1
|
Chuang YT, Yen CY, Tang JY, Chang FR, Tsai YH, Wu KC, Chien TM, Chang HW. Protein phosphatase 2A modulation and connection with miRNAs and natural products. ENVIRONMENTAL TOXICOLOGY 2024; 39:3612-3627. [PMID: 38491812 DOI: 10.1002/tox.24199] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/31/2023] [Revised: 01/28/2024] [Accepted: 02/10/2024] [Indexed: 03/18/2024]
Abstract
Protein phosphatase 2A (PP2A), a heterotrimeric holoenzyme (scaffolding, catalytic, and regulatory subunits), regulates dephosphorylation for more than half of serine/threonine phosphosites and exhibits diverse cellular functions. Although several studies on natural products and miRNAs have emphasized their impacts on PP2A regulation, their connections lack systemic organization. Moreover, only part of the PP2A family has been investigated. This review focuses on the PP2A-modulating effects of natural products and miRNAs' interactions with potential PP2A targets in cancer and non-cancer cells. PP2A-modulating natural products and miRNAs were retrieved through a literature search. Utilizing the miRDB database, potential PP2A targets of these PP2A-modulating miRNAs for the whole set (17 members) of the PP2A family were retrieved. Finally, PP2A-modulating natural products and miRNAs were linked via a literature search. This review provides systemic directions for assessing natural products and miRNAs relating to the PP2A-modulating functions in cancer and disease treatments.
Collapse
Affiliation(s)
- Ya-Ting Chuang
- Department of Biomedical Science and Environmental Biology, PhD Program in Life Sciences, College of Life Science, Kaohsiung Medical University, Kaohsiung, Taiwan
| | - Ching-Yu Yen
- School of Dentistry, Taipei Medical University, Taipei, Taiwan
- Department of Oral and Maxillofacial Surgery, Chi-Mei Medical Center, Tainan, Taiwan
| | - Jen-Yang Tang
- School of Post-Baccalaureate Medicine, Kaohsiung Medical University, Kaohsiung, Taiwan
- Department of Radiation Oncology, Kaohsiung Medical University Hospital, Kaohsiung Medical University, Kaohsiung, Taiwan
| | - Fang-Rong Chang
- Graduate Institute of Natural Products, Kaohsiung Medical University, Kaohsiung, Taiwan
| | - Yi-Hong Tsai
- Department of Pharmacy and Master Program, College of Pharmacy and Health Care, Tajen University, Pingtung, Taiwan
| | - Kuo-Chuan Wu
- Department of Computer Science and Information Engineering, National Pingtung University, Pingtung, Taiwan
| | - Tsu-Ming Chien
- Department of Urology, Kaohsiung Medical University Hospital, Kaohsiung, Taiwan
| | - Hsueh-Wei Chang
- Department of Biomedical Science and Environmental Biology, PhD Program in Life Sciences, College of Life Science, Kaohsiung Medical University, Kaohsiung, Taiwan
- Center for Cancer Research, Kaohsiung Medical University, Kaohsiung, Taiwan
- Department of Medical Research, Kaohsiung Medical University Hospital, Kaohsiung, Taiwan
| |
Collapse
|
2
|
Wu HM, Huang YY, Xu YQ, Xiang WL, Yang C, Liu RY, Li D, Guo XF, Zhang ZB, Bei CH, Tan SK, Zhu XN. Comprehensive analysis of the protein phosphatase 2A regulatory subunit B56ε in pan-cancer and its role and mechanism in hepatocellular carcinoma. World J Gastrointest Oncol 2024; 16:475-492. [PMID: 38425404 PMCID: PMC10900161 DOI: 10.4251/wjgo.v16.i2.475] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/17/2023] [Revised: 12/10/2023] [Accepted: 01/08/2024] [Indexed: 02/02/2024] Open
Abstract
BACKGROUND B56ε is a regulatory subunit of the serine/threonine protein phosphatase 2A, which is abnormally expressed in tumors and regulates various tumor cell functions. At present, the application of B56ε in pan-cancer lacks a comprehensive analysis, and its role and mechanism in hepatocellular carcinoma (HCC) are still unclear. AIM To analyze B56ε in pan-cancer, and explore its role and mechanism in HCC. METHODS The Cancer Genome Atlas, Genotype-Tissue Expression, Gene Expression Profiling Interactive Analysis, and Tumor Immune Estimation Resource databases were used to analyze B56ε expression, prognostic mutations, somatic copy number alterations, and tumor immune characteristics in 33 tumors. The relationships between B56ε expression levels and drug sensitivity, immunotherapy, immune checkpoints, and human leukocyte antigen (HLA)-related genes were further analyzed. Gene Set Enrichment Analysis (GSEA) was performed to reveal the role of B56ε in HCC. The Cell Counting Kit-8, plate cloning, wound healing, and transwell assays were conducted to assess the effects of B56ε interference on the malignant behavior of HCC cells. RESULTS In most tumors, B56ε expression was upregulated, and high B56ε expression was a risk factor for adrenocortical cancer, HCC, pancreatic adenocarcinoma, and pheochromocytoma and paraganglioma (all P < 0.05). B56ε expression levels were correlated with a variety of immune cells, such as T helper 17 cells, B cells, and macrophages. There was a positive correlation between B56ε expression levels with immune checkpoint genes and HLA-related genes (all P < 0.05). The expression of B56ε was negatively correlated with the sensitivity of most chemotherapy drugs, but a small number showed a positive correlation (all P < 0.05). GSEA analysis showed that B56ε expression was related to the cancer pathway, p53 downstream pathway, and interleukin-mediated signaling in HCC. Knockdown of B56ε expression in HCC cells inhibited the proliferation, migration, and invasion capacity of tumor cells. CONCLUSION B56ε is associated with the microenvironment, immune evasion, and immune cell infiltration of multiple tumors. B56ε plays an important role in HCC progression, supporting it as a prognostic marker and potential therapeutic target for HCC.
Collapse
Affiliation(s)
- Hong-Mei Wu
- Guangxi Key Laboratory of Environmental Exposomics and Entire Lifecycle Health, Guilin Medical University, Guilin 541199, Guangxi Zhuang Autonomous Region, China
| | - Yuan-Yuan Huang
- Guangxi Key Laboratory of Environmental Exposomics and Entire Lifecycle Health, Guilin Medical University, Guilin 541199, Guangxi Zhuang Autonomous Region, China
| | - Yu-Qiu Xu
- Guangxi Key Laboratory of Environmental Exposomics and Entire Lifecycle Health, Guilin Medical University, Guilin 541199, Guangxi Zhuang Autonomous Region, China
| | - Wei-Lai Xiang
- Guangxi Key Laboratory of Environmental Exposomics and Entire Lifecycle Health, Guilin Medical University, Guilin 541199, Guangxi Zhuang Autonomous Region, China
| | - Chang Yang
- Guangxi Key Laboratory of Environmental Exposomics and Entire Lifecycle Health, Guilin Medical University, Guilin 541199, Guangxi Zhuang Autonomous Region, China
| | - Ru-Yuan Liu
- Guangxi Key Laboratory of Environmental Exposomics and Entire Lifecycle Health, Guilin Medical University, Guilin 541199, Guangxi Zhuang Autonomous Region, China
| | - Di Li
- Guangxi Key Laboratory of Environmental Exposomics and Entire Lifecycle Health, Guilin Medical University, Guilin 541199, Guangxi Zhuang Autonomous Region, China
| | - Xue-Feng Guo
- Guangxi Key Laboratory of Environmental Exposomics and Entire Lifecycle Health, Guilin Medical University, Guilin 541199, Guangxi Zhuang Autonomous Region, China
| | - Zheng-Bao Zhang
- Guangxi Key Laboratory of Environmental Exposomics and Entire Lifecycle Health, Guilin Medical University, Guilin 541199, Guangxi Zhuang Autonomous Region, China
| | - Chun-Hua Bei
- Guangxi Key Laboratory of Environmental Exposomics and Entire Lifecycle Health, Guilin Medical University, Guilin 541199, Guangxi Zhuang Autonomous Region, China
| | - Sheng-Kui Tan
- Guangxi Key Laboratory of Environmental Exposomics and Entire Lifecycle Health, Guilin Medical University, Guilin 541199, Guangxi Zhuang Autonomous Region, China
| | - Xiao-Nian Zhu
- Guangxi Key Laboratory of Environmental Exposomics and Entire Lifecycle Health, Guilin Medical University, Guilin 541199, Guangxi Zhuang Autonomous Region, China
| |
Collapse
|
3
|
Kashani E, Vassella E. Pleiotropy of PP2A Phosphatases in Cancer with a Focus on Glioblastoma IDH Wildtype. Cancers (Basel) 2022; 14:5227. [PMID: 36358647 PMCID: PMC9654311 DOI: 10.3390/cancers14215227] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/16/2022] [Revised: 10/13/2022] [Accepted: 10/20/2022] [Indexed: 07/29/2023] Open
Abstract
Serine/Threonine protein phosphatase 2A (PP2A) is a heterotrimeric (or occasionally, heterodimeric) phosphatase with pleiotropic functions and ubiquitous expression. Despite the fact that they all contribute to protein dephosphorylation, multiple PP2A complexes exist which differ considerably by their subcellular localization and their substrate specificity, suggesting diverse PP2A functions. PP2A complex formation is tightly regulated by means of gene expression regulation by transcription factors, microRNAs, and post-translational modifications. Furthermore, a constant competition between PP2A regulatory subunits is taking place dynamically and depending on the spatiotemporal circumstance; many of the integral subunits can outcompete the rest, subjecting them to proteolysis. PP2A modulation is especially important in the context of brain tumors due to its ability to modulate distinct glioma-promoting signal transduction pathways, such as PI3K/Akt, Wnt, Ras, NF-κb, etc. Furthermore, PP2A is also implicated in DNA repair and survival pathways that are activated upon treatment of glioma cells with chemo-radiation. Depending on the cancer cell type, preclinical studies have shown some promise in utilising PP2A activator or PP2A inhibitors to overcome therapy resistance. This review has a special focus on "glioblastoma, IDH wild-type" (GBM) tumors, for which the therapy options have limited efficacy, and tumor relapse is inevitable.
