Heparan Sulfate Proteoglycans Research Articles

Syndecan-3 regulates the time of transition from cell cycle exit to initial differentiation stage in mouse cerebellar granule cell precursors

To analyze the role of syndecan-3 (SDC3), a heparan sulfate proteoglycan, in cerebellum development, we examined the effect of SDC3 on the transition from cell cycle exit to the initial differentiation stage of cerebellar granule cell precursors (CGCPs). First, we examined SDC3 localization in the developing cerebellum. SDC3 was mainly localized to the inner external granule layer where the transition from the cell cycle exit to the initial differentiation of CGCPs occurs. To examine how SDC3 regulates the cell cycle exit of CGCPs, we performed SDC3-knockdown (SDC3-KD) and -overexpression (Myc-SDC3) assays using primary CGCPs. SDC3-KD significantly increased the ratio of p27Kip1+ cells to total cells at day 3 in vitro (DIV3) and 4, but Myc-SDC3 reduced that at DIV3. Regarding the cell cycle exit efficiency using 24 h-labelled bromodeoxyuridine (BrdU) and a marker of cell cycling, Ki67, SDC3-KD significantly increased cell cycle exit efficiency (Ki67-; BrdU+ cells/BrdU+ cells) in primary CGCP at DIV4 and 5, but Myc-SDC3 reduced that at DIV4 and 5. However, SDC3-KD and Myc-SDC3 did not affect the efficiency of the final differentiation from CGCPs to granule cells at DIV3–5. Furthermore, the ratio of CGCPs in the cell cycle exiting stage to total cells, identified by initial differentiation markers TAG1 and Ki67 (TAG1+; Ki67+ cells), was considerably decreased by SDC3-KD at DIV4, but increased by Myc-SDC3 at DIV4 and 5. Altogether, these results indicate that SDC3 regulates the timing of the transition from the cell cycle exit stage to the initial differentiation stage of CGCP.

Relation between left ventricular relaxation and post-transcriptional regulation with exercise in pigs

Background: Regular exercise has been shown to induce physiological adaptations such as improved left ventricle (LV) function, but LV diastolic function, particularly LV chamber stiffness (LV Kc) is rarely examined. In addition, the relation between changes in LV function, particularly LV Kc with regular exercise and post-transcriptional regulator checkpoints, the microRNAs (miRs), remains unexplored. This project tested the hypothesis that an exercise protocol in pigs will cause a shift in miR profiles which would affect pathways relevant to LV Kc. Methods and Results: Pigs (n=9; 3 months) underwent a chronic treadmill protocol (4 weeks, 10° elevation, 2.5 mph, 10 minutes) and two-dimensional speckle-tracking echocardiography was performed to obtain LV ejection fraction (LV EF) and to compute LV Kc. Age and weight matched non-exercised pigs (n=6) served as referent controls. All results are reported as mean ± SEM. LV EF increased with exercise (66.7 ± 1.9 vs 82.0 ± 0.7 %, p≤0.05) whereas LV Kc fell by approximately 50% (0.56 ± 0.04 vs 0.27 ± 0.02 kPa, p≤0.05). Using an 84 miR array (rt-PCR), a total of 34 (40%) miRs changed with exercise whereas 8 miRs (miR-19a, miR-22, miR-30e, miR-99a, miR-142, miR-144, miR-199a, and miR-497) correlated to LV Kc (r= 0.543, r=0.646, r=0.671, r=0.638, r=0.814, r=0.613, r=0.575, r=0.726 respectively, p≤0.05). Specifically, these miRs mapped to functional domains relevant to LV Kc such as calcium handling/active relaxation and extracellular matrix remodeling (i.e. metallopeptidases, heparin sulfate proteoglycans, and transforming growth factor-beta). Conclusion: Chronic exercise in pigs reduced LV chamber stiffness and correlated to miRs that mapped to regulatory processes which likely contributed to this reduction. Thus, utilization of miR profiling may provide insight into exercise training effectiveness. This work was supported in part by National Institutes of Health grant R01HL130972-01A1 (F.G.S.) & R01HL5949 (F.G.S.) as well as a Merit Award from the Veterans Health Administration, BX000168-10A1 (F.G.S.) & BX005320 (F.G.S.). The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript. This is the full abstract presented at the American Physiology Summit 2023 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.

