ABCG2 and neoplasm: The predominant AETs refer to P-gp and BCRP, both of them mainly control brain distribution of many anti-tumor drugs and thus reinforce the BBB (Agarwal et al., 2010; Agarwal, Hartz, et al., 2011; Agarwal, Sane, et al., 2011; Agarwal, Sane, Ohlfest, et al., 2011).