Development of a novel type of angiogenesis inhibitor will be essential for further improvement of therapeutics against cancer patients. We examined whether an octahydronaphthalene derivative, AMF‐26, which was screened as an inhibitor of intercellular adhesion molecule‐1 (ICAM‐1) production stimulated by inflammatory stimuli in vascular endothelial cells, could block angiogenesis in response to vascular endothelial growth factor (VEGF) and/or inflammatory cytokines. Low dose AMF‐26 effectively inhibited the tumor necrosis factor‐α (TNF‐α)‐ or the interleukin‐1β (IL‐1β)‐induced production of ICAM‐1 in human umbilical vascular endothelial cells (HUVECs). We found that the TNF‐α‐induced phosphorylation of nuclear factor of kappa light polypeptide gene enhancer in B‐cells inhibitor, alpha (IκBα) and nuclear translocation of p65 were impaired by AMF‐26 in both endothelial cells and cancer cells. AMF‐26 was found to inhibit the phosphorylation of VEGF receptor 1 (VEGFR1), VEGFR2 and the downstream signaling molecules Akt, extracellular signal‐regulated kinase (ERK)1/2 stimulated by VEGF in HUVECs. Therefore, the VEGF‐induced proliferation, migration and tube formation of vascular endothelial cells was highly susceptible to inhibition by AMF‐26. Oral administration of AMF‐26 significantly blocked VEGF‐ or IL‐1β‐induced angiogenesis in the mouse cornea, and also tumor angiogenesis and growth. Together, our results indicate that AMF‐26 inhibits angiogenesis through suppression of both VEGFR1/2 and nuclear factor‐κB (NF‐κB) signaling pathways when stimulated by VEGF or inflammatory cytokines. AMF‐26 could be a promising novel candidate drug for cancer treatments.

Abstract. An anti-inflammatory enone fatty acid, (E)-9-oxooctadec-10-enoic acid (C10), was previously isolated from red alga (Gracilaria verrucosa). Of the many cellular signaling pathways activated in response to the inflammatory stimulus, lipopolysaccharide, the extracellular signalregulated kinase 1/2, the stress-activated protein kinase/Jun N-terminal kinase and the nuclear factor-κB pathways were specifically blocked by C10 in the macrophage-like cell line, RAW264.7. In this study, we investigated the anti-angiogenic and anti-inflammatory activities of C10 in endothelial cells. C10 only partially inhibited the proliferation of human cancer cell lines at relatively high concentrations of over 20 μg/ml. However, C10 inhibited the proliferation of RAW264.7 cells and human umbilical vein endothelial cells (HUVECs) with half-maximal inhibitory concentration (IC 50 ) values of 4-8 μg/ml. Both the proliferation and the migration of HUVECs induced by the vascular endothelial growth factor (VEGF) were markedly blocked by C10 with IC 50 values of 2-3 μg/ml. The activation of nuclear factor of κ light polypeptide gene enhancer in B-cells inhibitor, ·, by tumor necrosis factor-· or VEGF in these cells was also blocked by C10. Furthermore, in an in vivo model of angiogenesis in the mouse cornea, the neovascularization induced by VEGF was markedly inhibited by C10. The processes involved in inflammatory signaling, angiogenesis, and the development of malignancy in cancer are closely related, suggesting that C10 could be a useful lead compound for the development of novel anti-angiogenic therapies for cancer.