Antitumor activity exhibited by orally administered extract from fruit body of Grifola frondosa (Maitake).

The acid-insoluble, alkali-soluble, hot-water-extractable polymer (a polysaccharide containing approximately 30% of protein; D-fraction) obtained from the fruit bodies of Grifola frondosa (maitake) exhibited antitumor activities against allogenic and syngeneic tumors on oral administration to mice. Winn assay conducted to examine the tumor growth-suppressing effect revealed a complete inhibition of the tumor by the oral administration of D-fraction. This fact indicates that stimulation of the immune response system triggered by the tumor-bearing state is activated by D-fraction. Consequently, the activity of D-fraction on cells associated with immune response was examined. The cytolytic activity and interleukin-1 productivity of macrophages or T cells which exhibit antigen-specific cytotoxicity were enhanced. D-fraction was found to potentiate the delayed-type hypersensitivity response which is associated with tumor growth suppression.