Philinopside A, a novel marine-derived compound possessing dual anti-angiogenic and anti-tumor effects

Philinopside A is a novel sulfated saponin isolated from the sea cucumber, Pentacta quadrangulari. The effects of philinopside A on angiogenesis and tumor growth were assessed in a series of models in vitro and in vivo. Our results demonstrated that philinopside A significantly inhibited the proliferation, migration and tube formation of human microvascular endothelial cells (HMECs) in a dose-dependent manner, with average IC₅₀ values of 1.4 ± 0.17, 0.89 ± 0.23 and 0.98 ± 0.19 μM, respectively. Rat aortas culture assay provides a close imitation of in vivo angiogenesis process and 2-10 μM philinopside A suppressed the formation of new microvessels in cultured rat aortas. Philinopside A 2-10 nmol/egg obviously inhibited angiogenesis in chick embryo chorioallantoic membrane assay. In addition, philinopside A manifested strong anti-tumor activities both in vitro and in vivo. Through immunofluorescent analysis, we found the compound reduced mouse sarcoma 180 tumor volume by inducing apoptosis of tumor and tumor-associated endothelial cells. An examination of the effects of philinopside A on the angiogenesis-related receptor tyrosine kinases (RTKs) showed that philinopside A broadly inhibited all tested RTKs, including vascular endothelial growth factor (VEGF) receptor, fibroblast growth factor (FGF) receptor-1, platelet-derived growth factor (PDGF) receptor-β and epithelial growth factor (EGF) receptor, with IC₅₀ values ranging from 2.6-4.9 μM. These results suggest that philinopside A is a promising anti-cancer agent that possesses dual cytotoxic and anti-angiogenic effects that were at least partly due to its inhibitory effects on RTKs.