Collapse
Affiliation(s)
- Elham Kashani
- Institute of Pathology, University of Bern, 3008 Bern, Switzerland
- Graduate School for Cellular and Biomedical Sciences, University of Bern, 3012 Bern, Switzerland
| | - Erik Vassella
- Institute of Pathology, University of Bern, 3008 Bern, Switzerland
| |
Collapse
|
4
|
Shang D, Zhou T, Zhuang X, Wu Y, Liu H, Tu Z. Molecular dissection on inhibition of Ras-induced cellular senescence by small t antigen of SV40. Cell Mol Life Sci 2022; 79:242. [PMID: 35429286 PMCID: PMC11072472 DOI: 10.1007/s00018-022-04275-5] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/05/2021] [Revised: 03/21/2022] [Accepted: 03/25/2022] [Indexed: 11/28/2022]
Abstract
Simian virus 40 (SV40) is a potentially oncogenic virus of monkey origin. Transmission, prevalence, and pathogenicity rates of SV40 are unclear, but infection can occur in humans, for example individuals with high contact with rhesus macaques and individuals that received contaminated early batches of polio vaccines in 1950-1963. In addition, several human polyomaviruses, proven carcinogenic, are also highly common in global populations. Cellular senescence is a major mechanism of cancer prevention in vivo. Hyperactivation of Ras usually induces cellular senescence rather than cell transformation. Previous studies suggest small t antigen (ST) of SV40 may interfere with cellular senescence induced by Ras. In the current study, ST was demonstrated to inhibit Ras-induced cellular senescence (RIS) and accumulation of DNA damage in Ras-activated cells. In addition, ST suppressed the signal transmission from BRaf to MEK and thus blocked the downstream transmission of the activated Ras signal. B56γ knockdown mimicked the inhibitory effects of ST overexpression on RIS. Furthermore, KSR1 knockdown inhibited Ras activation and the subsequent cellular senescence. Further mechanism studies indicated that the phosphorylation level of KSR1 rather than the levels of the total protein regulates the activation of Ras signaling pathway. In sum, ST inhibits the continuous hyperactivation of Ras signals by interfering with the normal functions of PP2A-B56γ of dephosphorylating KSR1, thus inhibiting the occurrence of cellular senescence. Although the roles of SV40 in human carcinogenesis are controversial so far, our study has shown that ST of polyomaviruses has tumorigenic potential by inhibiting oncogene-induced senescence (OIS) as a proof of concept.
Collapse
Affiliation(s)
- Dongsheng Shang
- School of Life Sciences, Jiangsu University, Zhenjiang, 212013, Jiangsu, China
| | - Tianchu Zhou
- School of Life Sciences, Jiangsu University, Zhenjiang, 212013, Jiangsu, China
| | - Xinying Zhuang
- School of Chinese Material Medica, Yunnan University of Chinese Medicine, Kunming, 650500, Yunnan, China
| | - Yanfang Wu
- School of Life Sciences, Jiangsu University, Zhenjiang, 212013, Jiangsu, China
| | - Hanqing Liu
- School of Pharmacy, Jiangsu University, Zhenjiang, 212013, Jiangsu, China.
| | - Zhigang Tu
- School of Life Sciences, Jiangsu University, Zhenjiang, 212013, Jiangsu, China.
| |
Collapse
|
5
|
Cho E, Lou HJ, Kuruvilla L, Calderwood DA, Turk BE. PPP6C negatively regulates oncogenic ERK signaling through dephosphorylation of MEK. Cell Rep 2021; 34:108928. [PMID: 33789117 PMCID: PMC8068315 DOI: 10.1016/j.celrep.2021.108928] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/02/2020] [Revised: 01/26/2021] [Accepted: 03/10/2021] [Indexed: 12/21/2022] Open
Abstract
Flux through the RAF-MEK-ERK protein kinase cascade is shaped by phosphatases acting on the core components of the pathway. Despite being an established drug target and a hub for crosstalk regulation, little is known about dephosphorylation of MEK, the central kinase within the cascade. Here, we identify PPP6C, a phosphatase frequently mutated or downregulated in melanoma, as a major MEK phosphatase in cells exhibiting oncogenic ERK pathway activation. Recruitment of MEK to PPP6C occurs through an interaction with its associated regulatory subunits. Loss of PPP6C causes hyperphosphorylation of MEK at activating and crosstalk phosphorylation sites, promoting signaling through the ERK pathway and decreasing sensitivity to MEK inhibitors. Recurrent melanoma-associated PPP6C mutations cause MEK hyperphosphorylation, suggesting that they promote disease at least in part by activating the core oncogenic pathway driving melanoma. Collectively, our studies identify a key negative regulator of ERK signaling that may influence susceptibility to targeted cancer therapies. Through an shRNA screen, Cho et al. identify PPP6C as a phosphatase that inactivates the kinase MEK, sensitizing tumor cells to clinical MEK inhibitors. This study suggests that cancer-associated loss-of-function PPP6C mutations prevalent in melanoma serve to activate the core oncogenic RAF-MEK-ERK pathway that drives the disease.
Collapse
Affiliation(s)
- Eunice Cho
- Department of Pharmacology, Yale School of Medicine, New Haven, CT 06520, USA
| | - Hua Jane Lou
- Department of Pharmacology, Yale School of Medicine, New Haven, CT 06520, USA
| | - Leena Kuruvilla
- Department of Pharmacology, Yale School of Medicine, New Haven, CT 06520, USA
| | - David A Calderwood
- Department of Pharmacology, Yale School of Medicine, New Haven, CT 06520, USA; Department of Cell Biology, Yale School of Medicine, New Haven, CT 06520, USA
| | - Benjamin E Turk
- Department of Pharmacology, Yale School of Medicine, New Haven, CT 06520, USA.
| |
Collapse
|
6
|
Otani Y, Sur H, Rachaiah G, Namagiri S, Chowdhury A, Lewis CT, Shimizu T, Gangaplara A, Wang X, Vézina A, Maric D, Jackson S, Yan Y, Zhengping Z, Ray-Chaudhury A, Kumar S, Ballester LY, Chittiboina P, Yoo JY, Heiss J, Kaur B, Kumar Banasavadi-Siddegowda Y. Inhibiting protein phosphatase 2A increases the antitumor effect of protein arginine methyltransferase 5 inhibition in models of glioblastoma. Neuro Oncol 2021; 23:1481-1493. [PMID: 33556161 DOI: 10.1093/neuonc/noab014] [Citation(s) in RCA: 14] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022] Open
Abstract
BACKGROUND Despite multi-model therapy of maximal surgical resection, radiation, chemotherapy, and tumor treating fields, the median survival of Glioblastoma (GBM) patients is less than 15 months. Protein Arginine Methyltransferase 5 (PRMT5) catalyzes the symmetric di-methylation of arginine residues and is overexpressed in GBM. Inhibition of PRMT5 causes senescence in stem-like GBM tumor cells. LB100, a first-in-class small molecular inhibitor of Protein Phosphatase 2A (PP2A) can sensitize therapy-resistant tumor cells. Here, we tested the anti-GBM effect of concurrent PRMT5 and PP2A inhibition. METHODS Patient-derived primary GBM neurospheres (GBMNS), transfected with PRMT5 target-specific siRNA were treated with LB100 and subjected to in vitro assays including PP2A activity and western blot. The intracranial mouse xenograft model was used to test the in vivo antitumor efficacy of combination treatment. RESULTS We found that PRMT5-depletion increased PP2A activity in GBMNS. LB100 treatment significantly reduced the viability of PRMT5-depleted GBMNS compared to PRMT5 intact GBMNS. LB100 enhanced G1 cell cycle arrest induced by PRMT5-depletion. Combination therapy also increased the expression of phospho-MLKL. Necrostatin-1 rescued PRMT5-depleted cells from the cytotoxic effects of LB100, indicating that necroptosis caused the enhanced cytotoxicity of combination therapy. In the in vivo mouse tumor xenograft model, LB100 treatment combined with transient depletion of PRMT5 significantly decreased tumor size and prolonged survival, while LB100 treatment alone had no survival benefit. CONCLUSION Overall, combined PRMT5 and PP2A inhibition had significantly greater antitumor effects than PRMT5 inhibition alone.
