title: Lectin from Agaricus bisporus inhibited S phase cell population and Akt phosphorylation in human RPE cells.
abstract: OBJECTIVE
  Lectin from the edible mushroom Agaricus bisporus (ABL) was found to inhibit cell proliferation of some ocular and cancer cell lines. To elucidate how ABL inhibited RPE cell proliferation, we investigated the changes in cell cycle distribution and cell proliferation-related signaling pathways after ABL treatment.
  
  
  METHODS
  Primary human RPE cells were isolated and grown in DMEM/F12 with or without the ABL (20 or 90 μg/mL) for 3 days. Analysis of cell cycle was performed by flow cytometry. Phosphorylation status of Erk, Jnk, p38, and Akt as well as p53 expression levels were investigated by Western blotting. The role of phosphorylated-Akt in RPE cell proliferation was further evaluated using LY294002.
  
  
  RESULTS
  After ABL treatment (90 μg/mL), the amount of cells present in the S phase was found to be reduced. These changes were not apparent in cells treated with 20 μg/mL ABL. In addition, Erk and Akt were found to be hyperphosphorylated and hypophosphorylated, respectively. The expression levels of phosphorylated-Jnk, phosphorylated-p38, and p53 were not altered when compared with those of the control cells. When RPE cells were treated with LY294002 and deprived from phosphorylated-Akt expression, cell proliferation rate was reduced. Reduction in the amount of cells present in S phase was also observed.
  
  
  CONCLUSIONS
  Our results showed that ABL hypophosphorylated Akt and this observation is in line with the fact that ABL attenuates cell proliferation. As the level of p53 was not significantly altered by ABL, this indicated that ABL-arrested cell cycle progression was independent of p53 activation.
authors.affiliation: Eye Institute, The University of Hong Kong, Pokfulam, Hong Kong.
authors.forename: Yiu-Him
authors.initials: YH
authors.lastname: Cheung
authors.forename: Carl M
authors.initials: CM
authors.lastname: Sheridan
authors.forename: Amy C Y
authors.initials: AC
authors.lastname: Lo
authors.forename: Wico W
authors.initials: WW
authors.lastname: Lai
mesh_terms: D000364:Agaricus / Q000378:metabolism*; D015153:Blotting, Western; D002455:Cell Division; D049109:Cell Proliferation; D002470:Cell Survival; D002478:Cells, Cultured; D005434:Flow Cytometry; D006801:Humans; D037102:Lectins / Q000378:metabolism / Q000494:pharmacology*; D010766:Phosphorylation; D051057:Proto-Oncogene Proteins c-akt / Q000378:metabolism*; D055213:Retinal Pigment Epithelium / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D016196:S Phase / Q000187:drug effects*; D015398:Signal Transduction / Q000187:drug effects
chemical_list: D037102:Lectins; D051057:Proto-Oncogene Proteins c-akt