1
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Nag A, Mafi A, Das S, Yu MB, Alvarez-Villalonga B, Kim SK, Su Y, Goddard WA, Heath JR. Stereochemical engineering yields a multifunctional peptide macrocycle inhibitor of Akt2 by fine-tuning macrocycle-cell membrane interactions. Commun Chem 2023; 6:95. [PMID: 37202473 DOI: 10.1038/s42004-023-00890-w] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/17/2022] [Accepted: 04/26/2023] [Indexed: 05/20/2023] Open
Abstract
Macrocycle peptides are promising constructs for imaging and inhibiting extracellular, and cell membrane proteins, but their use for targeting intracellular proteins is typically limited by poor cell penetration. We report the development of a cell-penetrant high-affinity peptide ligand targeted to the phosphorylated Ser474 epitope of the (active) Akt2 kinase. This peptide can function as an allosteric inhibitor, an immunoprecipitation reagent, and a live cell immunohistochemical staining reagent. Two cell penetrant stereoisomers were prepared and shown to exhibit similar target binding affinities and hydrophobic character but 2-3-fold different rates of cell penetration. Experimental and computational studies resolved that the ligands' difference in cell penetration could be assigned to their differential interactions with cholesterol in the membrane. These results expand the tool kit for designing new chiral-based cell-penetrant ligands.
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Affiliation(s)
- Arundhati Nag
- California Institute of Technology, Pasadena, CA, USA
- Clark University, Worcester, MA, USA
| | - Amirhossein Mafi
- Materials and Process Simulation Center (139-74), California Institute of Technology, Pasadena, CA, USA
| | - Samir Das
- California Institute of Technology, Pasadena, CA, USA
- Clark University, Worcester, MA, USA
| | - Mary Beth Yu
- California Institute of Technology, Pasadena, CA, USA
| | | | - Soo-Kyung Kim
- Materials and Process Simulation Center (139-74), California Institute of Technology, Pasadena, CA, USA
| | - Yapeng Su
- California Institute of Technology, Pasadena, CA, USA
- Institute for Systems Biology, Seattle, WA, USA
| | - William A Goddard
- Materials and Process Simulation Center (139-74), California Institute of Technology, Pasadena, CA, USA
| | - James R Heath
- California Institute of Technology, Pasadena, CA, USA.
- Institute for Systems Biology, Seattle, WA, USA.
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2
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Machilin D Promotes Apoptosis and Autophagy, and Inhibits Necroptosis in Human Oral Squamous Cell Carcinoma Cells. Int J Mol Sci 2023; 24:ijms24054576. [PMID: 36902006 PMCID: PMC10002565 DOI: 10.3390/ijms24054576] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/31/2022] [Revised: 02/13/2023] [Accepted: 02/24/2023] [Indexed: 03/03/2023] Open
Abstract
Oral squamous cell carcinoma (OSCC) accounts for about 90% of all head and neck cancers, the prognosis is very poor, and there are no effective targeted therapies. Herein, we isolated Machilin D (Mach), a lignin, from the roots of Saururus chinensis (S. chinensis) and assessed its inhibitory effects on OSCC. Herein, Mach had significant cytotoxicity against human OSCC cells and showed inhibitory effects against cell adhesion, migration, and invasion by inhibiting adhesion molecules, including the FAK/Src pathway. Mach suppressed the PI3K/AKT/mTOR/p70S6K pathway and MAPKs, leading to apoptotic cell death. We investigated other modes of programmed cell death in these cells and found that Mach increased LC3I/II and Beclin1 and decreased p62, leading to autophagosomes, and suppressed the necroptosis-regulatory proteins RIP1 and MLKL. Our findings provide evidence that the inhibitory effects of Mach against human YD-10B OSCC cells are related to the promotion of apoptosis and autophagy and inhibition of necroptosis and are mediated via focal adhesion molecules.
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3
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Nuclear S6K1 Enhances Oncogenic Wnt Signaling by Inducing Wnt/β-Catenin Transcriptional Complex Formation. Int J Mol Sci 2022; 23:ijms232416143. [PMID: 36555784 PMCID: PMC9785994 DOI: 10.3390/ijms232416143] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/24/2022] [Revised: 12/09/2022] [Accepted: 12/15/2022] [Indexed: 12/23/2022] Open
Abstract
Ribosomal protein S6 kinase 1 (S6K1), a key downstream effector of the mammalian target of rapamycin (mTOR), regulates diverse functions, such as cell proliferation, cell growth, and protein synthesis. Because S6K1 was previously known to be localized in the cytoplasm, its function has been mainly studied in the cytoplasm. However, the nuclear localization and function of S6K1 have recently been elucidated and other nuclear functions are expected to exist but remain elusive. Here, we show a novel nuclear role of S6K1 in regulating the expression of the Wnt target genes. Upon activation of the Wnt signaling, S6K1 translocated from the cytosol into the nucleus and subsequently bound to β-catenin and the cofactors of the Wnt/β-catenin transcriptional complex, leading to the upregulation of the Wnt target genes. The depletion or repression of S6K1 downregulated the Wnt target gene expression by inhibiting the formation of the Wnt/β-catenin transcriptional complex. The S6K1-depleted colon cancer cell lines showed lower transcription levels of the Wnt/β-catenin target genes and a decrease in the cell proliferation and invasion compared to the control cell lines. Taken together, these results indicate that nuclear S6K1 positively regulates the expression of the Wnt target genes by inducing the reciprocal interaction of the subunits of the transcriptional complex.
