INDOLEAMINE 2,3 DIOXYGENASE AS AN IMMUNOTHERAPEUTIC TARGET BRINGS A NEW HOPE FOR CANCER PATIENTS

Therapeutic manipulation of immune system in cancer has been an extensive area of research in the field of oncoimmunology. Immunotherapy helps the immune system to combat against cancer. Tumour cells take an edge of immunosuppressive mechanisms and inhibit antitumour immune responses. Indoleamine 2,3 dioxygenase (IDO) is an immunosuppressive enzyme which is involved in tumour immune escape mechanism in various cancers. IDO can degrade the tryptophan into kynurenines and has an ability to enhance the immune tolerance through mammalian target of rapamycin pathway general control nonderepressible 2 (GCN2) pathway and induction of regulatory T (T-regs) cells. IDO-induced T-regs suppress the local immune responses in the tumour microenvironment and promote metastasis. IDO overexpression in various cancers is associated with poor prognosis. Several preclinical and clinical trials have been proceeding and recommend that IDO inhibitor may be an influential tool against a wide range of cancers. IDO inhibitors as adjuvant therapeutic agents may also have clinical implications. Thus, IDO has the potential to be used as an immunotherapeutic target. This review discusses the promising role of IDO in cancer and its implication in immunotherapy. Key words: Breast cancer, colorectal cancer, haematological malignancies, immunotherapy, indoleamine 2,3-dioxygenase, pancreatic cancer, prostate cancer