Effects of Corynebacterium parvum alone and in combination with adriamycin in experimental tumor systems

Corynebacterium parvum (C. parvum) was used in antitumor tests against four murine tumor models in B6D2F1 mice. The C. parvum was effective at all doses and schedules tested against P388 leukemia, B16 melanoma, and Lewis lung carcinoma but was ineffective against L1210 leukemia. Combination immunochemotherapy of P388 leukemia and Lewis lung carcinoma with C. parvum and adriamycin was better than either regimen alone in increasing the lifespan of mice with tumors. The results show that the effects of C. parvum are due to nonspecific stimulation of the host rather than direct cytotoxic action on tumor cells. C. parvum protected the mice when given before as well as after tumor challenge. In vitro 51Cr-release assay showed that the peritoneal cells were cytotoxic to P388 tumor cells but spleen cells were not. While the C. parvum was effective against P388 in conventional mice, it was ineffective against P388 growing in athymic (nude) mice. Thus, the antitumor effect in this tumor system is T-cell dependent.