Collapse
Affiliation(s)
- Yoshihiro Otani
- Department of Neurosurgery, University of Texas Health Science Center at Houston, Houston, TX, USA
| | - Hannah Sur
- Surgical Neurology Branch, National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, MD, USA
| | | | - Sriya Namagiri
- Surgical Neurology Branch, National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, MD, USA
| | - Ashis Chowdhury
- Surgical Neurology Branch, National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, MD, USA
| | - Cole T Lewis
- Department of Neurosurgery, University of Texas Health Science Center at Houston, Houston, TX, USA
| | - Toshihiko Shimizu
- Department of Neurosurgery, University of Texas Health Science Center at Houston, Houston, TX, USA
| | - Arunakumar Gangaplara
- Cellular and Molecular Therapeutics Branch, National Heart, Lung, and Blood Institute, National Institutes of Health, Bethesda, MD, USA
| | - Xiang Wang
- Surgical Neurology Branch, National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, MD, USA
| | - Amélie Vézina
- Surgical Neurology Branch, National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, MD, USA
| | - Dragan Maric
- Flow and Imaging Cytometry Core Facility, NINDS, NIH, Bethesda, MD, USA
| | - Sadhana Jackson
- Surgical Neurology Branch, National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, MD, USA
| | - Yuanqing Yan
- Department of Neurosurgery, University of Texas Health Science Center at Houston, Houston, TX, USA
| | - Zhuang Zhengping
- Surgical Neurology Branch, National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, MD, USA.,Neuro-Oncology Branch, Center for Cancer Research, National Cancer Institute, National Institutes of Health, Bethesda, MD, USA
| | - Abhik Ray-Chaudhury
- Surgical Neurology Branch, National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, MD, USA
| | - Sachin Kumar
- Department of Biosciences and Bioengineering, Indian Institute of Technology Guwahati, Guwahati, India
| | - Leomar Y Ballester
- Department of Pathology and Laboratory Medicine and Department of Neurosurgery, University of Texas Health Science Center at Houston, Houston, TX, USA
| | - Prashant Chittiboina
- Surgical Neurology Branch, National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, MD, USA
| | - Ji Young Yoo
- Department of Neurosurgery, University of Texas Health Science Center at Houston, Houston, TX, USA
| | - John Heiss
- Surgical Neurology Branch, National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, MD, USA
| | - Balveen Kaur
- Department of Neurosurgery, University of Texas Health Science Center at Houston, Houston, TX, USA
| | | |
Collapse
|
7
|
IER2-induced senescence drives melanoma invasion through osteopontin. Oncogene 2021; 40:6494-6512. [PMID: 34611309 PMCID: PMC8616759 DOI: 10.1038/s41388-021-02027-6] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/13/2020] [Revised: 09/01/2021] [Accepted: 09/17/2021] [Indexed: 01/07/2023]
Abstract
Expression of the immediate-early response gene IER2 has been associated with the progression of several types of cancer, but its functional role is poorly understood. We found that increased IER2 expression in human melanoma is associated with shorter overall survival, and subsequently investigated the mechanisms through which IER2 exerts this effect. In experimental melanoma models, sustained expression of IER2 induced senescence in a subset of melanoma cells in a p53/MAPK/AKT-dependent manner. The senescent cells produced a characteristic secretome that included high levels of the extracellular phosphoglycoprotein osteopontin. Nuclear localization of the IER2 protein was critical for both the induction of senescence and osteopontin secretion. Osteopontin secreted by IER2-expressing senescent cells strongly stimulated the migration and invasion of non-senescent melanoma cells. Consistently, we observed coordinate expression of IER2, p53/p21, and osteopontin in primary human melanomas and metastases, highlighting the pathophysiological relevance of IER2-mediated senescence in melanoma progression. Together, our study reveals that sustained IER2 expression drives melanoma invasion and progression through stimulating osteopontin secretion via the stochastic induction of senescence.
Collapse
|
8
|
Kim J, Novak D, Sachpekidis C, Utikal J, Larribère L. STAT3 Relays a Differential Response to Melanoma-Associated NRAS Mutations. Cancers (Basel) 2020; 12:E119. [PMID: 31906480 PMCID: PMC7016650 DOI: 10.3390/cancers12010119] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/10/2019] [Revised: 12/18/2019] [Accepted: 12/27/2019] [Indexed: 12/24/2022] Open
Abstract
Melanoma patients carrying an oncogenic NRAS mutation represent 20% of all cases and present worse survival, relapse rate and therapy response than patients with wild type NRAS or with BRAF mutations. Nevertheless, no efficient targeted therapy has emerged so far for this group of patients in comparison with the classical combination of BRAF and MEK inhibitors for the patient group carrying a BRAF mutation. NRAS key downstream actors should therefore be identified for drug targeting, possibly in combination with MEK inhibitors. Here, we investigated the influence of different melanoma-associated NRAS mutations (codon 12, 13 or 61) on several parameters such as oncogene-induced senescence, cell proliferation, migration or colony formation in immortalized melanocytes and in melanoma cell lines. We identified AXL/STAT3 axis as a main regulator of NRASQ61-induced oncogene-induced senescence (OIS) and observed that NRASQ61 mutations are not only more tumorigenic than NRASG12/13 mutations but also associated to STAT3 activation. In conclusion, these data bring new evidence of the potential tumorigenic role of STAT3 in NRAS-mutant melanomas and will help improving current therapy strategies for this particular patient group.
Collapse
Affiliation(s)
- James Kim
- Skin Cancer Unit, German Cancer Research Center (DKFZ), 69120 Heidelberg, Germany; (J.K.); (D.N.); (J.U.)
- Department of Dermatology, Venereology and Allergology, University Medical Center Mannheim, Ruprecht-Karl University of Heidelberg, 68167 Mannheim, Germany
| | - Daniel Novak
- Skin Cancer Unit, German Cancer Research Center (DKFZ), 69120 Heidelberg, Germany; (J.K.); (D.N.); (J.U.)
- Department of Dermatology, Venereology and Allergology, University Medical Center Mannheim, Ruprecht-Karl University of Heidelberg, 68167 Mannheim, Germany
| | - Christos Sachpekidis
- Clinical Cooperation Unit Nuclear Medicine, German Cancer Research Center (DKFZ), 69120 Heidelberg, Germany;
| | - Jochen Utikal
- Skin Cancer Unit, German Cancer Research Center (DKFZ), 69120 Heidelberg, Germany; (J.K.); (D.N.); (J.U.)
- Department of Dermatology, Venereology and Allergology, University Medical Center Mannheim, Ruprecht-Karl University of Heidelberg, 68167 Mannheim, Germany
| | - Lionel Larribère
- Skin Cancer Unit, German Cancer Research Center (DKFZ), 69120 Heidelberg, Germany; (J.K.); (D.N.); (J.U.)
- Department of Dermatology, Venereology and Allergology, University Medical Center Mannheim, Ruprecht-Karl University of Heidelberg, 68167 Mannheim, Germany
| |
Collapse
|
9
|
Kozlova NI, Morozevich GE, Ushakova NA, Berman AE. Implication of Integrin α2β1 in Proliferation and Invasion of Human Breast Carcinoma and Melanoma Cells: Noncanonical Function of Akt Protein Kinase. BIOCHEMISTRY (MOSCOW) 2018; 83:738-745. [PMID: 30195330 DOI: 10.1134/s0006297918060111] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/04/2023]
Abstract
Blocking the expression of integrin α2β1, which was accomplished by transduction of α2-specific shRNA, resulted in significant inhibition of proliferation and clonal activity in human MCF-7 breast carcinoma and SK-Mel-147 melanoma cells. Along with these changes, deprivation of α2β1 caused a sharp decrease in melanoma cell invasion in vitro. Analysis of integrin-mediating signal pathways that control cell behavior revealed a significant increase in activity of Akt protein kinase in response to depletion of α2β1. The increase in Akt activity that accompanies a suppressive effect on cell invasion contradicts well-known Akt function aimed at stimulation of tumor progression. This contradiction could be explained by the "reversed" (noncanonical) role played by Akt in some cells that consists in suppression rather than promotion of invasive phenotype. To test this suggestion, the effects of Akt inhibitors on invasive activity of SK-Mel-147 cells were investigated. If the above suggestion is true, then inhibition of Akt in cells depleted of α2β1 should result in the restoration of their invasive activity. It appeared that treatment with LY294002, which inhibits all Akt isoforms (Akt1, Akt2, Akt3), not only failed to restore the invasive phenotype of melanoma cells but further attenuated their invasive activity. However, treatment of the cells with an Akt1-specific inhibitor significantly increased their invasion. Thus, the stimulating effect of α2β1 integrin on invasion of melanoma cells is realized through a mechanism based on inhibition of one of the Akt isoforms, which in these cells exhibits a noncanonical function consisting in suppression of invasion.
