title: USP22 acts as an oncogene by the activation of BMI-1-mediated INK4a/ARF pathway and Akt pathway.
abstract: Recent studies provided strong support for the view that ubiquitin-specific protease 22 (USP22) plays a central role in cell-cycle progression and also in pathological processes such as oncogenesis. We have recently shown that USP22 levels are elevated in colorectal carcinoma with associated increase in the expression of several cell-cycle-related genes. However, the precise mechanism for these functions of USP22 at molecular level has not been fully elucidated. Currently, we investigated the role of USP22 in human colorectal cancer (CRC). We observed that USP22 expression was statistically significantly correlated positively with that of BMI-1, c-Myc and both, pAkt (Ser473), and pAkt (Thr308), in primary tumor tissues from 43 CRC patients. Down-regulation of USP22 expression in HCT116 colorectal cancer cells by siRNA resulted in the accumulation of cells in the G1 phase of the cell cycle. RNAi-knockdown of USP22 in HCT16 cells also led to the repression of BMI-1 and was accompanied by the up-regulation of p16INK4a and p14ARF, with a consequent decrease in E2F1 and p53 levels. In addition, down-regulation of c-Myc-targeted cyclin D2 was also noticed in cells treated with USP22-siRNA. Furthermore, our results showed that USP22 deletion also caused down-regulation of Akt/GSK3β activity, which can also contribute to the reduction of cyclin D2. Collectively, our current results suggest that USP22 may act as an oncogene in CRC as it positively regulates cell cycle via both BMI-1-mediated INK4a/ARF pathway and Akt signaling pathway.
authors.affiliation: Department of Colorectal Surgery, The Affiliated 3rd Hospital, Harbin Medical University, Harbin, China.
authors.forename: Yan-Long
authors.initials: YL
authors.lastname: Liu
authors.forename: Shi-Xiong
authors.initials: SX
authors.lastname: Jiang
authors.forename: Yan-Mei
authors.initials: YM
authors.lastname: Yang
authors.forename: Hui
authors.initials: H
authors.lastname: Xu
authors.forename: Jing-Lei
authors.initials: JL
authors.lastname: Liu
authors.forename: Xi-Shan
authors.initials: XS
authors.lastname: Wang
mesh_terms: D000368:Aged; D045744:Cell Line, Tumor; D015179:Colorectal Neoplasms / Q000378:metabolism* / Q000473:pathology; D056742:Cyclin D2 / Q000378:metabolism; D019941:Cyclin-Dependent Kinase Inhibitor p16 / Q000378:metabolism*; D050687:E2F1 Transcription Factor / Q000378:metabolism; D005260:Female; D059585:G1 Phase Cell Cycle Checkpoints; D006801:Humans; D008297:Male; D008875:Middle Aged; D009687:Nuclear Proteins / Q000378:metabolism*; D063150:Polycomb Repressive Complex 1; D011518:Proto-Oncogene Proteins / Q000378:metabolism*; D051057:Proto-Oncogene Proteins c-akt / Q000378:metabolism; D016271:Proto-Oncogene Proteins c-myc / Q000378:metabolism; D034622:RNA Interference; D034741:RNA, Small Interfering / Q000378:metabolism; D012097:Repressor Proteins / Q000378:metabolism*; D015398:Signal Transduction; D013869:Thiolester Hydrolases / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*; D025803:Tumor Suppressor Protein p14ARF / Q000378:metabolism; D016159:Tumor Suppressor Protein p53 / Q000378:metabolism; D043222:Ubiquitin Thiolesterase
chemical_list: C069077:BMI1 protein, human; D056742:Cyclin D2; D019941:Cyclin-Dependent Kinase Inhibitor p16; D050687:E2F1 Transcription Factor; D009687:Nuclear Proteins; D011518:Proto-Oncogene Proteins; D016271:Proto-Oncogene Proteins c-myc; D034741:RNA, Small Interfering; D012097:Repressor Proteins; C495901:TP53 protein, human; D025803:Tumor Suppressor Protein p14ARF; D016159:Tumor Suppressor Protein p53; D063150:Polycomb Repressive Complex 1; D051057:Proto-Oncogene Proteins c-akt; D013869:Thiolester Hydrolases; D043222:Ubiquitin Thiolesterase; C527170:Usp22 protein, human