ABCG2 and chronic myelogenous leukemia, BCR-ABL1 positive: Imatinib, which is used in clinic as first line of treatment for chronic myeloid leukemia, is an effective c-Abl inhibitor and has a minimal capacity to cross blood-brain barrier (BBB), with an increase in the transport in the presence of radiation or P-glycoprotein (ABCB1) and breast cancer resistance protein [BCRP (also known as ABCG2)]-inhibitors [15].