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Liu J, Han D, Xuan J, Xie J, Wang W, Zhou Q, Chen K. COP9 signalosome complex is a prognostic biomarker and corresponds with immune infiltration in hepatocellular carcinoma. Aging (Albany NY) 2024; 16:5264-5287. [PMID: 38466642 PMCID: PMC11006475 DOI: 10.18632/aging.205646] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/11/2023] [Accepted: 01/15/2024] [Indexed: 03/13/2024]
Abstract
Hepatocellular carcinoma (HCC) is among the most common deadly tumors but still lacks specific biomarkers for diagnosis, prognosis, and treatment guidance. The COP9 signalosome (COPS) is an essential regulator of the ubiquitin conjugation pathway upregulated in various cancers. We evaluated the contributions of COPS subunits to HCC tumorigenesis and their utility for prognosis. We comprehensively evaluated the tumor expression pattern and tumorigenic functions of COPS subunits using The Cancer Genome Atlas (TCGA), The Human Protein Atlas and immunohistochemistry. Kaplan-Meier, Cox regression, ROC curve, and nomogram analyses were used to assess the predictive values of COPS subunits for clinical outcome. Expression levels of COPS subunits were significantly upregulated in HCC tissues, which predicted shorter overall survival (OS). Further, Cox regression analysis identified COPS5, COPS7B, and COPS9 as independent prognostic biomarkers for OS. High mutation rates were also found in COPS subunits. Functional network analysis indicated that COPS and neighboring genes regulate 'protein neddylation', 'protein deneddylation', and 'protein ubiquitination'. The COPS PPI included strong interactions with p53, CUL1/2/3/4, and JUN. Moreover, the correlations between COPS subunit expression levels and tumor immune cell infiltration rates were examined using TIMER, TISIDB, ssGSEA, and ESTIMATE packages. COPS subunits expression levels were positively correlated with specific tumor immune cell infiltration rates, immunoregulator expression levels, and microsatellite instability in HCC. Finally, knockout of COPS6 and COPS9 in HCC cells reduced while overexpression enhanced proliferation rate and metastasis capacity. Our study revealed that COPS potential biomarker for unfavorable HCC prognosis and indicators of immune infiltration, tumorigenicity, and metastasis.
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Affiliation(s)
- Jiahui Liu
- Department of Clinical Laboratory, Zhongshan City People’s Hospital, The Affiliated Zhongshan Hospital of Sun Yat-Sen University, Zhongshan 528400, Guangdong, China
- Laboratory of Basic Medical Science, General Hospital of Southern Theater Command of PLA, Guangzhou 510000, Guangdong, China
| | - Dexing Han
- The Second Clinical Medical College, Guangzhou University of Chinese Medicine, Guangzhou 510000, Guangdong, China
| | - Junfeng Xuan
- Laboratory of Basic Medical Science, General Hospital of Southern Theater Command of PLA, Guangzhou 510000, Guangdong, China
| | - Jinye Xie
- Department of Clinical Laboratory, Zhongshan City People’s Hospital, The Affiliated Zhongshan Hospital of Sun Yat-Sen University, Zhongshan 528400, Guangdong, China
| | - Weijia Wang
- Department of Clinical Laboratory, Zhongshan City People’s Hospital, The Affiliated Zhongshan Hospital of Sun Yat-Sen University, Zhongshan 528400, Guangdong, China
| | - Quan Zhou
- Laboratory of Basic Medical Science, General Hospital of Southern Theater Command of PLA, Guangzhou 510000, Guangdong, China
- Research Centre of Basic Integrative Medicine, School of Basic Medical Sciences, Guangzhou University of Chinese Medicine, Guangzhou 510000, Guangdong, China
| | - Kang Chen
- Department of Clinical Laboratory, Zhongshan City People’s Hospital, The Affiliated Zhongshan Hospital of Sun Yat-Sen University, Zhongshan 528400, Guangdong, China
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Du W, Zhang R, Muhammad B, Pei D. Targeting the COP9 signalosome for cancer therapy. Cancer Biol Med 2022; 19:j.issn.2095-3941.2021.0605. [PMID: 35315259 PMCID: PMC9196064 DOI: 10.20892/j.issn.2095-3941.2021.0605] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/09/2021] [Accepted: 01/18/2022] [Indexed: 11/24/2022] Open
Abstract
The COP9 signalosome (CSN) is a highly conserved protein complex composed of 8 subunits (CSN1 to CSN8). The individual subunits of the CSN play essential roles in cell proliferation, tumorigenesis, cell cycle regulation, DNA damage repair, angiogenesis, and microenvironmental homeostasis. The CSN complex has an intrinsic metalloprotease that removes the ubiquitin-like activator NEDD8 from cullin-RING ligases (CRLs). Binding of neddylated CRLs to CSN is sensed by CSN4 and communicated to CSN5 with the assistance of CSN6, thus leading to the activation of deneddylase. Therefore, CSN is a crucial regulator at the intersection between neddylation and ubiquitination in cancer progression. Here, we summarize current understanding of the roles of individual CSN subunits in cancer progression. Furthermore, we explain how the CSN affects tumorigenesis through regulating transcription factors and the cell cycle. Finally, we discuss individual CSN subunits as potential therapeutic targets to provide new directions and strategies for cancer therapy.
