Given that doxorubicin is also a substrate of ABCG2 [60], the inhibition of ABCG2 and the resultant decreased efflux of doxorubicin likely underlie the observed synergism, similar to the interaction seen with the EGFR inhibitor gefitinib and doxorubicin in thyroid cancer [61]. The gene discussed is ABCG2; the disease is thyroid gland carcinoma.