Local interleukin 2 therapy of mouse mammary tumors of various immunogenicities

The local and systemic therapeutic effects of multiple injections of recombinant human interleukin 2 (IL-2), at doses of 5,000 to 100,000 units each, were tested against intramammary implants of 12 syngeneic C3H mouse mammary tumors of various immunogenicities. Among 5 tumors with transplantation-type immunogenicity and with mononuclear leukocyte infiltration, 4 tumors were affected by IL-2 therapy. A fast-growing, moderately immunogenic tumor was not affected. Among 7 tumors which did not display transplantation-type immunogenicity, 4 tumors did, nevertheless, attract mononuclear leukocytes. Among these 4 tumors, the 2 slowest growing tumors were affected by IL-2 therapy. Local and systemic therapeutic effects resulted from peritumor IL-2 injections, but not from injections 2 cm from a tumor. The results indicate that the therapeutic effectiveness of IL-2 depends on the ability of a tumor to attract IL-2 responsive immune effector cells and that therapeutic effectiveness is reduced by faster tumor growth.