Role of Two Species of Medicinal Mushrooms from Genus Ganoderma P. Karst. (G. lucidum and G. tsugae; Aphyllophoromycetideae) in Selective Estrogen-Receptor Modulations

摘要

Aqueous extracts were prepared from fruiting bodies artificially produced by solid-state fermentation and the vegetative mycelia produced by submerged fermentation of two strains of Ganoderma lucidum and two strains of G. tsugae (Basidiomycetes, Ganodermataceae). These aqueous extracts inhibited the proliferation of human breast cancer cells MCF-7 expressing estrogen receptor (ER) alpha and beta in a dose-dependent response in steroid-enriched media. Yet these extracts stimulated proliferation of MCF-7 in steroid-depleted media, as first revealed in the present study. This estrogenic feature was confirmed by competitive binding to ER alpha and -beta in vitro and upregulation of the ER-responsive gene pS2 of MCF-7 by reverse transcriptase-PCR. Although these G. lucidum and G. tsugae strains showed different estrogenic efficacies and antiproliferation capacities, such mycoestrogenic properties originated from the terpenes not polysaccharides as ER ligands. Among these 4 strains, G. lucidum extracts or terpene preparations showed higher estrogenicities. The aqueous extract of one G. tsugae strain demonstrated estrogenic properties at 0.5 mg/mL but antiproliferation causing DNA breakage detected by single cell gel electrophoresis at 1.0 mg/mL in steroid-depleted media. There was no synergistic effect on the proliferation of MCF-7 cells observed when 0.5 mg/mL G. tsugae extract was in combination with 1 nM 17 beta-estradiol for supplementation. Such extract upregulated the transcription of gene ER alpha but not ER beta of MCF-7 cells and peaked this ER alpha expression at 0.5 mg/mL by real-time polymerase chain reaction. Also, the pS2 expression of MCF-7 cells was in phase with its ER(x expression. In steroid-enriched media, MCF-7 showed lower expression of gene pS2 at day 4, whereas treatment with G. lucidum or G. tsugae extracts could maintain this transcription level, although the cell population showed a continuous drop and higher expression of tumor suppressor gene p53 and proapoptotic gene Bax. Thus, the antiproliferation effect of G. lucidum is not via the suppression of the ER pathway. This study first proves the selective responses between mitogenic effect and antiproliferative effect on MCF-7 cells under steroid-enriched and steroid-depleted media conditions by G. lucidum and G. tsugae extracts. Whereas the mitogenic effect is via estrogen receptor modulation, the antiproliferation is mediated via multiple pathways involving the induction of apoptosis. Nevertheless, the present study supports the traditional belief in consuming species of the genus Ganoderma, especially G. lucidum and G. tsugae, for maintaining the health of the aged, who usually show decreased production of sex hormones, and for preventing diseases, that is, breast cancer.