An arabinogalactan from flowers of Panax notoginseng inhibits angiogenesis by BMP2/Smad/Id1 signaling

Angiogenesis plays an essential role in tumor development. Blocking angiogenesis in tumor has become a promising tactic in limiting cancer progression. Here, an arabinogalactan polysaccharide, RN1 was isolated from flowers of Panax notoginseng. Its structure was determined to possess a backbone of 1,6-linked Galp branched at C3 by side 1,3-linked Galp, with branches attached at position O-3 of it. The branches mainly contained 1,5-linked, 1,3,5-linked, terminal Arabinose and terminal Galactose. RN1 could inhibit microvessel formation in the BxPC-3 pancreatic cancer cell xenograft tumor in nude mice. The antiangiogenesis assay showed that RN1 could reduce the migratory activity of endothelial cells and their ability of tube formation on matrigel, but no effect on endothelial cells growth. Further studies revealed that RN1 could inhibit BMP2/Smad1/5/8/Id1 signaling. All those data indicated the RN1 had an antiangiogenic effect via BMP2 signaling and could be a potential novel inhibitor of angiogenesis.