Currently, there are 48 known transporters in the ABC family, and 13 of the ABC transporters are related to tumor drug resistance, including P-glycoprotein (P-gp, MDR1/ABCB1), multidrug resistance proteins (MRPs/ABCCs), and breast cancer resistance protein (BCRP/ABCG2) [5,6]. Here, ABCG2 is linked to neoplasm.