Purpose: It has been reported that genistein, an isoflavone used in soybeans, has antiprostate cancer effects. Genistein Combined Polysaccharide (GCP trade mark; AMino Up, Sapporo, Japan), a nutritional supplement manufactured in Japan, is composed of genistein and a polysaccharide obtained from basidiomycetes (mycelia) that grows in a variety of mushrooms.
Methods: We report a case of a patient with a biopsy proven prostate cancer showing clinical and pathologic evidence of regression following administration of GCP. The patient was enrolled in an Institutional Review Board (IRB)-approved protocol and received GCP for 6 weeks prior to radical prostatectomy.
Results: The patient's prostate-specific antigen (PSA) decreased from an initial value of 19.7 to 4.2 ng/mL after 44 days of low-dose GCP. No cancer was identified in the radical prostatectomy specimen and no side effects were observed in this patient.
Conclusion: This case suggests that GCP, which has shown potent inhibitory effects against prostate cancer in vitro, may have some potential activity in the treatment and prevention of prostate cancer.