Downregulated miR-621 promotes cell proliferation via targeting CAPRIN1 in hepatocellular carcinoma

MicroRNAs (miRNAs) have been reported to play an essential role in tumor development and progression. However, the function of miR-621 in hepatocellular carcinoma (HCC) remains largely unexplored. In this study, we found that miR-621 was downregulated in the HCC specimens and cell lines, and lower expression of miR-621 indicated poor survival. Overexpression of miR-621 was shown to induce G0/G1 cell cycle arrest and inhibit cell proliferation in vitro and in vivo. Luciferase assays revealed that cell cycle-associated protein 1 (CAPRIN1) is a novel functional downstream target of miR-621. miR-621 could regulate c-MYC and cyclin D2 expression by directly targeting CAPRIN1. Further study revealed that CAPRIN1 was upregulated in the HCC specimens and cell lines. Restoration of CAPRIN1 neutralized the miR-621-induced cell cycle arrest and cell proliferation inhibition. Taken together, our findings suggest that miR-621 acts as a tumor suppressor gene in HCC progression by downregulating CAPRIN1 expression and could be a novel potential diagnostic and prognostic biomarker for HCC.