To further examine the role of IDO on DNA repair pathways and whether concurrent IDO and TS downregulation have value in sensitizing human tumor cells to the TS-targeting drug 5FUdR, we simultaneously downregulated IDO and BRCA2 (a DNA repair molecule not involved in enzymatic reactions mediated by TS), in A549 cells followed by treatment with 5FUdR. This evidence concerns the gene IDO1 and neoplasm.