Hiroshi Kobayashi, Kenichi Matsunaga,1 and Yoshiharu Oguchi
P5K, a protein-bound polysaccharide obtained from cultured mycelia of Coriolus versicolor in basidiomycetes, is a biological response modifier, diverse operations of which include an antitumor action. We have previously reviewed recent research which had demonstrated that in animals, P5K has a preventive effect on chemical carcinogen-induced, radiation induced, and spontaneously developed carcinogenesis (Kobayashi et aL, Cancer Epidemiol., Biomarkers & Prey., 2: 271-276, 1993). We now focus on the effects of PSK once the progression of carcinogenesis has begun, and review what is now known of the preventive action of PSK on cancer metastasis.