Vascular endothelial cell growth inhibitor (VEGI), a member of the tumor necrosis factor (TNF) family, is an endothelial cell-specific inhibitor of angiogenesis. Overexpression of a secretable VEGI fusion protein by cancer cells resulted in abrogation of xenograft tumor progression. 4-3H8B is a mouse monoclonal IgG1 raised against a recombinant VEGI isoform which shares a C-terminal 151-residue segment with previously reported VEGI with 174 residues.