Previous studies have reported that tyrosine kinase inhibitors (TKIs) such as imatinib [26,27,28,29] and sunitinib [30,31] are transported substrates of ABCB1 and ABCG2 and the overexpression of ABCB1 or ABCG2 in cancer cells results in reduced susceptibility to TKIs [32,33,34]. This evidence concerns the gene ABCG2 and cancer.