MECHANISM OF BACILLUS CALMETTE GUERIN-INDUCED SUPPRESSION OF METASTASES IN A POORLY IMMUNOGENIC FIBROSARCOMA

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  • 1 January 1976
    • journal article
    • research article
    • Vol. 36  (9) , 3255-3259
Abstract
BCG reduces the rate of spontaneous pulmonary metastases from a poorly immunogenic [mouse] fibrosarcoma. To be effective, BCG (1 .times. 106 organisms) must be given in admixture with (1 .times. 106) tumor cells at the time of transplantation. Reduction of metastases at this dosage of BCG occurs without a change in the size of the primary tumor or the extent of necrosis within it. Tumors transplanted in admixture with spleen cells from BCG exposed donors reduced the number of metastases, while spleen cells from normal or tumor-bearing donors had no effect on metastases. Fewer total tumor cells and clumps are collected from the venous effluent of tumors transplanted with BCG than control tumors. The BCG treated tumors had more host macrophages intimately associated with the effluent tumor cells than controls. These data indicate that BCG can inhibit the metastatic potential of a weakly immunogenic fibrosarcoma. The mechanism of this effect appears to be a depression of entry of tumor cells into the tumor vascular channels which may be related to the interaction of tumor cells with BCG stimulated macrophages.