Host-mediated antitumor action of schizophyllan, prepared from the culture filtrate of Schizophyllum commune, was examined against four kinds of transplantable tumors in both ascites and solid forms. Schizophyllan is a polymer of repeating units composed of three or four β-(1→3)-linked D-glucopyranose residues to one of which is attached, through β-(1→6)-linkage, a side chain consisting of a single β-D-glucopyranose residue. The most significant results were obtained with 0.5-10mg/kg doses of schizophyllan on all the subcutaneously implanted tumors, i.e., sarcoma-37, sarcoma-180, Ehrlich carcinoma, and Yoshida sarcoma, accompanied with many complete regressions. On the other hand, the treatment failed to inhibit the growth of ascites tumors or to induce prolongation of life span, with the exception of ascites sarcoma-180, and also no inhibitory effect on Friend virus disease and spontaneous mammary carcinoma arising in Swiss mice. The mechanism of this action was considered to be host-mediated on the basis of lack of effect in contact test in vitro.
