Opa interacting protein 5 acts as an oncogene in bladder cancer.

PURPOSE: To explore the biological functions and mechanism of Opa interacting protein 5 (OIP5) in bladder cancer (BC).

METHODS: We investigated the expression of OIP5 in BC through immunohistochemical staining (IHC) and its correlation with clinicopathologic features of BC patients. Moreover, knockdown of OIP5 was performed in BC cell lines and colony formation capacity, cell growth curve, cell cycle phase and cell apoptosis assay was applied for investigating the roles of OIP5 in BC. Moreover, the expression of OIP5 was validated through the Cancer Genome Atlas (TCGA) database. The diagnosis value of OIP5 was accessed by receiver operating characteristic (ROC) analysis in TCGA database.

RESULTS: The expression of OIP5 in BC tissues was significantly higher than that in adjacent non-tumor tissues and bladder mucosa tissues with chronic cystitis. Higher protein expression level of OIP5 predicted shorter survival time in patients with BC, which was significantly correlated with larger tumor size, high-grade tumor and advanced T classification. The expression of OIP5 was considerably decreased after lentivirus infection both at mRNA and protein levels. Functional assay displayed that silencing of OIP5 inhibited colony formation capacity and cell growth in BC cell lines. Cell cycle assays indicated that suppressed OIP5 disturbed the balance of the cell cycle in BC cell lines, which increased the cell population of the G1 phase and decreased the cell population of the S phase. Furthermore, knockdown of OIP5 expression enhanced cell apoptosis process. The expression of OIP5 was significantly up-regulated in BC compared with adjacent non-tumor tissues based on TCGA database. OIP5 had the potential diagnostic value for BC.

CONCLUSIONS: Our work demonstrated that OIP5 might function as an oncogene to promote colony formation capacity and cell growth, arrest cell cycle and suppress cell apoptosis in bladder cancer.