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Affiliation(s)
- Wenqi Du
- Department of Pathology, Xuzhou Medical University, Xuzhou 221004, China
- Department of Human Anatomy, Xuzhou Medical University, Xuzhou 221004, China
| | - Ruicheng Zhang
- Department of Neurology, Affiliated Hospital of Xuzhou Medical University, Xuzhou 221006, China
| | - Bilal Muhammad
- Department of Neurology, Affiliated Hospital of Xuzhou Medical University, Xuzhou 221006, China
| | - Dongsheng Pei
- Department of Pathology, Xuzhou Medical University, Xuzhou 221004, China
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3
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Mao Z, Chen C, Pei DS. The Emerging Role of CSN6 in Biological Behavior and Cancer Progress. Anticancer Agents Med Chem 2020; 19:1198-1204. [PMID: 30961513 DOI: 10.2174/1871520619666190408142131] [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: 10/12/2018] [Revised: 12/23/2018] [Accepted: 03/27/2019] [Indexed: 11/22/2022]
Abstract
BACKGROUND The Constitutive Photomorphogenesis 9 (COP9) signalosome (CSN) subunit 6 (CSN6) noticeably acts as a regulator of the degradation of cancer-related proteins, which contributes to cancerogenesis. The aims of this paper are to expound the research advances of CSN6, particularly focusing on roles of CSN6 in the regulation of biological behavior and cancer progress. METHODS Literature from PubMed and Web of Science databases about biological characteristics and application of CSN6 published in recent years was collected to conduct a review. RESULTS CSN6, not only the non-catalytic Mpr1p and Pad1p N-terminal (MPN) subunit of CSN, but also a relatively independent protein molecule, has received great attention as a regulator of a wide range of developmental processes by taking part in the ubiquitin-proteasome system and signal transduction, as well as regulating genome integrity and DNA damage response. In addition, phosphorylation of CSN6 increases the stability of CSN6, thereby promoting its regulatory capacity. Moreover, CSN6 is overexpressed in many types of cancer compared with normal tissues and is involved in the regulation of several important intracellular pathways, consisting of cell proliferation, migration, invasion, transformation, and tumorigenesis. CONCLUSION We mainly present insights into the function and research development of CSN6, hoping that it can help guide the treatment of developmental defects and improve clinical care, especially in the regulation of cancer signaling pathways.
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Affiliation(s)
- Zun Mao
- Laboratory of Clinical and Experimental Pathology, Xuzhou Medical University, 209 Tong-shan Road, Xuzhou 221004, Jiangsu, China
| | - Cheng Chen
- Laboratory of Clinical and Experimental Pathology, Xuzhou Medical University, 209 Tong-shan Road, Xuzhou 221004, Jiangsu, China
| | - Dong-Sheng Pei
- Laboratory of Clinical and Experimental Pathology, Xuzhou Medical University, 209 Tong-shan Road, Xuzhou 221004, Jiangsu, China
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Hou J, Cui H. CSN6: a promising target for cancer prevention and therapy. Histol Histopathol 2020; 35:645-652. [PMID: 32016946 DOI: 10.14670/hh-18-206] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
CSN6 has recently received increased attention as a multifunctional protein involved in protein stability. CSN6 plays an important role in controlling cellular proliferation, apoptosis and metastasis, modulating signal transduction, as well as regulating DNA damage and repair. Most studies have demonstrated that CSN6 is significantly upregulated in human malignant tumors such as cervical cancer, papillary thyroid cancer, colorectal cancer, breast cancer, lung adenocarcinoma, and glioblastoma, and its expression is usually correlated with poor prognosis. In this review, we summarize recent available findings regarding the oncogenic role of CSN6 in tumors, and provide a better understanding of CSN6 function at the molecular level and its potential therapeutic implications in combating human cancers.
