MiR-203 down-regulates Rap1A and suppresses cell proliferation, adhesion and invasion in prostate cancer

Objective: Evidence supports an important role for miR-203 in the regulation of the proliferation, migration and invasion of prostate cancer (PCa) cells. However, the exact mechanisms of miR-203 in PCa are not entirely clear. Methods: We examined the expression of miR-203 in prostate cancer tissues, adjacent normal tissues, PCa cell lines and normal prostate epithelial cells by qRT-PCR. Then, the effects of miR-203 or Rap1A on proliferation, adhesion and invasion of PCa cells were assayed using CKK-8, adhesion analysis, and transwell invasion assays. Luciferase reporter assay was performed to assess miR-203 binding to Rap1A mRNA. Tumor growth was assessed by subcutaneous inoculation of cells into BALB/c nude mice. Results: Here, we confirmed that the expression of miR-203 was significantly downregulated in prostate cancer specimens compared with matched adjacent normal prostate specimens. Mechanistic dissection revealed that miR-203 mediated cell proliferation, adhesion and invasion in vitro, and tumor growth in vivo, as evidenced by reduced RAC1, p-PAK1, and p-MEK1 expression. In addition, we identified Rap1A as a direct target suppressed by miR-203, and there was an inverse relationship between the expression of miR-203 and Rap1A in PCa. Knockdown of Rap1A phenocopied the effects of miR-203 on PCa cell growth and invasion. Furthermore, Rap1A overexpression in PCa cells partially reversed the effects of miR-203-expression on cell adhesion and invasion. Conclusions: These findings provide further evidence that a crucial role for miR-203 in inhibiting metastasis of PCa through the suppression of Rap1A expression.