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4
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Yun HM, Park JE, Lee JY, Park KR. Latifolin, a Natural Flavonoid, Isolated from the Heartwood of Dalbergia odorifera Induces Bioactivities through Apoptosis, Autophagy, and Necroptosis in Human Oral Squamous Cell Carcinoma. Int J Mol Sci 2022; 23:13629. [PMID: 36362414 PMCID: PMC9655104 DOI: 10.3390/ijms232113629] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/03/2022] [Revised: 11/04/2022] [Accepted: 11/04/2022] [Indexed: 08/13/2023] Open
Abstract
Oral squamous cell carcinoma (OSCC) is the most common malignant neoplasm with frequent metastasis and high mortality in the oral cavity. Plant-derived natural compounds are actively progressing as a trend for cancer treatment. Latifolin (Latif), is a natural flavonoid isolated from the heartwood of Dalbergia odorifera T. Chen (D. odorifera) has been known to have beneficial effects on anti-aging, anti-carcinogenic, anti-inflammatory, and cardio-protective activities. However, the anti-cancer effects of Latif are unknown in OSCC. Herein, as a result of analysis in terms of the aggressive features of OSCCs, we found that Latif significantly inhibited the cell proliferation of human YD-8 and YD-10B OSCCs, and caused the anti-metastatic activities by effectively blocking cell migration, invasion, and adhesion via the inactivation of focal adhesion kinase (FAK)/non-receptor tyrosine kinase (Src). Moreover, we found that Latif induced apoptotic cell death to suppress the cell survival and proliferation of YD-10B OSCCs by targeting PI3K/AKT/mTOR/p70S6K signaling. Finally, we analyzed in terms of autophagy and necroptosis, which are other mechanisms of programmed cell death and survival compared to apoptosis in YD-10B OSCCs. We found that Latif suppressed autophagic-related proteins and autophagosome formation, and also Latif inhibited necroptosis by dephosphorylating necroptosis-regulatory proteins (RIP1, RIP3, and MLKL). Given these findings, our results provided new evidence for Latif's biological effect and mechanism in YD-10B OSCCs, suggesting that Latif may be a new candidate for patients with OSCCs.
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Affiliation(s)
- Hyung-Mun Yun
- Department of Oral and Maxillofacial Pathology, School of Dentistry, Kyung Hee University, Seoul 02447, Korea
| | - Ji Eun Park
- National Development Institute for Korean Medicine, Gyeongsan 38540, Korea
| | - Joon Yeop Lee
- National Development Institute for Korean Medicine, Gyeongsan 38540, Korea
| | - Kyung-Ran Park
- Gwangju Center, Korea Basic Science Institute (KBSI), Gwangju 61751, Korea
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5
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Cheng GJ, Leung EY, Singleton DC. In vitro breast cancer models for studying mechanisms of resistance to endocrine therapy. EXPLORATION OF TARGETED ANTI-TUMOR THERAPY 2022; 3:297-320. [PMID: 36045910 PMCID: PMC9400723 DOI: 10.37349/etat.2022.00084] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/21/2022] [Accepted: 03/24/2022] [Indexed: 11/19/2022] Open
Abstract
The development of endocrine resistance is a common reason for the failure of endocrine therapies in hormone receptor-positive breast cancer. This review provides an overview of the different types of in vitro models that have been developed as tools for studying endocrine resistance. In vitro models include cell lines that have been rendered endocrine-resistant by ex vivo treatment; cell lines with de novo resistance mechanisms, including genetic alterations; three-dimensional (3D) spheroid, co-culture, and mammosphere techniques; and patient-derived organoid models. In each case, the key discoveries, different analysis strategies that are suitable, and strengths and weaknesses are discussed. Certain recently developed methodologies that can be used to further characterize the biological changes involved in endocrine resistance are then emphasized, along with a commentary on the types of research outcomes that using these techniques can support. Finally, a discussion anticipates how these recent developments will shape future trends in the field. We hope this overview will serve as a useful resource for investigators that are interested in understanding and testing hypotheses related to mechanisms of endocrine therapy resistance.
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Affiliation(s)
- Gary J. Cheng
- 1Auckland Cancer Society Research Centre, Faculty of Medical and Health Sciences, The University of Auckland, Auckland 1023, New Zealand
| | - Euphemia Y. Leung
- 1Auckland Cancer Society Research Centre, Faculty of Medical and Health Sciences, The University of Auckland, Auckland 1023, New Zealand 2Maurice Wilkins Centre for Molecular Biodiscovery, The University of Auckland, Auckland 1023, New Zealand 3Department of Molecular Medicine and Pathology, The University of Auckland, Auckland 1023, New Zealand
| | - Dean C. Singleton
- 1Auckland Cancer Society Research Centre, Faculty of Medical and Health Sciences, The University of Auckland, Auckland 1023, New Zealand 2Maurice Wilkins Centre for Molecular Biodiscovery, The University of Auckland, Auckland 1023, New Zealand 3Department of Molecular Medicine and Pathology, The University of Auckland, Auckland 1023, New Zealand
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6
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Megerian MF, Kim JS, Badreddine J, Hong SH, Ponsky LE, Shin JI, Ghayda RA. Melatonin and Prostate Cancer: Anti-tumor Roles and Therapeutic Application. Aging Dis 2022; 14:840-857. [PMID: 37191417 DOI: 10.14336/ad.2022.1010] [Citation(s) in RCA: 7] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/29/2022] [Accepted: 10/10/2022] [Indexed: 11/18/2022] Open
Abstract
Melatonin is an endogenous indoleamine that has been shown to inhibit tumor growth in laboratory models of prostate cancer. Prostate cancer risk has additionally been associated with exogenous factors that interfere with normal pineal secretory activity, including aging, poor sleep, and artificial light at night. Therefore, we aim to expand on the important epidemiological evidence, and to review how melatonin can impede prostate cancer. More specifically, we describe the currently known mechanisms of melatonin-mediated oncostasis in prostate cancer, including those that relate to the indolamine's ability to modulate metabolic activity, cell cycle progression and proliferation, androgen signaling, angiogenesis, metastasis, immunity and oxidative cell status, apoptosis, genomic stability, neuroendocrine differentiation, and the circadian rhythm. The outlined evidence underscores the need for clinical trials to determine the efficacy of supplemental, adjunct, and adjuvant melatonin therapy for the prevention and treatment of prostate cancer.
