ABCB1 and cancer: Notably, results of sitravatinib potentiating the drug-induced apoptosis in ABCB1- and ABCG2-overexpressing cancer cells (Figure 3) indicated that sitravatinib re-sensitized multidrug-resistant cancer cells by blocking the drug efflux function of both transporters and consequently restoring the cytotoxicity of respective cytotoxic drugs and not by merely reducing the growth rate of these cancer cells.