Induction of apoptosis in human prostatic cancer cells with beta-glucan (Maitake mushroom polysaccharide)

Purpose: To explore more effective treatment for hormone-refractory prostat e cancer, we investigated the potential antitumor effect of beta-glucan, a polysaccharide of the Maitake mushroom, on prostatic cancer cells in vitro. Materials and Methods: Human prostate cancer PC-3 cells were treated with v arious concentrations of the highly purified beta-glucan preparation Grifro n-D(R) (GD), and viability was determined at 24 h, Lipid peroxidation (LPO) assay and in situ hybridization (ISH) were performed to unravel the antitu mor mechanism of GD. Results: A dose-response study showed that almost complete (>95%) cell deat h was attained in 24 h with GD greater than or equal to 480 mu g/mL. Combin ations of GD in a concentration as low as 30 to 60 mu g/mL with 200 mu M vi tamin C were as effective as GD alone at 480 mu g/mL, inducing >90% cytotox ic cell death. Simultaneous use with various anticancer drugs showed little potentiation of their efficacy except for the carmustine/GD combination (s imilar to 90% reduction in cell viability). The significantly (twofold) ele vated LPO level and positive ISH staining of GD-treated cells indicated oxi dative membrane damage resulting in apoptotic cell death. Conclusion: A bioactive beta-glucan from the Maitake mushroom has a cytotox ic effect, presumably through oxidative stress, on prostatic cancer cells i n vitro, leading to apoptosis, Potentiation of GD action by vitamin C and t he chemosensitizing effect of GD on carmustine may also have clinical impli cations. Therefore, this unique mushroom polysaccharide may have great a po tential as an alternative therapeutic modality for prostate cancer.