The mushroom extract schizophyllan reduces cellular proliferation and induces G2/M arrest in MCF-7 human breast cancer cells

Breast cancer is the most common cancer in women worldwide. It is also the principle cause of death from cancer among women globally. Several lines of evidence suggest that dietary mushrooms may decrease breast cancer incidence. Schizohyllan (SCH) is a polysaccharide isolated from the medicinal mushroom S. commune and has potential anticancer effects. In a recent study we have demonstrated that SCH alone or in combination with tamoxifen (TAM) reduced the incidence of 7, 12 Dimethylbenz(α)anthracene (DMBA)-induced mammary carcinomas in mice through inhibition of cellular proliferation. The goal of the present work was to study the molecular mechanism through which SCH inhibits cell proliferation using the estrogen receptor positive human breast cancer cells (MCF-7) in vitro. MCF-7 cells were treated with different concentrations of SCH, and the following parameters were studied: cell growth, apoptosis, cell cycle kinetics using flow cytometry and expression of cell cycle regulatory proteins by Western blot. It was found that 1500 μg/ml of SCH reduced cell viability and this was not due to cell death by apoptosis but due to G2/M cell cycle phase arrest. Furthermore, the molecular mechanism underlying the G2/M phase arrest involved an increased phosphorylation at the inhibitory tyrosine 15 site of CDK1 associated with accumulation of p53. Taken together, this is the first study to show direct anticancer effects of SCH on human breast cancer cells in culture. The therapeutic implications of SCH in human breast cancer warrant further investigation.