Zheng X. Upregulation of fractalkine contributes to the proliferative response of prostate cancer cells to hypoxia via promoting the G1/S phase transition. Mol Med Rep 2015; 12:7907-14. [PMID: 26496926 PMCID: PMC4758273 DOI: 10.3892/mmr.2015.4438] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/03/2014] [Accepted: 08/25/2015] [Indexed: 12/31/2022] Open
Abstract
Hypoxia is a common phenomenon in prostate cancer, which leads to cell proliferation and tumor growth. Fractalkine (FKN) is a membrane-bound chemokine, which is implicated in the progression of human prostate cancer and skeletal metastasis. However, the association between FKN and hypoxia-induced prostate cancer cell proliferation remains to be elucidated. The present study demonstrated that hypoxia induced the expression and secretion of FKN in the DU145 prostate cancer cell line. Furthermore, inhibiting the activity of FKN with the anti-FKN FKN-specific antibody markedly inhibited hypoxia-induced DU145 cell proliferation. Under normoxic conditions, DU145 cell proliferation markedly increased following exogenous administration of human recombinant FKN protein, and the increase was significantly alleviated by anti-FKN, indicating the importance of FKN in DU145 cell proliferation. In addition, subsequent determination of cell cycle distribution and expression levels of two core cell cycle regulators, cyclin E and cyclin-dependent kinase (CDK)2, suggested that FKN promoted the G1/S phase transition by upregulating the expression levels of cyclin E and CDK2. The results of the present study demonstrated that hypoxia led to the upregulation of the secretion and expression of FKN, which enhanced cell proliferation by promoting cell cycle progression in the prostate cancer cells. These findings provide evidence of a novel function for FKN, and suggest that FKN may serve as a potential target for treating androgen-independent prostate cancer.
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Affiliation(s)
- Jiebing Tang
- Department of Biochemistry and Molecular Biology, Harbin Medical University, Harbin, Heilongjiang 150081, P.R. China
| | - Yuanyuan Chen
- Department of Biochemistry and Molecular Biology, Harbin Medical University, Harbin, Heilongjiang 150081, P.R. China
| | - Rongjun Cui
- Department of Biochemistry and Molecular Biology, Mudanjiang Medical University, Mudanjiang, Heilongjiang 157011, P.R. China
| | - Dong Li
- Department of Biochemistry and Molecular Biology, Harbin Medical University, Harbin, Heilongjiang 150081, P.R. China
| | - Lijie Xiao
- Department of Biochemistry and Molecular Biology, Harbin Medical University, Harbin, Heilongjiang 150081, P.R. China
| | - Ping Lin
- Department of Biochemistry and Molecular Biology, Harbin Medical University, Harbin, Heilongjiang 150081, P.R. China
| | - Yandan Du
- Department of Clinical Laboratory, The Second Clinical Medical School of Inner Mongolia University for the Nationalities, Inner Mongolia Forestry General Hospital, Hulunbuir, Inner Mongolia 022150, P.R. China
| | - Hui Sun
- Department of Biochemistry and Molecular Biology, Harbin Medical University, Harbin, Heilongjiang 150081, P.R. China
| | - Xiaoguang Yu
- Department of Biochemistry and Molecular Biology, Harbin Medical University, Harbin, Heilongjiang 150081, P.R. China
| | - Xiulan Zheng
- Department of Ultrasonography, The Affiliated Tumor Hospital of Harbin Medical University, Harbin, Heilongjiang 150081, P.R. China
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240
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Farioli-Vecchioli S, Tirone F. Control of the Cell Cycle in Adult Neurogenesis and its Relation with Physical Exercise. Brain Plast 2015; 1:41-54. [PMID: 29765834 PMCID: PMC5928538 DOI: 10.3233/bpl-150013] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022] Open
Abstract
In the adult brain the neurogenesis is mainly restricted to two neurogenic regions: newly generated neurons arise at the subventricular zone (SVZ) of the lateral ventricle and at the subgranular zone of the hippocampal subregion named the dentate gyrus. The hippocampus is involved in learning and memory paradigms and the generation of new hippocampal neurons has been hypothesized to be a pivotal form of plasticity involved in the process. Moreover the dysregulation of hippocampal adult neurogenesis has been recognized and could anticipate several varieties of brain disease such as Alzheimer disease, epilepsy and depression. Over the last few decades numerous intrinsic, epigenetic and environmental factors have been revealed to deeply influence the process of adult neurogenesis, although the underlying mechanisms remain largely unknown. Growing evidence indicates that physical exercise represents one of the main extrinsic factor able to profoundly increase hippocampal adult neurogenesis, by altering neurochemistry and function of newly generated neurons. The present review surveys how neurogenesis can be modulated by cell cycle kinetics and highlights the putative role of the cell cycle length as a key component of the beneficial effect of running for hippocampal adult neurogenesis, both in physiological conditions and in the presence of defective neurogenesis.
