The antitumor effect induced by local injections with interleukin-2 is diminished by combing with a local injection...

We investigated the antitumor effect of local injections with interleukin (IL)-2 in combination with an injection with mitomycin C (MMC). In BALB/c mice inoculated intraperitoneally (i.p.) with syngeneic Meth A fibrosarcoma on day 0, the i.p. injections with IL-2 at a dose of 20000U twice daily from day 7 to day 10 significantly prolonged survival of the treated mice and such treatment augmented a concomitant immunity specific for the tumor i.p. inoculated. On the other hand, the i.p. injections with IL-2 at a dose of either 5000U or 50000U resulted in no prolonged survival of the treated mice. In addition, neither intravenous nor subcutaneous injections with IL-2 at a dose of 20000U showed the prolonged survival of the treated mice. We further investigated a modulatory effect of a local injection with MMC on the IL-2-induced antitumor effect. The in vivo antitumor effect of local injections with IL-2 was not detected when combined with a local administration of MMC, whereas a systemic administration of MMC showed no such inhibitory effect on the IL-2-induced antitumor effect. Moreover, a delayed-type hypersensitivity response against Meth A, which was augmented by the local injections with IL-2, was significantly diminished by the local administration of MMC. Collectively, our results indicate that local injections with IL-2 could elicit the antitumor effect in vivo only when given at an optimal dose and that this effect could be rather diminished by combing with a local administration of MMC.