Published online Apr 7, 2017. doi: 10.3748/wjg.v23.i13.2286
Peer-review started: January 3, 2017
First decision: February 10, 2017
Revised: February 13, 2017
Accepted: March 15, 2017
Article in press: March 15, 2017
Published online: April 7, 2017
Processing time: 97 Days and 22.4 Hours
Tumor cells induce an immunosuppressive microenvironment which leads towards tumor immune escape. Understanding the intricacy of immunomodulation by tumor cells is essential for immunotherapy. Indoleamine 2,3-dioxygenase (IDO) is an immunosuppressive enzyme which mediates tumor immune escape in various cancers including hepatocellular carcinoma (HCC). IDO up-regulation in HCC may lead to recruitment of regulatory T-cells into tumor microenvironment and therefore inhibit local immune responses and promote metastasis. HCC associated fibroblasts stimulate natural killer cells dysfunction through prostaglandin E2 and subsequently IDO promotes favorable condition for tumor metastasis. IDO up-regulation induces immunosuppression and may enhance the risk of hepatitis C virus and hepatitis B virus induced HCC. Therefore, IDO inhibitors as adjuvant therapeutic agents may have clinical implications in HCC. This review proposes future prospects of IDO not only as a therapeutic target but also as a prognostic marker for HCC.
Core tip: Indoleamine 2,3-dioxygenase (IDO) is an immunosuppressive enzyme which mediates tumor immune escape in hepatocellular carcinoma (HCC). IDO up-regulation in HCC may lead to recruitment of regulatory T-cells into tumor microenvironment and therefore inhibit local immune responses and promote metastasis. IDO inhibitors as adjuvant therapeutic agents may have clinical implications in HCC.