ABCG2 and cancer: Imatinib is also a substrate of P‐glycoprotein (P‐gp) and breast cancer resistant protein (BCRP) efflux transporters, which contribute to the net intestinal absorption of imatinib (via expression of transporters on apical/luminal membrane of enterocytes), biotransformation and excretion of imatinib (via expression of transporters on the bile caniculi of hepatocytes),7, 13 and retention of imatinib in target cancer cells.14, 15, 16, 17