IDO1 and neoplasm: The binding of exogenous adenosine monophosphate (AMP) to the adenosine A2b receptor on TADCs elevates their pro-tumor functions, creating an immunosuppressive environment through the secretion of VEGF, TGF-beta, IL-10, and the expression of cyclooxygenase-2 (COX-2) and IDO (121, 122).