Abstract 677: Short Hydrocarbon-Stapled Apolipoprotein E Mimetic Peptides Enhance Lipoprotein Uptake

ApoE facilitates the clearance of apoB-containing lipoproteins by binding to heparan sulfate proteoglycans (HSPG), low density lipoprotein receptor (LDLR) and LDLR-related protein 1 (LRP1). ApoE has a receptor binding and a lipid binding domain, which are both needed for its biological function. Several apoE-based peptides have been developed that lower plasma lipid levels in animal models and in early-stage clinical trials. However, these peptides are long (28-61 residues), costly to synthesize and are potentially immunogenic as they often contain many amino acid substitutions that vary from the native apoE sequence. We developed novel short (10-12 residues) apoE mimetic peptides based on the apoE receptor binding region (residues 141-150) containing only 2 amino acid substitutions. We used hydrocarbon stapling to stabilize the native alpha helical structure of this region and to increase the lipid binding affinity of the peptides. In addition, octanoic or myristic acid was attached to the N-terminus of the peptides to further increase lipid binding affinity. Helical conformation and lipid binding of the peptides were confirmed by circular dichroism spectroscopy and phospholipid vesicle solubilization assay. Our peptides increased the uptake of fluorescent tagged VLDL and LDL in a concentration dependent manner (0.625-20 μM peptides) in both wild-type (WT) and LDLR knockout (KO) HepG2 cells as measured by flow cytometry. In addition, an all D-amino acid version of one of the peptides had a similar effect on LDL uptake as its all L-amino acid version. Altogether, this suggests that peptide-mediated uptake is LDLR independent. Treatment of WT HepG2 cells with heparinases diminished the low-dose effect (up to 2.5 μM) of the peptides on LDL uptake, indicating that HSPGs plays a role in peptide-mediated LDL uptake. Finally, the peptides (4.6 mg/kg, IV) lowered plasma total cholesterol (37% at 3h; 29% at 6h) and triglycerides (33% at 1h) in apoE-KO mice on a standard chow diet. In summary, the novel apoE peptides are shorter than previously reported peptides, are more similar to the native sequence of apoE, and are likely resistant to proteolysis, because of hydrocarbon stapling and, therefore, could potentially be developed into an oral therapy.

Group-3 innate lymphoid cells protect from intestinal inflammation via syndecan-4

Abstract Group-3 innate lymphoid cells (ILC3s) are a recently described set of tissue resident immune cells which are enriched in the intestine, express RORγt, and secrete a variety of effector cytokines to orchestrate homeostasis, inflammation, and immunity. Crucially, intestinal ILC3 function and frequency is dysregulated during inflammatory bowel disease (IBD). However, it remains unclear how ILC3s sense and respond to the heterogeneity of signals present in the intestinal microenvironment or how this cell type becomes disrupted during intestinal inflammation. Recently, a single-cell RNA-sequencing analysis in our laboratory identified that syndecan-4 is highly expressed within ILC3s. Syndecans are a class of heparan sulfate proteoglycans which can become dysregulated in the intestinal epithelium and the lamina propria of IBD patients. Further, mice lacking global expression of syndecan-4 show a heightened susceptibility to models of intestinal inflammation. However, cell-specific and molecular mechanisms for this protection have yet to be elucidated. Here, we unexpectedly identify that syndecan-4 is significantly enriched among ILC3s relative to other intestinal immune cells. IL-1 selectively upregulates ILC3-specific syndecan-4, but during acute and chronic mouse modeling of intestinal inflammation, ILC3 expression of syndecan-4 is reduced. Mice lacking ILC3-specific syndecan-4 exhibit exacerbated susceptibility to intestinal inflammation resulting in greater loss of intestinal epithelial architecture compared to controls. Collectively, our data indicate that syndecan-4 represents a novel pathway by which ILC3s orchestrate intestinal health and limit tissue damage during inflammation. Research in the Sonnenberg Laboratory is supported by the National Institutes of Health (R01AI143842, R01AI123368, R01AI145989, U01AI095608, R21CA249274, R01AI162936 and R01CA274534), the NIAID Mucosal Immunology Studies Team (MIST), an Investigators in the Pathogenesis of Infectious Disease Award from the Burroughs Wellcome Fund, Linda and Glenn Greenberg, the Dalton Family Foundation, and the Roberts Institute for Research in IBD. B.F. is supported by the NIAID of the National Institutes of Health training grant T32 (5 T32 AI 134632-5). G.F.S. is a CRI Lloyd J. Old STAR.