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Affiliation(s)
- Stefano Farioli-Vecchioli
- Institute of Cell Biology and Neurobiology, National Research Council, Fondazione S.Lucia, Rome, Italy
| | - Felice Tirone
- Institute of Cell Biology and Neurobiology, National Research Council, Fondazione S.Lucia, Rome, Italy
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241
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Engström W, Darbre P, Eriksson S, Gulliver L, Hultman T, Karamouzis MV, Klaunig JE, Mehta R, Moorwood K, Sanderson T, Sone H, Vadgama P, Wagemaker G, Ward A, Singh N, Al-Mulla F, Al-Temaimi R, Amedei A, Colacci AM, Vaccari M, Mondello C, Scovassi AI, Raju J, Hamid RA, Memeo L, Forte S, Roy R, Woodrick J, Salem HK, Ryan EP, Brown DG, Bisson WH. The potential for chemical mixtures from the environment to enable the cancer hallmark of sustained proliferative signalling. Carcinogenesis 2015; 36 Suppl 1:S38-60. [PMID: 26106143 DOI: 10.1093/carcin/bgv030] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/20/2023] Open
Abstract
The aim of this work is to review current knowledge relating the established cancer hallmark, sustained cell proliferation to the existence of chemicals present as low dose mixtures in the environment. Normal cell proliferation is under tight control, i.e. cells respond to a signal to proliferate, and although most cells continue to proliferate into adult life, the multiplication ceases once the stimulatory signal disappears or if the cells are exposed to growth inhibitory signals. Under such circumstances, normal cells remain quiescent until they are stimulated to resume further proliferation. In contrast, tumour cells are unable to halt proliferation, either when subjected to growth inhibitory signals or in the absence of growth stimulatory signals. Environmental chemicals with carcinogenic potential may cause sustained cell proliferation by interfering with some cell proliferation control mechanisms committing cells to an indefinite proliferative span.
