ABCG2 and neoplasm: Functionally, an ATP-binding cassette (ABC) transporter family, comprising P-glycoprotein (P-gp), multidrug resistance-associated protein (MRP) and BC resistance protein (BCRP), utilizes ATP-derived energy to pump chemotherapy drugs out of tumor cells and protect tumor tissues from chemical toxicity (Yuan et al., 2016; Tang et al., 2016).