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Luo W, Xu C, Phillips S, Gardenswartz A, Rosenblum JM, Ayello J, Lessnick SL, Hao HX, Cairo MS. Protein phosphatase 1 regulatory subunit 1A regulates cell cycle progression in Ewing sarcoma. Oncotarget 2020; 11:1691-1704. [PMID: 32477459 PMCID: PMC7233808 DOI: 10.18632/oncotarget.27571] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/15/2020] [Accepted: 04/10/2020] [Indexed: 12/02/2022] Open
Abstract
Ewing sarcoma (ES) is a malignant pediatric bone and soft tissue tumor. Patients with metastatic ES have a dismal outcome which has not been improved in decades. The major challenge in the treatment of metastatic ES is the lack of specific targets and rational combinatorial therapy. We recently found that protein phosphatase 1 regulatory subunit 1A (PPP1R1A) is specifically highly expressed in ES and promotes tumor growth and metastasis in ES. In the current investigation, we show that PPP1R1A regulates ES cell cycle progression in G1/S phase by down-regulating cell cycle inhibitors p21Cip1 and p27Kip1, which leads to retinoblastoma (Rb) protein hyperphosphorylation. In addition, we show that PPP1R1A promotes normal transcription of histone genes during cell cycle progression. Importantly, we demonstrate a synergistic/additive effect of the combinatorial therapy of PPP1R1A and insulin-like growth factor 1 receptor (IGF-1R) inhibition on decreasing ES cell proliferation and migration in vitro and limiting xenograft tumor growth and metastasis in vivo. Taken together, our findings suggest a role of PPP1R1A as an ES specific cell cycle modulator and that simultaneous targeting of PPP1R1A and IGF-1R pathways is a promising specific and effective strategy to treat both primary and metastatic ES.
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Affiliation(s)
- Wen Luo
- Department of Pediatrics, New York Medical College, Valhalla, NY, USA.,Department of Pathology, New York Medical College, Valhalla, NY, USA
| | - Changxin Xu
- James J. Peters Veterans Affairs Medical Center, Bronx, NY, USA
| | - Sarah Phillips
- Department of Medicine, New York Medical College, Valhalla, NY, USA
| | | | | | - Janet Ayello
- Department of Pediatrics, New York Medical College, Valhalla, NY, USA
| | | | - Huai-Xiang Hao
- Novartis Institutes for BioMedical Research, Cambridge, MA, USA
| | - Mitchell S Cairo
- Department of Pediatrics, New York Medical College, Valhalla, NY, USA.,Department of Pathology, New York Medical College, Valhalla, NY, USA.,Department of Medicine, New York Medical College, Valhalla, NY, USA.,Department of Immunology and Microbiology, New York Medical College, Valhalla, NY, USA.,Department of Cell Biology and Anatomy, New York Medical College, Valhalla, NY, USA
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2
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Schoos A, Knab VM, Gabriel C, Tripolt S, Wagner DA, Bauder B, Url A, Fux DA. In vitro study to assess the efficacy of CDK4/6 inhibitor Palbociclib (PD-0332991) for treating canine mammary tumours. Vet Comp Oncol 2019; 17:507-521. [PMID: 31207004 DOI: 10.1111/vco.12514] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/20/2018] [Revised: 05/23/2019] [Accepted: 05/27/2019] [Indexed: 12/15/2022]
Abstract
Therapy of canine mammary tumours (CMTs) with classical antitumour drugs is problematic, so better therapeutic options are needed. Palbociclib (PD-0332991) is an innovative and effective anticancer drug for the treatment of breast cancer in women. Palbociclib is an inhibitor of cyclin-dependent kinase 4 (CDK4) and CDK6, which are key regulators of the cell cycle machinery and thus cell proliferation. In the present in vitro study, we investigated whether Palbociclib also represents a candidate drug to combat CMT. For this purpose, the effect of Palbociclib was analysed in P114 and CF41 cells, two CMT cell lines with an endogenous CDK4/6 co-expression. Incubation of P114 and CF41 cells with Palbociclib resulted in a dose- and time-dependent loss of phosphorylated retinoblastoma protein (pRb), a classical CDK4/6 substrate within the cell cycle machinery. Moreover, treatment of CMT cells with Palbociclib-induced cell cycle arrest affected cell viability, prevented colony formation and impaired cell migration activity. Palbociclib also inhibited the growth of P114 and CF41 cell spheroids. Immunohistochemical analysis of canine patient samples revealed a consistent expression of CDK6 in different canine mammary carcinoma types, but an individual and tumour-specific expression pattern of phosphorylated pRb independent of the tumour grade. Together, our findings let us suggest that Palbociclib has antitumour effects on CMT cells and that canine patients may represent potential candidates for treatment with this CDK4/6 inhibitor.
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Affiliation(s)
- Alexandra Schoos
- Institute of Pharmacology and Toxicology, Unit of Clinical Pharmacology, University of Veterinary Medicine, Vienna, Austria
| | - Vanessa M Knab
- Institute of Pharmacology and Toxicology, Unit of Clinical Pharmacology, University of Veterinary Medicine, Vienna, Austria
| | - Cordula Gabriel
- Institute of Pathology and Forensic Veterinary Medicine, University of Veterinary Medicine, Vienna, Austria
| | - Sabrina Tripolt
- Institute of Pharmacology and Toxicology, Unit of Clinical Pharmacology, University of Veterinary Medicine, Vienna, Austria
| | - Daniela A Wagner
- Institute of Pharmacology and Toxicology, Unit of Clinical Pharmacology, University of Veterinary Medicine, Vienna, Austria
| | - Barbara Bauder
- Institute of Pathology and Forensic Veterinary Medicine, University of Veterinary Medicine, Vienna, Austria
| | - Angelika Url
- Institute of Pathology and Forensic Veterinary Medicine, University of Veterinary Medicine, Vienna, Austria
| | - Daniela A Fux
- Institute of Pharmacology and Toxicology, Unit of Clinical Pharmacology, University of Veterinary Medicine, Vienna, Austria
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3
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Mervai Z, Egedi K, Kovalszky I, Baghy K. Diethylnitrosamine induces lung adenocarcinoma in FVB/N mouse. BMC Cancer 2018; 18:157. [PMID: 29415661 PMCID: PMC5803903 DOI: 10.1186/s12885-018-4068-4] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/03/2016] [Accepted: 01/29/2018] [Indexed: 12/16/2022] Open
Abstract
Background Diethylnitrosamine is a well known carcinogen that induces cancers of various organs in mice and rats. Using FVB/N mouse strain, here we show that diethylnitrosamine induces primarily lung adenocarcinomas with modest tumor development in the liver, offering a new model to study chemical carcinogenesis in the lung. Methods Animals were exposed to a single high dose of diethylnitrosamine, and more than 70% of the mice developed lung cancer. To obtain a new transplantable tumor line, pieces of primary tumors were inoculated and maintained subcutaneously in the same mouse strain. We used immunohistochemistry to characterize the tumor for main lung adenocarcinoma markers. We searched for mutations in KRAS exon 2 and EGFR exon 19, 21 with Sanger sequencing. We also compared the normal lung tissue with the diethylnitrosamine induced primary adenocarcinoma, and with the subcutaneously maintained adenocarcinoma using Western blot technique for main cell cycle markers and to identify the main pathways. Results Primary and subcutaneous tumors express cytokeratin-7 and thyroid transcription factor-1, markers characteristic to lung adenocarcinoma. In addition, no mutations were found in the hot spot regions of KRAS and EGFR genes. We found high mTOR activation, but the level of p-Akt Ser473 and p-Akt Thr308 decreased in the tumorous samples. Conclusions We established a new lung adenocarcinoma model using FVB/N mouse strain and diethylnitrosamine. We believe that this new model system would be highly useful in lung cancer research. Electronic supplementary material The online version of this article (10.1186/s12885-018-4068-4) contains supplementary material, which is available to authorized users.
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Affiliation(s)
- Zsolt Mervai
- Department of Pathology and Experimental Cancer Research, Budapest, Hungary
| | - Krisztina Egedi
- Department of Pathology and Experimental Cancer Research, Budapest, Hungary
| | - Ilona Kovalszky
- Department of Pathology and Experimental Cancer Research, Budapest, Hungary
| | - Kornélia Baghy
- Department of Pathology and Experimental Cancer Research, Budapest, Hungary.
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4
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Luo W, Xu C, Ayello J, Dela Cruz F, Rosenblum JM, Lessnick SL, Cairo MS. Protein phosphatase 1 regulatory subunit 1A in ewing sarcoma tumorigenesis and metastasis. Oncogene 2017; 37:798-809. [PMID: 29059150 DOI: 10.1038/onc.2017.378] [Citation(s) in RCA: 33] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/25/2017] [Revised: 09/05/2017] [Accepted: 09/07/2017] [Indexed: 02/06/2023]
Abstract
Protein phosphatase inhibitors are often considered as tumor promoters. Protein phosphatase 1 regulatory subunit 1A (PPP1R1A) is a potent protein phosphatase 1 (PP1) inhibitor; however, its role in tumor development is largely undefined. Here we characterize, for the first time, the functions of PPP1R1A in Ewing sarcoma (ES) pathogenesis. We found that PPP1R1A is one of the top ranked target genes of EWS/FLI, the master regulator of ES, and is upregulated by EWS/FLI via a GGAA microsatellite enhancer element. Depletion of PPP1R1A resulted in a significant decrease in oncogenic transformation and cell migration in vitro as well as xenograft tumor growth and metastasis in an orthotopic mouse model. RNA-sequencing and functional annotation analyses revealed that PPP1R1A regulates genes associated with various cellular functions including cell junction, adhesion and neurogenesis. Interestingly, we found a significant overlap of PPP1R1A-regulated gene set with that of ZEB2 and EWS, which regulates metastasis and neuronal differentiation in ES, respectively. Further studies for characterization of the molecular mechanisms revealed that activation of PPP1R1A by PKA phosphorylation at Thr35, and subsequent PP1 binding and inhibition, was required for PPP1R1A-mediated tumorigenesis and metastasis, likely by increasing the phosphorylation levels of various PP1 substrates. Furthermore, we found that a PKA inhibitor impaired ES cell proliferation, tumor growth and metastasis, which was rescued by the constitutively active PPP1R1A. Together, these results offered new insights into the role and mechanism of PPP1R1A in tumor development and identified an important kinase and phosphatase pathway, PKA/PPP1R1A/PP1, in ES pathogenesis. Our findings strongly suggest a potential therapeutic value of inhibition of the PKA/PPP1R1A/PP1 pathway in the treatment of primary and metastatic ES.