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Affiliation(s)
- Wilhelm Engström
- Department of Biosciences and Veterinary Public Health, Faculty of Veterinary Medicine, Swedish University of Agricultural Sciences, PO Box 7028, 75007 Uppsala, Sweden,
| | - Philippa Darbre
- School of Biological Sciences, University of Reading, Whiteknights, Reading RG6 6UB, UK
| | - Staffan Eriksson
- Department of Biochemistry, Faculty of Veterinary Medicine, Swedish University of Agricultural Sciences, Box 575, 75123 Uppsala, Sweden
| | - Linda Gulliver
- Faculty of Medicine, University of Otago, PO Box 913, Dunedin 9050, New Zealand
| | - Tove Hultman
- Department of Biosciences and Veterinary Public Health, Faculty of Veterinary Medicine, Swedish University of Agricultural Sciences, PO Box 7028, 75007 Uppsala, Sweden, School of Biological Sciences, University of Reading, Whiteknights, Reading RG6 6UB, UK
| | - Michalis V Karamouzis
- Department of Biological Chemistry Medical School, Institute of Molecular Medicine and Biomedical Research, University of Athens, Marasli 3, Kolonaki, Athens 10676, Greece
| | - James E Klaunig
- Department of Environmental Health, School of Public Health, Indiana University Bloomington , 1025 E. 7th Street, Suite 111, Bloomington, IN 47405, USA
| | - Rekha Mehta
- Regulatory Toxicology Research Division, Bureau of Chemical Safety, Food Directorate, HPFB, Health Canada, 251 Sir F.G. Banting Driveway, AL # 2202C, Tunney's Pasture, Ottawa, Ontario K1A 0K9, Canada
| | - Kim Moorwood
- Department of Biochemistry and Biology, University of Bath , Claverton Down, Bath BA2 7AY, UK
| | - Thomas Sanderson
- INRS-Institut Armand-Frappier, 531 boulevard des Prairies, Laval, Quebec H7V 1B7, Canada
| | - Hideko Sone
- Environmental Exposure Research Section, Center for Environmental Risk Research, National Institute for Environmental Studies, 16-2 Onogawa, Tsukuba, Ibraki 3058506, Japan
| | - Pankaj Vadgama
- IRC in Biomedical Materials, School of Engineering & Materials Science, Queen Mary University of London, Mile End Road, London E1 4NS, UK
| | - Gerard Wagemaker
- Center for Stem Cell Research and Development, Hacettepe University, Ankara 06100, Turkey
| | - Andrew Ward
- Department of Biochemistry and Biology, University of Bath , Claverton Down, Bath BA2 7AY, UK
| | - Neetu Singh
- Centre for Advanced Research, King George's Medical University, Chowk, Lucknow, Uttar Pradesh 226003, India
| | - Fahd Al-Mulla
- Department of Pathology, Kuwait University, Safat 13110, Kuwait
| | | | - Amedeo Amedei
- Department of Experimental and Clinical Medicine, University of Firenze, Firenze 50134, Italy
| | - Anna Maria Colacci
- Center for Environmental Carcinogenesis and Risk Assessment, Environmental Protection and Health Prevention Agency, Bologna 40126, Italy
| | - Monica Vaccari
- Center for Environmental Carcinogenesis and Risk Assessment, Environmental Protection and Health Prevention Agency, Bologna 40126, Italy
| | - Chiara Mondello
- Institute of Molecular Genetics, National Research Council, Pavia 27100, Italy
| | - A Ivana Scovassi
- Institute of Molecular Genetics, National Research Council, Pavia 27100, Italy
| | - Jayadev Raju
- Regulatoty Toxicology Research Division, Bureau of Chemical Safety, Food Directorate, HPFB, Health Canada, Ottawa, Ontario K1A0K9, Canada
| | - Roslida A Hamid
- Department of Biomedical Science, Faculty of Medicine and Health Sciences, Universiti Putra Malaysia, 43400 Serdang, Selangor, Malaysia
| | - Lorenzo Memeo
- Mediterranean Institute of Oncology, Viagrande 95029, Italy
| | - Stefano Forte
- Mediterranean Institute of Oncology, Viagrande 95029, Italy
| | - Rabindra Roy
- Molecular Oncology Program, Lombardi Comprehensive Cancer Center, Georgetown University Medical Center, Washington, DC 20057, USA
| | - Jordan Woodrick