Profiling of idiopathic macular hole vitreous proteome identifies the role of extracellular matrix remodelling, epithelial–mesenchymal transformation and unfolded protein-response pathways

Purpose: To analyze and describe the proteome of the vitreous humour in eyes with idiopathic macular holes. Methods: We performed mass spectrometry (MS)-based label-free quantitative analysis of the vitreous proteome of idiopathic macular hole (IMH) and control donor vitreous. Comparative quantification was performed using SCAFFOLD software which calculated fold changes of differential expression. Bioinformatics analysis was performed using DAVID and STRING software. Results: A total of 448 proteins were identified by LC-MS/MS in IMH and cadaveric eye vitreous samples, of which 199 proteins were common. IMH samples had 189 proteins that were unique and 60 proteins were present only in the control cadaveric vitreous. We found upregulation of several extracellular matrix (ECM) and cytoskeletal proteins, namely collagen alpha-1 (XVIII) chain, N-cadherin, EFEMP1/fibulin-3, basement membrane-specific heparan sulfate proteoglycan core protein, and target of Nesh-3. Several cytoskeleton proteins, namely tubulin, actin, and fibronectin levels, were significantly lower in IMH vitreous, probably reflecting increased ECM degradation. IMH vitreous also had a downregulation of unfolded protein response-mediated-mediated apoptosis proteins, possibly related to a state of increased cell survival and proliferation, along with a remodelling and aberrant production of ECM contents. Conclusion: The pathogenesis of macular holes may involve ECM remodelling, epithelial–mesenchymal transformation, downregulation of apoptosis, protein folding defects, and complement pathway. The vitreo-retinal milieu in macular holes contain molecules related to both ECM degradation and inhibition of the same, thereby maintaining a homeostasis.

Neural Isoforms of Agrin Are Generated by Reduced PTBP1-RNA Interaction Network Spanning the Neuron-Specific Splicing Regions in AGRN.

Agrin is a heparan sulfate proteoglycan essential for the clustering of acetylcholine receptors at the neuromuscular junction. Neuron-specific isoforms of agrin are generated by alternative inclusion of three exons, called Y, Z8, and Z11 exons, although their processing mechanisms remain elusive. We found, by inspection of splicing cis-elements into the human AGRN gene, that binding sites for polypyrimidine tract binding protein 1 (PTBP1) were extensively enriched around Y and Z exons. PTBP1-silencing enhanced the coordinated inclusion of Y and Z exons in human SH-SY5Y neuronal cells, even though three constitutive exons are flanked by these alternative exons. Deletion analysis using minigenes identified five PTBP1-binding sites with remarkable splicing repression activities around Y and Z exons. Furthermore, artificial tethering experiments indicated that binding of a single PTBP1 molecule to any of these sites represses nearby Y or Z exons as well as the other distal exons. The RRM4 domain of PTBP1, which is required for looping out a target RNA segment, was likely to play a crucial role in the repression. Neuronal differentiation downregulates PTBP1 expression and promotes the coordinated inclusion of Y and Z exons. We propose that the reduction in the PTPB1-RNA network spanning these alternative exons is essential for the generation of the neuron-specific agrin isoforms.

Amino acid variation at VP1-145 of enterovirus A71 determines the viral infectivity and receptor usage in a primary human intestinal model.

