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 polysacch aride-protein complex, ATOM (antitumor organic substance Mie) prepared from cultured mycelia of Agaricus blazei (Iwade strain 101) ''Himemat sutake'' 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 subc utaneously implanted Sarcoma 180 in mice, and was also active against Ehrlich ascites carcinoma, Shionogi carcinoma 42 and Meth A fibrosarco ma 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 effe ct of ATOM is apparently due to immunological host-mediated mechanisms . The number of peritoneal macrophages, the phagocytosis of polystyren e latex beads and the proportion of the third component of complement (C3)-positive fluorescent cells were increased in the mice treated wit h ATOM. These results suggest that the macrophage activa-tion and alte rations of the C3 are necessary for the induction of an antitumor effe ct of ATOM.