Loss of HSulf-1 Up-regulates Heparin-binding Growth Factor Signaling in Cancer

Abstract

Emerging data suggest that signaling by heparinbinding growth factors is influenced by the sulfation state of N-acetylglucosamine residues of heparan sulfate proteoglycans (HSPGs). Here we report that the recently identified protein HSulf-1, a heparin-degrading endosulfatase, encodes a cell surface-associated enzyme that diminishes sulfation of cell surface HSPGs. The message encoding this enzyme is readily detectable in a variety of normal tissues, including normal ovarian surface epithelial cells, but is undetectable in 5 of 7 ovarian carcinoma cell lines and markedly diminished or undetectable in ϳ75% of ovarian cancers. Similar down-regulation is also observed in breast, pancreatic, renal cells, and hepatocellular carcinoma lines. Re-expression of HSulf-1 in ovarian cancer cell lines resulted in diminished HSPG sulfation, diminished phosphorylation of receptor tyrosine kinases that require sulfated HSPGs as co-receptors for their cognate ligands, and diminished downstream signaling through the extracellular signal-regulated kinase pathway after treatment with fibroblast growth factor-2 or heparin-binding epidermal growth factor. Consistent with these changes, HSulf-1 re-expression resulted in reduced proliferation as well as sensitivity to induction of apoptosis by the broad spectrum kinase inhibitor staurosporine and the chemotherapeutic agent cisplatin. Collectively, these observations provide evidence that HSulf-1 modulates signaling by heparin-binding growth factors, and HSulf-1 downregulation represents a novel mechanism by which cancer cells can enhance growth factor signaling.

Epigenetic silencing of HSulf-1 in ovarian cancer:implications in chemoresistance

“…Therefore, additional mechanisms of inactivation could also play a role in inactivating HSulf-1 expression. Our sequence analysis of HSulf-1 promoter revealed putative CpG-rich sequences in Exon 1A (Lai et al, 2003). This fragment (Z58846) was also identified as a putative CpG-rich sequence in previous study (Cross et al, 1994).…”

“…Methylation-associated silencing of HSulf-1 in ovarian cell lines and primary ovarian tumors Primers encompassing 12 CpG sites within the CpG-rich region in Exon 1A of HSulf-1 (Cross et al, 1994;Lai et al, 2003) were designed to amplify and sequence the bisulfite-modified DNA as described previously (Herman et al, 1996;Shridhar et al, 2001). Overall methylation was determined for a subset of cell lines and primary ovarian tumors (fresh frozen) with or without HSulf-1 expression.…”

“…Re-expression of HSulf-1 by demethylating agent sensitizes cancer cells to cisplatin treatment Our previous study showed that HSulf-1 expression conferred sensitivity to cisplatin and taxol (Lai et al, 2003(Lai et al, , 2004b. HSulf-1 represents a potential target of epigenetic therapy to re-sensitize cancer cells to cisplatin and taxol.…”

“…We have identified recently HSulf-1 as a downregulated gene in several tumor types including ovarian and breast cancer cell lines and primary ovarian tumors (Lai et al, 2003(Lai et al, , 2004a. Our initial analysis indicated that loss of heterozygosity (LOH) may represent a mechanism of HSulf-1 inactivation in ovarian tumors.…”

“…Our initial analysis indicated that loss of heterozygosity (LOH) may represent a mechanism of HSulf-1 inactivation in ovarian tumors. However, this mechanism alone could not account for complete loss of HSulf-1 expression in cell lines and in some primary tumors (Lai et al, 2003) as it would require deletion of both alleles. Therefore, additional mechanisms of inactivation could also play a role in inactivating HSulf-1 expression.…”