Abstract Introduction. nWASP, the neural Wiskott-Aldrich Syndrome Protein, is a member of the Wiskott-Aldrich syndrome (WAS) protein family which are known regulators of actin polymerization. Via interactions with actin, ERM (ezrin/moesin/radixin) family proteins, and other cytoskeletal associated proteins, nWASP is a key cell migration mediator. It has been shown that nWASP is aberrantly expressed in human breast cancer and that a reduction of nWASP is linked to a poor clinical outcome. Over-expression of nWASP in breast cancer cells also reduces their aggressiveness in vitro. In the present study, we investigated the potential influence of nWASP on the biological functions of endothelial cells and the angiogenic aspect of endothelial cells.Materials and methods. A panel of human cell lines of variety origins (n=43) were screened for the presence/absence of nWASP expression. A human vascular endothelial cell line, HECV, was found to be negative for nWASP expression and was chosen as a cell model in the present study. An expression construct for human nWASP was prepared using a mammalian expression vector, pcDNA3/V5/GFP/TOPO vector. HECV cells were transfected with the expression construct, or control vectors. The impact of nWASP over-expression in the endothelial cell line on the adhesiveness, migration and in vitro angiogenesis was assessed using a panel of in vitro models.Results. HECV cells, following transfection with the nWASP construct, successfully expressed nWASP, a subline subsequently established from which was so named as HECVnWASPexp7. Using an electric cell impedance sensing (ECIS) method, it was shown that HECVnWASPexp7 cells showed a significantly reduced adhesiveness to matrix surface (333.4±1.4 ohm), p<0.01 when compared with the wild type cells (HECVwt 419.7±1.6 ohm) and transfection control (HECVpControl 387.9±1.46 ohm). In a similar fashion, HECVnWASPexp7 cells also displayed a marked reduction in cell migration when compared with control cells. Using an in vitro microtubule formation assay, it was shown that both HECVwt and HECVpControl cells responded well in their microtubule formation to an angiogenic factor, hepatocyte growth factor (HGF). However, HECVnWASPexp7cells were less responsive to HGF when assessed for microtubules. We have further shown that in response to an nWASP inhibitor, Wiskostatin, HECVnWASPexp7 cells markedly increased their tubule formation, a clear contrast to the wild type and control cells.Conclusion. It is concluded that nWASP is a key regulator of the migratory property of vascular endothelial cells and that this effect on cell migration is reflected by changes in the angiogenic activities of the cells. Collectively, nWASP is a potential intrinsic angiogenic regulator in endothelial cells. Citation Information: Cancer Res 2009;69(24 Suppl):Abstract nr 2156.