C3Hf/Bu mice were given s.c. injections of cells of a syngeneic methylcholanthrene-induced fibrosarcoma, and 3, 7, or 13 days later were given i.v. injections of 0.25 mg Corynebacterium granulosum. The growth of tumors was followed for 100 days. C. granulosum, given at 3 and 7 days following transplantation of tumor cells, induced complete tumor regressions in 54 and 46% of the mice, respectively. Almost all regressions occurred during the second month from the tumor cell inoculation. The remaining tumors grew more slowly than those in untreated controls. Treatment of mice 13 days after tumor cell injection, when the tumors were between 4 and 9.5 mm in diameter, greatly slowed the growth of most tumors. Histology of regressing tumors revealed a heavy infiltration with lymphocytes, histiocytes, and macrophages.

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This investigation was supported by NIH Research Grants CA 6294 and CA 11138 from the National Cancer Institute and by Institutional Research Grant RR 5511-11, Allotment IN-19.

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