HS2ST1-dependent signaling pathways determine breast cancer cell viability, matrix interactions, and invasive behavior

Heparan sulfate proteoglycans (HSPGs) act as signaling co-receptors by interaction of their sulfated glycosaminoglycan chains with numerous signaling molecules. In breast cancer, the function of heparan sulfate 2-O-sulfotransferase (HS2ST1), the enzyme mediating 2-O-sulfation of HS, is largely unknown. Hence, a comparative study on the functional consequences ofHS2ST1overexpression and siRNA knockdown was performed in the breast cancer cell lines MCF-7 and MDA-MB-231.HS2ST1overexpression inhibited Matrigel invasion, while its knockdown reversed the phenotype. Likewise, cell motility and adhesion to fibronectin and laminin were affected by alteredHS2ST1expression. Phosphokinase array screening revealed a general decrease in signaling via multiple pathways. Fluorescent ligand binding studies revealed altered binding of fibroblast growth factor 2 (FGF-2) toHS2ST1-expressing cells compared with control cells.HS2ST1-overexpressing cells showed reduced MAPK signaling responses to FGF-2, and altered expression of epidermal growth factor receptor (EGFR), E-cadherin, Wnt-7a, and Tcf4. The increased viability ofHS2ST1-depleted cells was reduced to control levels by pharmacological MAPK pathway inhibition. Moreover, MAPK inhibitors generated a phenocopy of theHS2ST1-dependent delay in scratch wound repair. In conclusion,HS2ST1modulation of breast cancer cell invasiveness is a compound effect of altered E-cadherin and EGFR expression, leading to altered signaling via MAPK and additional pathways.