PURPOSE: Ovarian cancer has a difficult diagnosis and high mortality rate. Cisplatin, a platinum compound agent which has been widely used in the clinical treatment of ovarian cancer. However, development of chemoresistance is a major obstacle that limits the therapeutic efficacy. The precise roles and molecular mechanisms of cisplatin resistance in ovarian cancer remain unclear. METHODS: The expressions of microRNA (miR)-182-5p and CDK6 mRNA from ovarian tumors and cell lines were detected by qRT-PCR. MiR and siRNA were transfected into ovarian cancer cells using Lipofectamine 2000 transfection reagent. Cisplatin resistant ovarian cancer cell line was established by exposing parental cells to gradually increased cisplatin doses. The binding of miR-182-5p on CDK6 3'UTR was predicted from Targetscan.org and validated by Western blot and dual luciferase reporter assay. The cell viability was determined by MTT assay. RESULTS: miR-182-5p is downregulated in ovarian cancer tissues and cells. Overexpression of miR-182-5p significantly sensitized ovarian cancer cells to cisplatin. By creating cisplatin resistant cell line SKOV3, we observed miR-182-5p was apparently downregulated in cisplatin resistant cells. In addition, we identified cyclin-dependent kinase-6 (CDK6) as a direct target of miR-182-5p in both ovarian cancer cell line and patient tissues. Moreover, CDK6 was found to be upregulated in ovarian cancer and displayed and inverted expression pattern with miR-182-5p in ovarian cancer tissues. Silencing CDK6 by siRNA significantly increased the cisplatin sensitivity. Importantly, restoration of CDK6 in miR-182-5p overexpressed ovarian cancer cells successfully recovered the cisplatin resistance. CONCLUSIONS: miR-182-5p plays a tumor suppressive role in cisplatin resistance via direct targeting the CDK6, showing miR-182-5p-CDK6 axis as a promising therapeutic target against chemoresistant ovarian cancer.
PURPOSE:Ovarian cancer has a difficult diagnosis and high mortality rate. Cisplatin, a platinum compound agent which has been widely used in the clinical treatment of ovarian cancer. However, development of chemoresistance is a major obstacle that limits the therapeutic efficacy. The precise roles and molecular mechanisms of cisplatin resistance in ovarian cancer remain unclear. METHODS: The expressions of microRNA (miR)-182-5p and CDK6 mRNA from ovarian tumors and cell lines were detected by qRT-PCR. MiR and siRNA were transfected into ovarian cancer cells using Lipofectamine 2000 transfection reagent. Cisplatinresistant ovarian cancer cell line was established by exposing parental cells to gradually increased cisplatin doses. The binding of miR-182-5p on CDK6 3'UTR was predicted from Targetscan.org and validated by Western blot and dual luciferase reporter assay. The cell viability was determined by MTT assay. RESULTS:miR-182-5p is downregulated in ovarian cancer tissues and cells. Overexpression of miR-182-5p significantly sensitized ovarian cancer cells to cisplatin. By creating cisplatin resistant cell line SKOV3, we observed miR-182-5p was apparently downregulated in cisplatin resistant cells. In addition, we identified cyclin-dependent kinase-6 (CDK6) as a direct target of miR-182-5p in both ovarian cancer cell line and patient tissues. Moreover, CDK6 was found to be upregulated in ovarian cancer and displayed and inverted expression pattern with miR-182-5p in ovarian cancer tissues. Silencing CDK6 by siRNA significantly increased the cisplatin sensitivity. Importantly, restoration of CDK6 in miR-182-5p overexpressed ovarian cancer cells successfully recovered the cisplatin resistance. CONCLUSIONS:miR-182-5p plays a tumor suppressive role in cisplatin resistance via direct targeting the CDK6, showing miR-182-5p-CDK6 axis as a promising therapeutic target against chemoresistant ovarian cancer.