ABCG2 and cancer: ABCG2 plays a pivotal role in extruding exogenous and endogenous substrates and drugs (Ando et al., 2007; Chen YL et al., 2016; Halwachs et al., 2016; Gewin et al., 2019; Mares et al., 2019; Orlando et al., 2019; Traxl et al., 2019), which is related to many multidrug resistant cancer cell lines, including acute lymphoblastic leukemia (ALL), retinal progenitors, hepatic metastases, gastric carcinoma, fibrosarcoma, nonsmall cell lung cancer, glioblastoma and myeloma (Natarajan et al., 2012; Olarte Carrillo et al., 2017; Abdel Gaber et al., 2018; Reustle et al., 2018; Zhang et al., 2018).