Inhibition of in vivo angiogenesis by Anacardium occidentale L. involves repression of the cytokine VEGF gene expression.

Lethal tumor growth and progression cannot occur without angiogenesis, which facilitates cancer cell proliferation, survival, and dissemination. Among the many growth factors and cytokines engaged in angiogenesis, the cytokine vascular endothelial growth factor (VEGF) is regarded as the most potent and specific. Angiogenesis inhibitors are recognized as potentially useful agents for treating angiogenesis-associated diseases and VEGF represents a promising and well-studied target for antiangiogenic agents. In this study, we have tested the crude ethanolic extract of the leaves of Anacardium occidentale Linn, on Ehrlich ascites tumor cells (EAT) in vivo and in vitro. Anacardium occidentale extract (AOE) was able to suppress VEGF-induced angiogenesis in vivo in the chorioallantoic membrane, rat cornea, and tumorinduced angiogenesis in the peritoneum of EAT bearing mice. The extract inhibited cell proliferation of different tumor cells such as EAT, BeWo, and MCF-7 in vitro in a dose-dependent manner and it reduced the VEGF level in the ascites of treated mice. A decrease in the microvessel density count and CD31 antigen staining of treated mice peritoneum provide further evidence of its antiangiogenic activity. Our results from Northern blot analysis and ELISA demonstrate that AOE can downregulate endogenous VEGF gene expression at the mRNA and protein level. Furthermore, results of our gene analysis of VEGF-promoter luciferase reporter indicated that this effect is mediated by transcriptional repression of VEGF promoter activity in EAT cells treated with AOE. Taken together, the data suggest that the VEGF system of angiogenesis is the molecular target for the antiangiogenic action of AOE.