ABSTRACT
Indoleamine 2, 3-dioxygenase (IDO) is one of the rate-limiting enzymes that degrade tryptophan (Trp) into kynurenine (Kyn). Inflammatory factor IFN-γ mediates tumor′s immune escape by activating the IDO signaling pathway, upregulating theKyn/Trp (K/T ratio) and suppressing the activity of both CD 8+T and regulatory T cells. Radiotherapy plays a major role in treating non-small cell lung cancer. It not only bi-directionally regulates immune response of the host, but also collaborates with immunosuppressive agents to kill tumors. Meanwhile, immune status of the host can affect the therapeutic effect of radiotherapy. In recent years, studies have shown that IDO activity levels change before and after radiotherapy and is related to clinical prognosis. Nevertheless, relevant mechanism remains unclear. This article aims to elucidate the application of IDO signaling pathway in radiotherapy for non-small cell lung cancer.