With the near eradication of polio worldwide, polio-like illness (as is increasingly caused by EV-A71 infections) is of emerging concern. EV-A71 is indeed the most neurotropic enterovirus that poses a major threat globally to public health and specifically in infants and young children. Our findings will contribute to the understanding of the virulence and the pathogenicity of this virus. Further, our data also supports the identification of potential therapeutic targets against severe EV-A71 infection especially among infants and young children. Furthermore, our work highlights the key role of HSPG-binding mutations in the disease outcome of EV-A71. Additionally, EV-A71 is not able to infect the gut (the primary replication site in humans) in traditionally used animal models. Thus, our research highlights the need for human-based models to study human viral infections.Graphical Abstract.

PULMONARY VASCULAR ENDOTHELIAL GLYCOCALYX DEGRADATION CONTRIBUTES TO ACUTE LUNG INJURY IN EXPERIENCING HEATSTROKE.

Objectives: This study investigated the role and potential involvement of pulmonary vascular glycocalyx degradation in acute lung injury in rats with severe heatstroke (HS). Methods: Rats in an established HS model were exposed to a heated environment for 60 min in an incubator (temperature, 40°C ± 2°C; humidity, 65% ± 5%). Following pretreatment with heparanase III (HPSE III) or heparin, pathological lung injury, arterial blood gas, alveolar barrier disruption, and hemodynamic changes were evaluated. The vascular endothelial structures of the lungs were examined using electron microscopy. The concentration of Evans blue dye in the lungs and arterial blood gas were assessed. An enzyme-linked immunosorbent assay was used to quantify the plasma concentration of heparan sulfate proteoglycan. The expression of glypican-1 and syndecan-1 in pulmonary vessels was measured using immunofluorescence. Western blots were used to detect the expression of TNF-α, IL-6, and vascular endothelial biomarkers in the rat lungs. Pulmonary apoptosis was assessed using a TUNEL (terminal dUTP nick end labeling) assay, and the concentrations of malondialdehyde were measured. Results: Glycocalyx shedding aggravated lung injuries. Severe histopathological damage was observed, and indexes of lung function deviated from abnormal ranges. In addition, pulmonary vascular endothelial cells were disrupted. Compared with the HS group, the plasma concentration of heparan sulfate proteoglycan significantly increased in the HPSE group ( P < 0.05). The expression of glypican-1 and syndecan-1 decreased, and the extravasation of Evans blue dye increased ( P < 0.01). Endothelial biomarker expression increased in the lung tissue, whereas occludin expression decreased. Moreover, TNF-α and IL-6 were overexpressed following heat stress. Furthermore, apoptosis of pulmonary tissues and the concentration of malondialdehyde in rat lungs increased in the HS and HPSE groups. Conclusions : Heatstroke induced pulmonary glycocalyx degradation, which increased vascular permeability and aggravated vascular endothelial dysfunction, contributing to apoptosis, inflammation, and oxidation in the pulmonary tissues.

Development of an inhalable antiviral powder formulation against respiratory syncytial virus

Respiratory viruses including the respiratory syncytial virus (RSV) aggravate the global burden of virus-inflicted morbidity and mortality. Entry inhibitors are a promising class of antiviral drugs for combating these viruses, as they can prevent infection at the site of viral entry, i.e., the respiratory tract. Here we used a broad-spectrum entry inhibitor, composed of a β-cyclodextrin backbone, functionalized with 11-mercapto-1-undecanesulfonate (CD-MUS) that is capable of neutralizing a variety of viruses that employ heparan sulfate proteoglycans (HSPG) to infect host cells. CD-MUS inactivates viral particles irreversibly by binding to viral attachment proteins through a multivalent binding mechanism. In the present study, we show that CD-MUS is well tolerated when administered to the respiratory tract of mice. Based on this, we developed an inhalable spray-dried powder formulation that fits the size requirements for lung deposition and disperses well upon use with the Cyclops dry powder inhaler (DPI). Using an in vitro dose-response assay, we show that the compound retained its activity against RSV after the spray drying process. Our study sets the stage for further in vivo studies, exploring the efficacy of pulmonary administered CD-MUS in animal models of RSV infection.

