Angiogenesis is an inevitable event in
tumor progression and
metastasis, and thus has been a compelling target for
cancer therapy in recent years. Effective inhibition of
tumor progression and
metastasis could become a promising way to treat
tumor-induced angiogenesis. We discovered that a fungus, Neosartorya sp., isolated from a soil sample, produced a new
angiogenesis inhibitor, which we designated
azaspirene.
Azaspirene was previously shown to inhibit human umbilical vein endothelial cell (HUVEC) migration induced by
vascular endothelial growth factor (
VEGF) at an effective dose, 100% of 27 micromol/L without significant cell toxicity. In the present study, we investigated the antiangiogenic activity of
azaspirene in vivo.
Azaspirene treatment reduced the number of
tumor-induced blood vessels. Administration of
azaspirene at 30 microg/egg resulted in inhibition of angiogenesis (23.6-45.3% maximum inhibition relative to the controls) in a chicken chorioallantoic membrane assay. Next, we elucidated the molecular mechanism of antiangiogenesis of
azaspirene. We investigated the effects of
azaspirene on
VEGF-induced activation of the
mitogen-activated protein kinase signaling pathway in HUVEC. In vitro experiments indicated that
azaspirene suppressed Raf-1 activation induced by
VEGF without affecting the activation of
kinase insert domain-containing receptor/
fetal liver kinase 1 (
VEGF receptor 2). Additionally,
azaspirene preferentially inhibited the growth of HUVEC but not that of the non-vascular endothelial cells NIH3T3, HeLa, MSS31, and MCF-7. Taken together, these results demonstrate that
azaspirene is a novel inhibitor of angiogenesis and Raf-1 activation that contains a unique
carbon skeleton in its molecular structure.