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7
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Lee JH, Chung KS, Lee HH, Ko D, Kang M, Yoo H, Ahn J, Lee JY, Lee KT. Improved tumor-suppressive effect of OZ-001 combined with cisplatin mediated by mTOR/p70S6K and STAT3 inactivation in A549 human lung cancer cells. Biomed Pharmacother 2021; 142:111961. [PMID: 34329824 DOI: 10.1016/j.biopha.2021.111961] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/02/2021] [Revised: 07/16/2021] [Accepted: 07/22/2021] [Indexed: 02/09/2023] Open
Abstract
We previously reported the anticancer activity of 4-(4-fluorobenzylcarbamoylmethyl)-3-(4-cyclohexylphenyl)-2-[3-(N,N-dimethylureido)-N'-methylpropylamino]-3,4-dihydroquinazoline (OZ-001), a T-type calcium channel (TTCC) blocker, against non-small cell lung cancer (NSCLC) in vitro and in vivo. Here, we evaluated the synergistic effect of OZ-001 and cisplatin on A549 human lung cancer cells and A549 xenograft mice. Our study demonstrated that treatment with OZ-001 and cisplatin sensitized A549 cells to cisplatin and significantly inhibited cell growth, increased the number of terminal deoxynucleotidyl transferase dUTP nick end labeling (TUNEL)-positive cells, and induced poly (ADP-ribose) polymerase (PARP) cleavage in A549 cells and an A549 xenograft tumor mouse model. Moreover, our findings showed that mechanistic target of rapamycin (mTOR), ribosomal protein S6 kinase (p70S6K), and signal transducer and activator of transcription (STAT3) inactivation was required for apoptosis induced by the combination of OZ-001 and cisplatin in in vitro and in vivo experiments. Our results suggest that combined treatment with OZ-001 and cisplatin could potentiate antiproliferative effects via suppression of the mTOR/p70S6K and STAT3 pathways and may be considered a potential therapeutic agent for NSCLC.
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Affiliation(s)
- Jeong-Hun Lee
- Department of Pharmaceutical Biochemistry, College of Pharmacy, Kyung Hee University, 26, Kyungheedae-ro, Seoul 02447, Republic of Korea; Department of Life and Nanopharmaceutical Sciences, Graduate School, Kyung Hee University, 26, Kyungheedae-ro, Seoul 02447, Republic of Korea
| | - Kyung-Sook Chung
- Department of Pharmaceutical Biochemistry, College of Pharmacy, Kyung Hee University, 26, Kyungheedae-ro, Seoul 02447, Republic of Korea
| | - Hwi-Ho Lee
- Department of Pharmaceutical Biochemistry, College of Pharmacy, Kyung Hee University, 26, Kyungheedae-ro, Seoul 02447, Republic of Korea
| | - Dohyeong Ko
- Research Institute for Basic Sciences and Department of Chemistry, College of Sciences, Kyung Hee University, Seoul 02447, Republic of Korea
| | - Minji Kang
- Research Institute for Basic Sciences and Department of Chemistry, College of Sciences, Kyung Hee University, Seoul 02447, Republic of Korea
| | - Ho Yoo
- ONCOZEN Co., Ltd., ONCOZEN R&D Center, C-713, Beobwon-ro 11-gil, Songpa-gu, Seoul 05836, Republic of Korea
| | - JooHoon Ahn
- ONCOZEN Co., Ltd., ONCOZEN R&D Center, C-713, Beobwon-ro 11-gil, Songpa-gu, Seoul 05836, Republic of Korea
| | - Jae Yeol Lee
- Research Institute for Basic Sciences and Department of Chemistry, College of Sciences, Kyung Hee University, Seoul 02447, Republic of Korea.
| | - Kyung-Tae Lee
- Department of Pharmaceutical Biochemistry, College of Pharmacy, Kyung Hee University, 26, Kyungheedae-ro, Seoul 02447, Republic of Korea; Department of Life and Nanopharmaceutical Sciences, Graduate School, Kyung Hee University, 26, Kyungheedae-ro, Seoul 02447, Republic of Korea.
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8
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Zhong W, Tang X, Liu Y, Zhou C, Liu P, Li E, Zhong P, Lv H, Zou Q, Wang M. Benzoxazole Derivative K313 Induces Cell Cycle Arrest, Apoptosis and Autophagy Blockage and Suppresses mTOR/p70S6K Pathway in Nalm-6 and Daudi Cells. Molecules 2020; 25:molecules25040971. [PMID: 32098126 PMCID: PMC7070478 DOI: 10.3390/molecules25040971] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/26/2020] [Revised: 02/17/2020] [Accepted: 02/18/2020] [Indexed: 12/12/2022] Open
Abstract
Benzoxazole derivative K313 has previously been reported to possess anti-inflammatory effects in lipopolysaccharide-induced RAW264.7 macrophages. To date, there have been no related reports on the anticancer effects of K313. In this study, we found that K313 reduced the viability of human B-cell leukemia (Nalm-6) and lymphoma (Daudi) cells in a dose-dependent manner without affecting healthy peripheral blood mononuclear cells (PBMCs) and induced moderate cell cycle arrest at the G0/G1 phase. Meanwhile, K313 mediated cell apoptosis, which was accompanied by the activation of caspase-9, caspase-3, and poly ADP-ribose polymerase (PARP). Furthermore, cells treated with K313 showed a significant decrease in mitochondrial membrane potential (MMP), which may have been caused by the caspase-8-mediated cleavage of Bid, as detected by Western blot analysis. We also found that K313 led to the downregulation of p-p70S6K protein, which plays an important role in cell survival and cell cycle progression. In addition, treatment of these cells with K313 blocked autophagic flux, as reflected in the accumulation of LC3-II and p62 protein levels in a dose- and time-dependent manner. In conclusion, K313 decreases cell viability without affecting normal healthy PBMCs, induces cell cycle arrest and apoptosis, reduces p-p70S6K protein levels, and mediates strong autophagy inhibition. Therefore, K313 and its derivatives could be developed as potential anticancer drugs or autophagy blockers in the future.
