Antitumor activity of Lactobacillus casei in mice.

The effect of Lactobacillus casei YIT 9018 (LC 9018) on the growth of transplantable allogeneic and syngeneic mouse tumors was studied. Intraperitoneal treatment of LC 9018 caused a significant prolongation of the life span of ICR mice inoculated with sarcoma-180 intraperitoneally and BDF1 mice inoculated with L1210 leukemia intraperitoneally. Intravenous injection of LC 9018 markedly inhibited the growth of subcutaneously inoculated sarcoma-180. This organism was also effective against methylcholanthrene-induced syngeneic MCA K-1 tumor in BALB/c mice. The antitumor activity of LC 9018 was reduced by treatment with carrageenan, an anti-macrophage agent, and was also observed in T-cell deficient athymic nude mice. These results suggested that the antitumor activity of LC 9018 may be macrophage-dependent.