Extracellular Heparan 6-O-Endosulfatases SULF1 and SULF2 in Head and Neck Squamous Cell Carcinoma and Other Malignancies

Galectin-3-binding protein inhibits extracellular heparan 6-O-endosulfatase Sulf-2

Human extracellular 6-O-endosulfatases Sulf-1 and Sulf-2 are the only enzymes that post-synthetically alter the 6-O sulfation of heparan sulfate proteoglycans (HSPG), which regulates interactions of HSPG with many proteins. Oncogenicity of Sulf-2 in different cancers has been documented and we have shown that Sulf-2 is associated with poor survival outcomes in head and neck squamous cell carcinoma (HNSCC). In spite of its importance, limited information is available on direct protein-protein interactions of the Sulf-2 protein in the tumor microenvironment. In this study, we used monoclonal antibody (mAb) affinity purification and mass spectrometry to identify galectin-3-binding protein (LG3BP) as a highly specific binding partner of Sulf-2 in the conditioned media of HNSCC cell lines. We validated their direct interaction in vitro using recombinant proteins and have shown that the chondroitin sulfate (CS) covalently bound to the Sulf-2 influences the binding to LG3BP. We confirmed importance of the CS chain for the interaction by generating a mutant Sulf-2 protein that lacks the CS. Importantly, we have shown that the LG3BP inhibits Sulf-2 activity in vitro in a concentration dependent manner. As a consequence, the addition of LG3BP to a spheroid cell culture inhibited invasion of the HNSCC cells into Matrigel. Thus, Sulf-2 interaction with LG3BP may regulate physiological activity of the Sulf-2 enzyme as well as its activity in the tumor microenvironment.

A biological guide to glycosaminoglycans: current perspectives and pending questions

Mammalian glycosaminoglycans (GAGs), except hyaluronan (HA), are sulfated polysaccharides that are covalently attached to core proteins to form proteoglycans (PGs). This article summarizes key biological findings for the most widespread GAGs, namely HA, chondroitin sulfate/dermatan sulfate (CS/DS), keratan sulfate (KS), and heparan sulfate (HS). It focuses on the major processes that remain to be deciphered to get a comprehensive view of the mechanisms mediating GAG biological functions. They include the regulation of GAG biosynthesis and postsynthetic modifications in heparin (HP) and HS, the composition, heterogeneity, and function of the tetrasaccharide linkage region and its role in disease, the functional characterization of the new PGs recently identified by glycoproteomics, the selectivity of interactions mediated by GAG chains, the display of GAG chains and PGs at the cell surface and their impact on the availability and activity of soluble ligands, and on their move through the glycocalyx layer to reach their receptors, the human GAG profile in health and disease, the roles of GAGs and particular PGs (syndecans, decorin, and biglycan) involved in cancer, inflammation, and fibrosis, the possible use of GAGs and PGs as disease biomarkers, and the design of inhibitors targeting GAG biosynthetic enzymes and GAG-protein interactions to develop novel therapeutic approaches.

6-O-endosulfatases in tumor metastasis: heparan sulfate proteoglycans modification and potential therapeutic targets

Metastasis is the leading cause of cancer-associated mortality. Although advances in the targeted treatment and immunotherapy have improved the management of some cancers, the prognosis of metastatic cancers remains unsatisfied. Therefore, the specific mechanisms in tumor metastasis need further investigation. 6-O-endosulfatases (SULFs), comprising sulfatase1 (SULF1) and sulfatase 2 (SULF2), play pivotal roles in the post-synthetic modifications of heparan sulfate proteoglycans (HSPGs). Consequently, these extracellular enzymes can regulate a variety of downstream pathways by modulating HSPGs function. During the past decades, researchers have detected the expression of SULF1 and SULF2 in most cancers and revealed their roles in tumor progression and metastasis. Herein we reviewed the metastasis steps which SULFs participated in, elucidated the specific roles and mechanisms of SULFs in metastasis process, and discussed the effects of SULFs in different types of cancers. Moreover, we summarized the role of targeting SULFs in combination therapy to treat metastatic cancers, which provided some novel strategies for cancer therapy.

Galectin-3-binding protein inhibits extracellular heparan 6-O-endosulfatse Sulf-2

Human extracellular 6-O-endosulfatases Sulf-1 and Sulf-2 are the only enzymes that post-synthetically alter the 6-O sulfation of heparan sulfate proteoglycans (HSPG), which regulates interactions of HSPG with many proteins. Oncogenicity of Sulf-2 in different cancers has been documented and we have shown that Sulf-2 is associated with poor survival outcomes in head and neck squamous cell carcinoma (HNSCC). In spite of its importance, limited information is available on direct protein-protein interactions of the Sulf-2 protein in the tumor microenvironment. In this study, we used monoclonal antibody (mAb) affinity purification and mass spectrometry to identify galectin-3-binding protein (LG3BP) as a highly specific binding partner of Sulf-2 in the secretome of HNSCC cell lines. We validated their direct interaction in vitro using recombinant proteins and have shown that the chondroitin sulfate (CS) covalently bound to the Sulf-2 influences the binding to LG3BP. We confirmed importance of the CS chain for the interaction by generating a mutant Sulf-2 protein that lacks the CS. Importantly, we have shown that the LG3BP inhibits Sulf-2 activity in vitro in a concentration dependent manner. As a consequence, the addition of LG3BP to a spheroid cell culture inhibited invasion of the HNSCC cells into Matrigel. Thus, Sulf-2 interaction with LG3BP has functional relevance, and may regulate physiological activity of the Sulf-2 enzyme as well as its activity in the tumor microenvironment.

