ABSTRACT: Background: Circular RNAs (circRNAs), a subclass of noncoding RNAs, have been reported to be involved in the progression of various diseases. However, the exact role of circRIMS1, also termed hsa_circ_0132246, in human bladder cancer remains to be discovered. Methods: By performing RNA-seq comparing bladder cell lines and normal uroepithelial cells, circRIMS1 was selected as the research object. We further verified by qRT-PCR that circRIMS1 was upregulated in bladder cancer tissue and cell lines. Proliferation, colony formation, Transwell migration, Matrigel invasion, apoptosis, western blotting and in vivo tumorigenesis and metastasis assays were utilized to evaluate the roles of circRIMS1, miR-433-3p and CCAR1. For mechanistic investigation, RNA pull-down, fluorescence in situ hybridization (FISH) and luciferase reporter assay confirmed the binding of circRIMS1 with miR-433-3p. Results: CircRIMS1 was significantly upregulated in bladder cancer and circRIMS1 expression was associated with the pathological stage and histological grade of bladder cancer. Inhibition of circRIMS1 suppressed the proliferation, migration and invasion of bladder cancer cells in vitro and in vivo, while overexpression of circRIMS1 exerted the opposite effects. Moreover, the circRIMS1/miR-433-3p/CCAR1 regulatory axis was confirmed to be responsible for the biological functions of circRIMS1. Conclusions: CircRIMS1 acts as a tumor promoter in bladder cancer to enhance tumor growth, migration and invasion via the miR-433-3p/CCAR1 regulatory axis, which provides a new therapeutic target and a novel biomarker in bladder cancer. Keywords: CircRIMS1, Bladder cancer, miR-433-3p, CCAR1, Progression, Metastasis
