Major mechanisms involved in immune evasion include reduced immune recognition through the loss of tumor antigens and expression of cytokines (e.g., VEGF, IL-10, TGFβ) or immunoregulatory molecules (e.g., IDO and B7 family checkpoint molecules), that lead to the induction of an immunosuppressive tumor environment and enhance tumor resistance or survival via elevated expression of STAT3 or of BCL-2 [2, 3]. Here, IDO1 is linked to neoplasm.