Cytotoxic Activities of Fractions of the Willow Bracket Medicinal Mushroom, Phellinus igniarius (Agaricomycetes), and the Induction of Cell Cycle Arrest and Apoptosis in MGC-803 Cells.

Phellinus igniarius, a perennial medicinal mushroom, has been used in China and other countries of East Asia for the treatment of various diseases, including cancer. The purpose of this study is to evaluate the cytotoxic activities of different fractions of an ethanol extract from Ph. igniarius and to elucidate a possible antitumor mechanism. An ethanol extract of Ph. igniarius was partitioned into a petroleum ether fraction, an ethyl acetate fraction (EAF), an n-butanol fraction, and a water-soluble fraction. The cytotoxic activity of all the fractions was initially screened in a brine shrimp lethality test, then evaluated by the Cell Counting Kit-8 assay against 5 human tumor cell lines: MGC-803, BEL-7402, HeLa, MCF-7, and HCT-116. The cell cycle distribution induced by EAF on MGC-803 cells was analyzed by flow cytometry with propidium iodide staining, and apoptosis was determined using flow cytometry with Annexin V/propidium iodide staining. The results of the brine shrimp lethality test and the Cell Counting Kit-8 assay showed that EAF was the most active fraction, displaying strong inhibitory activity against the MGC-803, BEL-7402, and MCF-7 cancer cell lines. Flow cytometry analysis indicated that EAF could induce S-phase cell cycle arrest in MGC-803 cells and cause apoptosis in a concentration-dependent manner. This study demonstrated that EAF, as the most active fraction of Ph. igniarius, exerted antitumor activity by inducing MGC-803 cell apoptosis via S-phase cell cycle arrest.