To escape immune recognition, tumor cells, such as those of the melanoma, can activate several mechanisms, including the secretion of IDO, IL-10, and TGF-β, the control of T-cells’ function through PDL-1/PD-1 interaction, the generation of regulatory T-cells (Tregs), and the loss of tumor antigens, among others (3, 4). The gene discussed is IDO1; the disease is neoplasm.