“…These results suggest that, as discussed above for imatinib, gefitinib might also have a narrow window, especially in a low concentration range, where its active transport by BCRP is efficient. Consistent with gefitinib being a BCRP substrate, BCRP-transduced A431 cells were resistant to gefitinib compared with the parental cell line (Yanase et al, 2004;Elkind et al, 2005) and the resistant phenotype was reversed by the BCRP-specific inhibitor Ko143 (Elkind et al, 2005). Of note, consistent with EGFR amplification and dependence on EGFR signalling for survival, A431 cells are highly sensitive to gefitinib, with IC 50 values in the nanomolar range.…”