Abstract
We studied the role of miRNA-200 family members in cellular sensitivity to paclitaxel and carboplatin, using two ovarian cancer cell lines, OVCAR-3 and MES-OV, and their paclitaxel resistant variants OVCAR-3/TP and MES-OV/TP. Both resistant variants display a strong epithelial-mesenchymal transition (EMT) phenotype, with marked decreases in expression of miR-200c and miR-141 in OVCAR-3/TP, and down-regulation of all five members of the miR-200 family in MES-OV/TP. Lentiviral transfection of inhibitors of miR-200c or miR-141 in parental OVCAR-3 triggered EMT and rendered the cells resistant to paclitaxel and carboplatin. Conversely, the infection of OVCAR-3/TP cells with retroviral particles carrying the miR-200ab429 and 200c141 clusters triggered a partial mesenchymal to epithelial transition (MET). This partial MET was not sufficient to re-sensitize OVCAR-3/TP cells to paclitaxel. However, the miR-200c/miR-141 cluster transfectants became 6-8x resistant to carboplatin, an unexpected result, whereas miR-200a/miR-200b/miR-429 had no effect. Transfecting the OVCAR-3/TP GFP cells with specific miRNA mimics confirmed these data. MiR-200c and miR-141 mimics conferred resistance to carboplatin in MES-OV/TP cells, similar to OVCAR-3/TP, but sensitized MES-OV to paclitaxel. Several genes involved in balancing oxidative stress were altered in OVCAR-3/TP 200c141 cells compared to controls. The miR-200 family plays major, cell-context dependent roles in regulating EMT and sensitivity to carboplatin and paclitaxel in OVCAR-3 and MES-OV cells.