Inhibitor of indoleamine-2,3-dioxygenase 1-methyl-D-tryptophan can stimulate the growth of immunogenic tumors.

We studied the effect of 1-methyl-D-tryptophan, an inhibitor of indoleamine-2,3-dioxygenase, on the growth of transplanted hepatocarcinoma-29 in C3HA mice. Hepatocarcinoma-29 transplanted into the thigh muscles undergoes immunological rejection in more than 50% non-syngeneic recipients. Chronic local administration of 1-methyl-D-tryptophan promotes progressive growth of the tumor in recipient mice leading to 100% animal death. The stimulating effect of 1-methyl-D-tryptophan on tumor growth is discussed.