miR-205 inhibits cell growth by targeting AKT-mTOR signaling in progesterone-resistant endometrial cancer Ishikawa cells

PURPOSE miR-205 is significantly up-regulated in endometrioid adenocarcinoma. In this study, the significant anticancer effect of a miR-205 inhibitor was investigated in both endometrial carcinoma and progesterone-resistant endometrial carcinoma cells. RESULTS Compared with Ishikawa endometrial cancer cells, miR-205 was expressed at higher levels in a progesterone-resistant (PR) sub-cell line. Inhibition of miR-205 suppressed the growth of cancer cells in a dose- and time-dependent manner. Moreover, the miR-205 inhibitor induced a marked increase in the percentage of Ishikawa-PR cells in G2/M phases and a decrease in the percentage of cells in G0/G1 and S phases. In addition, miR-205 inhibitor-treated tumor cells exhibited increased apoptosis. Moreover, miR-205 was found to negatively regulate PTEN expression and lead to autophagy and activation of the AKT/mTOR pathway in PR cells, and PTEN protein levels significantly decreased with development of progesterone resistance in endometrial cancer cells. Western blot assay showed up-regulated autophagy, as indicated by expression of LC3-II/LC3-I and beclin1, in Ishikawa cells; in particular, autophagy was markedly induced in PR cells treated with the miR-205 inhibitor. MATERIALS AND METHODS We measured and analyzed cell growth curves with and without miR-205 inhibition with the MTT assay, miR-205 expression by qRT-PCR, cell cycle and apoptosis using annexin V/propidium iodide staining and flow cytometry, and autophagy, apoptosis, and AKT-mTOR signaling by western blotting. CONCLUSIONS Inhibition of miR-205, which targets the AKT-mTOR pathway, in endometrial cancer cells provides a potential, new treatment for PR endometrial carcinoma.