MicroRNA-18a Targets IRF2 and CBX7 to Promote Cell Proliferation in Hepatocellular Carcinoma

MicroRNAs (miRNAs) are a family of noncoding RNAs of ∼22 nt in length that play important roles in the tumor initiation and progression processes. The aberrant expression status of miR-18a has been reported in hepatocellular carcinoma (HCC). However, the biological role and the underlying mechanism of miR-18a in HCC progression are still to be elucidated. In this study, we examined the expression level of miR-18a in HCC cell lines using the quantitative real-time PCR method. We showed that miR-18a expression in human HCC cell lines was elevated compared with the normal liver cell line. Meanwhile, increasing miR-18a expression by an miR-18a mimic in HCC cell lines promoted cell proliferation and migration, while inhibiting miR-18a expression by an miR-18a inhibitor caused the opposite effects. Using the bioinformatic analyses method, we found that the 3′-untranslated regions (3′-UTRs) of interferon regulatory factor 2 (IRF2) and chromobox protein homolog 7 (CBX7) contain putative binding sequences for miR-18a. Further, luciferase assay validated that both IRF2 and CBX7 were the direct targets of miR-18a in HCC. Moreover, we revealed that overexpression of IRF2 and CBX7 has similar effects as miR-18a downregulation on HCC cell lines. Our results illustrated that miR-18a plays a positive role in HCC progression process by stimulating cell proliferation and migration partly through regulating IRF2 and CBX7.