The powdered fruit bodies of shiitake (Lentinus edodes) showed antitumor activity when given orally to mice. The growth of tumors, both syngeneic and allogeneic, was inhibited by 57.9 to 78.6% in shiitake-fed mice. The degree of inhibition was proportional to the consumption of the experimental diet (L-feed) and was evident even when the administration was started from the 7th day after tumor implantation. The inhibition of tumor growth was mainly due to a glucan contained in the fruit bodies, but the lipid fracton also had inhibitory effects, although mild. Feeding of the fruit bodies to mice in the diet was found to augment both the ability of macrophages to phagocytose latex particles and the spreading activity of the macrophages.

Interferon (IF) induction and antiviral activity by purified spherical (S) or filamentous (F) virus-like particles and S-derived RNA was studied. A single administration of S particles prior to virus challenge reduced significantly the mortality of mice infected with western equine encephalitis (WEE) virus.

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Antitumor activities of two types of purified virus-like particles (S and F) from Lentinus edodes (Shiitakc) and of S-derived RNA were studied in :mice. Multiple administration of the particles or of the RNA markedly reduced the mortality of mice injected with Ehrlich ascites carcinoma cells.Certain double-stranded (ds) RNAs of natural and synthetic origin have been found to inhibit the growth of various transplanted tumors or leukemias in animals (2,5,7,9). In previous reports (8, 13), we have demonstrated the interferon (IFN) induction and antiviral activity by purified virus-like particles from L. edodes and of the RIgA derived from these particles. The present study describes antitumor activities of the purified virus-like particles (VLPs) and of ds-RNA extracted from the S particles on Ehrlich ascites tumor in mice.Purification of VLPs from frozen fruit bodies of L. edodes was carried out by the modified method reported by HOLLI~GS (3) and DI~LV~MAN-VA~-ZAAY~ (1). Final purification of S and F particles was by density gradient ccntrifugation in CsC1 (8, 13). The nucleic acid was extracted from purified S particles by cold phenol method. The protein and t%NA content of S and F particles or of the RNA preparations were determined by the Lowry method (6) and orcinol reaction, respectively. Ehrlich ascites carcinoma cells were passed intraperitoneally (i.p.) every two weeks into 5-week-old male mice of the Jcl:ICl~ strain (Clca Japan Inc., Tokyo) by injecting 0.2 ml of a suspension containing 105 to 106 cells/ml. Mice were treated i.p. with the S or F particles or S-derived I~NA in

The basidiomycete, Pleurotus ostreatus, is one of the most widely cultivated mushrooms, and several related species, P. columbinus, P. pulmonarius, P. florida, etc., are also well known as edible mushrooms. Werecently reported the interspecific protoplast fusion between P. ostreatus and P. salmoneo-stramineus, which are sexually incompatible with each other.1} Thus, the protoplast fusion technique, which can facilitate interspecific hybridi-5) A