Endothelial cell-specific molecule 1 is a protein that in humans is encoded by the ESM1 gene. This gene encodes a secreted protein which is mainly expressed in the endothelial cells in human lung and kidney tissues. The expression of this gene is regulated by cytokines, suggesting that it may play a role in endothelium-dependent pathological disorders. The transcript contains multiple polyadenylation and mRNA instability signals. The ESM-1 gene product is also called endocan since 2001, when it was characterized as a dermatan sulfate proteoglycan by Bechard et al. Recently, endocan/ESM-1 has been described as a specific biomarker of tip cells during neoangiogenesis by independent teams. Endocan expression has been shown to be increase in presence of pro-angiogenic growth factors such as VEGF (vascular endothelial growth factor) or FGF-2 (fibroblast growth factor 2). In hypervascularized cancers, overexpression of endocan has been detected by immunohistochemistry using monoclonal antibodies against endocan/ESM-1.