In addition to P-GP, other members from this superfamily play an important role in the MRD phenotype in CRC and PAC, such as MDR-associated proteins (MRPs/ABCCs) and breast cancer resistance protein (BCRP/ABCG2) [9,19] and MDR1 [20,21]. The gene discussed is ABCG2; the disease is colorectal carcinoma.