miR-21 Induces Chemoresistance in Ovarian Cancer Cells via Mediating the Expression and Interaction of CD44v6 and P-gp

BACKGROUND: Ovarian cancer (OC), a representative female reproductive system tumor, is one of the most malignant tumors in female. The most important reason for its poor prognosis is because of its high rate of chemotherapy resistance. RESULTS: This study aims to explore the effects of miR-21 on the chemotherapy resistance of OC cells. The functions of miR-21 on proliferation, migration and invasion of OC cells were assessed by transwell, clonal formation and CCK8 assay. Expression levels of miR-21, P-gp and CD44v6 in SKOV3 (cisplatin sensitive) cells and SKOV3/DDP (cisplatin resistant) cells were detected by quantitative reverse transcription-polymerase chain reaction (qRT-PCR) and Western blotting. Si-CD44v6 was transfected into OC cells to detect the influence on P-glycoprotein (P-gp) expression. Immunofluorescence was used to detect the localization of CD44v6 and P-gp in cell. Co-immunoprecipitation was used to detect the relationship between CD44v6 and P-gp. Results showed that miR-21 expression in cisplatin-resistant SKOV3/DDP cells was significantly higher than that in SKOV3 cells, at the same time, cells proliferation, as well as invasion and migration ability were enhanced after the miR-21 mimics transfected into SKOV3 cisplatin-sensitive cells. Furthermore, miR-21 expression level affected the CD44v6 and P-gp expression. Immunofluorescence and co-immunoprecipitation showed that CD44v6 and P-gp protein could interact. CONCLUSION: In conclusion, the high miR-21 expression level could increase the proliferation, invasion, and migration ability of OC cells. And the interaction of CD44v6 and P-gp may mediate miR-21 involvement in chemotherapy resistance of OC cells.