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Affiliation(s)
- W Luo
- Departments of Pediatrics, New York Medical College, Valhalla, NY, USA.,Departments of Pathology, New York Medical College, Valhalla, NY, USA
| | - C Xu
- James J. Peters Veterans Affairs Medical Center, Bronx, NY, USA
| | - J Ayello
- Departments of Pediatrics, New York Medical College, Valhalla, NY, USA
| | - F Dela Cruz
- Memorial Sloan Kettering Cancer Center, New York, NY, USA
| | - J M Rosenblum
- Departments of Pediatrics, New York Medical College, Valhalla, NY, USA
| | - S L Lessnick
- Nationwide Children's Hospital, Columbus, OH, USA
| | - M S Cairo
- Departments of Pediatrics, New York Medical College, Valhalla, NY, USA.,Departments of Pathology, New York Medical College, Valhalla, NY, USA.,Departments of Medicine, New York Medical College, Valhalla, NY, USA.,Departments of Immunology and Microbiology, New York Medical College, Valhalla, NY, USA.,Departments of Cell Biology and Anatomy, New York Medical College, Valhalla, NY, USA
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5
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He Y, Luo Y, Liang B, Ye L, Lu G, He W. Potential applications of MEG3 in cancer diagnosis and prognosis. Oncotarget 2017; 8:73282-73295. [PMID: 29069869 PMCID: PMC5641212 DOI: 10.18632/oncotarget.19931] [Citation(s) in RCA: 84] [Impact Index Per Article: 12.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/01/2017] [Accepted: 07/25/2017] [Indexed: 12/25/2022] Open
Abstract
LncRNAs are emerging as integral functional and regulatory components of normal biological activities and are now considered as critically involved in the development of different diseases including cancer. In this review, we summarized recent findings on maternally expressed gene 3 (MEG3), a noncoding lncRNA, locates in the imprinted DLK1–MEG3 locus on human chromosome 14q32.3 region. MEG3 is expressed in normal tissues but is either lost or decreased in many human tumors and tumor derived cell lines. Studies have demonstrated that MEG3 is associated with cancer initiation, progression, metastasis and chemo-resistance. MEG3 may affect the activities of TP53, MDM2, GDF15, RB1 and some other key cell cycle regulators. In addition, the level of MEG3 showed good correlation with cancer clinicopathological grade. In summary, MEGs is an RNA-based tumor suppressor and is involved in the etiology, progression, and chemosensitivity of cancers. The alteration of MEG3 levels in various cancers suggested the possibility of using MEG3 level for cancer diagnosis and prognosis.
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Affiliation(s)
- Yuqing He
- Institute of Medical Systems Biology, Guangdong Medical University, Dongguan 523808, China.,Key Laboratory for Medical Molecular Diagnostics of Guangdong Province, Guangdong Medical University, Dongguan 523808, China
| | - Yanhong Luo
- Department of Epidemiology and Medical Statistics, Guangdong Medical University, Dongguan 523808, China
| | - Biyu Liang
- Department of Epidemiology and Medical Statistics, Guangdong Medical University, Dongguan 523808, China
| | - Lei Ye
- Department of Epidemiology and Medical Statistics, Guangdong Medical University, Dongguan 523808, China
| | - Guangxing Lu
- Department of Epidemiology and Medical Statistics, Guangdong Medical University, Dongguan 523808, China
| | - Weiming He
- Department of Epidemiology and Medical Statistics, Guangdong Medical University, Dongguan 523808, China
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6
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Xie Y, Si J, Wang Y, Li H, Di C, Yan J, Ye Y, Zhang Y, Zhang H. E2F is involved in radioresistance of carbon ion induced apoptosis via Bax/caspase 3 signal pathway in human hepatoma cell. J Cell Physiol 2017; 233:1312-1320. [DOI: 10.1002/jcp.26005] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/30/2017] [Accepted: 05/11/2017] [Indexed: 01/05/2023]
Affiliation(s)
- Yi Xie
- Institute of Modern PhysicsChinese Academy of SciencesLanzhouChina
- CAS Key Laboratory of Heavy Ion Radiation Biology and MedicineInstitute of Modern PhysicsLanzhouGansuChina
- Key Laboratory of Basic Research on Heavy Ion Radiation Application in MedicineGansu ProvinceLanzhouChina
| | - Jing Si
- Institute of Modern PhysicsChinese Academy of SciencesLanzhouChina
- CAS Key Laboratory of Heavy Ion Radiation Biology and MedicineInstitute of Modern PhysicsLanzhouGansuChina
- Key Laboratory of Basic Research on Heavy Ion Radiation Application in MedicineGansu ProvinceLanzhouChina
| | - Yu‐Pei Wang
- Institute of Modern PhysicsChinese Academy of SciencesLanzhouChina
- CAS Key Laboratory of Heavy Ion Radiation Biology and MedicineInstitute of Modern PhysicsLanzhouGansuChina
- Key Laboratory of Basic Research on Heavy Ion Radiation Application in MedicineGansu ProvinceLanzhouChina
- Graduate School of University of Chinese Academy of SciencesBeijingChina
| | - Hong‐Yan Li
- Institute of Modern PhysicsChinese Academy of SciencesLanzhouChina
- CAS Key Laboratory of Heavy Ion Radiation Biology and MedicineInstitute of Modern PhysicsLanzhouGansuChina
- Key Laboratory of Basic Research on Heavy Ion Radiation Application in MedicineGansu ProvinceLanzhouChina
- Graduate School of University of Chinese Academy of SciencesBeijingChina
| | - Cui‐Xia Di
- Institute of Modern PhysicsChinese Academy of SciencesLanzhouChina
- CAS Key Laboratory of Heavy Ion Radiation Biology and MedicineInstitute of Modern PhysicsLanzhouGansuChina
- Key Laboratory of Basic Research on Heavy Ion Radiation Application in MedicineGansu ProvinceLanzhouChina
| | - Jun‐Fang Yan
- Institute of Modern PhysicsChinese Academy of SciencesLanzhouChina
- CAS Key Laboratory of Heavy Ion Radiation Biology and MedicineInstitute of Modern PhysicsLanzhouGansuChina
- Key Laboratory of Basic Research on Heavy Ion Radiation Application in MedicineGansu ProvinceLanzhouChina
- Graduate School of University of Chinese Academy of SciencesBeijingChina
| | | | | | - Hong Zhang
- Institute of Modern PhysicsChinese Academy of SciencesLanzhouChina
- CAS Key Laboratory of Heavy Ion Radiation Biology and MedicineInstitute of Modern PhysicsLanzhouGansuChina
- Key Laboratory of Basic Research on Heavy Ion Radiation Application in MedicineGansu ProvinceLanzhouChina
- Gansu Wuwei Tumor HospitalWuweiChina
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7
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Cortese K, Daga A, Monticone M, Tavella S, Stefanelli A, Aiello C, Bisio A, Bellese G, Castagnola P. Carnosic acid induces proteasomal degradation of Cyclin B1, RB and SOX2 along with cell growth arrest and apoptosis in GBM cells. PHYTOMEDICINE : INTERNATIONAL JOURNAL OF PHYTOTHERAPY AND PHYTOPHARMACOLOGY 2016; 23:679-685. [PMID: 27235706 DOI: 10.1016/j.phymed.2016.03.007] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/12/2015] [Revised: 03/14/2016] [Accepted: 03/19/2016] [Indexed: 06/05/2023]
Abstract
BACKGROUND Carnosic acid (CA) is a diterpenoid found in Rosmarinus officinalis L. and Salvia officinalis L. as well as in many other Lamiaceae. This compound is reported to have antioxidant and antimicrobial properties. In addition, a number of reports showed that CA has a cytotoxic activity toward several cancer cell lines. PURPOSE The aim of this study was to establish whether CA has any specific antiproliferative effect toward human glioblastoma (GBM) cells and to analyze the molecular mechanisms involved. METHODS We evaluated cell survival by MTT assay, apoptosis and DNA content by flow cytometry, protein expression and phosphorylation by immunoblot analyses. RESULTS Our results showed that CA inhibited cell survival on both normal astrocytes and GBM cells. In GBM cells, in particular, CA caused an early G2 block, a reduction in the percentage of cells expressing Ki67, an enhanced expression of p21(WAF) and induced apoptosis. Furthermore, we showed that CA promoted proteasomal degradation of several substrate proteins, including Cyclin B1, retinoblastoma (RB), SOX2, and glial fibrillary acid protein (GFAP), whereas MYC levels were not modified. In addition, CA dramatically reduced the activity of CDKs. CONCLUSION In conclusion, our findings strongly suggest that CA promotes a profound deregulation of cell cycle control and reduces the survival of GBM cells via proteasome-mediated degradation of Cyclin B1, RB and SOX2.