- Molecular Oncology Program, Lombardi Comprehensive Cancer Center, Georgetown University Medical Center, Washington, DC 20057, USA
| | - Hosni K Salem
- Urology Dept. kasr Al-Ainy School of Medicine, Cairo University, El Manial, Cairo 12515, Egypt
| | - Elizabeth P Ryan
- Department of Environmental and Radiological Sciences, Colorado State University//Colorado School of Public Health, Fort Collins CO 80523-1680, USA and
| | - Dustin G Brown
- Department of Environmental and Radiological Sciences, Colorado State University//Colorado School of Public Health, Fort Collins CO 80523-1680, USA and
| | - William H Bisson
- Environmental and Molecular Toxicology, Environmental Health Sciences Center, Oregon State University, Corvallis, OR 97331, USA
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242
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Tsumagari K, Abd Elmageed ZY, Sholl AB, Friedlander P, Abdraboh M, Xing M, Boulares AH, Kandil E. Simultaneous suppression of the MAP kinase and NF-κB pathways provides a robust therapeutic potential for thyroid cancer. Cancer Lett 2015. [PMID: 26208433 DOI: 10.1016/j.canlet.2015.07.011] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/08/2023]
Abstract
The MAP kinase and NF-κB signaling pathways play an important role in thyroid cancer tumorigenesis. We aimed to examine the therapeutic potential of dually targeting the two pathways using AZD6244 and Bortezomib in combination. We evaluated their effects on cell proliferation, cell-cycle progression, apoptosis, cell migration assay, and the activation of the MAPK pathway in vitro and the in vivo using tumor size and immunohistochemical changes of Ki67 and ppRB. We found inhibition of cell growth rate by 10%, 20%, and 56% (p <0.05), migration to 55%, 61%, and 29% (p <0.05), and induction of apoptosis to 10%, 15%, and 38% (p <0.05) with AZD6244, Bortezomib, or combination, respectively. Induction of cell cycle arrest occurred only with drug combination. Dual drug treatment in the xenograft model caused a 94% reduction in tumor size (p <0.05) versus 15% with AZD6244 and 34% with Bortezomib (p < 0.05) and also reduced proliferative marker Ki67, and increased pRb dephosphorylation. Our results demonstrate a robust therapeutic potential of combining AZD6244 and Bortezomib as an effective strategy to overcome drug resistance encountered in monotherapy in the treatment of thyroid cancer, strongly supporting clinical trials to further test this strategy.
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Affiliation(s)
- Koji Tsumagari
- Departments of Surgery, Tulane University School of Medicine, New Orleans, LA 70112, USA; Tulane Cancer Center, Tulane University School of Medicine, New Orleans, LA 70112, USA
| | - Zakaria Y Abd Elmageed
- Departments of Surgery, Tulane University School of Medicine, New Orleans, LA 70112, USA; Tulane Cancer Center, Tulane University School of Medicine, New Orleans, LA 70112, USA
| | - Andrew B Sholl
- Departments of Pathology, Tulane University School of Medicine, New Orleans, LA 70112, USA
| | - Paul Friedlander
- Departments of Otolaryngology, Tulane University School of Medicine, New Orleans, LA 70112, USA
| | - Mohamed Abdraboh
- Departments of Surgery, Tulane University School of Medicine, New Orleans, LA 70112, USA
| | - Mingzhao Xing
- Division of Endocrinology and Metabolism, Department of Medicine, Johns Hopkins University School of Medicine, Baltimore, MD, USA
| | - A Hamid Boulares
- The Stanley Scott Cancer Center, Department of Pharmacology, Louisiana State University Health Science Center, New Orleans, LA 70112, USA
| | - Emad Kandil
- Departments of Surgery, Tulane University School of Medicine, New Orleans, LA 70112, USA; Tulane Cancer Center, Tulane University School of Medicine, New Orleans, LA 70112, USA.
