Combined with in vivo data showing that lectin-perfused, VCAM1-positive VM vessels lacking CD31-positive murine endothelial cells are present in CDX tumors in vivo (Figs. 1 and 5), this provides evidence that human tumor cells form VM vessels with endothelial properties enabling them to act as functional blood vessels in vivo. The gene discussed is VCAM1; the disease is neoplasm.