Collapse
Affiliation(s)
- N I Kozlova
- Orekhovich Institute of Biomedical Chemistry, Russian Academy of Sciences, Moscow, 119121, Russia
| | - G E Morozevich
- Orekhovich Institute of Biomedical Chemistry, Russian Academy of Sciences, Moscow, 119121, Russia
| | - N A Ushakova
- Orekhovich Institute of Biomedical Chemistry, Russian Academy of Sciences, Moscow, 119121, Russia
| | - A E Berman
- Orekhovich Institute of Biomedical Chemistry, Russian Academy of Sciences, Moscow, 119121, Russia.
| |
Collapse
|
10
|
Krayem M, Najem A, Journe F, Morandini R, Sales F, Awada A, Ghanem GE. Acquired resistance to BRAFi reverses senescence-like phenotype in mutant BRAF melanoma. Oncotarget 2018; 9:31888-31903. [PMID: 30159130 PMCID: PMC6112757 DOI: 10.18632/oncotarget.25879] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/08/2018] [Accepted: 07/12/2018] [Indexed: 02/06/2023] Open
Abstract
Targeting MAPK pathway in mutant BRAF melanoma with the specific BRAF inhibitor vemurafenib showed robust initial responses in the majority of patients followed by relapses due to acquired resistance to the drug. In V600EBRAF melanoma cell lines, senescence-associated β-galactosidase activity is often encountered in a constitutive manner or induced after MAPK inhibition. However, the link between the senescence-like phenotype and the resistance to BRAF inhibition is not fully understood yet. Our data validate a senescence-like phenotype (low cell proliferation, high cell volume, and high β-Gal activity) in mutant BRAF cells. Vemurafenib increased β-Gal activity in 4 out of 5 sensitive lines and in 2 out of 5 lines with intrinsic resistance to the drug. Interestingly, the 3 lines with acquired resistance to vemurafenib became depending on the drug for proliferation. In absence of drug, these lines showed a lower cell proliferation rate together with a substantial increase of β-Gal activity both in vitro and in vivo. In all settings, the senescence-like phenotype was significantly associated with an inhibition of pRB and cyclin D1, explaining the inhibition of cell proliferation. In conclusion, β-Gal activity is increased by V600EBRAF inhibition in the majority of sensitive and intrinsically resistant melanoma cells. Acquired resistance to vemurafenib is associated with a dependence to the drug for cell proliferation and tumor growth, and, in this case, drug removal stimulate β-Gal activity suggesting that the senescence-like phenotype could contribute to the acquired resistance to BRAF inhibition.
Collapse
Affiliation(s)
- Mohammad Krayem
- Laboratory of Oncology and Experimental Surgery, Institut Jules Bordet, Université Libre de Bruxelles, Brussels, Belgium
| | - Ahmad Najem
- Laboratory of Oncology and Experimental Surgery, Institut Jules Bordet, Université Libre de Bruxelles, Brussels, Belgium
| | - Fabrice Journe
- Laboratory of Oncology and Experimental Surgery, Institut Jules Bordet, Université Libre de Bruxelles, Brussels, Belgium.,Service d'Anatomie Humaine et d'Oncologie Expérimentale, Université de Mons, Mons, Belgium
| | - Renato Morandini
- Laboratory of Oncology and Experimental Surgery, Institut Jules Bordet, Université Libre de Bruxelles, Brussels, Belgium
| | - François Sales
- Laboratory of Oncology and Experimental Surgery, Institut Jules Bordet, Université Libre de Bruxelles, Brussels, Belgium
| | - Ahmad Awada
- Department of Internal Medicine, Institut Jules Bordet, Université Libre de Bruxelles, Brussels, Belgium
| | - Ghanem E Ghanem
- Laboratory of Oncology and Experimental Surgery, Institut Jules Bordet, Université Libre de Bruxelles, Brussels, Belgium
| |
Collapse
|
11
|
Kauko O, Westermarck J. Non-genomic mechanisms of protein phosphatase 2A (PP2A) regulation in cancer. Int J Biochem Cell Biol 2018; 96:157-164. [DOI: 10.1016/j.biocel.2018.01.005] [Citation(s) in RCA: 44] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/10/2017] [Revised: 12/03/2017] [Accepted: 01/09/2018] [Indexed: 02/08/2023]
|
12
|
Abstract
Activation of oncogenic signaling paradoxically results in the permanent withdrawal from cell cycle and induction of senescence (oncogene-induced senescence (OIS)). OIS is a fail-safe mechanism used by the cells to prevent uncontrolled tumor growth, and, as such, it is considered as the first barrier against cancer. In order to progress, tumor cells thus need to first overcome the senescent phenotype. Despite the increasing attention gained by OIS in the past 20 years, this field is still rather young due to continuous emergence of novel pathways and processes involved in OIS. Among the many factors contributing to incomplete understanding of OIS are the lack of unequivocal markers for senescence and the complexity of the phenotypes revealed by senescent cells in vivo and in vitro. OIS has been shown to play major roles at both the cellular and organismal levels in biological processes ranging from embryonic development to barrier to cancer progression. Here we will briefly outline major advances in methodologies that are being utilized for induction, identification, and characterization of molecular processes in cells undergoing oncogene-induced senescence. The full description of such methodologies is provided in the corresponding chapters of the book.
Collapse
|
13
|
Meeusen B, Janssens V. Tumor suppressive protein phosphatases in human cancer: Emerging targets for therapeutic intervention and tumor stratification. Int J Biochem Cell Biol 2017; 96:98-134. [PMID: 29031806 DOI: 10.1016/j.biocel.2017.10.002] [Citation(s) in RCA: 62] [Impact Index Per Article: 8.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/30/2017] [Revised: 10/04/2017] [Accepted: 10/05/2017] [Indexed: 02/06/2023]
Abstract
Aberrant protein phosphorylation is one of the hallmarks of cancer cells, and in many cases a prerequisite to sustain tumor development and progression. Like protein kinases, protein phosphatases are key regulators of cell signaling. However, their contribution to aberrant signaling in cancer cells is overall less well appreciated, and therefore, their clinical potential remains largely unexploited. In this review, we provide an overview of tumor suppressive protein phosphatases in human cancer. Along their mechanisms of inactivation in defined cancer contexts, we give an overview of their functional roles in diverse signaling pathways that contribute to their tumor suppressive abilities. Finally, we discuss their emerging roles as predictive or prognostic markers, their potential as synthetic lethality targets, and the current feasibility of their reactivation with pharmacologic compounds as promising new cancer therapies. We conclude that their inclusion in clinical practice has obvious potential to significantly improve therapeutic outcome in various ways, and should now definitely be pushed forward.
Collapse
Affiliation(s)
- Bob Meeusen
- Laboratory of Protein Phosphorylation & Proteomics, Dept. of Cellular & Molecular Medicine, Faculty of Medicine, KU Leuven & Leuven Cancer Institute (LKI), KU Leuven, Belgium
| | - Veerle Janssens
- Laboratory of Protein Phosphorylation & Proteomics, Dept. of Cellular & Molecular Medicine, Faculty of Medicine, KU Leuven & Leuven Cancer Institute (LKI), KU Leuven, Belgium.
| |
Collapse
|
14
|
Pathways from senescence to melanoma: focus on MITF sumoylation. Oncogene 2017; 36:6659-6667. [PMID: 28825724 DOI: 10.1038/onc.2017.292] [Citation(s) in RCA: 26] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/21/2017] [Revised: 07/09/2017] [Accepted: 07/11/2017] [Indexed: 12/11/2022]
Abstract
Cutaneous melanoma is a deadly skin cancer that originates from melanocytes. The development of cutaneous melanoma involves a complex interaction between environmental factors, mainly ultraviolet radiation from sunlight, and genetic alterations. Melanoma can also occur from a pre-existing nevus, a benign lesion formed from melanocytes harboring oncogenic mutations that trigger proliferative arrest and senescence entry. Senescence is a potent barrier against tumor progression. As such, the acquisition of mutations that suppress senescence and promote cell division is mandatory for cancer development. This topic appears central to melanoma development because, in humans, several somatic and germline mutations are related to the control of cellular senescence and proliferative activity. Consequently, primary melanoma can be viewed as a paradigm of senescence evasion. In support of this notion, a sumoylation-defective germline mutation in microphthalmia-associated transcription factor (MITF), a master regulator of melanocyte homeostasis, is associated with the development of melanoma. Interestingly, this MITF variant has also been recently reported to negatively impact the program of senescence. This article reviews the genetic alterations that have been shown to be involved in melanoma and that alter the process of senescence to favor melanoma development. Then, the transcription factor MITF and its sumoylation-defective mutant are described. How sumoylation misregulation can change MITF activity and impact the process of senescence is discussed. Finally, the contribution of such information to the development of anti-malignant melanoma strategies is evaluated.
