CircUBAP2 Inhibits Proliferation and Metastasis of Clear Cell Renal Cell Carcinoma via Targeting miR-148a-3p/FOXK2 Pathway

Clear cell renal cell carcinoma (ccRCC) is the prominent histological subtype of renal cell carcinoma (RCC) with high incidence of local recurrence and distant metastasis. It has been documented that circular ribonucleic acids (circRNAs) play crucial roles in the development of cancers; however, study on exploring the role of circRNAs in ccRCC still remains limited. In the present study, we aimed to evaluate the biological function of a novel circRNA UBAP2 (circUBAP2) in ccRCC and the underlying mechanism. Our results showed that circUBAP2 expression was significantly down-regulated in ccRCC tissues and cell lines. Overexpression of circUBAP2 significantly inhibited the proliferation, migration, and invasion of ccRCC cells. MiR-148a-3p was a target miRNA of circUBAP2 in ccRCC cells, and its expression levels in ccRCC tissues and cell lines were negatively correlated with circUBAP2 levels. Moreover, miR-148a-3p reversed the inhibitory effects of circUBAP2 on cell proliferation, migration, and invasion in ccRCC cells. Additionally, forkhead box K2 (FOXK2) was found to be a target gene of miR-148a-3p and regulated by miR-148a-3p in ccRCC cells. Furthermore, knockdown of FOXK2 reversed the inhibitory effects of miR-148a-3p inhibitor on ccRCC cells. In conclusion, these findings indicated that circUBAP2 functioned as a novel tumor suppressor in ccRCC through regulating the miR-148a-3p/FOXK2 axis. Therefore, circUBAP2 might serve as a potential therapeutic target for the treatment of ccRCC.