ABCG2 and cancer: Furthermore, we found that the drug transport mediated by ABCB1 and ABCG2 was inhibited by sitravatinib in a concentration-dependent manner (Figure 4) but the protein expression of ABCB1 and ABCG2 was not significantly altered by sitravatinib in multidrug-resistant cancer cells overexpressing ABCB1 or ABCG2 (Figure 5).