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243
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VanArsdale T, Boshoff C, Arndt KT, Abraham RT. Molecular Pathways: Targeting the Cyclin D-CDK4/6 Axis for Cancer Treatment. Clin Cancer Res 2015; 21:2905-10. [PMID: 25941111 DOI: 10.1158/1078-0432.ccr-14-0816] [Citation(s) in RCA: 278] [Impact Index Per Article: 30.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/03/2014] [Accepted: 04/13/2015] [Indexed: 11/16/2022]
Abstract
Cancer cells bypass normal controls over mitotic cell-cycle progression to achieve a deregulated state of proliferation. The retinoblastoma tumor suppressor protein (pRb) governs a key cell-cycle checkpoint that normally prevents G1-phase cells from entering S-phase in the absence of appropriate mitogenic signals. Cancer cells frequently overcome pRb-dependent growth suppression via constitutive phosphorylation and inactivation of pRb function by cyclin-dependent kinase (CDK) 4 or CDK6 partnered with D-type cyclins. Three selective CDK4/6 inhibitors, palbociclib (Ibrance; Pfizer), ribociclib (Novartis), and abemaciclib (Lilly), are in various stages of development in a variety of pRb-positive tumor types, including breast cancer, melanoma, liposarcoma, and non-small cell lung cancer. The emerging, positive clinical data obtained to date finally validate the two decades-old hypothesis that the cyclin D-CDK4/6 pathway is a rational target for cancer therapy.
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Affiliation(s)
- Todd VanArsdale
- Oncology Research Unit, Pfizer Worldwide Research and Development, San Diego, California
| | | | - Kim T Arndt
- Oncology Research Unit, Pfizer Worldwide Research and Development, Pearl River, New York
| | - Robert T Abraham
- Oncology Research Unit, Pfizer Worldwide Research and Development, San Diego, California.
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244
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Abstract
The complexity of cancer chemotherapy requires pharmacists be familiar with the complicated regimens and highly toxic agents used. This column reviews various issues related to preparation, dispensing, and administration of antineoplastic therapy, and the agents, both commercially available and investigational, used to treat malignant diseases. Questions or suggestions for topics should be addressed to Dominic A. Solimando, Jr, President, Oncology Pharmacy Services, Inc., 4201 Wilson Blvd #110-545, Arlington, VA 22203, e-mail: OncRxSvc@comcast.net; or J. Aubrey Waddell, Professor, University of Tennessee College of Pharmacy; Oncology Pharmacist, Pharmacy Department, Blount Memorial Hospital, 907 E. Lamar Alexander Parkway, Maryville, TN 37804, e-mail: waddfour@charter.net.
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245
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van der Linden MH, Willekes M, van Roon E, Seslija L, Schneider P, Pieters R, Stam RW. MLL fusion-driven activation of CDK6 potentiates proliferation in MLL-rearranged infant ALL. Cell Cycle 2015; 13:834-44. [PMID: 24736461 DOI: 10.4161/cc.27757] [Citation(s) in RCA: 39] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023] Open
Abstract
Acute lymphoblastic leukemia in infants (< 1 year-of-age) is characterized by a high incidence of MLL rearrangements. Recently, direct targets of the MLL fusion protein have been identified. However, functional validation of the identified targets remained unacknowledged. In this study, we identify CDK6 as a direct target of the MLL fusion protein and an important player in the proliferation advantage of MLL-rearranged leukemia. CDK6 mRNA was significantly higher expressed in MLL-rearranged infant ALL patients compared with MLL wild-type ALL patients (P < 0.001). Decrease of MLL-AF4 and MLL-ENL fusion mRNA expression by siRNAs resulted in downregulation of CDK6, affirming a direct relationship between the presence of the MLL fusion and CDK6 expression. Knockdown of CDK6 itself significantly inhibited proliferation in the MLL-AF4-positive cell line SEM, whereas knockdown of the highly homologous gene CDK4 had virtually no effect on the cell cycle. Furthermore, we show in vitro sensitivity of MLL-rearranged leukemia cell lines to the CDK4/6-inhibitor PD0332991, inducing a remarkable G 1 arrest, and downregulation of its downstream targets pRB1 and EZH2. We therefore conclude that CDK6 is indeed a direct target of MLL fusion proteins, playing an important role in the proliferation advantage of MLL-rearranged ALL cells.
