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Yiu-Him Cheung, A.C.Y. Lo, D Wong, W.W.K. Lai; Lectin from Agaricus Bisporus Suppresses Akt Phosphorylation and Arrests Cell Cycle Progression in Primary Human Retinal Pigment Epithelial Cells. Invest. Ophthalmol. Vis. Sci. 2011;52(14):5339.
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© ARVO (1962-2015); The Authors (2016-present)
Lectin from the edible mushroom Agaricus bisporus (ABL) was found to inhibit growth of certain cancer cell lines as well as proliferation of retinal pigment epithelial (RPE) cell lines in a potent manner. The mechanism for the observed inhibition is unclear. To elucidate the mechanism through which ABL inhibits RPE cell proliferation, we investigated the changes in cell proliferation-related signaling pathways and cell cycle distribution patterns.
Primary human RPE cells (passages 6 to 10) were utilized. Cells were grown in DMEM/F12 with or without the lectin (ABL) supplement (20µg or 90µg/ml) for three days. Phosphorylation statuses of Akt, Jnk and p38 as well as p53 expression level were investigated by Western blotting. Cellular distributions in various cell cycle phases were investigated using flow cytometry.
After ABL treatment (90µg/ml), Akt was found to be hypo-phosphorylated while the expression levels of p53, phosphorylated-Jnk and phosphorylated-p38 were not altered when compared with the control cells. The amount of cells present at S phase was found to be reduced. These changes were not apparent in cells treated with 20µg/ml ABL.
Our results showed that ABL hypo-phosphorylated Akt and this observation is in line with the fact that ABL could attenuate cell proliferation. At the same time, the reduction of cells present at S phase indicated that ABL inhibited RPE cells transiting from G1 to S phase. As the level of p53 was not significantly altered by ABL, this suggested that the mechanism in which ABL arrested cell proliferation was independent of Akt-mediated MDM2 activation.
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