Loss of Endocan tumorigenic properties after alternative splicing of exon 2

Stable, endocanΔ2-overexpressing cell lines were generated to investigate the biological activities of this new alternatively spliced product of endocan gene. Tumorigenesis was studied by inoculating endocan and endocanΔ2 expressing cell lines subcutaneously in SCID mice. Biochemical properties of endocan and endocanΔ2 were studied after production of recombinant proteins in various cell lines of human and murine origin.Our results showed that the exon 2 deletion impairs synthesis of the glycan chain, known to be involved in the pro-tumoral effect of endocan. EndocanΔ2 did not promote tumor formation by 293 cells implanted in the skin of severe combined immunodeficient (SCID) mice.Our results emphasize the key role of the polypeptide sequence encoded by the exon 2 of endocan gene in tumorigenesis, and suggest that this sequence could be a target for future therapies against cancer.Tumor development is a complex multi-step mechanism, involving not only the tumor cells but also the microenvironment (or the stroma) supporting them [1]. Crucial efforts were done to identify the key molecular players that orchestrate the tumor – stromal cell interactions, the neo-blood vessel recruitment and extracellular matrix organization [2-4]. The proteoglycans are major constituents of the tumor stroma and the vascular bed and are present at the cell surface and in the extracellular matrix [1]. They are constituted of a protein core with one or more covalently attached glycosaminoglycan (GAG) chains. Proteoglycans are produced by both tumor cells and cells from the tumor stroma and can interact with growth factors, cytokines and integrins regulating their actions, thereby potentially contributing to tumor growth and progression [5-11].Endocan, previously named Endothelial Specific Molecule-1 (ESM-1), a dermatan sulfate proteoglycan which is found freely circulating in the blood, is specifically secreted by endothelial cells and is preferentially expressed in lung and kidney tissues