Inhibitory effects of miRNA-200c on chemotherapy-resistance and cell proliferation of gastric cancer SGC7901/DDP cells.

BACKGROUND AND OBJECTIVE: miRNA-200c can not only inhibit the aggressiveness of cancer cells but also increase the sensitivity of cells to antitumor drugs. However, some mechanisms are still unclear. Recent researches revealed that E-cadherin is more than an inhibitor of metastasis, and it also plays important roles in reversing drug resistance. We had previously found that miRNA-200c could not only induce the expression of E-cadherin but also increase the sensitivity of gastric cancer SGC7901/DDP cells to cisplatin (DDP). This study aimed to explore the effects of miRNA-200c on biological characteristics of SGC7901/DDP cells and the roles of E-cadherin in the regulatory pathway of miRNA-200c.

METHODS: SGC7901/DDP cells and its parental cell line SGC7901 cells were transfected with miRNA-200c precursor (Pre-200c) and E-cadherin siRNA, respectively. Real-time RT-PCR was used to detect miRNA-200c expression after transfection with Pre-200c in SGC7901/DDP cell line. Drug sensitivities to DDP, 5-fluorouracil (5-FU), paclitaxel, and adriamycin (ADR) after transfection were tested using MTT assay. The proliferation of SGC7901/DDP cells was also detected after transfection. The protein changes of E-cadherin, Bax, and Bcl-2 after transfection were detected by Western blot.

RESULTS: The miRNA-200c expression in SGC7901/DDP cells after transfection of Pre-200c was 7.128 ± 0.159 times of that in negative control (P < 0.05). The IC50 of DDP, 5-FU, paclitaxel, and ADR in Pre-200c-transfected group were significantly lower than that in negative control group (P < 0.05). Compared to the control group, cell proliferation was significantly decreased (P < 0.05). The relative protein expressions of E-cadherin and Bax in Pre-200c-transfected group were significantly higher than those in negative control group (P < 0.05), whereas Bcl-2 was significantly lower than that in control (P < 0.05). Additionally, E-cadherin protein expression was significantly inhibited after transfected with E-cadherin siRNA in SGC7901 cells. The Bax protein expression was significantly down-regulated by E-cadherin siRNA (P < 0.05), whereas the Bcl-2 expression was significantly up-regulated (P < 0.05).

CONCLUSION: miRNA-200c can indirectly regulate apoptosis through E-cadherin in SGC7901/DDP cells, which may be a possible mechanism of miRNA-200c in reversing drug resistance and inhibiting proliferation.