Antitumor effects of a new polysaccharide-protein complex (ATOM) prepared from Agaricus blazei (Iwade strain 101) "Himematsutake" and its mechanisms in tumor-bearing mice.

The antitumor activity of the i.p. or p.o. administration of polysaccharide-protein complex, ATOM (antitumor organic substance Mie) prepared from cultured mycelia of Agaricus blazei (Iwade strain 101) "Himematsutake" examined against four kinds of established mouse tumors. ATOM was highly effective at the doses of 10 and 20 mg/kg/day x 10 on subcutaneously implanted Sarcoma 180 in mice, and was also active against Ehrlich ascites carcinoma, Shionogi carcinoma 42 and Meth A fibrosarcoma at doses of 50 and 100 mg/kg/day x 10. ATOM has no direct cytotoxic action on tumor cells in vitro. Thus the tumor growth-inhibitory effect of ATOM is apparently due to immunological host-mediated mechanisms. The number of peritoneal macrophages, the phagocytosis of polystyrene latex beads and the proportion of the third component of complement (C3)-positive fluorescent cells were increased in the mice treated with ATOM. These results suggest that the macrophage activa-tion and alterations of the C3 are necessary for the induction of an antitumor effect of ATOM.