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Affiliation(s)
- Jianbing Hou
- State Key Laboratory of Silkworm Genome Biology, Key Laboratory for Sericulture Biology and Genetic Breeding, Ministry of Agriculture and Rural Affairs, College of Biotechnology, Southwest University, Chongqing, China.,Cancer Center, Medical Research Institute, Southwest University, Chongqing, China.,Chongqing Engineering and Technology Research Centre for Silk Biomaterials and Regenerative Medicine, Chongqing, China
| | - Hongjuan Cui
- Cancer Center, Medical Research Institute, Southwest University, Chongqing, China.,Chongqing Engineering and Technology Research Centre for Silk Biomaterials and Regenerative Medicine, Chongqing, China.,State Key Laboratory of Silkworm Genome Biology, Key Laboratory for Sericulture Biology and Genetic Breeding, Ministry of Agriculture and Rural Affairs, College of Biotechnology, Southwest University, Chongqing, China.
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5
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Shi J, Guan X, Zhan F, Liu C, Li Z, Yao Y, Wang B, Lou C, Zhang Y. CSN6 expression is associated with pancreatic cancer progression and predicts poor prognosis. Cancer Biol Ther 2019; 20:1290-1299. [PMID: 31311398 DOI: 10.1080/15384047.2019.1632143] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022] Open
Abstract
Constitutive photomorphogenesis 9 (COP9) signalosome 6 (CSN6) plays an essential role in tumor development. The present study aims to demonstrate that CSN6 is an important biomarker and has prognostic value for patients with pancreatic ductal adenocarcinoma (PDAC). We analyzed CSN6 expression levels in PDAC and adjacent non-cancerous tissues using immunohistochemistry (IHC) and quantitative real-time PCR (qPCR) analysis. We found that CSN6 was highly expressed in PDAC tissues, contrasting to adjacent non-cancerous tissues. Interestingly, CSN6 expression was positively associated with proliferating cell nuclear antigen (PCNA) expression. Further investigation indicated that CSN6 knockdown significantly suppressed the proliferation of PDAC cells and decreased the expression levels of PCNA, while CSN6 overexpression increased the proliferation, as well as the expression levels of PCNA in PDAC cells. Furthermore, a χ2 test indicated that the expression of CSN6 in PDAC tissues was markedly associated with tumor infiltration and serum carbohydrate antigen 19-9 levels. In addition, univariate and multivariate analyses showed that CSN6 levels were significantly correlated with poor clinical outcomes of patients with PDAC. Kaplan-Meier analysis showed that patients with high expression of CSN6 had shorter overall survival. These results suggest that the expression of CSN6 correlates with the progression of PDAC, resulting in poor prognosis. Thus, CSN6 may play a significant role in the development of PDAC and is a potential target to prevent and treat PDAC.