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Affiliation(s)
- Wenying Zhong
- Key Laboratory of Bio-resources and Eco-environment of the Ministry of Education, College of Life Sciences, Sichuan University, Chengdu 610065, China;
| | - Xinwen Tang
- Center of Science and Research, Chengdu Medical College, Chengdu 610513, China; (X.T.); (Y.L.)
| | - Yang Liu
- Center of Science and Research, Chengdu Medical College, Chengdu 610513, China; (X.T.); (Y.L.)
| | - Chunyu Zhou
- School of Pharmacy, Chengdu Medical College, Chengdu 610083, China; (C.Z.); (E.L.); (P.Z.); (H.L.)
| | - Pan Liu
- College of Biological Science and Technology, Chengdu Medical College, Chengdu 610500, China;
| | - Enhui Li
- School of Pharmacy, Chengdu Medical College, Chengdu 610083, China; (C.Z.); (E.L.); (P.Z.); (H.L.)
| | - Peilin Zhong
- School of Pharmacy, Chengdu Medical College, Chengdu 610083, China; (C.Z.); (E.L.); (P.Z.); (H.L.)
| | - Haoxue Lv
- School of Pharmacy, Chengdu Medical College, Chengdu 610083, China; (C.Z.); (E.L.); (P.Z.); (H.L.)
| | - Qiang Zou
- Center of Science and Research, Chengdu Medical College, Chengdu 610513, China; (X.T.); (Y.L.)
- Correspondence: (Q.Z.); (M.W.); Tel.: +86-028-62739159 (Q.Z.); +86-028-85418776 (M.W.)
| | - Maolin Wang
- Key Laboratory of Bio-resources and Eco-environment of the Ministry of Education, College of Life Sciences, Sichuan University, Chengdu 610065, China;
- Correspondence: (Q.Z.); (M.W.); Tel.: +86-028-62739159 (Q.Z.); +86-028-85418776 (M.W.)
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9
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Ramzan AA, Bitler BG, Hicks D, Barner K, Qamar L, Behbakht K, Powell T, Jansson T, Wilson H. Adiponectin receptor agonist AdipoRon induces apoptotic cell death and suppresses proliferation in human ovarian cancer cells. Mol Cell Biochem 2019; 461:37-46. [PMID: 31292831 DOI: 10.1007/s11010-019-03586-9] [Citation(s) in RCA: 24] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/25/2018] [Accepted: 07/04/2019] [Indexed: 12/17/2022]
Abstract
We tested the hypothesis that stimulation of adiponectin receptors with the synthetic agonist AdipoRon suppresses proliferation and induces apoptotic death in human high grade serous ovarian tumor cell lines and in ex vivo primary tumors, mediated by activation of 5' AMP-activated protein kinase (AMPK) and inhibition of mechanistic target of rapamycin (mTOR). We determined the effect of AdipoRon on high grade serous ovarian tumor cells lines (OVCAR3, OVCAR4, A2780) and ex vivo primary tumor tissue. Western blotting analysis was performed to examine changes in activation of AMPK and mTOR signaling and flow cytometry was utilized to examine changes in cell cycle progression. Immunofluorescence of cleaved caspase-3 positive cells and flow cytometry of annexin V positive cells were used to determine changes in apoptotic response. The CyQUANT proliferation assay was used to assess cell proliferation. AdipoRon treatment increased AMPK phosphorylation (OVCAR3 P = 0.01; A2780 P = 0.02) but did not significantly alter mTOR activity. AdipoRon induced G1 cell cycle arrest in OVCAR3 (+ 12.1%, P = 0.03) and A2780 (+ 12.0%, P = 0.002) cells. OVCAR3 and OVCAR4 cells treated with AdipoRon underwent apoptosis based on cleaved caspase-3 and annexin V staining. AdipoRon treatment resulted in a dose dependent decrease in cell number versus vehicle treatment in OVCAR3 (-61.2%, P < 0.001), OVCAR4 (-79%, P < 0.001), and A2780 (-56.9%, P < 0.001). Ex vivo culture of primary tumors treated with AdipoRon resulted in an increase in apoptosis measured with cleaved caspase-3 immunohistochemistry. AdipoRon induces activation of AMPK and exhibits an anti-tumor effect in ovarian cancer cell lines and primary tumor via a mTOR-independent pathway.
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MESH Headings
- AMP-Activated Protein Kinases/metabolism
- Apoptosis/drug effects
- Cell Cycle Checkpoints/drug effects
- Cell Line, Tumor
- Cell Proliferation/drug effects
- Female
- Humans
- Mechanistic Target of Rapamycin Complex 1/metabolism
- Mitosis/drug effects
- Models, Biological
- Neoplasm Grading
- Neoplasms, Cystic, Mucinous, and Serous/enzymology
- Neoplasms, Cystic, Mucinous, and Serous/pathology
- Ovarian Neoplasms/enzymology
- Ovarian Neoplasms/pathology
- Piperidines/pharmacology
- Receptors, Adiponectin/agonists
- Receptors, Adiponectin/metabolism
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Affiliation(s)
- Amin A Ramzan
- Division of Gynecologic Oncology, Department of Obstetrics and Gynecology, University of Colorado School of Medicine, 12631 East 17th Avenue B198-6, Aurora, CO, 80045, USA.
