title: ROS-dependent mitochondria molecular mechanisms underlying antitumor activity of Pleurotus abalonus acidic polysaccharides in human breast cancer MCF-7 cells.
abstract: BACKGROUND
  A greater reduction in cancer risk associated with mushroom diet rich in fungus polysaccharides is generally accepted. Meanwhile, edible Pleurotus abalonus as a member of Abalone mushroom family is a popular nutritional supplement that purportedly prevents cancer occurrence. However, these anecdotal claims are supported by limited studies describing tumor-inhibitory responses to the promising polysaccharides, and the molecular mechanisms underlying these properties have not yet been elucidated.
  
  
  RESULTS
  We here fractionated the crude polysaccharide preparation from the fruiting bodies of P. abalonus into three fractions, namely PAP-1, PAP-2 and PAP-3, and tested these fractions for antiproliferative activity in human breast cancer MCF-7 cells. The largest PAP-3, an acidic polysaccharide fraction with a molecular mass of 3.68×10(5) Da, was the most active in inhibiting MCF-7 cancer cells with an IC50 of 193 µg/mL. The changes in cell normal morphology were observed by DAPI staining and the PAP-3-induced apoptosis was confirmed by annexin V/propidium iodide staining. The apoptosis was involved in mitochondria-mediated pathway including the loss of mitochondrial membrane potential (Δψm), the increase of Bax/Bcl-2 ratio, caspase-9/3 activation, and poly(ADP-ribose) polymerase (PARP) degradation, as well as intracellular ROS production. PAP-3 also induced up-regulation of p53, and cell cycle arrest at the S phase. The incubation of MCF-7 cells with antioxidant superoxide dismutase (SOD) and N-acetylcysteine (NAC) significantly attenuated the ROS generation and apoptosis caused by PAP-3, indicating that intracellular ROS plays a pivotal role in cell death.
  
  
  CONCLUSIONS
  These findings suggest that the polysaccharides, especially acidic PAP-3, are very important nutritional ingredients responsible for, at least in part, the anticancer health benefits of P. abalonus via ROS-mediated mitochondrial apoptotic pathway. It is a major breakthrough bringing new insight of the potential use of the polysaccharides as health-care food or medicine to provide significant natural defense against human cancer.
authors.affiliation: Key Laboratory of Medicinal Resources and Natural Pharmaceutical Chemistry, Ministry of Education, and National Engineering Laboratory for Resource Developing of Endangered Chinese Crude Drugs in Northwest of China, College of Food Engineering and Nutritional Science, Shaanxi Normal University, Xi'an, China.
authors.forename: Xiaolong
authors.initials: X
authors.lastname: Shi
authors.forename: Yan
authors.initials: Y
authors.lastname: Zhao
authors.forename: Yadong
authors.initials: Y
authors.lastname: Jiao
authors.forename: Tengrui
authors.initials: T
authors.lastname: Shi
authors.forename: Xingbin
authors.initials: X
authors.lastname: Yang
mesh_terms: D000970:Antineoplastic Agents / Q000737:chemistry / Q000494:pharmacology*; D017209:Apoptosis / Q000187:drug effects; D001943:Breast Neoplasms / Q000473:pathology*; D059447:Cell Cycle Checkpoints / Q000187:drug effects; D062610:Fungal Polysaccharides / Q000737:chemistry / Q000494:pharmacology*; D006801:Humans; D006863:Hydrogen-Ion Concentration; D061986:MCF-7 Cells; D008928:Mitochondria / Q000187:drug effects* / Q000378:metabolism*; D000073718:Pancreatitis-Associated Proteins; D020076:Pleurotus / Q000737:chemistry*; D017382:Reactive Oxygen Species / Q000378:metabolism*
chemical_list: D000970:Antineoplastic Agents; D062610:Fungal Polysaccharides; D000073718:Pancreatitis-Associated Proteins; C000612141:REG3A protein, human; D017382:Reactive Oxygen Species