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Affiliation(s)
- Katia Cortese
- DIMES, Dipartimento di Medicina Sperimentale, Anatomia Umana, Università di Genova, Via de Toni 14, 16132 Genova, Italy
| | - Antonio Daga
- IRCCS AOU - San Martino - IST, Largo Rosanna Benzi, 10, 16132 Genova, Italy
| | | | - Sara Tavella
- DIMES, Dipartimento di Medicina Sperimentale, Anatomia Umana, Università di Genova, Via de Toni 14, 16132 Genova, Italy; IRCCS AOU - San Martino - IST, Largo Rosanna Benzi, 10, 16132 Genova, Italy
| | - Alessia Stefanelli
- IRCCS AOU - San Martino - IST, Largo Rosanna Benzi, 10, 16132 Genova, Italy
| | - Cinzia Aiello
- IRCCS AOU - San Martino - IST, Largo Rosanna Benzi, 10, 16132 Genova, Italy
| | - Angela Bisio
- Dip. Farmacia, Università di Genova, Via Brigata Salerno 13, 16147 Genova, Italy
| | - Grazia Bellese
- DIMES, Dipartimento di Medicina Sperimentale, Anatomia Umana, Università di Genova, Via de Toni 14, 16132 Genova, Italy
| | - Patrizio Castagnola
- IRCCS AOU - San Martino - IST, Largo Rosanna Benzi, 10, 16132 Genova, Italy.
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Harajly M, Zalzali H, Nawaz Z, Ghayad SE, Ghamloush F, Basma H, Zainedin S, Rabeh W, Jabbour M, Tawil A, Badro DA, Evan GI, Saab R. p53 Restoration in Induction and Maintenance of Senescence: Differential Effects in Premalignant and Malignant Tumor Cells. Mol Cell Biol 2016; 36:438-51. [PMID: 26598601 PMCID: PMC4719431 DOI: 10.1128/mcb.00747-15] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/30/2015] [Revised: 08/23/2015] [Accepted: 11/05/2015] [Indexed: 11/20/2022] Open
Abstract
The restoration of p53 has been suggested as a therapeutic approach in tumors. However, the timing of p53 restoration in relation to its efficacy during tumor progression still is unclear. We now show that the restoration of p53 in murine premalignant proliferating pineal lesions resulted in cellular senescence, while p53 restoration in invasive pineal tumors did not. The effectiveness of p53 restoration was not dependent on p19(Arf) expression but showed an inverse correlation with Mdm2 expression. In tumor cells, p53 restoration became effective when paired with either DNA-damaging therapy or with nutlin, an inhibitor of p53-Mdm2 interaction. Interestingly, the inactivation of p53 after senescence resulted in reentry into the cell cycle and rapid tumor progression. The evaluation of a panel of human supratentorial primitive neuroectodermal tumors (sPNET) showed low activity of the p53 pathway. Together, these data suggest that the restoration of the p53 pathway has different effects in premalignant versus invasive pineal tumors, and that p53 activation needs to be continually sustained, as reversion from senescence occurs rapidly with aggressive tumor growth when p53 is lost again. Finally, p53 restoration approaches may be worth exploring in sPNET, where the p53 gene is intact but the pathway is inactive in the majority of examined tumors.
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Affiliation(s)
- Mohamad Harajly
- Department of Pediatric and Adolescent Medicine, American University of Beirut Medical Center, Beirut, Lebanon
| | - Hasan Zalzali
- Department of Pediatric and Adolescent Medicine, American University of Beirut Medical Center, Beirut, Lebanon
| | - Zafar Nawaz
- Cytogenetics and Molecular Cytogenetic Laboratory, Hamad General Hospital, Doha, Qatar
| | - Sandra E Ghayad
- Department of Pediatric and Adolescent Medicine, American University of Beirut Medical Center, Beirut, Lebanon
| | - Farah Ghamloush
- Department of Pediatric and Adolescent Medicine, American University of Beirut Medical Center, Beirut, Lebanon
| | - Hussein Basma
- Department of Pediatric and Adolescent Medicine, American University of Beirut Medical Center, Beirut, Lebanon
| | - Samiha Zainedin
- Cytogenetics and Molecular Cytogenetic Laboratory, Hamad General Hospital, Doha, Qatar
| | - Wissam Rabeh
- Department of Pediatric and Adolescent Medicine, American University of Beirut Medical Center, Beirut, Lebanon
| | - Mark Jabbour
- Department of Pathology and Laboratory Medicine, American University of Beirut Medical Center, Beirut, Lebanon
| | - Ayman Tawil
- Department of Pathology and Laboratory Medicine, American University of Beirut Medical Center, Beirut, Lebanon
| | - Danielle A Badro
- Department of Pediatric and Adolescent Medicine, American University of Beirut Medical Center, Beirut, Lebanon
| | - Gerard I Evan
- Department of Biochemistry, University of Cambridge, Cambridge, United Kingdom
| | - Raya Saab
- Department of Pediatric and Adolescent Medicine, American University of Beirut Medical Center, Beirut, Lebanon
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9
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Antonucci LA, Egger JV, Krucher NA. Phosphorylation of the Retinoblastoma protein (Rb) on serine-807 is required for association with Bax. Cell Cycle 2015; 13:3611-7. [PMID: 25483096 PMCID: PMC4614104 DOI: 10.4161/15384101.2014.964093] [Citation(s) in RCA: 28] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022] Open
Abstract
The recent finding that the Retinoblastoma protein (Rb) is able to regulate apoptosis in a non-transcriptional manner directly at the mitochondria by interaction with the pro-apoptotic protein Bax prompted this investigation of the complex formed between Rb and Bax. Because the function of Rb in the cellular processes of proliferation, apoptosis, senescence and differentiation is regulated by phosphorylation we endeavored to elucidate the phosphorylation status of Rb with respect to its association with Bax and its role in apoptosis. In this study we found that Rb phosphorylated on at least 4 C-terminal phosphorylation sites (S608, S795, S807/S811, and T821) is present at the mitochondria under non-stressed cellular conditions. An in vitro binding assay showed that Bax binds to Rb phosphorylated at S807/S811 in 3 cancer cell types. Physiologically relevant association between Bax and Rb phosphorylated on S807/S811 was demonstrated by reciprocal co-immunoprecipitation experiments using antibodies specific for Rb phosphorylated on S807/S811 and Bax. Mutant Rb proteins expressed in Rb-null C33A cells showed that phosphorylation of S807 of Rb promotes association with Bax and that mimicking phosphorylation at S807 of Rb can block the induction of apoptosis due to PNUTS downregulation. Finally using siRNA to activate phosphatase activity in MCF7 cells, Rb is dephosphorylated at several sites including S807/S811, dissociates from Bax and apoptosis is triggered. These studies show that phosphorylation of Rb regulates its association with Bax and its role in apoptosis.
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Affiliation(s)
- Lisa A Antonucci
- a Department of Biology and Health Science ; Pace University ; Pleasantville , NY USA
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10
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Lv H, Liu R, Fu J, Yang Q, Shi J, Chen P, Ji M, Shi B, Hou P. Epithelial cell-derived periostin functions as a tumor suppressor in gastric cancer through stabilizing p53 and E-cadherin proteins via the Rb/E2F1/p14ARF/Mdm2 signaling pathway. Cell Cycle 2015; 13:2962-74. [PMID: 25486483 DOI: 10.4161/15384101.2014.947203] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022] Open
Abstract
Periostin is usually considered as an oncogene in diverse human cancers, including breast, prostate, colon, esophagus, and pancreas cancers, whereas it acts as a tumor suppressor in bladder cancer. In gastric cancer, it has been demonstrated that periglandular periostin expression is decreased whereas stromal periostin expression is significantly increased as compared with normal gastric tissues. Moreover, periostin produced by stromal myofibroblasts markedly promotes gastric cancer cell growth. These observations suggest that periostin derived from different types of cells may play distinct biological roles in gastric tumorigenesis. The aim of this study was to explore the biological functions and related molecular mechanisms of epithelial cell-derived periostin in gastric cancer. Our data showed that periglandular periostin was significantly down-regulated in gastric cancer tissues as compared with matched normal gastric mucosa. In addition, its expression in metastatic lymph nodes was significantly lower than that in their primary cancer tissues. Our data also demonstrated that periglandular periostin expression was negatively associated with tumor stage. More importantly, restoration of periostin expression in gastric cancer cells dramatically suppressed cell growth and invasiveness. Elucidation of the mechanisms involved revealed that periostin restoration enhanced Rb phosphorylation and sequentially activated the transcription of E2F1 target gene p14(ARF), leading to Mdm2 inactivation and the stabilization of p53 and E-cadherin proteins. Strikingly, these effects of periostin were abolished upon Rb deletion. Collectively, we have for the first time demonstrated that epithelial cell-derived periostin exerts tumor-suppressor activities in gastric cancer through stabilizing p53 and E-cadherin proteins via the Rb/E2F1/p14(ARF)/Mdm2 signaling pathway.
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Affiliation(s)
- Hongjun Lv
- a Department of Endocrinology ; The First Affiliated Hospital of Xi'an Jiaotong University School of Medicine ; Xi'an , The People's Republic of China
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11
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Wu XQ, Huang C, He X, Tian YY, Zhou DX, He Y, Liu XH, Li J. Feedback regulation of telomerase reverse transcriptase: new insight into the evolving field of telomerase in cancer. Cell Signal 2013; 25:2462-8. [DOI: 10.1016/j.cellsig.2013.08.009] [Citation(s) in RCA: 39] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/02/2013] [Accepted: 08/23/2013] [Indexed: 01/07/2023]
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12
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Glypican 1 stimulates S phase entry and DNA replication in human glioma cells and normal astrocytes. Mol Cell Biol 2013; 33:4408-21. [PMID: 24019070 DOI: 10.1128/mcb.00238-13] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Malignant gliomas are highly lethal neoplasms with limited treatment options. We previously found that the heparan sulfate proteoglycan glypican 1 (GPC1) is universally and highly expressed in human gliomas. In this study, we investigated the biological activity of GPC1 expression in both human glioma cells and normal astrocytes in vitro. Expression of GPC1 inactivates the G1/S checkpoint and strongly stimulates DNA replication. Constitutive expression of GPC1 causes DNA rereplication and DNA damage, suggesting a mutagenic activity for GPC1. GPC1 expression leads to a significant downregulation of the tumor suppressors pRb, Cip/Kip cyclin-dependent kinase inhibitors (CKIs), and CDH1, and upregulation of the pro-oncogenic proteins cyclin E, cyclin-dependent kinase 2 (CDK2), Skp2, and Cdt1. These GPC1-induced changes are accompanied by a significant reduction in all types of D cyclins, which is independent of serum supplementation. It is likely that GPC1 stimulates the so-called Skp2 autoinduction loop, independent of cyclin D-CDK4/6. Knockdown of Skp2, CDK2, or cyclin E, three key elements within the network modulated by GPC1, results in a reduction of the S phase and aneuploid fractions, implying a functional role for these regulators in GPC1-induced S phase entry and DNA rereplication. In addition, a significant activation of both the extracellular signal-regulated kinase (ERK)/mitogen-activated protein kinase (MAPK) and phosphatidylinositol 3-kinase (PI3K)/Akt signaling pathways by GPC1 is seen in normal human astrocytes even in the presence of growth factor supplement. Both pathways are constitutively activated in human gliomas. The surprising magnitude and the mitogenic and mutagenic nature of the effect exerted by GPC1 on the cell cycle imply that GPC1 may play an important role in both glioma tumorigenesis and growth.
