Purpose: Cyclooxygenase-2 (COX-2) and its metabolite, PGE2 affect multiple tumorigenesis, including angiogenesis, invasion, and tumor-induced immune suppression. Their overexpression is association with impaired immune cell function in many tumors. Indoleamine 2,3-dioxygenase (IDO) is an emerging immuno-regulatory enzyme that can catalyze the initial rate-limiting step in tryptophan catabolism,...