Abstract: Indoleamine 2, 3-dioxygenase (IDO) is known as an endogenous immunosuppressive enzyme which plays a significant role in the process of tumor. IDO is not only found in tumor cells but also detected in dendritic cell (DC) in tumor microenvironment, which participates in the formation of tumor immune tolerance through expressing IDO enzyme. Signal transducer and activator of transcription (STAT) is the main signal protein family which participates in the IDO transcriptional regulation of DC.It is necessary to detail the signaling pathway in regulating IDO expression, which will help us develop high specific andmore active IDO inhibitors and provide new options for anti-cancer targeted therapy.

Key words: Trans-activation(genetics), Supressor of cytokine signaling proteins, Dendritic cells, Indoleamine 2, 3-dioxygenase