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Balik V, Srovnal J, Sulla I, Kalita O, Foltanova T, Vaverka M, Hrabalek L, Hajduch M. MEG3: a novel long noncoding potentially tumour-suppressing RNA in meningiomas. J Neurooncol 2013; 112:1-8. [PMID: 23307326 DOI: 10.1007/s11060-012-1038-6] [Citation(s) in RCA: 84] [Impact Index Per Article: 7.6] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/19/2012] [Accepted: 12/29/2012] [Indexed: 10/27/2022]
Abstract
Meningiomas represent one of the most common types of primary intracranial tumours. However, the specific molecular mechanisms underlying their pathogenesis remain uncertain. Loss of chromosomes 22q, 1p, and 14q have been implicated in most meningiomas. Inactivation of the NF2 gene at 22q12 has been identified as an early event in their pathogenesis, whereas abnormalities of chromosome 14 have been reported in higher-grade as well as recurrent tumours. It has long been supposed that chromosome 14q32 contains a tumour suppressor gene. However, the identity of the potential 14q32 tumour suppressor remained elusive until the Maternally Expressed Gene 3 (MEG3) was recently suggested as an ideal candidate. MEG3 is an imprinted gene located at 14q32 that encodes a non-coding RNA (ncRNA). In meningiomas, loss of MEG3 expression, its genomic DNA deletion and degree of promoter methylation have been found to be associated with aggressive tumour growth. These findings indicate that MEG3 may have a significant role as a novel long noncoding RNA tumour suppressor in meningiomas.
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Affiliation(s)
- Vladimir Balik
- Department of Neurosurgery, Faculty Hospital Olomouc, I.P. Pavlova 6, 775 20 Olomouc, Czech Republic.
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14
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Mitra R, Bhagavatula ID, Gope R. BAY 61-3606, CDKi, and sodium butyrate treatments alter gene expression in human vestibular schwannomas and cause cell death in vitro. Ecancermedicalscience 2013; 6:285. [PMID: 23304241 PMCID: PMC3530378 DOI: 10.3332/ecancer.2012.285] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/05/2012] [Indexed: 11/24/2022] Open
Abstract
Background: Disrupted kinase and signaling pathways are found in many human cancers and they are implicated in carcinogenesis. Therefore, kinases have been important targets for the development of cancer therapeutics. Human vestibular schwannomas (VS) are the third most common intracranial tumours which occur in the vestibular branch of VIIIth cranial nerve. Sodium butyrate (Na-Bu) is a potent histone deacetylase inhibitor (HDACi) and with therapeutic efficacy. Spleen tyrosine kinase (Syk) has been implicated in many immunological consequences and is a putative target for cancer treatment. Aims and objectives: The present study was undertaken in order to evaluate the effect Na-Bu, 2,4-Diamino-5-oxo-pyrimidine hydrochloride (CDKi), a broad spectrum kinase inhibitor and BAY 61-3606 (Syk inhibitor) on the survival of VS tumour tissues in vitro and their possible effects on cell survival/death and levels of a few key proteins in the treated cells as compared to the untreated cells. Materials and methods Fresh tumour tissues were collected randomly from 16 patients with sporadic, VS tumours, minced into pieces and maintained in primary cultures. Twenty four hours later these cells were exposed to Na-Bu, BAY 61-3606 or CDKi. Forty eight hours after exposure, the tissue lysates were analysed by western blotting for expression of pRb and other proteins involved in cell survival/death. Summary and significance of the findings: The tissue samples used were positive for S100A protein, the maker for schwann cells confirming the VS tumour samples. The three individual treatments led to morphological change, DNA fragmentation and cell death and significantly reduced level of total and phosphorylated forms of pRb protein and drastically reduced EGF-R protein. These treatments also modulated levels of other proteins involved in cell survival/death such as PI3K, Caspase 3, TGF-β1, JNK, ASK1, Shh, NF-κB, p21cip1/waf1. The Untreated cells had uncleaved PARP-1 protein and the treated cells had cleaved PARP-1. The results show that the observed cell death in treated cells perhaps is mediated by modulation of the levels and processing of certain key proteins. The possible development of these components as therapeutics is discussed.
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Affiliation(s)
- Rohan Mitra
- Department of Human Genetics, NIMHANS, 2900 Hosur road, Bangalore 560029, India
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15
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Lee TC, Gombos DS, Harbour JW, Mansfield NC, Murphree AL. Retinoblastoma. Retina 2013. [DOI: 10.1016/b978-1-4557-0737-9.00128-4] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
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16
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Morales LD, Pena K, Kim DJ, Lieman JH. SHP-2 and PTP-pest induction during Rb-E2F associated apoptosis. Cell Mol Biol Lett 2012; 17:422-32. [PMID: 22644489 PMCID: PMC6275625 DOI: 10.2478/s11658-012-0020-9] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/25/2011] [Accepted: 05/22/2012] [Indexed: 12/28/2022] Open
Abstract
Apoptosis is intimately connected to cell cycle regulation via the Retinoblastoma (Rb)-E2F pathway and thereby serves an essential role in tumor suppression by eliminating aberrant hyperproliferative cells. Upon loss of Rb activity, an apoptotic response can be elicited through both p53-dependent and p53-independent mechanisms. While much of this apoptotic response has been attributed to the p19ARF/p53 pathway, increasing evidence has supported the role of protein tyrosine phosphatases (PTPs) in contributing to the initiation of the Rb-E2F-associated apoptotic response. One protein tyrosine phosphatase, PTP-1B, which is induced by the Rb-E2F pathway, has been shown to contribute to a p53-independent apoptotic pathway by inactivating focal adhesion kinase. This report identifies two additional PTPs, SHP-2 and PTP-PEST, that are also directly activated by the Rb-E2F pathway and which can contribute to signal transduction during p53-independent apoptosis.
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Affiliation(s)
- Liza D. Morales
- Department of Biology, The University of Texas-Pan American, Edinburg, TX USA
- Edinburg Regional Academic Health Center, Medical Research Division, University of Texas Health Science Center at San Antonio, Edinburg, TX USA
| | - Karina Pena
- Department of Biology, The University of Texas-Pan American, Edinburg, TX USA
| | - Dae Joon Kim
- Department of Pharmacology, University of Texas Health Science Center at San Antonio, Edinburg, TX USA
- Edinburg Regional Academic Health Center, Medical Research Division, University of Texas Health Science Center at San Antonio, Edinburg, TX USA
| | - Jonathan H. Lieman
- Department of Biology, The University of Texas-Pan American, Edinburg, TX USA
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17
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Lentine B, Antonucci L, Hunce R, Edwards J, Marallano V, Krucher NA. Dephosphorylation of threonine-821 of the retinoblastoma tumor suppressor protein (Rb) is required for apoptosis induced by UV and Cdk inhibition. Cell Cycle 2012; 11:3324-30. [PMID: 22895174 DOI: 10.4161/cc.21693] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022] Open
Abstract
The Retinoblastoma protein (Rb) is important in the control of cell proliferation and apoptosis. Its activity is controlled by reversible phosphorylation on several serine and threonine residues. When Rb is hypophosphorylated, it inhibits proliferation by preventing passage through the G 1- S phase transition. Hyperphosphorylated Rb promotes cell cycle progression. The role of Rb phosphorylation in the control of apoptosis is largely unknown, although several apoptotic stimuli result in dephosphorylation of Rb. It may be that dephosphorylation of specific amino acids signals apoptosis vs. cell cycle arrest. Using glutamic acid mutagenesis, we have generated 15 single phosphorylation site mutants of Rb to alter serine/threonine to glutamic acid to mimic the phosphorylated state. By calcium phosphate transfection, mutant plasmids were introduced into C33A Rb-null cells, and apoptosis was induced using UV. Apoptosis was measured by ELISA detection of degraded DNA and by immunoblotting to assess proteolytic cleavage of PARP. Our results show that only mutation of threonine-821 to glutamic acid (T821E) blocked apoptosis by 50%, whereas other sites tested had little effect. In Rb-null Saos-2 and SKUT-1 cells, the T821E mutation also blocked apoptosis induced by the cdk inhibitor, Roscovitine, by 50%. In addition, we show that endogenous Rb is dephosphorylated on threonine-821 when cells are undergoing apoptosis. Thus, our data indicates that dephosphorylation of threonine-821 of Rb is required for cells to undergo apoptosis.
