Antitumor effect of antiplatelet agents in gastric cancer cells: an in vivo and in vitro study

Background: The antitumor effects of antiplatelet agents in gastric cancer cells are not well known. In this study, the possibility of gastric cancer treatment with an antiplatelet agent, mainly aspirin, was examined both in vivo and in vitro. Methods: For in vivo experiments, tumor-bearing mice were treated by an antiplatelet antibody or aspirin, and the tumor growth was compared. For in vitro experiments, human gastric cancer cell lines were used to confirm the cancer cell growth and inhibition by reducing the platelet count or using aspirin. We also examined several cytokines by using an ELISA assay and conducted microRNA microarray analysis of MKN-45 tumor cells to determine the influence of platelets or aspirin. Results: In vivo experiments showed that tumor growth was inhibited by halving the circulating platelet count by using an antiplatelet antibody or peroral daily aspirin. In vitro experiments showed that the proliferation rates of gastric cancer cell lines were increased after coincubation with platelets and that the effect was inhibited by aspirin. Although the expression of interleukin-6, platelet-derived growth factor, transforming growth factor-β, and prostaglandin E2 did not correlate with tumor growth inhibition by aspirin, seven microRNAs showed altered expression in cancer cells in response to coincubation with platelets or addition of aspirin. Cells transfected with mir-4670-5p showed a significant increase in proliferation compared to negative control cells. Conclusions: Our study showed that platelets increased the proliferation of gastric cancer cells and that this increase was inhibited by antiplatelet antibody or aspirin. Mir-4670-5p may play an important role in these responses.