MicroRNA-133a functions as a tumor suppressor by targeting IGF-1R in hepatocellular carcinoma

MicroRNAs (miRNAs) are a class of small non-coding RNAs and have critical roles in tumorigenesis and metastasis. A growing body of evidence showed that microRNA-133a (miR-133a) was downregulated and played tumor suppressor roles in gastric, colorectal, bladder, and lung cancer. However, the role and underlying molecular mechanism of miR-133a in hepatocellular carcinoma (HCC) remain unclear. In this study, we analyzed the expression of miR-133a in HCC tissues and HCC cell lines. We find that miR-133a was downregulated in HCC tissues and cell lines and that miR-133a expression negatively correlated with tumor differentiation (P < 0.01), TNM stage (P < 0.01), and lymph node metastasis (P < 0.01). Then, functional studies demonstrate that restoration of miR-133a in HepG2 cells significantly suppressed proliferation, colony formation, migration, and invasion, induced cell cycle arrest at G0/G1 stage and cell apoptosis in vitro, and decreased tumor size and weight in a nude mouse HepG2 xenograft model. Using bioinformatics method and dual luciferase assays identified insulin-like growth factor 1 receptor (IGF-1R) as a direct target of miR-133a in HCC cells. Furthermore, overexpression of miR-133a inhibited activation AKT and ERK signal pathway, which contributed to suppression of HCC cell growth. These findings suggest that miR-133a may act as a tumor suppressor and inhibited survival of HCC cells by targeting IGF-1R.