Collapse
|
15
|
Babagana M, Johnson S, Slabodkin H, Bshara W, Morrison C, Kandel ES. P21-activated kinase 1 regulates resistance to BRAF inhibition in human cancer cells. Mol Carcinog 2017; 56:1515-1525. [PMID: 28052407 DOI: 10.1002/mc.22611] [Citation(s) in RCA: 26] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/13/2016] [Revised: 12/16/2016] [Accepted: 12/31/2016] [Indexed: 12/13/2022]
Abstract
BRAF is a commonly mutated oncogene in various human malignancies and a target of a new class of anti-cancer agents, BRAF-inhibitors (BRAFi). The initial enthusiasm for these agents, based on the early successes in the management of metastatic melanoma, is now challenged by the mounting evidence of intrinsic BRAFi-insensitivity in many BRAF-mutated tumors, by the scarcity of complete responses, and by the inevitable emergence of drug resistance in initially responsive cases. These setbacks put an emphasis on discovering the means to increase the efficacy of BRAFi and to prevent or overcome BRAFi-resistance. We explored the role of p21-activated kinases (PAKs), in particular PAK1, in BRAFi response. BRAFi lowered the levels of active PAK1 in treated cells. An activated form of PAK1 conferred BRAFi-resistance on otherwise sensitive cells, while genetic or pharmacologic suppression of PAK1 had a sensitizing effect. While activation of AKT1 and RAC1 proto-oncogenes increased BRAFi-tolerance, the protective effect was negated in the presence of PAK inhibitors. Furthermore, combining otherwise ineffective doses of PAK- and BRAF-inhibitors synergistically affected intrinsically BRAFi-resistant cells. Considering the high incidence of PAK1 activation in cancers, our findings suggests PAK inhibition as a strategy to augment BRAFi therapy and overcome some of the well-known resistance mechanisms.
Collapse
Affiliation(s)
- Mahamat Babagana
- Department of Cell Stress Biology, Roswell Park Cancer Institute, Elm and Carlton Streets, Buffalo, New York
| | - Sydney Johnson
- Department of Cell Stress Biology, Roswell Park Cancer Institute, Elm and Carlton Streets, Buffalo, New York
| | - Hannah Slabodkin
- Department of Cell Stress Biology, Roswell Park Cancer Institute, Elm and Carlton Streets, Buffalo, New York
| | - Wiam Bshara
- Department of Pathology, Roswell Park Cancer Institute, Elm and Carlton Streets, Buffalo, New York
| | - Carl Morrison
- Department of Pathology, Roswell Park Cancer Institute, Elm and Carlton Streets, Buffalo, New York
| | - Eugene S Kandel
- Department of Cell Stress Biology, Roswell Park Cancer Institute, Elm and Carlton Streets, Buffalo, New York
| |
Collapse
|
16
|
Nikiforov MA, Shewach DS. Detection of Nucleotide Disbalance in Cells Undergoing Oncogene-Induced Senescence. Methods Mol Biol 2017; 1534:165-173. [PMID: 27812878 PMCID: PMC5579839 DOI: 10.1007/978-1-4939-6670-7_16] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/20/2022]
Abstract
DNA damage response has been characterized as an important mediator of senescence phenotypes induced by activated oncogenes in normal human cells. Depletion of intracellular deoxyribonucleotide pools has been recently recognized as one of the major causes for DNA damage in these cells. Cells undergoing oncogene-induced senescence display decreased expression of several rate-limiting enzymes involved in the biosynthesis of deoxyribonucleotides, including thymidylate synthase (TS) and ribonucleotide reductase (RR). Individual depletion of these enzymes leads to premature senescence. Reciprocally, ectopic expression of TS and RR or addition of deoxyribonucleosides resulted in suppression of senescence phenotypes in normal or tumor cells caused by overexpression of activated HRAS or depletion of C-MYC, respectively. Therefore, in the current chapter, we will describe a methodology for the quantitative measurement of nucleotide pools in senescent cells.
Collapse
Affiliation(s)
- Mikhail A Nikiforov
- Department of Cell Stress Biology, Roswell Park Cancer Institute, BLSC L3-317, Elm & Carlton Streets, Buffalo, NY, 14263, USA.
| | - Donna S Shewach
- Department of Pharmacology, University of Michigan, Ann Arbor, MI, 48109, USA
| |
Collapse
|
17
|
Grech G, Baldacchino S, Saliba C, Grixti MP, Gauci R, Petroni V, Fenech AG, Scerri C. Deregulation of the protein phosphatase 2A, PP2A in cancer: complexity and therapeutic options. Tumour Biol 2016; 37:11691-11700. [PMID: 27444275 DOI: 10.1007/s13277-016-5145-4] [Citation(s) in RCA: 42] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/22/2016] [Accepted: 07/11/2016] [Indexed: 01/26/2023] Open
Abstract
The complexity of the phosphatase, PP2A, is being unravelled and current research is increasingly providing information on the association of deregulated PP2A function with cancer initiation and progression. It has been reported that decreased activity of PP2A is a recurrent observation in many types of cancer, including colorectal and breast cancer (Baldacchino et al. EPMA J. 5:3, 2014; Cristobal et al. Mol Cancer Ther. 13:938-947, 2014). Since deregulation of PP2A and its regulatory subunits is a common event in cancer, PP2A is a potential target for therapy (Baldacchino et al. EPMA J. 5:3, 2014). In this review, the structural components of the PP2A complex are described, giving an in depth overview of the diversity of regulatory subunits. Regulation of the active PP2A trimeric complex, through phosphorylation and methylation, can be targeted using known compounds, to reactivate the complex. The endogenous inhibitors of the PP2A complex are highly deregulated in cancer, representing cases that are eligible to PP2A-activating drugs. Pharmacological opportunities to target low PP2A activity are available and preclinical data support the efficacy of these drugs, but clinical trials are lacking. We highlight the importance of PP2A deregulation in cancer and the current trends in targeting the phosphatase.
Collapse
Affiliation(s)
- Godfrey Grech
- Department of Pathology, Faculty of Medicine & Surgery, Medical School, University of Malta, Msida, MSD2090, Malta.
| | - Shawn Baldacchino
- Department of Pathology, Faculty of Medicine & Surgery, Medical School, University of Malta, Msida, MSD2090, Malta
| | - Christian Saliba
- Centre for Molecular Medicine and Biobanking, University of Malta, Msida, Malta
| | - Maria Pia Grixti
- Department of Pathology, Faculty of Medicine & Surgery, Medical School, University of Malta, Msida, MSD2090, Malta
| | - Robert Gauci
- Department of Pathology, Faculty of Medicine & Surgery, Medical School, University of Malta, Msida, MSD2090, Malta
| | - Vanessa Petroni
- Department of Anatomy, Faculty of Medicine & Surgery, University of Malta, Msida, Malta
| | - Anthony G Fenech
- Department of Clinical Pharmacology & Therapeutics, Faculty of Medicine & Surgery, University of Malta, Msida, Malta
| | - Christian Scerri
- Department of Physiology and Biochemistry, Faculty of Medicine & Surgery, University of Malta, Msida, Malta.,Molecular Genetics Clinic, Mater Dei Hospital, Msida, Malta
| |
Collapse
|
18
|
RAB7 counteracts PI3K-driven macropinocytosis activated at early stages of melanoma development. Oncotarget 2016; 6:11848-62. [PMID: 26008978 PMCID: PMC4494909 DOI: 10.18632/oncotarget.4055] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/12/2015] [Accepted: 04/20/2015] [Indexed: 12/28/2022] Open
Abstract
Derailed endolysosomal trafficking is emerging as a widespread feature of aggressive neoplasms. However, the oncogenic signals that alter membrane homeostasis and their specific contribution to cancer progression remain unclear. Understanding the upstream drivers and downstream regulators of aberrant vesicular trafficking is distinctly important in melanoma. This disease is notorious for its inter- and intra-tumoral heterogeneity. Nevertheless, melanomas uniformly overexpress a cluster of endolysosomal genes, being particularly addicted to the membrane traffic regulator RAB7. Still, the underlying mechanisms and temporal determinants of this dependency have yet to be defined. Here we addressed these questions by combining electron microscopy, real time imaging and mechanistic analyses of vesicular trafficking in normal and malignant human melanocytic cells. This strategy revealed Class I PI3K as the key trigger of a hyperactive influx of macropinosomes that melanoma cells counteract via RAB7-mediated lysosomal degradation. In addition, gain- and loss-of-function in vitro studies followed by histopathological validation in clinical biopsies and genetically-engineered mouse models, traced back the requirement of RAB7 to the suppression of premature cellular senescence traits elicited in melanocytes by PI3K-inducing oncogenes. Together, these results provide new insight into the regulators and modes of action of RAB7, broadening the impact of endosomal fitness on melanoma development.
