ABCB1 and cancer: Overexpression of ABCB1 contributes to chemotherapy resistance of cancer cells in vitro and was related to worse survival of cancer patients in several studies (Trock et al., 1997; Schinkel and Jonker, 2003; Schaich et al., 2005; Haber et al., 2006; Stordal et al., 2012; Barbuti and Chen, 2015).