3-O-Acetyloleanolic acid inhibits angiopoietin-1-induced angiogenesis and lymphangiogenesis via suppression of angiopoietin-1/Tie-2 signaling

Tumor angiogenesis and lymphangiogenesis are important processes in tumor progression and metastasis. The inhibitory effects of 3-O-acetyloleanolic acid (3AOA), a pentacyclic triterpenoid compound isolated from Vigna sinensis K., on tumor-induced angiogenesis and lymphangiogenesis in vitro and in vivo were studied. Angiopoietin-1 is an important angiogenic and lymphangiogenic factor secreted from colon carcinoma CT-26 cells under hypoxia conditions. 3AOA inhibited proliferation, migration, and tube formation of angiopoietin-1-treated human umbilical vein endothelial cells (HUVEC) and human lymphatic microvascular endothelial cells (HLMEC). 3AOA reduced angiogenesis and lymphangiogenesis in angiopoietin-1-stimulated Matrigel plugs. Also, 3AOA inhibited tumor growth and tumor-induced angiogenesis and lymphangiogenesis in an angiopoietin-1-induced CT-26 allograft colon carcinoma animal model. 3AOA inhibited activation of the angiopoietin-1 receptor Tie-2 and activation of the downstream signaling factors FAK, AKT, and ERK1/2 that are involved in the angiopoietin-1/Tie-2-signaling pathway. Thus, 3AOA has an inhibitory effect on angiogenesis and lymphangiogenesis induced by angiopoietin-1 both in vitro and in vivo, and the inhibitory effect of 3AOA is probably due to suppression of angiopoietin-1/Tie-2 signaling in HUVEC and HLMEC.