AST lacks anti-angiogenic activity in animals gene targeted for the IL-12 receptor or for IL-12. AST was able to inhibit angiogenesis in wild-type (WT) animals but not in animals gene targeted for either the IL-12 specific receptor IL-12Rβ2 (IL-12Rβ2-/-) for the IL-12 signal system or for the IL-12 p40 subunit (IL-12p40-/-). Another angioegensis inhibitor, fenretinide (4HPR), retained anti-angiogenic activity. N = indicates the number of samples in each group. *** = P < 0.001 (Mann-Whitney) as compared to respective controls.