Prevention of the development of preneoplastic lesions, aberrant crypt foci, by a water-soluble extract from cultured medium of Ganoderma lucidum (Rei-shi) mycelia in male F344 rats

The modifying effects of a dietary water-soluble extract from cultured medi um of Ganoderma lucidum (Reishi or Mannentake) mycelia (MAK) on the develop ment of azoxymethane (AOM)-induced colonic aberrant crypt foci (ACF) were i nvestigated in male F344 rats. Rats were given subcutaneous injections of A OM (20 mg/kg body weight) once a week for three weeks to induce ACF and fed on diets containing 0, 1.25, 2.5 and 5.0% MAK for five weeks, starting one week before the first dose of carcinogen. MAK significantly and dose-depen dently prevented the development of ACF, decreasing the total number of AC and inhibiting cyst formation. MAK (2.5 and 5.0%) also significantly reduce d the longitudinal-cross section areas of colon epithelium. MAK in all dose s significantly reduced the PCNA positive index, area of the germinal regio n and number of cells per half crypt. In an additional in vitro experiment, MAK inhibited anchorage-independent growth of several colon carcinoma cell lines. The present results thus indicate that dietary MAK could act as a p reventive agent for colon carcinogenesis.