Collapse
|
19
|
Sangodkar J, Farrington C, McClinch K, Galsky MD, Kastrinsky DB, Narla G. All roads lead to PP2A: exploiting the therapeutic potential of this phosphatase. FEBS J 2016; 283:1004-24. [PMID: 26507691 PMCID: PMC4803620 DOI: 10.1111/febs.13573] [Citation(s) in RCA: 230] [Impact Index Per Article: 28.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/29/2015] [Revised: 09/29/2015] [Accepted: 10/21/2015] [Indexed: 12/22/2022]
Abstract
Protein phosphatase 2A (PP2A) is a serine/threonine phosphatase involved in the regulation of many cellular processes. A confirmed tumor suppressor protein, PP2A is genetically altered or functionally inactivated in many cancers highlighting a need for its therapeutic reactivation. In this review we discuss recent literature on PP2A: the elucidation of its structure and the functions of its subunits, and the identification of molecular lesions and post-translational modifications leading to its dysregulation in cancer. A final section will discuss the proteins and small molecules that modulate PP2A and how these might be used to target dysregulated forms of PP2A to treat cancers and other diseases.
Collapse
Affiliation(s)
- Jaya Sangodkar
- Department of Genetics and Genomic Sciences, Icahn School of Medicine at Mt. Sinai, New York, NY, USA
| | - Caroline Farrington
- Department of Medicine and Institute for Transformative Molecular Medicine, Case Western Reserve University, Cleveland, OH, USA
| | - Kimberly McClinch
- Department of Hematology and Medical Oncology, Icahn School of Medicine at Mount Sinai, New York, NY, USA
| | - Matthew D. Galsky
- Department of Hematology and Medical Oncology, Icahn School of Medicine at Mount Sinai, New York, NY, USA
| | - David B. Kastrinsky
- Department of Structural and Chemical Biology, Icahn School of Medicine at Mount Sinai, New York, NY, USA
| | - Goutham Narla
- Department of Medicine and Institute for Transformative Molecular Medicine, Case Western Reserve University, Cleveland, OH, USA
| |
Collapse
|
20
|
Maertens GN. B'-protein phosphatase 2A is a functional binding partner of delta-retroviral integrase. Nucleic Acids Res 2015; 44:364-76. [PMID: 26657642 PMCID: PMC4705670 DOI: 10.1093/nar/gkv1347] [Citation(s) in RCA: 28] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/07/2015] [Accepted: 11/19/2015] [Indexed: 12/31/2022] Open
Abstract
To establish infection, a retrovirus must insert a DNA copy of its RNA genome into host chromatin. This reaction is catalysed by the virally encoded enzyme integrase (IN) and is facilitated by viral genus-specific host factors. Herein, cellular serine/threonine protein phosphatase 2A (PP2A) is identified as a functional IN binding partner exclusive to δ-retroviruses, including human T cell lymphotropic virus type 1 and 2 (HTLV-1 and HTLV-2) and bovine leukaemia virus (BLV). PP2A is a heterotrimer composed of a scaffold, catalytic and one of any of four families of regulatory subunits, and the interaction is specific to the B' family of the regulatory subunits. B'-PP2A and HTLV-1 IN display nuclear co-localization, and the B' subunit stimulates concerted strand transfer activity of δ-retroviral INs in vitro. The protein-protein interaction interface maps to a patch of highly conserved residues on B', which when mutated render B' incapable of binding to and stimulating HTLV-1 and -2 IN strand transfer activity.
Collapse
Affiliation(s)
- Goedele N Maertens
- Division of Infectious Diseases, St. Mary's campus, Imperial College London, Norfolk Place, London, W2 1PG, UK
| |
Collapse
|
21
|
Bianchi-Smiraglia A, Wawrzyniak JA, Bagati A, Marvin EK, Ackroyd J, Moparthy S, Bshara W, Fink EE, Foley CE, Morozevich GE, Berman AE, Shewach DS, Nikiforov MA. Pharmacological targeting of guanosine monophosphate synthase suppresses melanoma cell invasion and tumorigenicity. Cell Death Differ 2015; 22:1858-64. [PMID: 25909885 PMCID: PMC4648332 DOI: 10.1038/cdd.2015.47] [Citation(s) in RCA: 28] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/26/2015] [Revised: 03/12/2015] [Accepted: 03/16/2015] [Indexed: 12/20/2022] Open
Abstract
Malignant melanoma possesses one of the highest metastatic potentials among human cancers. Acquisition of invasive phenotypes is a prerequisite for melanoma metastases. Elucidation of the molecular mechanisms underlying melanoma invasion will greatly enhance the design of novel agents for melanoma therapeutic intervention. Here, we report that guanosine monophosphate synthase (GMPS), an enzyme required for the de novo biosynthesis of GMP, has a major role in invasion and tumorigenicity of cells derived from either BRAF(V600E) or NRAS(Q61R) human metastatic melanomas. Moreover, GMPS levels are increased in metastatic human melanoma specimens compared with primary melanomas arguing that GMPS is an attractive candidate for anti-melanoma therapy. Accordingly, for the first time we demonstrate that angustmycin A, a nucleoside-analog inhibitor of GMPS produced by Streptomyces hygroscopius efficiently suppresses melanoma cell invasion in vitro and tumorigenicity in immunocompromised mice. Our data identify GMPS as a powerful driver of melanoma cell invasion and warrant further investigation of angustmycin A as a novel anti-melanoma agent.
Collapse
Affiliation(s)
- A Bianchi-Smiraglia
- Department of Cell Stress Biology, Roswell Park Cancer Institute, Buffalo, NY 14263, USA
| | - J A Wawrzyniak
- Department of Cell Stress Biology, Roswell Park Cancer Institute, Buffalo, NY 14263, USA
| | - A Bagati
- Department of Cell Stress Biology, Roswell Park Cancer Institute, Buffalo, NY 14263, USA
| | - E K Marvin
- Department of Cell Stress Biology, Roswell Park Cancer Institute, Buffalo, NY 14263, USA
| | - J Ackroyd
- Department of Pharmacology, University of Michigan, Ann Arbor, MI 48109, USA
| | - S Moparthy
- Department of Cell Stress Biology, Roswell Park Cancer Institute, Buffalo, NY 14263, USA
| | - W Bshara
- Department of Pathology, Roswell Park Cancer Institute, Buffalo, NY 14263, USA
| | - E E Fink
- Department of Cell Stress Biology, Roswell Park Cancer Institute, Buffalo, NY 14263, USA
| | - C E Foley
- Department of Cell Stress Biology, Roswell Park Cancer Institute, Buffalo, NY 14263, USA
| | - G E Morozevich
- Orekhovich Institute of Biomedical Chemistry, Moscow 119121, Russia
| | - A E Berman
- Orekhovich Institute of Biomedical Chemistry, Moscow 119121, Russia
| | - D S Shewach
- Department of Pharmacology, University of Michigan, Ann Arbor, MI 48109, USA
| | - M A Nikiforov
- Department of Cell Stress Biology, Roswell Park Cancer Institute, Buffalo, NY 14263, USA
| |
Collapse
|
22
|
Hong CS, Ho W, Zhang C, Yang C, Elder JB, Zhuang Z. LB100, a small molecule inhibitor of PP2A with potent chemo- and radio-sensitizing potential. Cancer Biol Ther 2015; 16:821-33. [PMID: 25897893 DOI: 10.1080/15384047.2015.1040961] [Citation(s) in RCA: 79] [Impact Index Per Article: 8.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023] Open
Abstract
Protein phosphatase 2A (PP2A) is a serine/threonine phosphatase that plays a significant role in mitotic progression and cellular responses to DNA damage. While traditionally viewed as a tumor suppressor, inhibition of PP2A has recently come to attention as a novel therapeutic means of driving senescent cancer cells into mitosis and promoting cell death via mitotic catastrophe. These findings have been corroborated in numerous studies utilizing naturally produced compounds that selectively inhibit PP2A. To overcome the known human toxicities associated with these compounds, a water-soluble small molecule inhibitor, LB100, was recently developed to competitively inhibit the PP2A protein. This review summarizes the pre-clinical studies to date that have demonstrated the anti-cancer activity of LB100 via its chemo- and radio-sensitizing properties. These studies demonstrate the tremendous therapeutic potential of LB100 in a variety of cancer types. The results of an ongoing phase 1 trial are eagerly anticipated.
Collapse
Key Words
- ABC, ATP-binding cassette.