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Affiliation(s)
- Brandon Lentine
- Department of Biology and Health Science, Pace University, 219 Pleasantville, NY, USA
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18
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Morales A, Alvarez A, Arvelo F, Suárez AI, Compagnone RS, Galindo-Castro I. The natural diterpene ent-16β-17α-dihydroxykaurane down-regulates Bcl-2 by disruption of the Ap-2α/Rb transcription activating complex and induces E2F1 up-regulation in MCF-7 cells. Apoptosis 2012; 16:1245-52. [PMID: 21850486 DOI: 10.1007/s10495-011-0638-5] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023]
Abstract
ent-Kauranes are diterpene-type compounds commonly found in most plant species, especially from the Euphorbiaceae family. These compounds have been studied due to their anti-inflammatory and anti-tumor properties. Regulation of apoptosis, or programmed cell death, is commonly bypassed by tumoral cells, giving rise to uncontrolled proliferating cells, which eventually become carcinogenic. In a previous work, we showed that both mRNA and protein expression levels of the antiapoptotic gene Bcl-2 are reduced in MCF-7 cancer cells by the effect of the natural diterpene ent-16β-17α-dihydroxykaurane (DHK). This effect was not directly associated with the inactivation of NF-κB, as has been shown with other diterpenes compounds. Herein, we report that DHK is dissociating the Ap2α-Rb activating complex, affecting its binding ability for the Bcl-2 gene promoter. These events down-regulate Bcl-2 and is temporally accompanied by the induction of E2F1 and its target pro-apoptotic gene Puma. Disruption of the Rb-Ap2α activation complex was corroborated by chromatin immunoprecipitation and protein immunolocalization, which also revealed that Ap2α sorts out from the nucleus and relocalizes in the cell periphery. Taken together, our study confirms the regulation of Bcl-2 gene transcription by the Ap2α-Rb complex and describes a singular protein relocalization for Ap2α induced by DHK, implicating a new potential therapeutic target to differentially onset apoptosis in tumor cells.
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Affiliation(s)
- Alvaro Morales
- Laboratorio de Genómica y Proteómica, Fundación IDEA, Caracas, Venezuela
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19
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The cell cycle regulator phosphorylated retinoblastoma protein is associated with tau pathology in several tauopathies. J Neuropathol Exp Neurol 2011; 70:578-87. [PMID: 21666500 DOI: 10.1097/nen.0b013e3182204414] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/20/2023] Open
Abstract
Retinoblastoma protein (pRb) is a ubiquitous 928-amino acid cell cycle regulatory molecule with diverse biologic activities. One critical function of pRb is the control of the G1-to-S phase checkpoint of the cell cycle. In the hypophosphorylated state, pRb suppresses the activity of E2F transcription factors thereby inhibiting transcription of cell cycle-promoting genes. On phosphorylation, primarily by cyclin-dependent kinases, phosphorylated pRb dissociates from E2F and permits cell cycle progression. We previously found phosphorylated pRb to be intimately associated with hyperphosphorylated tau-containing neurofibrillary tangles of Alzheimer disease (AD), the pathogenesis of which is believed to involve dysregulation of the cell cycle and marked neuronal death. Here, we used immunohistochemistry to investigate the presence of phosphorylated pRb in other distinct neurodegenerative diseases that share the common characteristic of hyperphosphorylated tau pathology and neuronal loss with AD.We found colocalized labeling of tau pathology and phosphorylated pRb in Pick disease and progressive supranuclear palsy (3 cases each), neurodegeneration with brain iron accumulation type 1 (2 cases), and Parkinson-amyotrophic lateral sclerosis of Guam, subacute sclerosing panencephalitis, frontotemporal dementia and Parkinsonism linked to chromosome 17, and dementia pugilistica (1 case each). These observations further implicate aberrant neuronal cell cycle progression in neurodegenerative diseases, particularly tauopathies, and suggest a novel target for therapeutic intervention.
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20
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Delston RB, Matatall KA, Sun Y, Onken MD, Harbour JW. p38 phosphorylates Rb on Ser567 by a novel, cell cycle-independent mechanism that triggers Rb-Hdm2 interaction and apoptosis. Oncogene 2010; 30:588-99. [PMID: 20871633 PMCID: PMC3012146 DOI: 10.1038/onc.2010.442] [Citation(s) in RCA: 40] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Abstract
The retinoblastoma protein (Rb) inhibits both cell division and apoptosis, but the mechanism by which Rb alternatively regulates these divergent outcomes remains poorly understood. Cyclin dependent kinases (Cdks) promote cell division by phosphorylating and reversibly inactivating Rb by a hierarchical series of phosphorylation events and sequential conformational changes. The stress-regulated mitogen activated protein kinase (MAPK) p38 also phosphorylates Rb, but it does so in a cell cycle-independent manner that is associated with apoptosis rather than with cell division. Here, we show that p38 phosphorylates Rb by a novel mechanism that is distinct from that of Cdks. p38 bypasses the cell cycle-associated hierarchical phosphorylation and directly phosphorylates Rb on Ser567, which is not phosphorylated during the normal cell cycle. Phosphorylation by p38, but not Cdks, triggers an interaction between Rb and the human homologue of murine double minute 2 (Hdm2), leading to degradation of Rb, release of E2F1 and cell death. These findings provide a mechanistic explanation for how Rb regulates cell division and apoptosis through different kinases, and reveal how Hdm2 may functionally link the tumor suppressors Rb and p53.
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Affiliation(s)
- R B Delston
- Department of Ophthalmology and Visual Sciences, Washington University School of Medicine, St Louis, MO, USA
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21
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Landreville S, Ma D, Wu J, Harbour JW. Loss of Id2 potentiates the tumorigenic effect of Rb inactivation in a mouse model of retinoblastoma. Curr Eye Res 2010; 35:435-9. [PMID: 20450257 DOI: 10.3109/02713680903509428] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
PURPOSE In some cancers, the oncogenic consequences of inactivating the retinoblastoma protein (Rb) appear to be mediated by unrestrained activity of the inhibitor of DNA binding protein Id2. The role of Id2 has not yet been investigated in the prototype cancer Rb-defective cancer, retinoblastoma itself. This study investigated whether loss of Id2 modified the effects of Rb inactivation in a mouse model of retinoblastoma. METHODS Id2 was analyzed in cultured cells using qPCR, Western blot, and colony formation assays. LH beta-Tag transgenic mice were crossed with Id2 heterozygotes to obtain mice with all three Id2 genotypes. Intraocular tumors were assessed for size, degree of differentiation, mitotic index, and tumor vascular density at 15 weeks of age. RESULTS Retinoblastoma cell lines expressed low levels of Id2 mRNA and protein. Depletion of Id2 in Rb-inactivated cells increased clonogenic activity. Id2-deficient tumors in vivo were significantly larger, less differentiated, and more vascularized than Id2-wild-type tumors (P = 0.02, P = 0.01, P = 0.0001, respectively). There was a dosage effect for loss of each Id2 allele with respect to differentiation and vascular density. CONCLUSIONS Id2 suppresses rather than promotes tumor progression in this mouse model of retinoblastoma. Id2 can act as either an oncogene or a tumor suppressor depending on context.
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Affiliation(s)
- Solange Landreville
- Department of Ophthalmology & Visual Sciences, Washington University School of Medicine, St. Louis, Missouri, USA
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22
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Yoo NK, Pyo CW, Kim Y, Ahn BY, Choi SY. Vaccinia virus-mediated cell cycle alteration involves inactivation of tumour suppressors associated with Brf1 and TBP. Cell Microbiol 2007; 10:583-92. [PMID: 17877750 DOI: 10.1111/j.1462-5822.2007.01047.x] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
Abstract
The vaccinia virus (VV) replicates robustly and alters the progression of the cell cycle via an unknown mechanism. Herein, we provide evidence for the existence of a unique VV infection-induced cell cycle control mechanism. The regulation is correlated with the inactivation of p53 and Rb, which are associated with the RNA polymerase III transcription factor B (TFIIIB) subunits, TBP and Brf1 respectively. VV infection induced the expression of Mdm2 and its translocation into the nucleus, thereby resulting in a disruption of p53. VV also stimulated the expression of TFIIIB and TFIIIC, and consequently induced tRNA synthesis. On the other hand, the total level of Rb was not significantly influenced, but the level of hypo-phosphorylated Rb was enhanced, partially due to the VV-induced downregulation of cyclin-dependent kinases 4 and 6. However, the hypo-phosphorylated Rb appeared to be largely sequestered into a complex with Brf1, which resulted in the blockage of Rb function to repress E2F1 transactivation, thereby leading to a moderately higher proportion of cells in the S and G(2) phases. Conversely, the enforced expression of exogenous Rb restored the normally observed cell cycle patterns. Overall, these controls may contribute to the efficient replication of the virus in rapidly growing cells.
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Affiliation(s)
- Na-Kyung Yoo
- School of Life Sciences and Biotechnology, Korea University, Seoul 136-701, Korea
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23
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Srinivasan SV, Mayhew CN, Schwemberger S, Zagorski W, Knudsen ES. RB loss promotes aberrant ploidy by deregulating levels and activity of DNA replication factors. J Biol Chem 2007; 282:23867-77. [PMID: 17556357 DOI: 10.1074/jbc.m700542200] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022] Open
Abstract
The retinoblastoma tumor suppressor (RB) is functionally inactivated in many human cancers. Classically, RB functions to repress E2F-mediated transcription and inhibit cell cycle progression. Consequently, RB ablation leads to loss of cell cycle control and aberrant expression of E2F target genes. Emerging evidence indicates a role for RB in maintenance of genomic stability. Here, mouse adult fibroblasts were utilized to demonstrate that aberrant DNA content in RB-deficient cells occurs concomitantly with an increase in levels and chromatin association of DNA replication factors. Furthermore, following exposure to nocodazole, RB-proficient cells arrest with 4 n DNA content, whereas RB-deficient cells bypass the mitotic block, continue DNA synthesis, and accumulate cells with higher ploidy and micronuclei. Under this condition, RB-deficient cells also retain high levels of tethered replication factors, MCM7 and PCNA, indicating that DNA replication occurs in these cells under nonpermissive conditions. Exogenous expression of replication factors Cdc6 or Cdt1 in RB-proficient cells does not recapitulate the RB-deficient cell phenotype. However, ectopic E2F expression in RB-proficient cells elevated ploidy and bypassed the response to nocodazole-induced cessation of DNA replication in a manner analogous to RB loss. Collectively, these results demonstrate that deregulated S phase control is a key mechanism by which RB-deficient cells acquire elevated ploidy.
