HSulf‐2, an Extracellular Endosulfatase, is Secreted by MCF‐7 Breast Carcinoma Cells and Selectively Mobilizes Heparin‐Bound VEGF, FGF‐1, and SDF‐1

Heparin/heparan sulfate (HS) proteoglycans interact with numerous protein ligands including FGFs, VEGF and chemokines through their glycosaminoglycan side chains. These interactions are highly dependent upon the pattern of sulfation modifications within the chains. We previously cloned and identified HSulf‐2, a novel heparin/HS endoglucosamine‐6‐sulfatase. We have found that the level of HSulf‐2 transcripts was significantly upregulated in human breast cancer tissue and was highly expressed in MCF‐7, a human breast cancer cell line. HSulf‐2 was secreted by the cells into the conditioned medium (CM) in an enzymatically active form. In the present study, we have employed both recombinant HSulf‐2 and a native form of the enzyme from the CM. To determine whether HSulf‐2 modulates the interactions between heparin‐binding factors and heparin, we developed ELISAs. Our results show that the binding of VEGF, FGF‐1, and SDF‐1/CXCL12 to immobilized heparin was abolished or greatly diminished by pre‐treating the heparin with HSulf‐2. Intriguingly, HSulf‐2 released these soluble proteins from pre‐ association with heparin. Moreover, our in vivo analysis has shown that HSulf‐2 promotes angiogenesis in the chick chorioallantoic membrane assay. The ability of HSulf‐2 to mobilize ECM‐sequestered factors and to promote angiogenesis could be an important mechanism by which tumor cells modify their microenvironment to facilitate tumor angiogenesis and/or their own growth.