Several mouse models of tumor xenografts in nude mice using human renal cell carcinoma cells 786-0, human non small lung cancer cells NCI-H1437, or C6 rat glioma cells, demonstrated that endocan overexpression is restricted to the tumor endothelial cells, and notably to the endothelial tip cells [7-10, 32]. This evidence concerns the gene ESM1 and hereditary clear cell renal cell carcinoma.