ABCB1 and breast cancer: In this study, we identified specifically expressed circABCB1 in docetaxel-resistant breast cancer cells, and the qPCR experiment confirmed the overexpression of circABCB1 in docetaxel-resistant breast cancer cells in comparison to the sensitive parental cells, which indicated that the expression of circABCB1 in docetaxel-resistant breast cancer cells may also has been caused by the amplification of ABCB1 gene.