| | - Benjamin G Bitler
- Division of Reproductive Sciences, Department of Obstetrics and Gynecology, University of Colorado School of Medicine, Aurora, CO, USA
| | - Douglas Hicks
- Division of Reproductive Sciences, Department of Obstetrics and Gynecology, University of Colorado School of Medicine, Aurora, CO, USA
| | - Kelsey Barner
- Division of Reproductive Sciences, Department of Obstetrics and Gynecology, University of Colorado School of Medicine, Aurora, CO, USA
| | - Lubna Qamar
- Division of Reproductive Sciences, Department of Obstetrics and Gynecology, University of Colorado School of Medicine, Aurora, CO, USA
| | - Kian Behbakht
- Division of Gynecologic Oncology, Department of Obstetrics and Gynecology, University of Colorado School of Medicine, 12631 East 17th Avenue B198-6, Aurora, CO, 80045, USA
| | - Theresa Powell
- Division of Reproductive Sciences, Department of Obstetrics and Gynecology, University of Colorado School of Medicine, Aurora, CO, USA
| | - Thomas Jansson
- Division of Reproductive Sciences, Department of Obstetrics and Gynecology, University of Colorado School of Medicine, Aurora, CO, USA
| | - Heidi Wilson
- Division of Reproductive Sciences, Department of Obstetrics and Gynecology, University of Colorado School of Medicine, Aurora, CO, USA
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10
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Rapamycin restores p14, p15 and p57 expression and inhibits the mTOR/p70S6K pathway in acute lymphoblastic leukemia cells. Int J Hematol 2015; 102:558-68. [DOI: 10.1007/s12185-015-1858-1] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/25/2015] [Revised: 08/11/2015] [Accepted: 08/12/2015] [Indexed: 12/23/2022]
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11
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Padmanabhan J, Brown KR, Padilla A, Shelanski ML. Functional role of RNA polymerase II and P70 S6 kinase in KCl withdrawal-induced cerebellar granule neuron apoptosis. J Biol Chem 2015; 290:5267-79. [PMID: 25568312 DOI: 10.1074/jbc.m114.575225] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
KCl withdrawal-induced apoptosis in cerebellar granule neurons is associated with aberrant cell cycle activation, and treatment with cyclin-dependent kinase (Cdk) inhibitors protects cells from undergoing apoptosis. Because the Cdk inhibitor flavopiridol is known to inhibit RNA polymerase II (Pol II)-dependent transcription elongation by inhibiting the positive transcription elongation factor b (P-TEFb, a complex of CDK9 and cyclin T), we examined whether inhibition of RNA Pol II protects neurons from apoptosis. Treatment of neurons with 5, 6-dichloro-1-β-D-ribobenzimidazole (DRB), an RNA Pol II-dependent transcription elongation inhibitor, and flavopiridol inhibited phosphorylation and activation of Pol II and protected neurons from undergoing apoptosis. In addition to Pol II, neurons subjected to KCl withdrawal showed increased phosphorylation and activation of p70 S6 kinase, which was inhibited by both DRB and flavopiridol. Immunostaining analysis of the neurons deprived of KCl showed increased nuclear levels of phospho-p70 S6 kinase, and neurons protected with DRB and flavopiridol showed accumulation of the kinase into large spliceosome assembly factor-positive speckle domains within the nuclei. The formation of these foci corresponded with cell survival, and removal of the inhibitors resulted in dispersal of the speckles into smaller foci with subsequent apoptosis induction. Because p70 S6 kinase is known to induce translation of mRNAs containing a 5'-terminal oligopyrimidine tract, our data suggest that transcription and translation of this subset of mRNAs may contribute to KCl withdrawal-induced apoptosis in neurons.
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Affiliation(s)
- Jaya Padmanabhan
- From the Department of Molecular Medicine, University of South Florida Health Byrd Alzheimer's Institute, University of South Florida, Tampa, Florida 33613 and
| | - Kristy R Brown
- the Department of Pathology and Cell Biology, Taub Center for Alzheimer's Disease, College of Physicians and Surgeons, Columbia University, New York, New York 10032
| | - Amelia Padilla
- From the Department of Molecular Medicine, University of South Florida Health Byrd Alzheimer's Institute, University of South Florida, Tampa, Florida 33613 and
| | - Michael L Shelanski
- the Department of Pathology and Cell Biology, Taub Center for Alzheimer's Disease, College of Physicians and Surgeons, Columbia University, New York, New York 10032
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12
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Qin J, Rajaratnam R, Feng L, Salami J, Barber-Rotenberg JS, Domsic J, Reyes-Uribe P, Liu H, Dang W, Berger SL, Villanueva J, Meggers E, Marmorstein R. Development of organometallic S6K1 inhibitors. J Med Chem 2014; 58:305-14. [PMID: 25356520 PMCID: PMC4289024 DOI: 10.1021/jm5011868] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
![]()
Aberrant activation of S6 kinase
1 (S6K1) is found in many diseases,
including diabetes, aging, and cancer. We developed ATP competitive
organometallic kinase inhibitors, EM5 and FL772, which are inspired
by the structure of the pan-kinase inhibitor staurosporine, to specifically
inhibit S6K1 using a strategy previously used to target other kinases.
Biochemical data demonstrate that EM5 and FL772 inhibit the kinase
with IC50 value in the low nanomolar range at 100 μM
ATP and that the more potent FL772 compound has a greater than 100-fold
specificity over S6K2. The crystal structures of S6K1 bound to staurosporine,
EM5, and FL772 reveal that the EM5 and FL772 inhibitors bind in the
ATP binding pocket and make S6K1-specific contacts, resulting in changes
to the p-loop, αC helix, and αD helix when compared to
the staurosporine-bound structure. Cellular data reveal that FL772
is able to inhibit S6K phosphorylation in yeast cells. Together, these
studies demonstrate that potent, selective, and cell permeable S6K1
inhibitors can be prepared and provide a scaffold for future development
of S6K inhibitors with possible therapeutic applications.
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Affiliation(s)
- Jie Qin
- The Wistar Institute , 3601 Spruce Street, Philadelphia, Pennsylvania 19104, United States
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Bioinformatic analysis reveals a pattern of STAT3-associated gene expression specific to basal-like breast cancers in human tumors. Proc Natl Acad Sci U S A 2014; 111:12787-92. [PMID: 25139989 DOI: 10.1073/pnas.1404881111] [Citation(s) in RCA: 43] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022] Open
Abstract
Signal transducer and activator of transcription 3 (STAT3), a latent transcription factor associated with inflammatory signaling and innate and adaptive immune responses, is known to be aberrantly activated in a wide variety of cancers. In vitro analysis of STAT3 in human cancer cell lines has elucidated a number of specific targets associated with poor prognosis in breast cancer. However, to date, no comparison of cancer subtype and gene expression associated with STAT3 signaling in human patients has been reported. In silico analysis of human breast cancer microarray and reverse-phase protein array data was performed to identify expression patterns associated with STAT3 in basal-like and luminal breast cancers. Results indicate clearly identifiable STAT3-regulated signatures common to basal-like breast cancers but not to luminal A or luminal B cancers. Furthermore, these differentially expressed genes are associated with immune signaling and inflammation, a known phenotype of basal-like cancers. These findings demonstrate a distinct role for STAT3 signaling in basal breast cancers, and underscore the importance of considering subtype-specific molecular pathways that contribute to tissue-specific cancers.
