title: Antiproliferative and pro-apoptotic effects of three fungal exocellular β-glucans in MCF-7 breast cancer cells is mediated by oxidative stress, AMP-activated protein kinase (AMPK) and the Forkhead transcription factor, FOXO3a.
abstract: Fungal β-d-glucans of the (1→3)-type are known to exhibit direct antitumor effects, and can also indirectly decrease tumor proliferation through immunomodulatory responses. The underlying molecular mechanisms involved in decreasing tumor formation, however, are not well understood. In this study, we examined the antiproliferative role and mechanism of action of three different fungal exocellular β-glucans in MCF-7 breast cancer cells. The β-glucans were obtained from Botryosphaeria rhodina MAMB-05 [two botryosphaerans; (1→3)(1→6)-β-d-glucan; one produced on glucose, the other on fructose] and Lasiodiplodia theobromae MMPI [lasiodiplodan; (1→6)-β-d-glucan, produced on glucose]. Using the cell proliferation-MTT assay, we showed that the β-glucans exhibited a time- and concentration-dependent antiproliferative activity (IC50, 100μg/ml). Markers of cell cycle, apoptosis, necrosis and oxidative stress were analyzed using flow cytometry, RT-PCR and Western blotting. Exposure to β-glucans increased apoptosis, necrosis, oxidative stress, mRNA expression of p53, p27 and Bax; the activity of AMP-activated protein-kinase, Forkhead transcription factor FOXO3a, Bax and caspase-3; and decreased the activity of p70S6K in MCF-7 cells. In the presence of hydrogen peroxide, the fungal β-glucans increased oxidative stress, which was associated with reduced cell viability. We showed that these β-glucans exhibited an antiproliferative effect that was associated with apoptosis, necrosis and oxidative stress. This study demonstrated for the first time that the apoptosis induced by β-glucans was mediated by AMP-activated protein-kinase and Forkhead transcription factor, FOXO3a. Our findings provide novel mechanistic insights into their antiproliferative roles, and compelling evidence that these β-glucans possess a broad range of biomodulatory properties that may prove useful in cancer treatment.
authors.affiliation: Department of Pharmacology, Institute of Biomedical Sciences, University of São Paulo, São Paulo 05508-900, SP, Brazil; Biorefining Research Institute (BRI), Lakehead University, Thunder Bay, ON, Canada P7B 5E1; Medical Sciences Division, Northern Ontario School of Medicine (NOSM), Lakehead University, Thunder Bay, ON, Canada P7B 5E1.
authors.forename: Eveline A I F
authors.initials: EA
authors.lastname: Queiroz
authors.affiliation: Department of Pharmacology, Institute of Biomedical Sciences, University of São Paulo, São Paulo 05508-900, SP, Brazil.
authors.forename: Zuleica B
authors.initials: ZB
authors.lastname: Fortes
authors.affiliation: Departamento de Química, Universidade Tecnológica Federal do Paraná, Pato Branco 85503-390, PR, Brazil.
authors.forename: Mário A A
authors.initials: MA
authors.lastname: da Cunha
authors.affiliation: Biorefining Research Institute (BRI), Lakehead University, Thunder Bay, ON, Canada P7B 5E1; Biorefining and Biotechnology Consultancy, Rua João Huss 200, Gleba Palhano, CEP 86050-490 Londrina, PR, Brazil.
authors.forename: Aneli M
authors.initials: AM
authors.lastname: Barbosa
authors.affiliation: Medical Sciences Division, Northern Ontario School of Medicine (NOSM), Lakehead University, Thunder Bay, ON, Canada P7B 5E1. Electronic address: nkhaper@nosm.ca.
authors.forename: Neelam
authors.initials: N
authors.lastname: Khaper
authors.affiliation: Biorefining Research Institute (BRI), Lakehead University, Thunder Bay, ON, Canada P7B 5E1; Biorefining and Biotechnology Consultancy, Rua João Huss 200, Gleba Palhano, CEP 86050-490 Londrina, PR, Brazil. Electronic address: rdekker@lakeheadu.ca.
authors.forename: Robert F H
authors.initials: RF
authors.lastname: Dekker
mesh_terms: D055372:AMP-Activated Protein Kinases / Q000235:genetics* / Q000378:metabolism; D000970:Antineoplastic Agents / Q000494:pharmacology*; D017209:Apoptosis / Q000187:drug effects*; D053148:Caspase 3 / Q000235:genetics / Q000378:metabolism; D002453:Cell Cycle / Q000187:drug effects; D049109:Cell Proliferation / Q000187:drug effects; D050760:Cyclin-Dependent Kinase Inhibitor p27 / Q000235:genetics / Q000378:metabolism; D005260:Female; D000071316:Forkhead Box Protein O3; D051858:Forkhead Transcription Factors / Q000819:agonists / Q000235:genetics* / Q000378:metabolism; D062610:Fungal Polysaccharides / Q000494:pharmacology*; D015972:Gene Expression Regulation, Neoplastic; D006801:Humans; D006861:Hydrogen Peroxide / Q000494:pharmacology; D061986:MCF-7 Cells; D018384:Oxidative Stress / Q000187:drug effects; D038762:Ribosomal Protein S6 Kinases, 70-kDa / Q000235:genetics / Q000378:metabolism; D015398:Signal Transduction; D016159:Tumor Suppressor Protein p53 / Q000235:genetics / Q000378:metabolism; D051028:bcl-2-Associated X Protein / Q000235:genetics / Q000378:metabolism; D047071:beta-Glucans / Q000494:pharmacology*
chemical_list: D000970:Antineoplastic Agents; C494826:BAX protein, human; C499517:FOXO3 protein, human; D000071316:Forkhead Box Protein O3; D051858:Forkhead Transcription Factors; D062610:Fungal Polysaccharides; D016159:Tumor Suppressor Protein p53; D051028:bcl-2-Associated X Protein; D047071:beta-Glucans; D050760:Cyclin-Dependent Kinase Inhibitor p27; D006861:Hydrogen Peroxide; D038762:Ribosomal Protein S6 Kinases, 70-kDa; D055372:AMP-Activated Protein Kinases; D053148:Caspase 3
keywords: AMPK; Apoptosis; Botryosphaeran; FOXO3a; Lasiodiplodan; Oxidative stress