Although we failed to identify the intracellular mechanism of FTY720, FTY720 could sensitize human renal carcinoma (Caki, ACHN, and A498 cells), human breast carcinoma (MDA-MB-231), and human colon carcinoma (HT29) cells to TRAIL-mediated apoptosis. This evidence concerns the gene TNFSF10 and breast carcinoma.