Abstract 6312: Targeting HSPG is more efficient than using soluble heparin for interfering with cancer cell adhesion and migration

Abstract Given the relevance of heparan sulfate proteoglycans (HSPG) and of heparin binding ligands in the regulation of cancer cell adhesion, migration and invasiveness, drugs that may interfere with HSPG functions have been studied for decades for their possible use in oncology. In this view heparin analogues have been tested for their effectiveness not only in cancer associated thromboembolism but also for their potential effects on cancer growth and metastasis. Despite a number of promising preclinical results and clinical hypothesis, many different clinical trials on the use of heparin analogues in different cancers reported no significant benefits in tumor progression and overall survival, indicating that using heparin as a soluble decoy for the many HSPG ligands does not appear to be the best possible approach (1,2). Taking advantage of the tetra-branched peptide NT4, which is a specific ligand of HSPG sulfated glycosaminoglycan (GAG) chains (3, 4), we tested the effectiveness of targeting cell membrane HSPG, as a potential alternative approach for interfering with HSPG functions in cancer cell invasiveness. We had demonstrated that NT4 can either inhibit or increase oriented migration in respectively PANC-1 pancreas adenocarcinoma and TE671 rhabdomyosarcoma human cancer cells, indicating a crucial but diverse role of HSPGs in oriented cell migration in different cancer cells. NT4 and heparin were here compared for their effect on adhesion and migration of different cancer cell lines on extracellular matrix (ECM) supports, as well as for their effect on proliferation and in vitro invasiveness of the same cell lines. We found that inhibition of cancer cells adhesion to ECM proteins by NT4 varies in different cancer cell lines, ranging from 90% inhibition to as low as 20%, whereas heparin has no effect. Analogous results were obtained when testing cancer cell migration. NT4 inhibited migration and in vitro invasiveness of different human cancer cell lines, with the sole exception of TE671 cells. Heparin did not modify cell migration in any of the tested cancer cell lines. NT4 had no effect on cell proliferation, whereas, notably, heparin resulted to stimulate cell proliferation in some cancer cell lines. Differently from using heparin as an unspecific soluble decoy, targeting HSPG with well-defined ligands can result in an efficient tumor-specific treatment. Nevertheless, as for most cancer cellular targets, a detailed definition of cellular mechanisms and a related personalized approach is mandatory. 1) Schünemann HJ et al. Lancet Haematol. 2020;7(10):e746. 2) Posch F et al. ibid:e703. 3) Brunetti J et al. Sci. Rep. 2016,6,27174. 4) Depau L et al. J Med Chem 2020;63(24):15997. Citation Format: Lorenzo Depau, Elisabetta Mandarini, Jlenia Brunetti, Marta Zanchi, Chiara Falciani, Luisa Bracci. Targeting HSPG is more efficient than using soluble heparin for interfering with cancer cell adhesion and migration [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 6312.

Abstract 3105: Design principle of heparanase inhibitors: A combined in vitro and in silico study

Abstract Heparanase (HPSE) is an endo-β-D-glucuronidase and the only known enzyme responsible for the cleavage of heparan sulfate (HS) side chains from heparan sulfate proteoglycans (HSPGs). The enzymatic activity of HPSE mediates ECM remodeling, regulates growth factors, and modulates related signaling pathways, thus HPSE has emerged as a novel therapeutic target for various diseases, including most types of cancers. In the last two decades, a number of HPSE inhibitors have been reported by several labs worldwide, with most of them belonging to the heparan sulfate mimics category. So far, few of the small molecule HPSE inhibitors have progressed into clinical trials and none has gained approval by regulatory agencies, leaving a blank in HPSE drug discovery. Here we present the discovery of a novel HPSE small molecule inhibitor by high-throughput screening using an ultrasensitive HPSE enzymatic detecting probe developed in our lab and provide the mechanisms of action behind the small molecule’s HPSE inhibitory activity. By doing a series of molecular dynamics (MD) simulations, we discovered the binding profiles on the derivatives of the lead compound. We summarized the essential structural features of the lead compound to provide insights into the design of future HPSE small molecule inhibitors. Citation Format: Yuzhao Zhang, Meijun Xiong, Zixin Chen, Gustavo Seabra, Jun Liu, Chenglong Li, Lina Cui. Design principle of heparanase inhibitors: A combined in vitro and in silico study [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 3105.

