Gallic acid suppresses cell viability, proliferation, invasion and angiogenesis in human glioma cells

Abstract

Gallic acid, an organic acid, also known as 3,4,5-trihydroxybenzoic acid, is cytotoxic against certain cancer cells, without harming normal cells. The objective of this study is to evaluate whether gallic acid can inhibit glioma cell viability, proliferation, invasion and reduce glioma cell mediated angiogenesis. Treatment of U87 and U251n glioma cells with gallic acid inhibited cell viability in a dose-dependent manner. BrdU and tube formation assays indicated that gallic acid significantly decreased glioma cell proliferation and tube formation in mouse brain endothelial cells, respectively. In addition, gallic acid decreased U87 cell invasion in vitro. Western blot analysis showed that expression of ADAM17, p-Akt and p-Erk was suppressed by gallic acid in both U87 and U251n cell lines. These data suggest that suppression of ADAM17 and downregulation of PI3K/Akt and Ras/MAPK signaling pathways may contribute to gallic acid-induced decrease of invasiveness. Gallic acid may be a valuable candidate for treatment of brain tumor.

Figure 1

Effect of gallic acid on cell viability and proliferation of glioma cells. A: MTT assay of U87 and U251n glioma cells treated with various concentrations of gallic acid. B: SRB assay of U87 and U251n glioma cells treated with the same concentrations. C: U87 and U251n were treated with the indicated concentration of gallic acid for up to 96 h in complete medium. MTT assay was used to assess growth of cells in culture. D: BrdU proliferation assay of U87 and U251n cells treated with different doses of gallic acid for 24 h. The cell nuclear incorporation of BrdU was measured. The proliferation rate was presented as mean ± SEM value of percentage from BrdU-labeled cells vs. DAPI-labeled cells (data obtained from three independent experiments). *P<0.01, control vs. treated groups.

Figure 2

Gallic acid inhibits U87 and U251n cell migration and reduces invasiveness of U87 cells. A: In the wound scratch assay, the migration ability was presented as mean ± SEM of the migration distance. B: Microscopy images of detected cells that migrated into the lower chamber (magnification ×200). C: The cell migration was quantified by the cell number from treated groups versus control group. ^#P<0.05, *P<0.01, as compared with the control group.

Figure 3

Effect of gallic acid on mouse brain endothelial cell tubulogenesis in vitro. A: Representative photomicrographs during the tube formation of mouse brain endothelial cells pretreated with indicated concentrations of gallic acid for 24 h. B: The ability to form tubes was expressed as ratios of length of formed tubes per picture field. ^*P<0.01, as compared with the control group.

Figure 4

A: Western blot analysis of expression of ADAM17, Erk/p-Erk and Akt/p-Akt in U87 and U251n cells. The cells were treated with 20, 30, and 40μg/ml gallic acid for 24 h and subjected to immunoblotting with antibodies against ADAM17, Erk/p-Erk, and Akt/p-Akt. Actin was used as sample loading controls. B: Effect of gallic acid on ADAM17 activity in U87 cells. ^#P<0.05, *P<0.01 as compared with the control cells.