Cell-cycle arrest and apoptosis induction in human breast carcinoma MCF-7 cells by carboxymethylated β-glucan from the mushroom sclerotia of Pleurotus tuber-regium

The mechanism for the anti-tumor activity of a water-soluble carboxymethylated P-glucan (CMPTR), partially synthesized from an insoluble native glucan isolated from the sclerotia of Pleurotus tuber-regium, was studied using human breast carcinoma MCF-7 breast cancer cells in vitro. CMPTR-induced anti-proliferative activity dose-dependently, with an IC50 of 204 mu g/ml. CMPTR inhibited the cell proliferation of MCF-7 by arresting the G, phase of its cell cycle after 48 h of incubation as shown by flow cytometry. Such G, phase arrest was associated with the down-regulation of cyclin D I and cyclin E expressions in the breast cancer cells. In addition, the CMPTR-treated MCF-7 cancer cells-were associated with decreased expression of anti-apoptotic Bcl-2 protein and increased expression of Bax/ Bcl-2 ratio. This study shows that CMPTR can inhibit the proliferation of MCF-7 by cell-cycle arrest and apoptosis induction. The potential development of this mushroom polysaccharide as a water-soluble anti-tumor agent requires further investigation. (c) 2006 Elsevier Ltd. All rights reserved.