- APC, adenomatous polyposis coli
- ARPP19, cyclic AMP-regulated phosphoprotein 19
- ATM, ataxia-telangiectasia mutated
- CIP2A, cancerous inhibitor of PP2A
- CNTF, ciliary neurotrophic factor
- DISC, death-inducing signaling complex
- DVL, dishevelled
- ENSA, α-endosulphine
- GBM, glioblastoma
- GFAP, glial fibrillary acidic protein
- HCC, hepatocellular carcinoma
- HDACs, histone deacetylase complexes
- HIF-1a, hypoxia-inducible factor-1a
- HRR, homologous recombination repair
- MDM2, mouse double minute 2 homolog
- MRI, magnetic resonance imaging
- NPC, nasopharyngeal carcinoma
- PP2A, protein phosphatase 2A
- Plk1, polo-like kinase 1
- TCTP, translationally-controlled tumor protein
- TMZ, temozolomide
- TRAIL, TNF-related apoptosis-inducing ligand
- VEGF, vascular endothelial growth factor
- cell cycle
- chemosensitization
- mitotic catastrophe
- protein phosphatase 2A
- radiosensitizationreview
- small molecule inhibitor
Collapse
Affiliation(s)
- Christopher S Hong
- a The Ohio State University Wexner Medical Center ; Department of Neurological Surgery ; Columbus , OH USA
| | | | | | | | | | | |
Collapse
|
23
|
Flørenes VA, Emilsen E, Dong HP, Førsund M, Holm R, Slipicevic A. Cellular localization of CIP2A determines its prognostic impact in superficial spreading and nodular melanoma. Cancer Med 2015; 4:903-13. [PMID: 25663244 PMCID: PMC4472213 DOI: 10.1002/cam4.425] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/28/2014] [Revised: 12/15/2014] [Accepted: 12/23/2014] [Indexed: 01/31/2023] Open
Abstract
Cancerous inhibitor of protein phosphatase 2A (CIP2A) is an important oncogene contributing to cancer progression partially by regulating cMYC and AKT. We examined CIP2A expression in cutaneous melanomas, its association with clinicopathological parameters and mapped molecular mechanisms regulated by CIP2A in vitro. CIP2A expression was analyzed by immunohistochemistry in 17 nevi, 132 primary melanomas and 49 metastases. Effects of siRNA-mediated down-regulation on proliferation, apoptosis and signaling pathways were assessed in melanoma cell lines. In superficial spreading melanomas (SSM), high nuclear CIP2A expression was associated with poor overall survival (OS) (P = 0.0018). Surprisingly, high cytoplasmic expression was related to improved relapse-free (P = 0.031) and OS (P = 0.014) in nodular melanomas (NM). In vitro experiments revealed that CIP2A can regulate proliferation and/or apoptosis partially through the PI3K/AKT pathway but also independently. In summary, CIP2A could represent a potential therapeutic target in SSM. However, in NM cytoplasmic CIP2A is associated with improved prognosis indicating that CIP2A has distinct, complex functions dependent on the molecular context and histological subtype. As seen in other cancer types, CIP2A can influence cMYC and AKT, but our data also suggest that in melanoma it has additional targets which need to be identified.
Collapse
Affiliation(s)
- Vivi Ann Flørenes
- Department of Pathology, Norwegian Radium Hospital, Oslo University Hospital, N-0310, Oslo, Norway
| | - Elisabeth Emilsen
- Department of Pathology, Norwegian Radium Hospital, Oslo University Hospital, N-0310, Oslo, Norway
| | - Hiep Phuc Dong
- Department of Pathology, Norwegian Radium Hospital, Oslo University Hospital, N-0310, Oslo, Norway
| | - Mette Førsund
- Department of Pathology, Norwegian Radium Hospital, Oslo University Hospital, N-0310, Oslo, Norway
| | - Ruth Holm
- Department of Pathology, Norwegian Radium Hospital, Oslo University Hospital, N-0310, Oslo, Norway
| | - Ana Slipicevic
- Department of Pathology, Norwegian Radium Hospital, Oslo University Hospital, N-0310, Oslo, Norway
| |
Collapse
|
24
|
Meng P, Ghosh R. Transcription addiction: can we garner the Yin and Yang functions of E2F1 for cancer therapy? Cell Death Dis 2014; 5:e1360. [PMID: 25101673 PMCID: PMC4454301 DOI: 10.1038/cddis.2014.326] [Citation(s) in RCA: 46] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/12/2014] [Revised: 06/24/2014] [Accepted: 06/26/2014] [Indexed: 12/29/2022]
Abstract
Classically, as a transcription factor family, the E2Fs are known to regulate the expression of various genes whose products are involved in a multitude of biological functions, many of which are deregulated in diseases including cancers. E2F is deregulated and hyperactive in most human cancers with context dependent, dichotomous and contradictory roles in almost all cancers. Cancer cells have an insatiable demand for transcription to ensure that gene products are available to sustain various biological processes that support their rapid growth and survival. In this context, cutting-off hyperactivity of transcription factors that support transcription dependence could be a valuable therapeutic strategy. However, one of the greatest challenges of targeting a transcription factor is the global effects on non-cancerous cells given that they control cellular functions in general. Recently, there is growing realization regarding the possibility to target the oncogenic activation of transcription factors to modulate transcription addiction without affecting the normal activity required for cell functions. In this review, we used E2F1 as a prototype transcription factor to address transcription factor activity in cancer cell functions. We focused on melanoma considering that E2F1 executes critical functions in response to UV, an etiological factor of cutaneous melanoma and lies immediately downstream of the CDKN2A/pRb axis, which is frequently deregulated in melanoma. Further, activation of E2F1 in melanomas can also occur independent of loss of CDKN2A. Given its activated status and the ability to transcriptionally control a plethora of genes involved in regulating melanoma development and progression, we review the current literature on its differential role in controlling signaling pathways involved in melanoma as well as therapeutic resistance, and discuss the practical value of weaning melanoma cells from E2F1-mediated transcription dependence for melanoma management.
Collapse
Affiliation(s)
- P Meng
- Department of Urology, School of Medicine, University of Texas Health Science Center at San Antonio, San Antonio, TX, USA
| | - R Ghosh
- 1] Department of Urology, School of Medicine, University of Texas Health Science Center at San Antonio, San Antonio, TX, USA [2] Department of Pharmacology, School of Medicine, University of Texas Health Science Center at San Antonio, San Antonio, TX, USA [3] Department of Molecular Medicine, School of Medicine, University of Texas Health Science Center at San Antonio, San Antonio, TX, USA [4] Cancer Therapy and Research Center, School of Medicine, University of Texas Health Science Center at San Antonio, San Antonio, TX, USA
| |
Collapse
|
25
|
Laine A, Westermarck J. Molecular pathways: harnessing E2F1 regulation for prosenescence therapy in p53-defective cancer cells. Clin Cancer Res 2014; 20:3644-50. [PMID: 24788101 DOI: 10.1158/1078-0432.ccr-13-1942] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Induction of terminal proliferation arrest, senescence, is important for in vivo tumor-suppressive function of p53. Moreover, p53-mutant cells are highly resistant to senescence induction by either oncogenic signaling during cellular transformation or in response to different therapies. Senescence resistance in p53-mutant cells has been attributed mostly to inhibition of the checkpoint function of p53 in response to senescence-inducing stress signals. Here, we review very recent evidence that offers an alternative explanation for senescence resistance in p53-defective cancer cells: p21-mediated E2F1 expression. We discuss the potential relevance of these findings for senescence-inducing therapies and highlight cyclin-dependent kinases (CDK) and mechanisms downstream of retinoblastoma protein (RB) as prospective prosenescence therapeutic targets. In particular, we discuss recent findings indicating an important role for the E2F1-CIP2A feedback loop in causing senescence resistance in p53-compromised cancer cells. We further propose that targeting of the E2F1-CIP2A feedback loop could provide a prosenescence therapeutic approach that is effective in both p53-deficient and RB-deficient cancer cells, which together constitute the great majority of all cancer cells. Diagnostic evaluation of the described senescence resistance mechanisms in human tumors might also be informative for patient stratification for already existing therapies.
Collapse
Affiliation(s)
- Anni Laine
- Authors' Affiliations: Turku Centre for Biotechnology, University of Turku and Åbo Akademi University; and
| | - Jukka Westermarck
- Authors' Affiliations: Turku Centre for Biotechnology, University of Turku and Åbo Akademi University; and Department of Pathology, University of Turku, Turku, Finland
| |
Collapse
|
26
|
Abstract
The MYC oncoprotein is an essential transcription factor that regulates the expression of many genes involved in cell growth, proliferation, and metabolic pathways. Thus, it is important to keep MYC activity in check in normal cells in order to avoid unwanted oncogenic changes. Normal cells have adapted several ways to control MYC levels, and these mechanisms can be disrupted in cancer cells. One of the major ways in which MYC levels are controlled in cells is through targeted degradation by the ubiquitin-proteasome system (UPS). Here, we discuss the role of the UPS in the regulation of MYC protein levels and review some of the many proteins that have been shown to regulate MYC protein stability. In addition, we discuss how this relates to MYC transcriptional activity, human cancers, and therapeutic targeting.
Collapse
Affiliation(s)
- Amy S Farrell
- Department of Molecular and Medical Genetics, Oregon Health and Science University, Portland, Oregon 97239
| | | |
Collapse
|
27
|
Abstract
Protein phosphatase 2A (PP2A), one of the main serine-threonine phosphatases in mammalian cells, maintains cell homoeostasis by counteracting most of the kinase-driven intracellular signalling pathways. Unrestrained activation of oncogenic kinases together with inhibition of tumour suppressors is often required for development of cancer. PP2A has been shown to be genetically altered or functionally inactivated in many solid cancers and leukaemias, and is therefore a tumour suppressor. For example, the phosphatase activity of PP2A is suppressed in chronic myeloid leukaemia and other malignancies characterised by aberrant activity of oncogenic kinases. Preclinical studies show that pharmacological restoration of PP2A tumour-suppressor activity by PP2A-activating drugs (eg, FTY720) effectively antagonises cancer development and progression. Here, we discuss PP2A as a druggable tumour suppressor in view of the possible introduction of PP2A-activating drugs into anticancer therapeutic protocols.
