Anti-angiogenic effect of tanshinone IIA involves inhibition of the VEGF/VEGFR2 pathway in vascular endothelial cells

Tanshinone IIA (TSA) is one of the major lipophilic components of Salvia miltiorrhiza Bunge reported to exhibit an antitumor effect. The exact intracellular signaling mechanisms involved remain elusive and were therefore the subject of this study. The process of angiogenesis is related to tumor progression, invasion and metastasis and is generally perceived as an indicator of tumor prognosis. Among the most critical factors that induce angiogenesis, the vascular endothelial growth factor (VEGF)/VEGF receptor 2 (VEGFR2) pathway and CD146 (melanoma adhesion molecule) play key roles in this process. This study aimed to demonstrate that TSA has potent anti-angiogenic activity in vitro and ex vivo. Additionally, we evaluated the role of TSA in the VEGF/ VEGFR2 pathway. Through a series of in vitro experiments, we found that TSA has a negative effect on cell proliferation, migration and tube formation of human umbilical vascular endothelial cells. We further showed that TSA can inhibit angiogenesis using chorioallantoic membrane (CAM) and rat aortic ring assays. Furthermore, western blotting demonstrated that TSA effectively suppressed the expression of VEGR2 and CD146. These results suggest that TSA inhibits angiogenesis by downregulation of the VEGF/VEGFR2 pathway.