We found that the reduced intracellular accumulation of citarinostat in KB-V-1 and S1-M1-80 cancer cells (Figure 4B) was significantly restored by tariquidar and Ko143, signifying that the activity of ABCB1 and ABCG2 contributes greatly to the reduced efficacy of citarinostat in these cancer cells. Here, ABCG2 is linked to cancer.