Here, we found that ABC transporters including P-gp and BCRP, which can recognize and actively extrude various cytotoxic drugs from cells (62), were overexpressed in multi-drug resistant ovarian cancer cells (Figures 2A,B), indicating that P-gp and BCRP were involved in the MDR of ovarian cancer. Here, ABCG2 is linked to ovarian carcinoma.