In turn, afatinib may enhance the efficacy of YM155 in breast cancer cells by inhibiting YM155 efflux; indeed, afatinib has been shown to inhibit the ABCB1 drug efflux transporter in ovarian cancer87 and the ABCG2 drug efflux transporter in other cancer types88. This evidence concerns the gene ABCG2 and breast carcinoma.