Chemoresistance in ovarian cancer linked to expression of microRNAs.

We evaluated the differential expression of several microRNAs (miRNAs) among malignant cells in ascites and matched omental metastasis in patients with epithelial ovarian cancer (EOC). Ascites and omental tumors were collected prospectively from five patients who were undergoing primary surgical cytoreduction. Patient samples were processed and treated with carboplatin, paclitaxel and combination chemotherapy. Cell viability was evaluated and miRNA profiling was performed on both tumor cells from ascites fluid and omental cake. Quantitative real-time PCR (RT-q-PCR) and western blots were used to evaluate expressions of miRNA-21 and miRNA -214 and associated proteins. Malignant cells in ascites showed greater cell viability when treated with carboplatin compared to omental metastasis. A significant up-regulation of miRNA-21 and miRNA-214 was observed in malignant cells of ascites compared to omental metastasis; this was confirmed by both cell viability assay and RT-q-PCR. Ours is the first report that demonstrates significant up-regulation of miRNA-21 and miRNA-214 in tumor cells from ascites of patients with EOC compared to omental metastasis. This finding has important implications for intrinsic carboplatin resistance in these patients.