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Affiliation(s)
- Jiaqi Shi
- Department of Gastrointestinal Medical Oncology, Harbin Medical University Cancer Hospital , Harbin , Heilongjiang Province , P. R. China.,Translational Medicine Research and Cooperation Center of Northern China, Heilongjiang Academy of Medical Sciences , Harbin , P. R. China
| | - Xin Guan
- Department of Gastrointestinal Medical Oncology, Harbin Medical University Cancer Hospital , Harbin , Heilongjiang Province , P. R. China.,Translational Medicine Research and Cooperation Center of Northern China, Heilongjiang Academy of Medical Sciences , Harbin , P. R. China
| | - Fei Zhan
- Department of Gastrointestinal Medical Oncology, Harbin Medical University Cancer Hospital , Harbin , Heilongjiang Province , P. R. China.,Translational Medicine Research and Cooperation Center of Northern China, Heilongjiang Academy of Medical Sciences , Harbin , P. R. China
| | - Chao Liu
- Department of Gastrointestinal Medical Oncology, Harbin Medical University Cancer Hospital , Harbin , Heilongjiang Province , P. R. China.,Translational Medicine Research and Cooperation Center of Northern China, Heilongjiang Academy of Medical Sciences , Harbin , P. R. China
| | - Zhiwei Li
- Department of Gastrointestinal Medical Oncology, Harbin Medical University Cancer Hospital , Harbin , Heilongjiang Province , P. R. China
| | - Yuanfei Yao
- Department of Gastrointestinal Medical Oncology, Harbin Medical University Cancer Hospital , Harbin , Heilongjiang Province , P. R. China.,Translational Medicine Research and Cooperation Center of Northern China, Heilongjiang Academy of Medical Sciences , Harbin , P. R. China
| | - Bojun Wang
- Department of Gastrointestinal Medical Oncology, Harbin Medical University Cancer Hospital , Harbin , Heilongjiang Province , P. R. China.,Translational Medicine Research and Cooperation Center of Northern China, Heilongjiang Academy of Medical Sciences , Harbin , P. R. China
| | - Changjie Lou
- Department of Gastrointestinal Medical Oncology, Harbin Medical University Cancer Hospital , Harbin , Heilongjiang Province , P. R. China
| | - Yanqiao Zhang
- Department of Gastrointestinal Medical Oncology, Harbin Medical University Cancer Hospital , Harbin , Heilongjiang Province , P. R. China.,Translational Medicine Research and Cooperation Center of Northern China, Heilongjiang Academy of Medical Sciences , Harbin , P. R. China
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6
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Zhu Y, Li F, Shi W, Zhai C, Wang J, Yan X, Wang Q, Zhang Q, Yang L, Gao L, Li M. COP9 signalosome subunit 6 mediates PDGF -induced pulmonary arterial smooth muscle cells proliferation. Exp Cell Res 2018; 371:379-388. [PMID: 30180991 DOI: 10.1016/j.yexcr.2018.08.032] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/04/2018] [Revised: 08/08/2018] [Accepted: 08/27/2018] [Indexed: 12/27/2022]
Abstract
Up-regulation of mammalian COP9 signalosome subunit 6 (CSN6) and consequent reduction of SCF ubiquitin ligase substrate receptor β-transduction repeat-containing protein (β-TrCP) have been shown to be associated with cancer cells proliferation. However, it is unclear whether CSN6 and β-TrCP are also involved in PDGF-induced pulmonary arterial smooth muscle cells (PASMCs) proliferation. This study aims to address this issue and further explore its potential mechanisms. Our results indicated that PDGF phosphorylated Akt, stimulated PASMCs proliferation; while inhibition of PDGF receptor (PDGFR) by imatinib prevented these effects. PDGF further up-regulated CSN6 protein expression, this was accompanied with β-TrCP reduction and increase of Cdc25A. Inhibition of PDGFR/PI3K/Akt signaling pathway reversed PDGF-induced such changes and cell proliferation. Prior transfection of CSN6 siRNA blocked PDGF-induced β-TrCP down-regulation, Cdc25A up-regulation and cell proliferation. Furthermore, pre-treatment of cells with MG-132 also abolished PDGF-induced β-TrCP reduction, Cdc25A elevation and cell proliferation. In addition, pre-depletion of Cdc25A by siRNA transfection suppressed PDGF-induced PASMCs proliferation. Taken together, our study indicates that up-regulation of CSN6 by PDGFR/PI3K/Akt signaling pathway decreases β-TrCP by increasing its ubiquitinated degradation, and thereby increases the expression of Cdc25A, which promotes PDGF-induced PASMCs proliferation.
