FTY720 assisted in the VP16-induced apoptosis due to a prolonged accumulation of intracellular DOX in both 5-FU-sensitive and -resistant colon cancer cells, where it also inhibited P-glycoprotein and the multidrug resistance protein 1 (MRP1), the higher level of which are fundamental towards the drug resistance in cancer cells [127]. Here, ABCB1 is linked to colonic neoplasm.