ABCB1 and breast carcinoma: Methods: Human breast carcinoma cell lines MCF-7 (Doxorubicin-sensitive and not expressing ABCB1) and KCR (Doxorubicin-resistant and expressing ABCB1) were used to evaluate the expression levels of miR-200c and miR-203 by Real-time quantitative PCR (RT-qPCR).