MicroRNA-133b inhibits proliferation and invasion of ovarian cancer cells through Akt and Erk1/2 inactivation by targeting epidermal growth factor receptor.

Aberrant expression of microRNA-133b (miR-133b) has been frequently reported in some cancers excluding ovarian cancer (OC). The role and its molecular mechanism of miR-133b in OC have not been reported. In this study, we explored the effects of miR-133b overexpression on proliferation and invasion in OC cells. The mRNA level of miR-133b in OC cell lines was determined by real-time PCR. The miR-133b mimic was transiently transfected into OC cells using Lipofectamine™ 2000 reagent. Subsequently, cell proliferation and invasion were assessed by MTT, Brdu-ELISA and Transwell assays. Moreover, the effects of miR-133b overexpression on the MAPK and PI3K/Akt signaling pathways were determined by Western blot. Protein level of EGFR was also measured by Western blotting. Meanwhile, luciferase assays were performed to validate EGFR as miR-133b target in OC cells. Our results showed that the mRNA level of miR-133b was remarkably decreased in OC cell lines compared with normal colon epithelium cells, whereas the protein expression of EGFR was significantly increased. Up-regulation of miR-133b inhibited the proliferation and invasion of OC cells. We also found that miR-133b overexpression evidently decreased the phosphorylation of Erk1/2 and Akt. Bioinformatics analysis predicted that the EGFR was a potential target gene of miR-133b. Luciferase reporter assay demonstrated that miR-133b could directly target EGFR. Altogether, our results indicated that miR-133b overexpression was shown to inhibit proliferation and invasion of OC cells through suppression of the MAPK and PI3K/Akt signaling pathways by targeting EGFR.