Abstract 6295: Belzupacap sarotalocan, an investigational virus-like drug conjugate, preferentially binds cancer cell glycosaminoglycans associated with the epithelial to mesenchymal transition

Abstract Human papillomaviruses (HPVs) are non-enveloped, double-stranded DNA viruses that utilize modified glycosaminogycans (GAGs) such as heparan sulfate proteoglycans, within the epidermal basement membrane as initial attachment factors prior to cell entry and infection. Similarly modified GAGs are also commonly found on the surface of tumor cells, enabling HPV capsids with tumor-selective binding properties. Belzupacap sarotalocan (bel-sar, formerly AU-011), is a virus-like drug conjugate composed of an HPV virus-like particle (VLP) conjugated to a cytotoxic payload (phthalocyanine dye) which upon light activation, causes rapid immunogenic tumor necrosis of bound tumor cells in vivo and has the potential to induce long-term anti-tumor immunity. Bel-sar has been shown to bind to and kill a wide variety of tumor types in preclinical models and is entering a Phase 3 clinical trial for the treatment of early-stage choroidal melanoma. To investigate the precise GAG modifications as well as the overall genetic signature which mediates the binding specificity of bel-sar, a large, multi-tumor type binding screen of bel-sar on 124 cancer cell lines was performed in vitro, where we identified a strong relationship between drug binding and pathways involved in the epithelial to mesenchymal transition (EMT). Additionally, through dose escalation treatments, HeLa subclones were generated which fail to bind and are resistant to the cytotoxic effects of bel-sar. Gene expression profiling and biochemical characterization of these resistant HeLa cell lines demonstrated a strong reduction in the expression of GAGs and a marked down-regulation of TGF-β signaling, ultimately resulting in the induction of a mesenchymal to epithelial transition (MET). Furthermore, gene-gene correlation studies showed that a variety of GAG biosynthesis genes are associated with TGF-β signaling and EMT progression, and that these genes are important determinates of bel-sar binding. Overall, these data suggest that the binding of bel-sar and HPV VLPs is strongly dependent on the expression and modification of GAGs that occurs during the EMT process. As many cancers, especially metastatic tumors, are thought to undergo at least partial EMT, these data provide mechanistic insights into the tumor-targeting ability of HPV VLP-conjugates such as bel-sar and suggest possible applications for such therapies across a wide variety of other tumor types. Citation Format: Nathan R. Fons, Rhonda C. Kines, John T. Schiller. Belzupacap sarotalocan, an investigational virus-like drug conjugate, preferentially binds cancer cell glycosaminoglycans associated with the epithelial to mesenchymal transition [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 6295.

Abstract 4977: Development of small molecule inhibitors of protein interaction with glycosaminoglycans

