Andrographolide Inhibits the Adhesion of Gastric Cancer Cells to Endothelial Cells by Blocking E-selectin Expression

Abstract

Background: Andrographolide, an active component isolated from the Chinese official herbal Andrographis paniculata, has recently been reported to have anticancer activity. However the molecular mechanism responsible for its anticancer action has not been fully defined. In this study, we investigated the effect of andrographolide on the adhesion of gastric cancer cells to the activated endothelial cells and the expression of some cell adhesion molecules. Materials and Methods: Human endothelial cells were pre-incubated with andrographolide for 6 h and then incubated with the cytokine tumor necrosis factor for 4 h. Endothelial surface expression of E-selectin was evaluated by flow cytometry, immunostaining and ELISA. Further, we investigated E-selectin mRNA expression by RT-PCR. Surface expression of sialyl Lewis^X of three gastric cancer cell lines (SGC7901, MGC803, BGC823) and a normal gastric epithelial cell line GES-1 was evaluated by flow cytometry and immunostaining. Adherence of CFSE-labeled gastric cancer cells and GES-1 cells to endothelial cell monolayers was then determined. Results: Andrographolide significantly reduced E-selectin expression of activated endothelial cells, and inhibited the E-selectin expression on mRNA level. Three gastric cancer cell lines expressed high levels of sialyl Lewis^X, whereas GES-1 did not. Andrographolide also significantly decreased gastric cancer cells adherence to stimulated endothelial cells. The inhibition of E-selectin expression corresponded to the reduction of tumor cell adherence. The effects of andrographolide on tumor adhesion were almost nullified by pre-incubation with E-selectin and sialyl Lewis^X antibody. Conclusion: These findings demonstrate that andrographolide suppresses the adhesion of gastric cancer cells which express high level sialyl Lewis^X to human vascular endothelial cells by blocking E-selectin expression and, thus, may represent a candidate therapeutic agent for cancer.