Deregulation of miR-520d-3p promotes hepatocellular carcinoma development via lncRNA MIAT regulation and EPHA2 signaling activation

MicroRNA-520d-3p (miR-520d-3p) is a novel cancer-related miRNA and functions as a tumor suppressor in human cancers. However, the expression patterns and mechanisms of miR-520d-3p involved in hepatocellular carcinoma (HCC) remain rarely known. Here, we found that the expression levels of miR-520d-3p in HCC tissues and cells were significantly lower than in tumor-adjacent tissues and L02 cells. Decreased level of miR-520d-3p was relevant to poor overall survival, whereas miR-520d-3p up-regulation resulted in a marked inhibition of cell growth, migration and invasion. In addition, the long non-coding RNA, myocardial infarction associated transcript (MIAT) was up-regulated in both HCC tissues and cell lines. MIAT suppressed the expression and function of miR-520d-3p. Moreover, erythropoietin-producing hepatocellular A2 (EPHA2) was speculated and confirmed as a direct target of miR-520d-3p. We also demonstrated that MIAT may function as a sponge competitive endogenous RNA for miR-520d-3p, and thus regulate the molecular expression of EPHA2. In summary, our study has identified a novel signaling pathway through which miR-520d-3p exerts its anticarcinogenic roles and suggested that the MIAT/miR-520d-3p/EPHA2 may be a new target for HCC therapy.