A. Cesario, B. Rocca and S. Rutella Pages 2263 - 2271 ( 9 )
The enzyme indoleamine 2,3-dioxygenase 1 (IDO1) degrades the essential amino acid tryptophan into kynurenine and other downstream metabolites that suppress effector T-cell function and favor the differentiation of regulatory T cells. IDO1 is traditionally viewed as a general suppressor of T-cell activation and mediator of immune escape in cancer. Recently, evidence has emerged to support a greater functional complexity of IDO1 as modifier of pathogenic inflammation. For instance, IDO1 activity may sustain autoantibody production by B cells, and elicit the development of cancer in the context of chronic inflammation. Cyclooxygenase (COX)-2 metabolizes the first enzymatic step in the conversion of arachidonic acid into prostanoids. In particular, prostaglandin (PG)E2 generated at sites of inflammation and/or immune response is mainly COX-2-derived and has pro-inflammatory and immune regulatory activities. Pharmacological blockade of COX-2 in animal models of cancer translates into down-regulation of IDO1 expression at tumor sites and decreased levels of kynurenine in the circulation, underpinning the view that IDO1 might be downstream of COX-2. This article reviews preclinical studies focusing on IDO1 and COX-2 as inter-related molecular targets for therapeutic intervention in chronic inflammation and cancer. COX-2 inhibition might, in principle, be pursued in cancer-associated inflammation characterized by IDO1 hyper-activity, with the foreseeable aim at altering the immune response within the tumor microenvironment.
Indoleamine 2,3-dioxygenase,immune tolerance,regulatory T cell,hematopoietic growth factors,cancer,cyclooxygenase-2,prostaglandins,IDO1,amino acid tryptophan,kynurenine
, , Department of Hematology, Laboratory of Immunology, Catholic University Med. School, Largo Agostino Gemelli 8, 00168 Rome, Italy.