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Affiliation(s)
- Seetha V Srinivasan
- Department of Cell and Cancer Biology, Vontz Center for Molecular Studies, Ohio 45267, USA
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24
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Mathivanan J, Rohini K, Gope ML, Anandh B, Gope R. Altered structure and deregulated expression of the tumor suppressor gene retinoblastoma (RB1) in human brain tumors. Mol Cell Biochem 2007; 302:67-77. [PMID: 17318405 DOI: 10.1007/s11010-007-9428-3] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/14/2006] [Accepted: 02/02/2007] [Indexed: 12/24/2022]
Abstract
A total of 40 human brain tumor samples were analyzed for tumor-specific alterations at the RB1 gene locus. Gliomas were more prevalent in younger males and meningiomas in older females. Southern blot analysis revealed loss of heterozygosity (LOH) at the intron 1 locus of RB1 gene in 19.4% of informative cases and this is the first report showing LOH at this locus in human brain tumors. Levels of RB1 mRNA and protein, pRb, and the percentage of hyperphosphorylated form of pRb were also analyzed in these tumors. Normal human fibroblast cell line WI38 was used as control in northern and western analysis. Normal sized RB1 mRNA and protein were present in all the tumor samples. Majority of the gliomas had 2.0-fold or higher levels of RB1 mRNA and most meningiomas had less than 2.0-fold of RB1 mRNA compared to control WI38 cells. The total pRb levels were 2.0-fold or higher in all the tumor samples compared to control. More than 50% of pRb existed in hyperphosphorylated form in all gliomas except two. However, six out of 13 meningiomas had less than 50% of total pRb in the hyperphosphorylated form. These results indicate that the increased percentage of hyperphosphorylated form of pRb in gliomas could provide growth advantage to these tumors. Presence of LOH at the RB1 gene locus and the increased levels of RB1 RNA and protein and increased percentage of hyperphosphorylated form of pRb are indicative of an overall deregulation of pRb pathway in human brain tumors.
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Affiliation(s)
- J Mathivanan
- Department of Human Genetics, National Institute of Mental Health and Neurosciences (NIMHANS), Bangalore, 560 029, India
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25
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Schmitz NMR, Hirt A, Aebi M, Leibundgut K. Limited redundancy in phosphorylation of retinoblastoma tumor suppressor protein by cyclin-dependent kinases in acute lymphoblastic leukemia. THE AMERICAN JOURNAL OF PATHOLOGY 2006; 169:1074-9. [PMID: 16936279 PMCID: PMC1698824 DOI: 10.2353/ajpath.2006.051137] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
Abstract
Cyclin-dependent kinases (CDKs) successively phosphorylate the retinoblastoma protein (RB) at the restriction point in G1 phase. Hyperphosphorylation results in functional inactivation of RB, activation of the E2F transcriptional program, and entry of cells into S phase. RB unphosphorylated at serine 608 has growth suppressive activity. Phosphorylation of serines 608/612 inhibits binding of E2F-1 to RB. In Nalm-6 acute lymphoblastic leukemia extracts, serine 608 is phosphorylated by CDK4/6 complexes but not by CDK2. We reasoned that phosphorylation of serines 608/612 by redundant CDKs could accelerate phospho group formation and determined which G1 CDK contributes to serine 612 phosphorylation. Here, we report that CDK4 complexes from Nalm-6 extracts phosphorylated in vitro the CDK2-preferred serine 612, which was inhibited by p16INK4a, and fascaplysin. In contrast, serine 780 and serine 795 were efficiently phosphorylated by CDK4 but not by CDK2. The data suggest that the redundancy in phosphorylation of RB by CDK2 and CDK4 in Nalm-6 extracts is limited. Serine 612 phosphorylation by CDK4 also occurred in extracts of childhood acute lymphoblastic leukemia cells but not in extracts of mobilized CD34+ hemopoietic progenitor cells. This phenomenon could contribute to the commitment of childhood acute lymphocytic leukemia cells to proliferate and explain their refractoriness to differentiation-inducing agents.
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Affiliation(s)
- Nicole M R Schmitz
- Department of Clinical Research, University of Bern, and the Department of Paediatrics, University Children's Hospital Inselspital, Switzerland.
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Abstract
The Rb protein is a tumor suppressor, which plays a pivotal role in the negative control of the cell cycle and in tumor progression. It has been shown that Rb protein (pRb) is responsible for a major G1 checkpoint, blocking S-phase entry and cell growth. The retinoblastoma family includes three members, Rb/p105, p107 and Rb2/p130, collectively referred to as 'pocket proteins'. The pRb protein represses gene transcription, required for transition from G1 to S phase, by directly binding to the transactivation domain of E2F and by binding to the promoter of these genes as a complex with E2F. pRb represses transcription also by remodeling chromatin structure through interaction with proteins such as hBRM, BRG1, HDAC1 and SUV39H1, which are involved in nucleosome remodeling, histone acetylation/deacetylation and methylation, respectively. Loss of pRb functions may induce cell cycle deregulation and so lead to a malignant phenotype. Gene inactivation of pRB through chromosomal mutations is one of the principal reasons for retinoblastoma tumor development. Functional inactivation of pRb by viral oncoprotein binding is also shown in many neoplasias such as cervical cancer, mesothelioma and AIDS-related Burkitt's lymphoma.
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Affiliation(s)
- C Giacinti
- Sbarro Institute for Cancer Research and Molecular Medicine, Temple University, Philadelphia, PA 19122, USA
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Murphree AL, Samuel MA, Harbour JW, Mansfield NC. Retinoblastoma. Retina 2006. [DOI: 10.1016/b978-0-323-02598-0.50028-8] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
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Nagano K, Itagaki C, Izumi T, Nunomura K, Soda Y, Tani K, Takahashi N, Takenawa T, Isobe T. Rb plays a role in survival of Abl-dependent human tumor cells as a downstream effector of Abl tyrosine kinase. Oncogene 2005; 25:493-502. [PMID: 16158058 DOI: 10.1038/sj.onc.1208996] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
The retinoblastoma (Rb) gene product is a tumor suppressor that is mutated or inactivated in many types of human cancers. Although Rb is known to be an upstream negative regulator of Abl protein tyrosine kinase, we propose here that Rb also functions as a downstream effector of Abl that plays a positive role in survival of Abl-dependent human tumor cells, including Bcr/Abl-positive chronic myelogenous leukemia (CML). We show that Rb is constitutively phosphorylated at tyrosine in Abl-dependent tumor cells, and that Abl phosphorylates Rb specifically at Y805 within the C-terminal domain of the molecule. We also show that ectopic expression of Rb induces apoptosis in Abl-dependent tumor cells by inhibiting the Abl tyrosine kinase activity, and that Rb-induced apoptosis is compromised by Abl-catalysed phosphorylation of Rb at Y805. Furthermore, the silencing of endogenous Rb by RNA interference induced apoptosis in Abl-dependent tumor cells. Thus, our findings suggest that Abl-catalysed tyrosine phosphorylation of Rb is necessary for survival of Abl-dependent human tumor cells, and raises the possibility that this phosphorylated Rb can be a molecular target for cancer therapy aimed at inducing apoptosis of Abl-dependent tumor cells, such as Bcr/Abl-positive CML.
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Affiliation(s)
- K Nagano
- Division of Proteomics Research, Institute of Medical Science, University of Tokyo, Minato-ku, Japan
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30
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Thomas R, Prabhu PDAH, Mathivanan J, Sivakumar D, Jayakumar PN, Devi BI, Satish S, Sastry KVR, Gope R. Altered structure and expression of RB1 gene and increased phosphorylation of pRb in human vestibular schwannomas. Mol Cell Biochem 2005; 271:113-21. [PMID: 15881662 DOI: 10.1007/s11010-005-5617-0] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
Abstract
Tumor-specific alterations at the RB1 gene locus in 30 human vestibular schwannomas including 10 NF2 and 20 sporadic cases were analysed. Southern blot analysis of DNA from these samples revealed loss of heterozygosity (LOH) at the RB1 locus in 6 of 24 informative cases (25%) compared to normal blood DNAs from the same patients. Northern blot analysis showed normal size RB1 mRNA in all the tumor samples. However, there was a 2-5-fold increase in the level of expression of the RB1 gene in all the tumor samples compared to the WI38 cell line which was used as control. Western blot analysis of the RB1 protein, pRb showed a 2.5-5-fold increase in the level of total pRb as compared to normal WI38 cell line. Sixty five to seventy five percent of the total pRb were in phosphorylated form in most tumors. The LOH at the RB1 gene locus suggests genetic instability in these patients. Further, increased levels of RB1 mRNA, total pRb and the phosphorylated form of pRb suggests that RB1 gene in these tumors may have anti-apoptotic function. These results suggest that the RB1 gene has a major role in the development of human vestibular schwannomas.
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Affiliation(s)
- R Thomas
- Department of Human Genetics, National Institute of Mental Health and Neuro Sciences (NIMHANS), Bangalore, India
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31
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Talos F, Mena P, Fingerle-Rowson G, Moll U, Petrenko O. MIF loss impairs Myc-induced lymphomagenesis. Cell Death Differ 2005; 12:1319-28. [PMID: 15947793 DOI: 10.1038/sj.cdd.4401653] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022] Open
Abstract
Macrophage migration inhibitory factor (MIF) is a potent regulator of inflammation and cell growth. Using the Emu-Myc lymphoma mouse model, we demonstrate that loss of MIF markedly delays the onset of B-cell lymphoma development in vivo. The molecular basis for this MIF-loss-induced phenotype is the perturbed DNA-binding activity of E2F factors and the concomitantly enhanced tumor suppressor activity of the p53 pathway. Accordingly, premalignant MIF-null Emu-Myc B-cells are predisposed to delayed S-phase progression and increased apoptosis. MIF-deficient lymphomas that do arise under these conditions contain frequent ARF deletions and p53 inactivating mutations. Conversely, MIF expression is retained in tumors developed by wild-type Emu-Myc animals, and the presence of one or both MIF alleles is sufficient to accelerate the development of Myc-induced lymphomas. Collectively, these results indicate that MIF promotes Myc-mediated tumorigenesis, at least in the B-lymphoid compartment, and implicate MIF as a mediator of malignant cell growth in vivo.
