Abstract We have previously shown that an extract (B1000) of the epithelial layer of the Atlantic sea cucumber, Cucumaria frondosa inhibited cancer cell proliferation. A pure triterpenoid glycoside, Frondoside A was purified from this extract, and has shown potent growth inhibitory effects, both in vitro and in vivo in pancreatic, colon, prostate, and breast cancer cells but no effect on normal cells. The present studies were aimed at investigating the effects of Frondoside A on angiogenesis. The parent sea cucumber extract, B1000, has marked anti-angiogenic effects in the chick chorioallantoic membrane (CAM) assay. B1000 virtually eliminated vasculature in this model (B1000 mean score of 3.8±0.1; hydrocortisone/heparin positive control: 3.2±0.1, P<0.001, where a score of 3 = almost complete inhibition of vasculature and 4 = complete inhibition). The anti-angiogenic effects of B1000 were confirmed in the endothelial tube formation assay employing human umbilical vein endothelial cells (HUVEC) on matrigel coated slides. B1000 also inhibited migration of C8161 melanoma cells and RA116 synovial fibroblasts in a membrane invasion culture system. Based on these data, we investigated the effect of pure Frondoside A on the ability of HUVEC cells to differentiate into capillary-like structures. At a concentration of 1µM, Frondoside A virtually abolished endothelial tube formation (88±6% inhibition, P<0.0001) and was more than ten-fold more potent than the Suramin positive control in this assay (74±3% inhibition at 10µM). This was not due to cytotoxicity, since the HUVEC cells were viable in the culture, however, they failed to form the tube-like structures seen in control. These findings indicate that Frondoside A has anti-angiogenic effects in addition to its cancer growth-inhibitory effects. B1000 and Frondoside A may be valuable in the prevention or treatment of solid tumors. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 101st Annual Meeting of the American Association for Cancer Research; 2010 Apr 17-21; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2010;70(8 Suppl):Abstract nr 1382.