Abstract Glycosaminoglycans (GAGs), such as heparan sulfate and chondroitin sulfate, are an important component of the tumor microenvironment (TME). These carbohydrates are attached to proteoglycans at the surface of tumor cells and play a vital role in malignant transformation. Heparan sulfate (HS) glycosaminoglycans have been demonstrated to play a pleiotropic role in regulating the activity of important cellular receptors and downstream signaling pathways, and are implicated in cancer cell proliferation, angiogenesis, invasion, and metastasis. Heparinase, an endoglycosidase that specifically cleaves heparan sulfate side chains of heparan sulfate proteoglycans is expressed in several sarcoma subtypes. We measured heparinase activity in several cell lines and found that A673, CHP100, CHLA9 and RD-ES Ewing’s sarcoma cell lines have significantly higher levels of heparinase activity compared to the heparinase-deficient CHO-K1 psgD-677 cell line. Interference with heparinase or heparin sulfate function(s) may represent a therapeutic approach in sarcoma. To this end, we tested these cell lines by measuring cell growth using a cell viability assay, in the presence or absence of GTC3300P, a small molecule inhibitor of protein interaction with glycosaminoglycan. We demonstrate that the Ewing’s sarcoma cell lines exhibit potent and significant inhibition in cell growth in vitro, in the presence of drug. Western blot analysis shows induction of cleaved Poly-ADP Ribose Polymerase (PARP), yH2AX, as well as cleaved caspase-3, known markers of apoptosis and down regulation of mTORC1 targets such as phospho-S6 (p-S6), in Ewing’s sarcoma. Apoptosis was confirmed by the induction of sub-G1 population in Ewing’s sarcoma by cell cycle analysis. Previous reports have indicated that heparinase activity is strongly implicated in cell migration and invasion and is associated with tumor metastasis, angiogenesis and inflammation. This was confirmed by LC-MS/MS proteomics and bioinformatics (gene ontology and gene set enrichment) analysis of these multiple cell lines, which identified alterations in numerous biomarkers in these pathways, including multiple ribosomal protein subunits, spliceosomes components, and complement coagulation cascade. We further conducted a cell migration assay and demonstrate that GTC3300 significantly inhibits cell migration in Ewing’s sarcoma cell lines, but not in heparinase-deficient psg677 cells. Taken together our data strongly suggests that targeting protein interaction with glycosaminoglycans including heparan sulfate in Ewing’s sarcoma represents a novel approach and merits further investigation Citation Format: Tahir N. Sheikh, Elgilda Musi, Alex J. Rai, Gary K. Schwartz. Development of small molecule inhibitors of protein interaction with glycosaminoglycans. [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 4977.

Abstract 2394: Activatable fluorogenic probe for two-photon imaging of heparanase in vivo

Abstract Heparanase, an endo-β-glucuronidase, is the only known enzyme that is responsible for the cleavage of heparan sulfate chains of heparan sulfate proteoglycans. Its enzymatic activity plays a key role in remodeling and degradation of the extracellular matrix, generation of biologically active carbohydrate fragments, and liberation of effector molecules, such as growth factors and chemokines, that are bound to the heparan sulfate side chains. Overexpression of heparanase has been implicated in most types of cancers and various inflammatory diseases that usually involve extensive heparan sulfate degradation and extracellular matrix remodeling. In particular, the role of heparanase in cancer is highly significant as it regulates multiple biological activities that fosters tumor progression, angiogenesis, metastases. Consequently, heparanase has been considered a biological target for various therapeutic applications including anti-cancer drug development. However, one of the major challenges in this research area is the development of robust and feasible heparanase probes to study the enzymes’ fundamental biology in the extracellular matrix, to provide heparanase-targeted diagnostics, and to aid in drug discovery efforts. Our lab has been developing various small-molecule-based heparanase activatable probes, and we have successfully developed chemical strategies that allow sensitive detection of heparanase activity in various contexts. Two-photon microscopy allows for deeper tissue penetration, excellent spatial resolution, and efficient light detection with reduced photobleaching effects. Herein, we extend our chemical strategies to develop a heparanase-activatable two-photon fluorogenic probe for real-time detection of heparanase activity in animal models of highly-aggressive brain cancer using two-photon imaging. Citation Format: Zachary Rabinowitz, Zhishen Wang, Johnathan Somers, Jun Liu, Joyce Jiang, Nina Zhang, Lina Cui. Activatable fluorogenic probe for two-photon imaging of heparanase in vivo [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 2394.

