Overall, our findings show that the mouse mAb IgM 3E2 specific for globotriaosylceramide Gb3, over-expressed in proliferating endothelial cells, displays anti-angiogenic properties, including in vitro modulation of the viability, inhibition of proliferating endothelial cells, ex vivo inhibition of endothelial cell sprouting in mouse aorta ring assay, and in vivo tumor growth suppression. The gene discussed is CD40LG; the disease is neoplasm.