The ethyl acetate extract of Phellinus linteus grown on germinated brown rice induces G0/G1 cell cycle arrest and apoptosis in human colon carcinoma HT29 cells

It is well known that Phellinus linteus has a variety of biological functions, such as antitumor and immunomodulating activities. In our previous studies, we developed a P. linteus grown on germinated brown rice (PBR) and found that organic solvent extracts of PBR possessed immunomodulating activity to regulate a balance of cytokine network in mice. The components of PBR are ergosterol peroxide, γ‐aminobutyric acid (GABA) and B‐glucan. In this study, we demonstrate that an organic solvent extract of P. linteus grown on PBR induced apoptotic cell death through the induction of G₀/G₁ arrest of cell cycle and the apoptosis via DNA fragmentation in human colon carcinoma HT‐29 cells. Cell death induced by the extract of P. linteus grown on PBR was shown to be associated with the upregulation of p21^CIP1/WAF1, the downregulation of cyclin D1, anti‐apoptotic protein, Bcl‐2, the release of cytochrome c, and the activation of caspase‐9, caspase‐3 and caspase‐8. This study suggests that the ethyl acetate extract of P. linteus grown on PBR induces apoptosis accompanied by cell cycle arrest at G₀/G₁ phase and regulates apoptosis‐regulatory proteins, which may be applicable to anticancer therapy. Copyright © 2009 John Wiley & Sons, Ltd.