Collapse
Affiliation(s)
- Danilo Perrotti
- Human Cancer Genetics Program, Department of Molecular Virology, Immunology, and Medical Genetics, and Comprehensive Cancer Center, Ohio State University, Columbus, OH 43210-2207, USA.
| | | |
Collapse
|
28
|
Mannava S, Moparthy KC, Wheeler LJ, Natarajan V, Zucker SN, Fink EE, Im M, Flanagan S, Burhans WC, Zeitouni NC, Shewach DS, Mathews CK, Nikiforov MA. Depletion of deoxyribonucleotide pools is an endogenous source of DNA damage in cells undergoing oncogene-induced senescence. THE AMERICAN JOURNAL OF PATHOLOGY 2012; 182:142-51. [PMID: 23245831 DOI: 10.1016/j.ajpath.2012.09.011] [Citation(s) in RCA: 68] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/29/2012] [Revised: 08/10/2012] [Accepted: 09/18/2012] [Indexed: 12/26/2022]
Abstract
In normal human cells, oncogene-induced senescence (OIS) depends on induction of DNA damage response. Oxidative stress and hyperreplication of genomic DNA have been proposed as major causes of DNA damage in OIS cells. Here, we report that down-regulation of deoxyribonucleoside pools is another endogenous source of DNA damage in normal human fibroblasts (NHFs) undergoing HRAS(G12V)-induced senescence. NHF-HRAS(G12V) cells underexpressed thymidylate synthase (TS) and ribonucleotide reductase (RR), two enzymes required for the entire de novo deoxyribonucleotide biosynthesis, and possessed low dNTP levels. Chromatin at the promoters of the genes encoding TS and RR was enriched with retinoblastoma tumor suppressor protein and histone H3 tri-methylated at lysine 9. Importantly, ectopic coexpression of TS and RR or addition of deoxyribonucleosides substantially suppressed DNA damage, senescence-associated phenotypes, and proliferation arrest in two types of NHF-expressing HRAS(G12V). Reciprocally, short hairpin RNA-mediated suppression of TS and RR caused DNA damage and senescence in NHFs, although less efficiently than HRAS(G12V). However, overexpression of TS and RR in quiescent NHFs did not overcome proliferation arrest, suggesting that unlike quiescence, OIS requires depletion of dNTP pools and activated DNA replication. Our data identify a previously unknown role of deoxyribonucleotides in regulation of OIS.
Collapse
Affiliation(s)
- Sudha Mannava
- Department of Cell Stress Biology, Roswell Park Cancer Institute, Buffalo, New York 14263, USA
| | | | | | | | | | | | | | | | | | | | | | | | | |
Collapse
|
29
|
Bianchi-Smiraglia A, Nikiforov MA. Controversial aspects of oncogene-induced senescence. Cell Cycle 2012; 11:4147-51. [PMID: 23095636 DOI: 10.4161/cc.22589] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023] Open
Abstract
Oncogene-induced senescence (OIS) is a fail-safe mechanism that is developed to suppress cell proliferation caused by aberrant activation of oncoproteins in normal cells. Most of the available literature considers senescence to be caused by activated RAS or RAF proteins. In the current review, we will discuss some of the controversial aspects of RAS- or RAF-induced senescence in different types of normal cells: are tumor suppressors important for OIS? What is the role of DNA damage in OIS? Are there different types of OIS?
Collapse
|
30
|
Liu L, Eisenman RN. Regulation of c-Myc Protein Abundance by a Protein Phosphatase 2A-Glycogen Synthase Kinase 3β-Negative Feedback Pathway. Genes Cancer 2012; 3:23-36. [PMID: 22893788 DOI: 10.1177/1947601912448067] [Citation(s) in RCA: 38] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/14/2012] [Accepted: 04/12/2012] [Indexed: 12/11/2022] Open
Abstract
Regulation of Myc protein abundance is critical for normal cell growth as evidenced by the fact that deregulated Myc expression is a hallmark of many cancers. One of several important mechanisms that control Myc levels involves its phosphorylation-dependent proteolysis. Previous studies have shown that phosphorylation of threonine 58 by glycogen synthase kinase 3β (GSK3β) within the conserved Myc Box I sequence results in binding by the ubiquitin ligase Fbw7-SCF complex, followed by ubiquitination and proteasome-mediated degradation of Myc. Here, we show that induction of Myc in several cell types correlates with loss of the inhibitory serine 9 phosphorylation of GSK3β and its increased kinase activity. The Myc-induced decrease in serine 9 phosphorylation is blocked by okadaic acid, an inhibitor of protein phosphatase 2A (PP2A). We therefore examined components of PP2A complexes and found that, among the regulatory B56 subunits, only the promoter of the ppp2r5d gene, encoding the B56δ isoform, is directly bound and transcriptionally activated by Myc in an E-box-dependent manner. Furthermore, we find that B56δ associates with both GSK3β and Myc, resulting in phosphorylation of Myc threonine 58, the well-established signal for ubiquitination and degradation. Furthermore, overexpression, or siRNA-mediated knockdown, of B56δ respectively results in accelerated, or retarded, rates of Myc degradation. Together, our data indicate that Myc limits its own abundance through a negative feedback pathway involving PP2A and GSK3β.
Collapse
Affiliation(s)
- Lingfeng Liu
- Fred Hutchinson Cancer Research Center, Seattle, WA, USA
| | | |
Collapse
|
31
|
Tay KH, Jin L, Tseng HY, Jiang CC, Ye Y, Thorne RF, Liu T, Guo ST, Verrills NM, Hersey P, Zhang XD. Suppression of PP2A is critical for protection of melanoma cells upon endoplasmic reticulum stress. Cell Death Dis 2012; 3:e337. [PMID: 22739989 PMCID: PMC3388246 DOI: 10.1038/cddis.2012.79] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
Endoplasmic reticulum (ER) stress triggers apoptosis by activating Bim in diverse types of cells, which involves dephosphorylation of BimEL by protein phosphatase 2A (PP2A). However, melanoma cells are largely resistant to ER stress-induced apoptosis, suggesting that Bim activation is suppressed in melanoma cells undergoing ER stress. We show here that ER stress reduces PP2A activity leading to increased ERK activation and subsequent phosphorylation and proteasomal degradation of BimEL. Despite sustained upregulation of Bim at the transcriptional level, the BimEL protein expression was downregulated after an initial increase in melanoma cells subjected to pharmacological ER stress. This was mediated by increased activity of ERK, whereas the phosphatase activity of PP2A was reduced by ER stress in melanoma cells. The increase in ERK activation was, at least in part, due to reduced dephosphorylation by PP2A, which was associated with downregulation of the PP2A catalytic C subunit. Notably, instead of direct dephosphorylation of BimEL, PP2A inhibited its phosphorylation indirectly through dephosphorylation of ERK in melanoma cells. Taken together, these results identify downregualtion of PP2A activity as an important protective mechanism of melanoma cells against ER stress-induced apoptosis.
Collapse
Affiliation(s)
- K H Tay
- School of Medicine and Public Health, University of Newcastle, Newcastle, New South Wales 2308, Australia
| | | | | | | | | | | | | | | | | | | | | |
Collapse
|
32
|
Abstract
Cutaneous melanoma originates from pigment producing melanocytes or their precursors and is considered the deadliest form of skin cancer. For the last 40 years, few treatment options were available for patients with late-stage melanoma. However, remarkable advances in the therapy field were made recently, leading to the approval of two new drugs, the mutant BRAF inhibitor vemurafenib and the immunostimulant ipilimumab. Although these drugs prolong patients' lives, neither drug cures the disease completely, emphasizing the need for improvements of current therapies. Our knowledge about the complex genetic and biological mechanisms leading to melanoma development has increased, but there are still gaps in our understanding of the early events of melanocyte transformation and disease progression. In this review, we present a summary of the main contributing factors leading to melanocyte transformation and discuss recent novel findings and technologies that will help answer some of the key biological melanoma questions and lay the groundwork for novel therapies.
Collapse
Affiliation(s)
- Ana Slipicevic
- The Wistar Institute, Philadelphia, Pennsylvania, USA
- Department of Pathology, The Norwegian Radium Hospital, Oslo University Hospital, Oslo, Norway
| | | |
Collapse
|
33
|
Niemelä M, Kauko O, Sihto H, Mpindi JP, Nicorici D, Pernilä P, Kallioniemi OP, Joensuu H, Hautaniemi S, Westermarck J. CIP2A signature reveals the MYC dependency of CIP2A-regulated phenotypes and its clinical association with breast cancer subtypes. Oncogene 2012; 31:4266-78. [DOI: 10.1038/onc.2011.599] [Citation(s) in RCA: 64] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
|