Immuno-histochemical staining for the endothelial cell markers human CD31 (huCD31) (Fig. 3), CD34 and vWF (not shown) in primary xenografts of human benign prostate tissue and prostate cancer tissue demonstrated a dramatic increase in microvessel density (MVD) during the 14 days after transplantation (Fig. 3b–g) as compared to the MVD in the corresponding initial tissue specimen harvested before transplantation (Fig. 3a). The gene discussed is CD34; the disease is prostate cancer.