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Affiliation(s)
- Yanting Zhu
- Department of Respiratory and Critical Care Medicine, the First Affiliated Hospital of Xi'an Jiaotong University, Xi'an, Shaanxi 710061, People's Republic of China
| | - Fangwei Li
- Department of Respiratory and Critical Care Medicine, the First Affiliated Hospital of Xi'an Jiaotong University, Xi'an, Shaanxi 710061, People's Republic of China
| | - Wenhua Shi
- Department of Respiratory and Critical Care Medicine, the First Affiliated Hospital of Xi'an Jiaotong University, Xi'an, Shaanxi 710061, People's Republic of China
| | - Cui Zhai
- Department of Respiratory and Critical Care Medicine, the First Affiliated Hospital of Xi'an Jiaotong University, Xi'an, Shaanxi 710061, People's Republic of China
| | - Jian Wang
- Department of Respiratory and Critical Care Medicine, the First Affiliated Hospital of Xi'an Jiaotong University, Xi'an, Shaanxi 710061, People's Republic of China
| | - Xin Yan
- Department of Respiratory and Critical Care Medicine, the First Affiliated Hospital of Xi'an Jiaotong University, Xi'an, Shaanxi 710061, People's Republic of China
| | - Qingting Wang
- Department of Respiratory and Critical Care Medicine, the First Affiliated Hospital of Xi'an Jiaotong University, Xi'an, Shaanxi 710061, People's Republic of China
| | - Qianqian Zhang
- Department of Respiratory and Critical Care Medicine, the First Affiliated Hospital of Xi'an Jiaotong University, Xi'an, Shaanxi 710061, People's Republic of China
| | - Lan Yang
- Department of Respiratory and Critical Care Medicine, the First Affiliated Hospital of Xi'an Jiaotong University, Xi'an, Shaanxi 710061, People's Republic of China
| | - Li Gao
- Division of Allergy and Clinical Immunology, Department of Medicine, The Johns Hopkins University School of Medicine, Baltimore, MD 21224, USA
| | - Manxiang Li
- Department of Respiratory and Critical Care Medicine, the First Affiliated Hospital of Xi'an Jiaotong University, Xi'an, Shaanxi 710061, People's Republic of China.
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7
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COP9 signalosome subunit 6 binds and inhibits avian leukosis virus integrase. Biochem Biophys Res Commun 2014; 453:527-32. [PMID: 25285639 DOI: 10.1016/j.bbrc.2014.09.116] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/12/2014] [Accepted: 09/26/2014] [Indexed: 12/26/2022]
Abstract
The retroviral integrase plays an essential role in the integration of reverse-transcribed retroviral cDNA into the host cell genome, and serves as an important target for anti-viral therapeutics. In this study, we identified the COP9 signalosome subunit 6 (CSN6) as a novel avian leukosis virus (ALV) integrase binding protein. Co-immunoprecipitation and GST pull-down assays showed that CSN6 bound to ALV integrase likely through direct interaction of CSN6 to the catalytic core of the integrase. We further demonstrated CSN6 inhibited integrase activity in vitro; knockdown of CSN6 in DF-1 promoted ALV production. These results indicated that CSN6 may be a negative regulator of ALV replication by binding to and inhibiting integrase. Our findings provided the insight into the integrase-based host defense system and may have implications in the development of integrase-based anti-viral strategies.
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8
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Zhang SN, Pei DS, Zheng JN. The COP9 signalosome subunit 6 (CSN6): a potential oncogene. Cell Div 2013; 8:14. [PMID: 24286178 PMCID: PMC4175502 DOI: 10.1186/1747-1028-8-14] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/17/2013] [Accepted: 11/18/2013] [Indexed: 01/11/2023] Open
Abstract
CSN6 is one subunit of the constitutive photomorphogenesis 9 (COP9) signalosome (CSN), which is an evolutionarily conserved multiprotein complex found in plants and animals and originally described as a repressor of light-dependent growth and transcription in Arabidopsis. CSN is homologous to the 19S lid subcomplex of the 26S proteasome, thus it has been postulated to be a regulator of the ubiquitin-proteasome pathway. In mammalian cells, it consists of eight subunits (CSN1-CSN8). Among the CSN subunits, CSN5 and CSN6 are the only two that each contains an MPN (Mpr1p and Pad1p N-terminal) domain. The deneddylating activity of an MPN domain toward cullin-RING ubiquitin ligases (CRL) may coordinate CRL-mediated ubiquitination activity. More and more studies about CSN6 are emerging, and its overexpression is found in many types of cancers. Evidence has shown that CSN6 is a molecule platform between protein degradation and signal transduction. Here, we provide a summary of human CSN6, especially its roles in cancer, hoping that it can lay the groundwork for cancer prevention or therapy.
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Affiliation(s)
| | - Dong-Sheng Pei
- Jiangsu Key Laboratory of Biological Cancer Therapy, Xuzhou Medical College, 84 West Huai-hai Road, Xuzhou, Jiangsu, P,R, China.
