ABCG2 and neoplasm: In addition to their profound physiological functions, various ABC transporters are implicated in tumour cell resistance to anticancer therapy, particularly, p-glycoprotein (P-gp; ABCB1, ATP-binding cassette sub-family B member 1), ATP binding cassette subfamily C member 1 (ABCC1), ABCC2, ABCG2 (also known as BCRP, breast cancer resistance protein), and the lung resistance protein.