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Couty S, Westwood IM, Kalusa A, Cano C, Travers J, Boxall K, Chow CL, Burns S, Schmitt J, Pickard L, Barillari C, McAndrew PC, Clarke PA, Linardopoulos S, Griffin RJ, Aherne GW, Raynaud FI, Workman P, Jones K, van Montfort RLM. The discovery of potent ribosomal S6 kinase inhibitors by high-throughput screening and structure-guided drug design. Oncotarget 2014; 4:1647-61. [PMID: 24072592 PMCID: PMC3858552 DOI: 10.18632/oncotarget.1255] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/16/2023] Open
Abstract
The ribosomal P70 S6 kinases play a crucial role in PI3K/mTOR regulated signalling pathways and are therefore potential targets for the treatment of a variety of diseases including diabetes and cancer. In this study we describe the identification of three series of chemically distinct S6K1 inhibitors. In addition, we report a novel PKA-S6K1 chimeric protein with five mutations in or near its ATP-binding site, which was used to determine the binding mode of two of the three inhibitor series, and provided a robust system to aid the optimisation of the oxadiazole-substituted benzimidazole inhibitor series. We show that the resulting oxadiazole-substituted aza-benzimidazole is a potent and ligand efficient S6 kinase inhibitor, which blocks the phosphorylation of RPS6 at Ser235/236 in TSC negative HCV29 human bladder cancer cells by inhibiting S6 kinase activity and thus provides a useful tool compound to investigate the function of S6 kinases.
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Affiliation(s)
- Sylvain Couty
- Cancer Research UK Cancer Therapeutics Unit, The Institute of Cancer Research, London, SM2 5NG, UK
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15
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Circumventing cellular control of PP2A by methylation promotes transformation in an Akt-dependent manner. Neoplasia 2013; 14:585-99. [PMID: 22904676 DOI: 10.1593/neo.12768] [Citation(s) in RCA: 48] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/04/2012] [Revised: 06/13/2012] [Accepted: 06/18/2012] [Indexed: 12/28/2022]
Abstract
Heterotrimeric protein phosphatase 2A (PP2A) consists of catalytic C (PP2Ac), structural A, and regulatory B-type subunits, and its dysfunction has been linked to cancer. Reversible methylation of PP2Ac by leucine carboxyl methyltransferase 1 (LCMT-1) and protein phosphatase methylesterase 1 (PME-1) differentially regulates B-type subunit binding and thus PP2A function. Polyomavirus middle (PyMT) and small (PyST) tumor antigens and SV40 small tumor antigen (SVST) are oncoproteins that block PP2A function by replacing certain B-type subunits, resulting in cellular transformation. Whereas the B-type subunits replaced by these oncoproteins seem to exhibit a binding preference for methylated PP2Ac, PyMT does not. We hypothesize that circumventing the normal cellular control of PP2A by PP2Ac methylation is a general strategy for ST- and MT-mediated transformation. Two predictions of this hypothesis are (1) that PyST and SVST also bind PP2A in a methylation-insensitive manner and (2) that down-regulation of PP2Ac methylation will activate progrowth and prosurvival signaling and promote transformation. We found that SVST and PyST, like PyMT, indeed form PP2A heterotrimers independently of PP2Ac methylation. In addition, reducing PP2Ac methylation through LCMT-1 knockdown or PME-1 overexpression enhanced transformation by activating the Akt and p70/p85 S6 kinase (S6K) pathways, pathways also activated by MT and ST oncoproteins. These results support the hypothesis that MT and ST oncoproteins circumvent cellular control of PP2A by methylation to promote transformation. They also implicate LCMT-1 as a negative regulator of Akt and p70/p85 S6K. Therefore, disruption of PP2Ac methylation may contribute to cancer, and modulation of this methylation may serve as an anticancer target.
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16
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AlQurashi N, Hashimi SM, Wei MQ. Chemical Inhibitors and microRNAs (miRNA) Targeting the Mammalian Target of Rapamycin (mTOR) Pathway: Potential for Novel Anticancer Therapeutics. Int J Mol Sci 2013; 14:3874-900. [PMID: 23434669 PMCID: PMC3588076 DOI: 10.3390/ijms14023874] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/13/2012] [Revised: 01/08/2013] [Accepted: 01/10/2013] [Indexed: 12/27/2022] Open
Abstract
The mammalian target of rapamycin (mTOR) is a critical regulator of many fundamental features in response to upstream cellular signals, such as growth factors, energy, stress and nutrients, controlling cell growth, proliferation and metabolism through two complexes, mTORC1 and mTORC2. Dysregulation of mTOR signalling often occurs in a variety of human malignant diseases making it a crucial and validated target in the treatment of cancer. Tumour cells have shown high susceptibility to mTOR inhibitors. Rapamycin and its derivatives (rapalogs) have been tested in clinical trials in several tumour types and found to be effective as anticancer agents in patients with advanced cancers. To block mTOR function, they form a complex with FKBP12 and then bind the FRB domain of mTOR. Furthermore, a new generation of mTOR inhibitors targeting ATP-binding in the catalytic site of mTOR showed potent and more selective inhibition. More recently, microRNAs (miRNA) have emerged as modulators of biological pathways that are essential in cancer initiation, development and progression. Evidence collected to date shows that miRNAs may function as tumour suppressors or oncogenes in several human neoplasms. The mTOR pathway is a promising target by miRNAs for anticancer therapy. Extensive studies have indicated that regulation of the mTOR pathway by miRNAs plays a major role in cancer progression, indicating a novel way to investigate the tumorigenesis and therapy of cancer. Here, we summarize current findings of the role of mTOR inhibitors and miRNAs in carcinogenesis through targeting mTOR signalling pathways and determine their potential as novel anti-cancer therapeutics.