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Affiliation(s)
- Marieke H van der Linden
- Department of Pediatric Oncology/Hematology; Erasmus MC - Sophia Children's Hospital; Rotterdam, The Netherlands
| | - Merel Willekes
- Department of Pediatric Oncology/Hematology; Erasmus MC - Sophia Children's Hospital; Rotterdam, The Netherlands
| | - Eddy van Roon
- Department of Pediatric Oncology/Hematology; Erasmus MC - Sophia Children's Hospital; Rotterdam, The Netherlands
| | - Lidija Seslija
- Department of Pediatric Oncology/Hematology; Erasmus MC - Sophia Children's Hospital; Rotterdam, The Netherlands
| | - Pauline Schneider
- Department of Pediatric Oncology/Hematology; Erasmus MC - Sophia Children's Hospital; Rotterdam, The Netherlands
| | - Rob Pieters
- Department of Pediatric Oncology/Hematology; Erasmus MC - Sophia Children's Hospital; Rotterdam, The Netherlands
| | - Ronald W Stam
- Department of Pediatric Oncology/Hematology; Erasmus MC - Sophia Children's Hospital; Rotterdam, The Netherlands
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246
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WANG XIAOBO, PAN JINGXUAN, LI JUAN. Cytokine-induced apoptosis inhibitor 1 inhibits the growth and proliferation of multiple myeloma. Mol Med Rep 2015; 12:2056-62. [DOI: 10.3892/mmr.2015.3656] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/28/2014] [Accepted: 12/09/2014] [Indexed: 11/06/2022] Open
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247
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Abstract
Maintenance of peripheral tolerance is essential for homeostasis of the immune system. While central tolerance mechanisms result in deletion of the majority of self-reactive T cells, T lymphocytes specific for self-antigens also escape this process and circulate in the periphery. To control the development of autoimmunity, multiple mechanisms of peripheral tolerance have evolved, including T cell anergy, deletion, and suppression by regulatory T (Treg) cells. The pathway consisting of the programmed cell death 1 (PD-1) receptor (CD279) and its ligands PD-L1 (B7-H1, CD274) and PD-L2 (B7-DC; CD273) plays a vital role in the induction and maintenance of peripheral tolerance. This pathway also regulates the balance between stimulatory and inhibitory signals needed for effective immunity and maintenance of T cell homeostasis. In contrast to this important beneficial role in maintaining T cell homeostasis, PD-1 mediates potent inhibitory signals that prevent the expansion and function of T effector cells and have detrimental effects on antiviral and antitumor immunity. Despite the compelling studies on the significant functional role of PD-1 in mediating inhibition of activated T cells, little is known about how PD-1 blocks T cell activation. Here, we will provide a brief overview of the signaling events that are regulated by PD-1 triggering, and we will discuss their implications on cell intrinsic and extrinsic mechanisms that determine the fate and function of T effector cells.
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248
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Dai B, Wang W, Liu R, Wang H, Zhang Y. Novel taspine derivative 12k inhibits cell growth and induces apoptosis in lung cell carcinoma. Biomed Pharmacother 2015; 70:227-33. [PMID: 25776505 DOI: 10.1016/j.biopha.2015.01.024] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/10/2015] [Accepted: 01/23/2015] [Indexed: 01/15/2023] Open
Abstract
Taspine is an active compound in anticancer agent development. 12k was synthesized with taspine as lead compound bearing biphenyl scaffold and showed potent anticancer activity. Here, we investigated the effect of taspine derivative 12k on A549 lung cells. We showed that 12k not only decreased significantly A549 cell viability, A549 cell colony formation but also impaired A549 cell migration. Moreover, 12k treatment blocked cell cycle progression by increasing cell number in S phase to 42.80% for 6 μmol/L vs. 28.86% for control while decreasing cell number in G1 phase. Accordingly, this was associated with an increase protein expression of cyclin E and a decrease protein expression of cyclin D1, cyclin B1 and its associated CDK1 (cdc2). Meanwhile, we found that 12k induced A549 cell apoptosis, which was closely associated with the effect of the Bcl-2 family. Increase of Bad, Bak and Bax expression levels, decrease of Bcl-2 and Mcl-1 expression levels were observed. SiRNA knockdown of c-myc in A549 cells significantly attenuated tumor inhibition effects of 12k. In conclusion, our results demonstrate that 12k has an inhibitory effect on growth of A549 cell by inducing cell cycle arrest and apoptosis.