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Affiliation(s)
- F Talos
- Department of Pathology, State University of New York at Stony Brook, Stony Brook, NY 11794, USA
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32
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Tan L, Fu XY, Liu SQ, Li HH, Hong Y, Wu MC, Wang HY. Expression of p28GANK and its correlation with RB in human hepatocellular carcinoma. Liver Int 2005; 25:667-76. [PMID: 15910504 DOI: 10.1111/j.1478-3231.2005.01003.x] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/07/2023]
Abstract
BACKGROUND Aberrance of retinoblastoma protein (RB) signal pathway is known to play an important role in the carcinogenesis of human hepatocellular carcinoma (HCC). p28GANK, originally purified from human 26S proteasome as a non-ATPase subunit, was recently found in HCC and shown to interact with RB. The aim of this study was to investigate the expression profile of p28GANK and its correlation with RB in HCC. METHODS The expression of p28GANK was evaluated in 55 surgically resected HCCs by immunohistochemistry (IHC), and the associations were explored between p28GANK level and clinicopathologic features as well as tumor suppressor RB. Western blotting was performed to determine p28GANK expression level in 12 HCCs. Immunofluorescence stainings of p28GANK and RB in U2-OS cells were examined by confocal microscopy. RESULTS Positive p28GANK cytoplasmic staining was recognized in 55 HCCs. Nuclear positive occurrence of p28(GANK) in HCCs was more frequent than paracancerous hepatic tissues (P < 0.05). The overexpression probability of p28GANK was inversely associated with Edmonson's grade: overexpression occurred in nine out of 11 (81.8%), 22 out of 35 (62.9%) and two out of nine (22.2%) in I-II, III and IV graded cases, respectively (P = 0.004). Total cellular expression of p28GANK had curvilinear correlation with the nuclear expression of RB (r = 0.475, P = 0.019), while the nuclear expression of p28GANK had not. Western blot analysis showed that up-regulation of p28GANK expression was found in nine out of 12 HCCs compared with paracancerous liver tissues. Exogenously expressed p28GANK colocalized with RB in cytoplasm of U2-OS cells. CONCLUSIONS These results confirm the role of p28GANK as a highly expressed oncoprotein in HCC by in situ examination. Its overexpression correlates with the differentiation status of HCC. The whole cellular p28GANK activation, not nuclear portion only, influences the alteration of RB. Underlying nuclear translocation of p28GANK may contribute to the counteraction against RB through a feed back loop. These data provide new evidence for p28GANK to be used as a promising drug target of a therapeutic agent against HCC.
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Affiliation(s)
- Lu Tan
- International Cooperation Laboratory on Signal Transduction, Eastern Hepatobiliary Surgery Institute, Second Military Medical University, Shanghai, China
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33
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Abstract
The retinoblastoma protein (pRB) and the pRB-related p107 and p130 comprise the 'pocket protein' family of cell cycle regulators. These proteins are best known for their roles in restraining the G1-S transition through the regulation of E2F-responsive genes. pRB and the p107/p130 pair are required for the repression of distinct sets of genes, potentially due to their selective interactions with E2Fs that are engaged at specific promoter elements. In addition to regulating E2F-responsive genes in a reversible manner, pocket proteins contribute to silencing of such genes in cells that are undergoing senescence or differentiation. Pocket proteins also affect the G1-S transition through E2F-independent mechanisms, such as by inhibiting Cdk2 or by stabilizing p27(Kip1), and they are implicated in the control of G0 exit, the spatial organization of replication, and genomic rereplication. New insights into pocket protein regulation have also been obtained. Kinases previously thought to be crucial to pocket protein phosphorylation have been shown to be redundant, and new modes of phosphorylation and dephosphorylation have been identified. Despite these advances, much remains to be learned about the pocket proteins, particularly with regard to their developmental and tumor suppressor functions. Thus continues the story of the pocket proteins and the cell cycle.
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Affiliation(s)
- David Cobrinik
- Dyson Vision Research Institute and Department of Ophthalmology, Weill Medical College of Cornell University, 1300 York Avenue, LC303, New York, NY 10021, USA.
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34
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Petrenko O, Moll UM. Macrophage migration inhibitory factor MIF interferes with the Rb-E2F pathway. Mol Cell 2005; 17:225-36. [PMID: 15664192 DOI: 10.1016/j.molcel.2004.11.052] [Citation(s) in RCA: 67] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/02/2004] [Revised: 10/08/2004] [Accepted: 11/19/2004] [Indexed: 11/17/2022]
Abstract
Macrophage migration inhibitory factor (MIF) is implicated in the regulation of inflammation and cell growth. We previously showed that MIF is a potent modulator of p53- and E2F-dependent pathways that are activated in response to oncogenic signaling. Here, we characterize the functional link between MIF and E2F transcription factors. Our results demonstrate that MIF-deficient cells exhibit E2F-dependent growth alterations and reduced susceptibility to oncogenic transformation. The basis for this transformation resistance is a perturbed function of the C-terminal Rb binding region of E2F4. However, inactivation of Rb or substitution of the E2F4 C-terminal domain by the E2F1 C-terminal region rescues the transformation defect. Importantly, the involvement of E2F factors in DNA replication rather than in regulation of transcription determines their oncogenic properties in the context of MIF deficiency. A proinflammatory molecule interfering with tumor suppression and DNA replication provides a compelling molecular link for the association of chronic inflammation and tumorigenesis.
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Affiliation(s)
- Oleksi Petrenko
- Department of Pathology, Health Science Center, State University of New York at Stony Brook, Stony Brook, NY 11794, USA.
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35
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Lieman JH, Worley LA, Harbour JW. Loss of Rb-E2F Repression Results in Caspase-8-mediated Apoptosis through Inactivation of Focal Adhesion Kinase. J Biol Chem 2005; 280:10484-90. [PMID: 15640164 DOI: 10.1074/jbc.m409371200] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/17/2023] Open
Abstract
Molecular hardwiring of the cell cycle to the apoptotic machinery is a critical tumor suppressor mechanism for eliminating hyperproliferative cells. Deregulation of the Rb-E2F repressor complex by genetic deletion or functional inhibition of Rb triggers apoptosis through both the intrinsic (caspase-9 mediated) and extrinsic (caspase-8 mediated) death pathways. Induction of the intrinsic pathway has been studied extensively and involves release of free E2F and direct transcriptional activation of E2F-responsive apoptotic genes such as ARF, APAF1, and CASP9. In contrast, the mechanisms leading to activation of the extrinsic pathway are less well understood. There is growing evidence that Rb-E2F perturbation induces the extrinsic pathway, at least in part, through derepression (as opposed to transactivation) of apoptotic genes. Here, we explore this possibility using cells in which Rb-E2F complexes are displaced from promoters without stimulating E2F transactivation. This derepression of Rb-E2F-regulated genes leads to apoptosis through inactivation of focal adhesion kinase and activation of caspase-8. These findings reveal a new mechanistic link between Rb-E2F and the extrinsic (caspase 8-mediated) apoptotic pathway.
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Affiliation(s)
- Jonathan H Lieman
- Department of Ophthalmology & Visual Sciences, Washington University School of Medicine, 660 South Euclid Ave, St. Louis, Missouri 63110, USA
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36
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Adegbola O, Pasternack GR. Phosphorylated retinoblastoma protein complexes with pp32 and inhibits pp32-mediated apoptosis. J Biol Chem 2005; 280:15497-502. [PMID: 15716273 DOI: 10.1074/jbc.m411382200] [Citation(s) in RCA: 34] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The retinoblastoma gene product (Rb) is a tumor suppressor that affects apoptosis paradoxically. Most sporadic cancers inactivate Rb by preferentially targeting the pathway that regulates Rb phosphorylation, resulting in resistance to apoptosis; this contrasts with Rb inactivation by mutation, which is associated with high rates of apoptosis. How phosphorylated Rb protects cells from apoptosis is not well understood, but there is evidence that Rb may sequester a pro-apoptotic nuclear factor. pp32 (ANP32A) is a pro-apoptotic nuclear phosphoprotein, the expression of which is commonly increased in cancer. We report that hyperphosphorylated Rb interacts with pp32 but not with the closely related proteins pp32r1 and pp32r2. We further demonstrate that pp32-Rb interaction inhibits the apoptotic activity of pp32 and stimulates proliferation. These results suggest a mechanism whereby cancer cells gain both a proliferative and survival advantage when Rb is inactivated by hyperphosphorylation.
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Affiliation(s)
- Onikepe Adegbola
- Division of Molecular Pathology, Department of Pathology, The Johns Hopkins University School of Medicine, Baltimore, Maryland 21205, USA
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37
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Loercher AE, Tank EMH, Delston RB, Harbour JW. MITF links differentiation with cell cycle arrest in melanocytes by transcriptional activation of INK4A. ACTA ACUST UNITED AC 2004; 168:35-40. [PMID: 15623583 PMCID: PMC2171666 DOI: 10.1083/jcb.200410115] [Citation(s) in RCA: 180] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Abstract
Cell cycle exit is required for proper differentiation in most cells and is critical for normal development, tissue homeostasis, and tumor suppression. However, the mechanisms that link cell cycle exit with differentiation remain poorly understood. Here, we show that the master melanocyte differentiation factor, microphthalmia transcription factor (MITF), regulates cell cycle exit by activating the cell cycle inhibitor INK4A, a tumor suppressor that frequently is mutated in melanomas. MITF binds the INK4A promoter, activates p16Ink4a mRNA and protein expression, and induces retinoblastoma protein hypophosphorylation, thereby triggering cell cycle arrest. This activation of INK4A was required for efficient melanocyte differentiation. Interestingly, MITF was also required for maintaining INK4A expression in mature melanocytes, creating a selective pressure to escape growth inhibition by inactivating INK4A. These findings demonstrate that INK4A can be regulated by a differentiation factor, establish a mechanistic link between melanocyte differentiation and cell cycle exit, and potentially explain the tissue-specific tendency for INK4A mutations to occur in melanoma.