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Affiliation(s)
- Naif AlQurashi
- Division of Molecular and Gene Therapies, Griffith Health Institute, School of Medical Science, Griffith University, Gold Coast, QLD 4215, Australia
- Biology Department, College of Medicine, University of Dammam, Dammam 31451, Saudi Arabia; E-Mail:
| | - Saeed M. Hashimi
- Division of Molecular and Gene Therapies, Griffith Health Institute, School of Medical Science, Griffith University, Gold Coast, QLD 4215, Australia
- Authors to whom correspondence should be addressed; E-Mails: (S.M.H.); (M.Q.W.); Tel.: +61-7-567-807-45; Fax: +61-7-576-807-89
| | - Ming Q. Wei
- Division of Molecular and Gene Therapies, Griffith Health Institute, School of Medical Science, Griffith University, Gold Coast, QLD 4215, Australia
- Authors to whom correspondence should be addressed; E-Mails: (S.M.H.); (M.Q.W.); Tel.: +61-7-567-807-45; Fax: +61-7-576-807-89
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17
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Xiao L, Wang YC, Li WS, Du Y. The role of mTOR and phospho-p70S6K in pathogenesis and progression of gastric carcinomas: an immunohistochemical study on tissue microarray. JOURNAL OF EXPERIMENTAL & CLINICAL CANCER RESEARCH : CR 2009; 28:152. [PMID: 20003385 PMCID: PMC2797794 DOI: 10.1186/1756-9966-28-152] [Citation(s) in RCA: 51] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 09/17/2009] [Accepted: 12/13/2009] [Indexed: 12/16/2022]
Abstract
Background mTOR signaling pathway and its downstream serine/threonine kinase p70S6k were frequently activated in human cancers. The dysregulation of the mTOR pathway has been found to be a contributing factor of a variety of different cancer. To investigate the role of mTOR signal pathway in the stepwise development of gastric carcinomas, we analyzed the correlations between the mTOR and P70S6K expression and clinic pathological factors and studied its prognostic role in gastric carcinomas. Methods mTOR and phospho-p70S6K proteins were examined by immunohistochemistry on tissue microarray containing gastric carcinomas (n = 412), adenomas (n = 47) and non-neoplastic mucosa (NNM, n = 197) with a comparison of their expression with clinicopathological parameters of carcinomas. Results There was no difference of mTOR expression between these three tissues (p > 0.05). Cytoplasmic phospho(p)-P706SK was highly expressed in adenoma, compared with ANNMs (p < 0.05), whereas its nuclear expression was lower in gastric carcinomas than gastric adenoma and ANNMs (p < 0.05). These three markers were preferably expressed in the older patients with gastric cancer and intestinal-type carcinoma (p < 0.05). mTOR expression was positively correlated with the cytoplasmic and nuclear expression of p-P70S6K(p < 0.05). Nuclear P70S6K was inversely linked to tumor size, depth of invasion, lymph node metastasis and UICC staging (p < 0.05). Univariate analysis indicated that expression of mTOR and nuclear p-P70S6K was closely linked to favorable prognosis of the carcinoma patients (p < 0.05). Multivariate analysis showed that age, depth of invasion, lymphatic invasion, lymph node metastasis, Lauren's classification and mTOR expression were independent prognostic factors for overall gastric carcinomas (p < 0.05). Conclusion Aberrant expression of p-P70S6K possibly contributes to pathogenesis, growth, invasion and metastasis of gastric carcinomas. It was considered as a promising marker to indicate the aggressive behaviors and prognosis of gastric carcinomas.
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Affiliation(s)
- Li Xiao
- Department of Emergency, Shengjing Hospital of China Medical University, Shenyang, Liaoning, China.
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18
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Zhao XF, Gartenhaus RB. Phospho-p70S6K and cdc2/cdk1 as therapeutic targets for diffuse large B-cell lymphoma. Expert Opin Ther Targets 2009; 13:1085-93. [PMID: 19614561 DOI: 10.1517/14728220903103833] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Abstract
p70S6K/p85S6K and cdc2/cdk1 are members of the serine/threonine protein kinase family. p70S6K/p85S6K is one of the downstream effectors of the PI3K/Akt/mTOR signal transduction pathway. It phosphorylates S6 protein of 40S ribosomal subunit and thus functions in protein synthesis and cell growth. cdc2/cdk1 is a cyclin-dependent protein kinase that controls the cell cycle entry from G2 to M phase. Overexpression of phospho-p70S6K and cdc2/cdk1 has recently been identified in the majority of diffuse large B-cell lymphoma (DLBCL) specimens. Combination of small molecules that target phosphorylation of p70S6K and cdc2/cdk1 synergistically induced cell apoptosis and cell cycle G1 and G2 arrest, suggesting that they are potential molecular targets for DLBCL therapy. This review will summarize recent advances in the study of phospho-p70S6K and cdc2/cdk1 as molecular markers and therapeutic targets for DLBCL. We propose that multilevel inhibition of the PI3K/Akt/mTOR pathway and double brake at the G1 and G2 phases of the cell cycle progression are effective strategies in treating DLBCL that overexpress phospho-p70S6K and cdc2/cdk1.
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Affiliation(s)
- Xianfeng Frank Zhao
- University of Maryland, Marlene and Stewart Greenebaum Cancer Center, Baltimore, Maryland 21201, USA.
