IDO1 and neoplasm: The tumor associated antigens are recognised by T-cells, which leads to tumors being eradicated; however, tumoral cells escape from immunoediting by expressing programmed cell death ligand (PDL-1) and similar inhibitory gene products like IDO (indolamine 2,3 dioxygenase), TGF-β (transforming growth factor-β), and Interleukin-10 (IL-10).