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Affiliation(s)
- Amy E Loercher
- Department of Ophthalmology and Visual Sciences, Washington University School of Medicine, St. Louis, MO 63110, USA
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38
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Hoek K, Rimm DL, Williams KR, Zhao H, Ariyan S, Lin A, Kluger HM, Berger AJ, Cheng E, Trombetta ES, Wu T, Niinobe M, Yoshikawa K, Hannigan GE, Halaban R. Expression profiling reveals novel pathways in the transformation of melanocytes to melanomas. Cancer Res 2004; 64:5270-82. [PMID: 15289333 DOI: 10.1158/0008-5472.can-04-0731] [Citation(s) in RCA: 399] [Impact Index Per Article: 20.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/11/2023]
Abstract
Affymetrix and spotted oligonucleotide microarrays were used to assess global differential gene expression comparing normal human melanocytes with six independent melanoma cell strains from advanced lesions. The data, validated at the protein level for selected genes, confirmed the overexpression in melanoma cells relative to normal melanocytes of several genes in the growth factor/receptor family that confer growth advantage and metastasis. In addition, novel pathways and patterns of associated expression in melanoma cells not reported before emerged, including the following: (a) activation of the NOTCH pathway; (b) increased Twist expression and altered expression of additional transcriptional regulators implicated in embryonic development and epidermal/mesenchymal transition; (c) coordinated activation of cancer/testis antigens; (d) coordinated down-regulation of several immune modulation genes, in particular in the IFN pathways; (e) down-regulation of several genes implicated in membrane trafficking events; and (f) down-regulation of growth suppressors, such as the Prader-Willi gene NECDIN, whose function was confirmed by overexpression of ectopic Flag-necdin. Validation of differential expression using melanoma tissue microarrays showed that reduced ubiquitin COOH-terminal esterase L1 in primary melanoma is associated with worse outcome and that increased expression of the basic helix-loop-helix protein Twist is associated with worse outcome. Some differentially expressed genes reside on chromosomal regions displaying common loss or gain in melanomas or are known to be regulated by CpG promoter methylation. These results provide a comprehensive view of changes in advanced melanoma relative to normal melanocytes and reveal new targets that can be used in assessing prognosis, staging, and therapy of melanoma patients.
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Affiliation(s)
- Keith Hoek
- Department of Molecular Biophysics and Biochemistry, Yale University School of Medicine, 15 York Street, New Haven, CT 06520-8059, USA
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39
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Abstract
Phosphorylation of target proteins by cyclin D1-Cdk4 requires both substrate docking and kinase activity. In addition to the ability of cyclin D1-Cdk4 to catalyze the phosphorylation of consensus sites within the primary amino acid sequence of a substrate, maximum catalytic activity requires the enzyme complex to anchor at a site remote from the phospho-acceptor site. A novel Cdk4 docking motif has been defined within a stretch of 19 amino acids from the C-terminal domain of the Rb protein that are essential for Cdk4 binding. Mutation or deletion of the docking motif prevents Cdk4-dependent phosphorylation of full-length Rb protein or C-terminal Rb fragments in vitro and in cells, while a peptide encompassing the Cdk4 docking motif specifically inhibits Cdk4-dependent phosphorylation of Rb. Cyclin D1-Cdk4 can overcome the growth-suppressive activity of Rb in both cell cycle progression and colony formation assays; however, while mutants of Rb in which the Cdk4 docking site has been either deleted or mutated retain growth suppressor activity, they are resistant to inactivation by cyclin D1-Cdk4. Finally, binding of Cdk4 to its docking site can inhibit cleavage of exogenous and endogenous Rb in response to distinct apoptotic signals. The Cdk4 docking motif in Rb gives insight into the mechanism by which enzyme specificity is ensured and highlights a role for Cdk4 docking in maintaining the Rb protein in a form that favors cell survival rather than apoptosis.
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Affiliation(s)
- Maura Wallace
- CRUK Laboratories, University of Dundee Medical School, Dundee DD1 9SY, United Kingdom
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40
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Garnovskaya MN, Mukhin YV, Vlasova TM, Grewal JS, Ullian ME, Tholanikunnel BG, Raymond JR. Mitogen-induced Rapid Phosphorylation of Serine 795 of the Retinoblastoma Gene Product in Vascular Smooth Muscle Cells Involves ERK Activation. J Biol Chem 2004; 279:24899-905. [PMID: 15069084 DOI: 10.1074/jbc.m311622200] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023] Open
Abstract
We examined the relationship between mitogen-activated MEK (mitogen and extracellular signal-regulated protein kinase kinase) and phosphorylation of the gene product encoded by retinoblastoma (hereafter referred to as Rb) in vascular smooth muscle cells. Brief treatment of the cells with 100 nm angiotensin II or 1 microm serotonin resulted in serine phosphorylation of Rb that was equal in magnitude to that induced by treating cells for 20 h with 10% fetal bovine serum ( approximately 3 x basal). There was no detectable rapid phosphorylation of two close cousins of Rb, p107 and p130. Phosphorylation state-specific antisera demonstrated that the rapid phosphorylation occurred on Ser(795), but not on Ser(249), Thr(252), Thr(373), Ser(780), Ser(807), or Ser(811). Phosphorylation of Rb Ser(795) peaked at 10 min, lagging behind phosphorylation of MEK and ERK (extracellular signal-regulated protein kinase). Rb Ser(795) phosphorylation could be blocked by PD98059, a MEK inhibitor, and greatly attenuated by apigenin, an inhibitor of the Ras --> Raf --> MEK --> ERK pathway. The effect also appears to be mediated by CDK4. Immunoprecipitation/immunoblot studies revealed that serotonin and angiotensin II induced complex formation between CDK4, cyclin D1, and phosphorylated ERK. These studies show a rapid, novel, and selective phosphorylation of Rb Ser(795) by mitogens and demonstrate an unexpected rapid linkage between the actions of the Ras --> Raf --> MEK --> ERK pathway and the phosphorylation state of Rb.
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Affiliation(s)
- Maria N Garnovskaya
- Medical and Research Services of the Ralph H. Johnson Veterans Affairs Medical Center and Department of Medicine (Nephrology Division) of the Medical University of South Carolina, Charleston, South Carolina 29425, USA.
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41
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Young AP, Longmore GD. Differential regulation of apoptotic genes by Rb in human versus mouse cells. Oncogene 2004; 23:2587-99. [PMID: 15048095 DOI: 10.1038/sj.onc.1207330] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/16/2023]
Abstract
The retinoblastoma protein (Rb) controls cellular proliferation and suppresses tumor formation through its effects upon E2F transcriptional regulation of the cell cycle. Unexpectedly, however, in proliferating human cells, Rb was present at the promoters of eight of eight E2F-regulated apoptotic genes tested, but zero of six E2F-regulated cell cycle genes tested. Binding of apoptotic gene promoters by Rb was constitutive, and inhibition of Rb in human cells by E2Fdb or E1A expression resulted in induction of these apoptotic genes and efficient cell death. E1A induced apoptosis much more efficiently in human fibroblasts than in mouse fibroblasts, suggesting a difference in susceptibility to loss of Rb function between human cells and mouse cells. Abrogation of Rb function in mouse cells did not induce expression of these apoptotic genes. Underlying this species difference in susceptibility to apoptosis following loss of Rb function was the absence of Rb on apoptotic gene promoters in mouse cells. Rb protein levels were 20-35-fold higher in primary human cells than in primary mouse cells. The constitutive repression of a multitude of apoptotic genes by Rb in human cells but not in mouse cells may provide a partial explanation for the well-known difference between human and mouse cells in transformation and tumorigenic potential.
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Affiliation(s)
- Arthur P Young
- Department of Medicine, Washington University School of Medicine, 4940 Parkview Place, St Louis, MO 63110, USA
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42
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Suzuki S, Chuang LF, Doi RH, Chuang RY. Morphine suppresses lymphocyte apoptosis by blocking p53-mediated death signaling. Biochem Biophys Res Commun 2003; 308:802-8. [PMID: 12927789 DOI: 10.1016/s0006-291x(03)01472-4] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Opiates such as morphine or heroin may promote cell apoptosis and cause dysfunction of immune cells. In simian immunodeficiency virus (SIV)-infected lymphocytic cells, however, morphine may protect the cells from apoptotic lysis and allow the virus to continue to replicate. To further explore this apparently antithetical effect of opiates, we evaluated in the present study the effects of morphine on human lymphocytic CEM x174 cells induced to undergo apoptosis in the presence of actinomycin D. It was found that induction of apoptosis (characterized by DNA laddering) by actinomycin D was accompanied by a stimulation of the expression of active (phosphorylated) form of p53. Pretreatment of the cells with 10nM morphine caused a transient, naloxone-reversible suppression of the appearance of activated p53 and the generation of DNA laddering. Parallel evaluation of the growth of CEM x174 indicated that morphine treatment delays the inception of cell death triggered by actinomycin D. Inasmuch as Bcl-2 suppresses while Bax accelerates apoptosis, treatment of cells with morphine reduced the expression of Bax and enhanced the expression of Bcl-2. Taken together, morphine, through binding at the opioid receptor, may protect lymphocytic cells from apoptotic lysis if cell death is initiated by apoptosis-inducing agents such as human immunodeficiency virus (HIV), SIV or actinomycin D.
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Affiliation(s)
- Shunji Suzuki
- Department of Medical Pharmacology and Toxicology, School of Medicine, University of California, Davis, CA 95616, USA
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