title: Maitake (D fraction) mushroom extract induces apoptosis in breast cancer cells by BAK-1 gene activation.
abstract: For many years mushrooms have been used empirically in traditional medicine to treat several diseases. Study of the maitake mushroom, with its immunomodulatory and antitumoral properties, has led to the isolation of several bioactive compounds. One of these, D fraction, is known to reduce tumor cell viability. This study examined the effect of isolated D fraction on viability and apoptosis of human breast cancer cells (MCF7). These cells were treated with maitake (D fraction) extract at 18 μg/mL, 36 μg/mL, 91 μg/mL, 183 μg/mL, or 367 μg/mL or were left untreated (control) for 24 hours. MCF7 incubation with the maitake extract resulted in decreased cell viability [3-(4,5-dimethylthiazol-2-yl)-5-(3-carboxymethoxyphenyl)-2-(4-sulfophenyl)-2H-tetrazolium assay] in a dose-dependent manner. Apoptosis was statistically significantly increased in a dose-dependent manner at every concentration tested (terminal deoxynucleotidyl transferase-mediated deoxyuridine triphosphate nick-end labeling assay). Upon incubation with D fraction, a microarray assay revealed upregulation of BAK-1 and cytochrome c transcripts, 2 proteins directly involved in the apoptotic pathway. Reverse transcriptase polymerase chain reaction studies confirmed these findings; BAK-1 was one of most overexpressed gene, as observed by microarray assay. These findings confirm the apoptotic effect of maitake D fraction in breast cancer cells and further highlight the involvement of cytochrome c release to the cytoplasm. Cytoplasmic release of cytochrome c, another player in the apoptotic pathway, was also increased after incubation with D fraction in a dose-dependent manner. This finding indicates that the effect of this compound involves mitochondrial dysfunction. The identification of the molecular mechanisms by which D fraction exerts its effects is crucial for the development of preventive and therapeutic strategies for cancer.
authors.affiliation: Department of Biochemistry, Faculty of Medicine, University of Porto Foundation, Porto, Portugal.
authors.forename: Raquel
authors.initials: R
authors.lastname: Soares
authors.forename: Manuela
authors.initials: M
authors.lastname: Meireles
authors.forename: Ana
authors.initials: A
authors.lastname: Rocha
authors.forename: Ana
authors.initials: A
authors.lastname: Pirraco
authors.forename: Diego
authors.initials: D
authors.lastname: Obiol
authors.forename: Eliana
authors.initials: E
authors.lastname: Alonso
authors.forename: Gisela
authors.initials: G
authors.lastname: Joos
authors.forename: Gabriela
authors.initials: G
authors.lastname: Balogh
mesh_terms: D017209:Apoptosis / Q000187:drug effects*; D001685:Biological Factors / Q000302:isolation & purification / Q000494:pharmacology*; D001943:Breast Neoplasms / Q000235:genetics* / Q000378:metabolism / Q000503:physiopathology; D045744:Cell Line, Tumor; D005260:Female; D015972:Gene Expression Regulation, Neoplastic / Q000187:drug effects; D048691:Grifola / Q000737:chemistry*; D006801:Humans; D015533:Transcriptional Activation / Q000187:drug effects*; D050998:bcl-2 Homologous Antagonist-Killer Protein / Q000235:genetics* / Q000378:metabolism
chemical_list: C494772:BAK1 protein, human; D001685:Biological Factors; D050998:bcl-2 Homologous Antagonist-Killer Protein