Salmonella inhibits tumor angiogenesis by downregulation of vascular endothelial growth factor

Salmonella is a Gram-negative, facultative anaerobe that is a common cause of host intestinal infections. Salmonella grows under aerobic and anaerobic conditions, and it has been proven capable of inhibiting tumor growth. However, the molecular mechanism by which Salmonella inhibits tumor growth is still unclear. Angiogenesis plays an important role in the development and progression of tumors. We investigated the antitumor effect of Salmonella in a syngeneic murine tumor model. Hypoxia-inducible factor-1 (HIF-1)α plays a significant role in tumor angiogenesis. We examined the molecular mechanism by which Salmonella regulated vascular endothelial growth factor (VEGF), which is an important angiogenic factor. The expression of VEGF in tumor cells was decreased by treatment with Salmonella. The conditioned medium from Salmonella-treated cells inhibited the proliferation of endothelial cells. Salmonella inhibited the expression of HIF-1α as well as downregulated its upstream signal mediator protein kinase B (AKT). Salmonella significantly inhibited tumor growth in vivo, and immunohistochemical studies of the tumors revealed decreased intratumoral microvessel density. These results suggest that Salmonella therapy, which exerts anti-angiogenic activities, represents a promising strategy for the treatment of tumors.