A Translational Study of Human 6-O-Endosulfatases in Head and Neck Squamous Cell Carcinoma and Other Malignancies

Abstract

Heparan sulfate proteoglycans (HSPGs) regulate growth factor signaling and extracellular matrix remodeling via specific interactions with sulfate groups. 6-O-Sulfation of HSPGs is an impactful modification regulated by the activity of extracellular endosulfatases SULF1 and SULF2. Specifically, SULF1 and SULF2 remove 6-O-sulfate from HS chains, modulate the affinity of HSPG to its ligands, and thereby influence activity of downstream pathways. In this study, we conducted translational analyses of the SULFs in head and neck squamous cell carcinoma (HNSCC) using data from publicly available large-scale multi-omic studies and from our own analyses. We found significant overexpression of both SULF1 and SULF2 in HNSCC tumors that differs by tumor location and etiology. SULF1 overexpression derives from cancer-associated fibroblasts (CAFs), while SULF2 originates primarily in tumor epithelial cells. High SULF1 mRNA expression is significantly correlated with poor progression-free interval in early-stage patients while high SULF2 mRNA is adversely prognostic in late-stage patients. Among all the HS-related enzymes, SULF2 expression showed the highest hazard ratio in a survival analysis. Expression of the enzymes modifying 6-O-sulfation in HNSCC tumors suggest that HSPG sulfation is carried out by co-regulated activities of multiple genes, of which the SULFs are the most upregulated in HNSCC tissue. Although the content of 6-O-sulfated HS was higher in benign mucosa compared to tumor tissues, we did not see a difference by SULF2 staining. LC-MS/MS analysis showed low abundance of sulfated HS in tumors from HNSCC patients and did not identify a significant difference between SULF2-positive and SULF2-negative tumors. We expect the alteration of 6-O-sulfate to be non-uniform and occurred in specific domains of HS chains that regulate HSPG-dependent activities affecting tumor progression. Our pan-cancer analysis found SULF1 overexpression in multiple cancers with a possible connection to CAF, whereas SULF2 differential expression varied by tissue type. Overall, our findings show that both SULF1 and SULF2 correlate with clinical outcomes in HNSCC patients. The expression of the SULFs in HNSCC is differentially regulated in a temporal and spatial manner. These enzymes represent a regulatory hub that could potentially serve as a prognostic factor and a target for therapeutic interventions.