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9
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Zhao R, Yang HY, Shin J, Phan L, Fang L, Che TF, Su CH, Yeung SCJ, Lee MH. CDK inhibitor p57 (Kip2) is downregulated by Akt during HER2-mediated tumorigenicity. Cell Cycle 2013; 12:935-43. [PMID: 23421998 DOI: 10.4161/cc.23883] [Citation(s) in RCA: 34] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022] Open
Abstract
HER2/neu oncogene is frequently deregulated in cancers, and the (PI3K)-Akt signaling is one of the major pathways in mediating HER2/neu oncogenic signal. p57 (Kip2) , an inhibitor of cyclin-depependent kinases, is pivotal in regulating cell cycle progression, but its upstream regulators remain unclear. Here we show that the HER2-Akt axis is linked to p57 (Kip2) regulation, and that Akt is a negative regulator of p57 (Kip2) . Ectopic expression of Akt can decrease the expression of p57 (Kip2) , while Akt inhibition leads to p57 (Kip2) stabilization. Mechanistic studies show that Akt interacts with p57 (Kip2) and causes cytoplasmic localization of p57 (Kip2) . Akt phosphorylates p57 on Ser 282 or Thr310. Akt activity results in destabilization of p57 by accelerating turnover rate of p57 and enhancing p57 ubiquitination. Importantly, the negative impact of HER2/Akt on p57 stability contributes to HER2-mediated cell proliferation, transformational activity and tumorigenicity. p57 restoration can attenuate these defects caused by HER2. Significantly, Kaplan-Meier analysis of tumor samples demonstrate that in tumors where HER2 expression was observed, high expression levels of p57 (Kip2) were associated with better overall survival. These data suggest that HER2/Akt is an important negative regulator of p57 (Kip2) , and that p57 restoration in HER2-overexpressing cells can reduce breast tumor growth. Our findings indicate the applicability of employing p57 regulation as a therapeutic intervention in HER2-overexpressing cancers.
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Affiliation(s)
- Ruiying Zhao
- Department of Molecular and Cellular Oncology, The University of Texas MD Anderson Cancer Center, Houston, TX, USA
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10
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Chen B, Zhao R, Su CH, Linan M, Tseng C, Phan L, Fang L, Yang HY, Yang H, Wang W, Xu X, Jiang N, Cai S, Jin F, Yeung SCJ, Lee MH. CDK inhibitor p57 (Kip2) is negatively regulated by COP9 signalosome subunit 6. Cell Cycle 2012. [PMID: 23187808 DOI: 10.4161/cc.22887] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022] Open
Abstract
Subunit 6 of the COP9 signalosome complex, CSN6, is known to be critical to the regulation of the MDM2-p53 axis for cell proliferation and anti-apoptosis, but its many targets remain unclear. Here we show that p57 (Kip2) is a target of CSN6, and that CSN6 is a negative regulator of p57 (Kip2) . CSN6 associates with p57 (Kip2) , and its overexpression can decrease the steady-state expression of p57 (Kip2) ; accordingly, CSN6 deficiency leads to p57 (Kip2) stabilization. Mechanistic studies show that CSN6 associates with p57 (Kip2) and Skp2, a component of the E3 ligase, which, in turn, facilitates Skp2-mediated protein ubiquitination of p57 (Kip2) . Loss of Skp2 compromised CSN6-mediated p57 (Kip2) destabilization, suggesting collaboration between Skp2 and CSN6 in degradation of p57 (Kip2) . CSN6's negative impact on p57 (Kip2) elevation translates into cell growth promotion, cell cycle deregulation and potentiated transformational activity. Significantly, univariate Kaplan-Meier analysis of tumor samples demonstrates that high CSN6 expression or low p57 expression is associated with poor overall survival. These data suggest that CSN6 is an important negative regulator of p57 (Kip2) , and that overexpression of CSN6 in many types of cancer could lead to decreased expression of p57 (Kip2) and result in promoted cancer cell growth.
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Affiliation(s)
- Bo Chen
- Department of Molecular and Cellular Oncology, The University of Texas MD Anderson Cancer Center, Houston, TX, USA.
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Affiliation(s)
- Swathi V Iyer
- Department of Cancer Biology, University of Kansas Medical Center, Kansas City, KS, USA
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