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Affiliation(s)
- Bingling Dai
- School of Pharmacy, Health Science Center, Xi'an Jiaotong University, Xi'an 710061, PR China
| | - Wenjie Wang
- School of Pharmacy, Health Science Center, Xi'an Jiaotong University, Xi'an 710061, PR China
| | - Rui Liu
- School of Pharmacy, Health Science Center, Xi'an Jiaotong University, Xi'an 710061, PR China
| | - Hongying Wang
- School of Pharmacy, Health Science Center, Xi'an Jiaotong University, Xi'an 710061, PR China
| | - Yanmin Zhang
- School of Pharmacy, Health Science Center, Xi'an Jiaotong University, Xi'an 710061, PR China.
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249
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The control operated by the cell cycle machinery on MEF2 stability contributes to the downregulation of CDKN1A and entry into S phase. Mol Cell Biol 2015; 35:1633-47. [PMID: 25733682 DOI: 10.1128/mcb.01461-14] [Citation(s) in RCA: 48] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/04/2014] [Accepted: 02/23/2015] [Indexed: 02/06/2023] Open
Abstract
MEF2s are pleiotropic transcription factors (TFs) which supervise multiple cellular activities. During the cell cycle, MEF2s are activated at the G0/G1 transition to orchestrate the expression of the immediate early genes in response to growth factor stimulation. Here we show that, in human and murine fibroblasts, MEF2 activities are downregulated during late G1. MEF2C and MEF2D interact with the E3 ligase F-box protein SKP2, which mediates their subsequent degradation through the ubiquitin-proteasome system. The cyclin-dependent kinase 4 (CDK4)/cyclin D1 complex phosphorylates MEF2D on serine residues 98 and 110, and phosphorylation of these residues is an important determinant for SKP2 binding. Unscheduled MEF2 transcription during the cell cycle reduces cell proliferation, whereas its containment sustains DNA replication. The CDK inhibitor p21/CDKN1A gene is a MEF2 target gene required to exert this antiproliferative influence. MEF2C and MEF2D bind a region within the first intron of CDKN1A, presenting epigenetic markers of open chromatin. Importantly, H3K27 acetylation within this regulative region depends on the presence of MEF2D. We propose that following the initial engagement in the G0/G1 transition, MEF2C and MEF2D must be polyubiquitylated and degraded during G1 progression to diminish the transcription of the CDKN1A gene, thus favoring entry into S phase.
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250
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MDMX exerts its oncogenic activity via suppression of retinoblastoma protein. Oncogene 2015; 34:5560-9. [PMID: 25703327 DOI: 10.1038/onc.2015.11] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/17/2014] [Revised: 12/12/2014] [Accepted: 01/14/2015] [Indexed: 12/15/2022]
Abstract
Inactivation of the retinoblastoma protein (RB) has a major role in the development of human malignancies. We have previously shown that MDM2, an ubiquitin E3 ligase and major negative regulator of p53, binds to and promotes proteasome-mediated degradation of RB. MDMX, a homolog of MDM2, also binds to and inhibits p53 transactivation activity, yet it does not possess intrinsic ubiquitin ligase activity. Here, we show that MDMX binds to and promotes RB degradation in an MDM2-dependent manner. Specifically, the MDMX C-terminal ring domain binds to the RB C-pocket and enhances MDM2-RB interaction. Silencing MDMX induces RB accumulation, cell cycle arrest and senescence-like phenotypes, which are reverted by simultaneous RB knockdown. Furthermore, MDMX ablation leads to significant retardation of xenograft tumor growth, concomitant with RB accumulation. These results demonstrate that MDMX exerts oncogenic activity via suppression of RB, and suggest that both MDM2 and MDMX could be chemotherapeutic targets.
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