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Jastrzebski K, Hannan KM, Tchoubrieva EB, Hannan RD, Pearson RB. Coordinate regulation of ribosome biogenesis and function by the ribosomal protein S6 kinase, a key mediator of mTOR function. Growth Factors 2007; 25:209-26. [PMID: 18092230 DOI: 10.1080/08977190701779101] [Citation(s) in RCA: 149] [Impact Index Per Article: 8.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Abstract
Current understanding of the mechanisms by which cell growth is regulated lags significantly behind our knowledge of the complex processes controlling cell cycle progression. Recent studies suggest that the mammalian target of rapamycin (mTOR) pathway is a key regulator of cell growth via the regulation of protein synthesis. The key mTOR effectors of cell growth are eukaryotic initiation factor 4E-binding protein 1 (4EBP-1) and the ribosomal protein S6 kinase (S6K). Here we will review the current models for mTOR dependent regulation of ribosome function and biogenesis as well as its role in coordinating growth factor and nutrient signaling to facilitate homeostasis of cell growth and proliferation. We will place particular emphasis on the role of S6K1 signaling and will highlight the points of cross talk with other key growth control pathways. Finally, we will discuss the impact of S6K signaling and the consequent feedback regulation of the PI3K/Akt pathway on disease processes including cancer.
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Affiliation(s)
- Katarzyna Jastrzebski
- Growth Control and Differentiation Program, Trescowthick Research Laboratories, Peter MacCallum Cancer Centre, Melbourne, Australia
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20
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Paglin S, Lee NY, Nakar C, Fitzgerald M, Plotkin J, Deuel B, Hackett N, McMahill M, Sphicas E, Lampen N, Yahalom J. Rapamycin-Sensitive Pathway Regulates Mitochondrial Membrane Potential, Autophagy, and Survival in Irradiated MCF-7 Cells. Cancer Res 2005; 65:11061-70. [PMID: 16322256 DOI: 10.1158/0008-5472.can-05-1083] [Citation(s) in RCA: 170] [Impact Index Per Article: 8.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Radiation-induced inhibition of rapamycin-sensitive pathway and its effect on the cellular response to radiation were studied in the human breast cancer cell line MCF-7. Both radiation and rapamycin shared molecular targets and induced similar physiologic responses. Each of these treatments increased immunostaining of mammalian target of rapamycin (mTOR) in the nucleus, and radiation led to decreased phosphorylation of its autophosphorylation site Ser2481. In addition to dephosphorylation of established mTOR downstream effectors 4E-binding protein 1 and p70 ribosomal S6 kinase, both treatments decreased the level of eukaryotic initiation factor 4G. Experiments with the potentiometric dye, JC-1, revealed an oligomycin-dependent increase in mitochondrial membrane potential following radiation or rapamycin treatment, suggesting that both lead to reversal of F0F1ATPase activity. Both radiation and rapamycin induced sequestration of cytoplasmic material in autophagic vacuoles. In both cases, appearance of autophagic vacuoles involved the participation of microtubule-associated protein 1 light chain 3 (LC3). Transient cotransfection of green fluorescent protein-LC3 with either wild-type or dominant-negative mTOR further showed that inactivation of mTOR pathway is sufficient to induce autophagy in these cells. Finally, administration of rapamycin in combination with radiation led to enhanced mitochondria hyperpolarization, p53 phosphorylation, and increased cell death. Taken together, these experiments show that radiation-induced inhibition of rapamycin-sensitive pathway in MCF-7 cells causes changes in mitochondria metabolism, development of autophagy, and an overall decrease in cell survival.
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Affiliation(s)
- Shoshana Paglin
- Department of Radiation Oncology, Memorial Sloan-Kettering Cancer Center, New York, New York 10021, USA.
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Takeuchi H, Kondo Y, Fujiwara K, Kanzawa T, Aoki H, Mills GB, Kondo S. Synergistic Augmentation of Rapamycin-Induced Autophagy in Malignant Glioma Cells by Phosphatidylinositol 3-Kinase/Protein Kinase B Inhibitors. Cancer Res 2005; 65:3336-46. [PMID: 15833867 DOI: 10.1158/0008-5472.can-04-3640] [Citation(s) in RCA: 428] [Impact Index Per Article: 22.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
The mammalian target of rapamycin (mTOR) is a downstream effector of the phosphatidylinositol 3-kinase (PI3K)/protein kinase B (Akt) signaling pathway and a central modulator of cell proliferation in malignant gliomas. Therefore, the targeting of mTOR signaling is considered a promising therapy for malignant gliomas. However, the mechanisms underlying the cytotoxic effects of a selective mTOR inhibitor, rapamycin, on malignant glioma cells are poorly understood. The purpose of this study was thus to elucidate how rapamycin exerts its cytotoxic effects on malignant glioma cells. We showed that rapamycin induced autophagy but not apoptosis in rapamycin-sensitive malignant glioma U87-MG and T98G cells by inhibiting the function of mTOR. In contrast, in rapamycin-resistant U373-MG cells, the inhibitory effect of rapamycin was minor, although the phosphorylation of p70S6 kinase, a molecule downstream of mTOR, was remarkably inhibited. Interestingly, a PI3K inhibitor, LY294002, and an Akt inhibitor, UCN-01 (7-hydroxystaurosporine), both synergistically sensitized U87-MG and T98G cells as well as U373-MG cells to rapamycin by stimulating the induction of autophagy. Enforced expression of active Akt in tumor cells suppressed the combined effects of LY294002 or UCN-01, whereas dominant-negative Akt expression was sufficient to increase the sensitivity of tumor cells to rapamycin. These results indicate that rapamycin exerts its antitumor effect on malignant glioma cells by inducing autophagy and suggest that in malignant glioma cells a disruption of the PI3K/Akt signaling pathway could greatly enhance the effectiveness of mTOR inhibitors.
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Affiliation(s)
- Hayato Takeuchi
- Department of Neurosurgery, University of Texas M.D. Anderson Cancer Center, 1515 Holcombe Boulevard, Houston, TX 77030, USA
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Affiliation(s)
- Mary-Ann Bjornsti
- Department of Molecular Pharmacology, St. Jude Children's Research Hospital, Memphis, Tennessee 38105, USA
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