Local induction of a cytotoxic factor (CF), which was reported by us to be a
tumor necrosis factor (TNF)-like molecule, in murine
tumor tissues by i.v. administration of antitumor
polysaccharides was studied. The CF was measured by cytolysis assay against L929 fibroblasts in vitro. The antitumor
polysaccharides mannoglucan polyalcohol (MGA),
lentinan, carboxymethyl-(1----3)-beta-D-linear
glucan DP540 (CM-TAK) and yeast
mannan induced the CF in MH134
hepatoma tissues inoculated intradermally, with MGA inducing the highest level of the CF. MGA induced the CF in MM46 mammary
carcinoma, Ehrlich
carcinoma, and MH134
hepatoma, the growth of which were all inhibited by MGA, but not in
Lewis lung carcinoma and EL-4
lymphoma, which are therapeutically resistant to MGA. MGA induced the CF in solid MH134
hepatoma tissues inoculated subcutaneously or intramuscularly as well as intradermally, but not in ascitic fluids with intraperitoneal MH134
hepatoma on which MGA is ineffective. These findings suggest that CF induction is correlated with the antitumor activity of
polysaccharides. CF induction in
tumor tissues was detectable 6 h after i.d. inoculation of MH134
hepatoma. Even in nontumorous inflammatory skin tissues produced by injection of TAK, the CF was induced by MGA. Thus, the early inflammatory reaction with accumulation of host cells and MGA treatment act cooperatively in local induction of the CF.