Downregulation of TMEM40 by miR-138-5p suppresses cell proliferation and mobility in clear cell renal cell carcinoma

Abstract

<strong>Background: </strong>Clear cell renal cell carcinoma (ccRCC) represents approximately 70% of RCC,as the most frequent histological subtype of RCC. MiR-138-5p, a tumor-related microRNA (miRNA), has been reported to be implicated in the diverse types of human malignancies, but its role in ccRCCremains unclear.<br /> <strong>Objective</strong>: The study was designed to investigate the functional behaviors and regulatory mechanisms of miR-138-5p in ccRCC.<br /> <strong>Materials and Methods</strong>: Quantitative real-time PCR and western blotting analyses were performed to determine the expression of miR-138-5p and TMEM40 in ccRCC tissues. Pearson's correlation coefficient was utilized to evaluate the correlation between miR-138-5p and TMEM40 expression. The function of miR-138-5p and TMEM40 in the cell proliferation, migration and invasion of ccRCC cells (786-O and ACHN) was assessed by CCK-8, colony formation, wound healing and transwell assay, respectively. A luciferase reporter assay was performed to confirm the direct binding of miR-138-5p to the target gene TMEM40.<br /> <strong>Results</strong>: We found the expression of miR-138-5p was significantly down-regulated, while TMEM40 was remarkably up-regulated in ccRCC tissues. TMEM40 expression was discovered to be inversely correlated with miR-138-5p expression in ccRCC tissues. Functional studies demonstrated that miR-138-5p overexpression or TMEM40 knockdown significantly suppressed ccRCC cell proliferation, migration and invasion <em>in vitro</em>. Notably, we experimentally confirmed that miR-138-5p directly recognizes the 3'-UTR of the TMEM40 transcript and down-regulated its expression in ccRCC cells.<br /> <strong>Conclusions</strong>: Taken together, our findings provide the first clues regarding the role of miR-138-5p as a tumor suppressor in ccRCC by directly targeting of TMEM40.