[Identification of SULF1 as a Shared Gene in Idiopathic Pulmonary Fibrosis and Lung Adenocarcinoma]

BACKGROUND

Idiopathic pulmonary fibrosis (IPF) is an idiopathic chronic, progressive interstitial lung disease with a diagnosed median survival of 3-5 years. IPF is associated with an increased risk of lung cancer. Therefore, exploring the shared pathogenic genes and molecular pathways between IPF and lung adenocarcinoma (LUAD) holds significant importance for the development of novel therapeutic approaches and personalized precision treatment strategies for IPF combined with lung cancer.

METHODS

Bioinformatics analysis was conducted using publicly available gene expression datasets of IPF and LUAD from the Gene Expression Omnibus (GEO) database. Weighted gene co-expression network analysis was employed to identify common genes involved in the progression of both diseases, followed by functional enrichment analysis. Subsequently, additional datasets were used to pinpoint the core shared genes between the two diseases. The relationship between core shared genes and prognosis, as well as their expression patterns, clinical relevance, genetic characteristics, and immune-related functions in LUAD, were analyzed using The Cancer Genome Atlas (TCGA) database and single-cell RNA sequencing datasets. Finally, potential therapeutic drugs related to the identified genes were screened through drug databases.

RESULTS

A total of 529 shared genes between IPF and LUAD were identified. Among them, SULF1 emerged as a core shared gene associated with poor prognosis. It exhibited significantly elevated expression levels in LUAD tissues, concomitant with high mutation rates, genomic heterogeneity, and an immunosuppressive microenvironment. Subsequent single-cell RNA-seq analysis revealed that the high expression of SULF1 primarily originated from tumor-associated fibroblasts. This study further demonstrated an association between SULF1 expression and tumor drug sensitivity, and it identified potential small-molecule drugs targeting SULF1 highly expressed fibroblasts.

CONCLUSIONS

This study identified a set of shared molecular pathways and core genes between IPF and LUAD. Notably, SULF1 may serve as a potential immune-related biomarker and therapeutic target for both diseases.

Sulfatase 2 Inhibition Sensitizes Triple-Negative Breast Cancer Cells to Chemotherapy Through Augmentation of Extracellular ATP

Background

Breast cancer is the leading cause of cancer-related death among women worldwide. Patients diagnosed with triple-negative breast cancer (TNBC) have limited therapeutic options that produce durable responses. Hence, a diagnosis of TNBC is associated with a poor prognosis compared to other types of breast cancer. As a result, there is a critical need for novel therapies that can deepen and prolong responses.We previously found that chemotherapy causes the release of extracellular adenosine triphosphate (eATP). Augmenting eATP release can boost the response of TNBC cells to chemotherapy and cause increased cell death. However, eATP concentrations are limited by several families of extracellular ATPases, which complicates the design of compounds that attenuate eATP degradation.In this study, we hypothesized that heparan sulfate (HS) would inhibit extracellular ATPases and accentuate chemotherapy-induced cytotoxicity in TNBC by augmenting eATP. HS can be desulfated by sulfatase 1 and 2; sulfatase 2 is consistently highly expressed in a variety of cancers including breast cancer, whereas sulfatase 1 is not. We hypothesized that the sulfatase 2 inhibitor OKN-007 would exacerbate chemotherapy-induced eATP release and TNBC cell death.

Methods

TNBC cell lines and nontumorigenic immortal mammary epithelial cells were treated with paclitaxel in the presence of heparan sodium sulfate and/or OKN-007; eATP content and cell viability were evaluated. In addition, protein and cell surface expression of sulfatases 1 and 2 were determined in all examined cell lines via ELISA, Western blot, and flow cytometry analyses.

Results

Sulfatase 2 was highly expressed in TNBC cell lines and human breast cancer samples but not in immortal mammary epithelial cells and much less so in normal human breast tissue and ductal carcinoma in situ samples. OKN-007 exacerbated chemotherapy-induced eATP release and chemotherapy-induced TNBC cell death. When combined with chemotherapy, OKN-007 attenuated cells with a cancer-initiating cell phenotype.

Conclusions

These results suggest that sulfatase 2 inhibitors in combination with chemotherapy attenuate the viability of TNBC cells more than chemotherapy alone by exacerbating eATP release. These effects, as well as their capacity to attenuate the cancer-initiating cell fraction, may translate into combination therapies for TNBC that induce deeper and more durable responses.

A 6-O-endosulfatase activity assay based on synthetic heparan sulfate oligomers

Sulf-2 is an extracellular heparan 6-O-endosulfatase involved in the postsynthetic editing of heparan sulfate (HS), which regulates many important biological processes. The activity of the Sulf-2 and its substrate specificity remain insufficiently characterized in spite of more than two decades of studies of this enzyme. This is due, in part, to the difficulties in the production and isolation of this highly modified protein and due to the lack of well-characterized synthetic substrates for the probing of its catalytic activity. We introduce synthetic HS oligosaccharides to fill this gap, and we use our recombinant Sulf-2 protein to show that a paranitrophenol (pNP)-labeled synthetic oligosaccharide allows a reliable quantification of its enzymatic activity. The substrate and products of the desulfation reaction are separated by ion exchange high-pressure liquid chromatography and quantified by UV absorbance. This simple assay allows the detection of the Sulf-2 activity at high sensitivity (nanograms of the enzyme) and specificity. The method also allowed us to measure the heparan 6-O-endosulfatase activity in biological samples as complex as the secretome of cancer cell lines. Our in vitro measurements show that the N-glycosylation of the Sulf-2 enzyme affects the activity of the enzyme and that phosphate ions substantially decrease the Sulf-2 enzymatic activity. This assay offers an efficient, sensitive, and specific measurement of the heparan 6-O-endosulfatase activity that could open avenues to in vivo activity measurements and improve our understanding of the enzymatic editing of the sulfation of heparan.