Enhanced immunogenic tumor rejection in mice when inhibiting activity of indoleamine 2,3-dioxygenase with ethyl pyruvate

Indoleamine-2,3-dioxygenase (IDO) is a recently founded enzyme that catalyzes tryptophan, thus causing local deficiency of this essential amino acid and inhibiting proliferation and function of immune lymphocytes in the given region. Inhibitors of IDO activity, therefore, can contribute to tumor immunoresistance breaking. The influence of systemic and local administration of IDO inhibitor (ethyl pyruvate) on the frequency and the rate of rejection of H-29 repeated grafts was studied on C3HA-line mice immunized with H-29 tumor cells. Both methods of ethyl pyruvate administration increased the frequency and enhanced tumor regression as compared to the control. Thus, IDO activity inhibitors can be useful for increasing anti-tumor efficiency