miR-124 inhibits proliferation and invasion of human retinoblastoma cells by targeting STAT3.

A growing body of evidence suggests that microRNA-124 (miR-124) functions as tumor-suppressor, and involves in tumor initiation, development and metastasis in major classes of human cancers; however, the biological role and underlying molecular mechanism of miR-124 in retinoblastoma (RB) remain unknown. Therefore, we investigated the biological activity and underlying molecular mechanism of miR-124 in human retinoblastoma. In the present study, our results demonstrated the downregulation of miR-124 in RB tissues and RB cell lines compared with normal retinal tissues. The ectopic expression of miR-124 in the RB cell lines (Y79 and SO-RB50) suppresses cell proliferation, migration and invasion, induced cell apoptosis in vitro. Furthermore, signal transducer and activator of transcription 3 (STAT3) was identified as a new target of miR-124, and overexpression of miR-124 decreased STAT3 expression on mRNA level and protein level in human RB cells. We also found that STAT3 mRNA expression was upregulated and inversely correlated with miR-124 expression in the RB tissues (r=-0.683; P<0.001). Restoration of the expression of STAT3 rescues the effects induced by miR-124 in RB cells. The findings of the present study suggested that miR-124 functioned as tumor suppressor in RB, at least in part, by targeting STAT3, and that it could serve as a potential candidate for RB therapeutics.