Cimetidine inhibits the adhesion of gastric cancer cells expressing high levels of sialyl Lewis x in human vascular endothelial cells by blocking E-selectin expression

Cimetidine has been shown to have anti-metastatic activity and improves the survival of patients with colorectal cancer. One hypothesis is its modulation of the expression of the cell adhesion molecule by target organ endothelial cells. Because of the inconclusive results in clinical trials of gastric cancer, we investigated the effects of cimetidine on the adhesion of gastric cancer cells to activated endothelial cells and on the expression of some cell adhesion molecules. Human endothelial cells were pre-incubated with cimetidine for 6 h, incubated with the cytokine tumor necrosis factor for 4 h, and the endothelial surface expression of E-selectin was evaluated by flow cytometry, immunostaining and ELISA. Further, we investigated E-selectin mRNA expression by RT-PCR. Three gastric cancer cell lines (SGC-7901, MGC-803, BGC-823) and a normal gastric epithelial cell line, GES-1, were studied for the surface expression of sialyl Lewis x by flow cytometry and immunostaining. Adherence of CFSE-labeled gastric cancer cells and GES-1 cells to endothelial cell monolayers was determined. Cimetidine significantly reduced E-selectin expression of activated endothelial cells, but did not influence E-selectin expression at the mRNA level. Three gastric cancer cell lines expressed high levels of sialyl Lewis x, whereas GES-1 did not. Cimetidine also significantly decreased gastric cancer cell adherence to stimulated endothelial cells. The inhibition of E-selectin expression corresponded to the reduction of tumor cell adherence. The effects of cimetidine on tumor adhesion were almost nullified by pre-incubation with E-selectin and sialyl Lewis x antibody. Furthermore, there was no significant change of GES-1 adherence to endothelial cells by TNF-α, cimetidine, E-selectin and sialyl Lewis x antibody. The inhibiton of gastric cancer cell adherence to cytokine-stimulated endothelial cells treated with cimetidine appears to result from blocking endothelial E-selectin expression. These data support the hypothesis that cimetidine may exert its anti-metastatic effects in gastric cancer, in part, by inhibiting E-selectin/sialyl Lewis x-mediated adherence of gastric cancer cells to endothelial cells in the metastasis target organs.