THE IMPACT OF SEX ON BONE STRUCTURE AND ANGIOGENESIS IN SYNDECAN-1 DEFICIENT MICE

Neoangiogenesis drives the replacement of mineralised cartilage by trabecular bone during bone growth regulated by molecules like e.g. VEGF, OPG and RANKL. The Heparan sulfate proteoglycan Syndecan-1 (Sdc1) plays a role in the interaction of osteoclasts and osteoblasts and the development of blood vessels. We expected Sdc1 to have an influence on bone structure and vessel development. Therefore, bone structure and angiogenesis at the growth plate in mice was compared and the influence of Syndecan-1 deficiency was characterised.Animals: Femura of male and female C57BL/6 WT (5♀, 6♂) and Sdc1-/- (9♀, 5♂) mice were used for native bone analysis at 4 month age. Histology: Bone structure was analysed using microCT scans with a resolution of 9µm. Vascularisation was visualised using an anti-Endomucin antibody in 80µm thick cryosections. In vitro angiogenesis: Bone marrow isolates were used to generate endothelial progenitor cells by sequential cultivation on fibronectin. Microvessel development was analysed 4h after plating on matrigel.Bone structure in male Sdc1 deficient mice was significantly reduced compare to male WT, whereas female mice of both genotypes did not differ. Sdc1 deficient mice at the age of 4 month showed a high decrease in the number of vessel bulbs at the chondro-osseous border (growth plate) compared to WT mice. However, no sex related differences were shown. Quantification of microvessel outgrowth of endothelial cells revealed a decreased amount of sprouting, but increased length of microvessels of Sdc1-/- cells compared to WT.Syndecan-1 has a significant impact on neoangiogenesis at the chondro-osseous border of the native bone, but the impact of Syndecan-1 deficiency on the loss of bone structure was significantly higher in male mice. This emphasises the importance to further characterise the function of Syndecan-1 regulated processes during enchondral ossification in a sex dependent manner.

Regulation of morphogen pathways by a Drosophila chondroitin sulfate proteoglycan Windpipe.

Morphogens provide quantitative and robust signaling systems to achieve stereotypic patterning and morphogenesis. Heparan sulfate (HS) proteoglycans (HSPGs) are key components of such regulatory feedback networks. In Drosophila, HSPGs serve as co-receptors for a number of morphogens, including Hedgehog (Hh), Wingless (Wg), Decapentaplegic (Dpp) and Unpaired (Upd, or Upd1). Recently, Windpipe (Wdp), a chondroitin sulfate (CS) proteoglycan (CSPG), was found to negatively regulate Upd and Hh signaling. However, the roles of Wdp, and CSPGs in general, in morphogen signaling networks are poorly understood. We found that Wdp is a major CSPG with 4-O-sulfated CS in Drosophila. Overexpression of wdp modulates Dpp and Wg signaling, showing that it is a general regulator of HS-dependent pathways. Although wdp mutant phenotypes are mild in the presence of morphogen signaling buffering systems, this mutant in the absence of Sulf1 or Dally, molecular hubs of the feedback networks, produces high levels of synthetic lethality and various severe morphological phenotypes. Our study indicates a close functional relationship between HS and CS, and identifies the CSPG Wdp as a novel component in morphogen feedback pathways.

RSPO3 Furin domain-conjugated liposomes for selective drug delivery to LGR5-high cells.

The transmembrane receptor LGR5 potentiates Wnt/β-catenin signaling by binding both secreted R-spondin (RSPOs) and the Wnt tumor suppressors RNF43/ZNRF3, directing clearance of RNF43/ZNRF3 from the cell surface. Besides being widely used as a stem cell marker in various tissues, LGR5 is overexpressed in many types of malignancies, including colorectal cancer. Its expression characterizes a subpopulation of cancer cells that play a crucial role in tumor initiation, progression and cancer relapse, known as cancer stem cells (CSCs). For this reason, ongoing efforts are aimed at eradicating LGR5-positive CSCs. Here, we engineered liposomes decorated with different RSPO proteins to specifically detect and target LGR5-positive cells. Using fluorescence-loaded liposomes, we show that conjugation of full-length RSPO1 to the liposomal surface mediates aspecific, LGR5-independent cellular uptake, largely mediated by heparan sulfate proteoglycan binding. By contrast, liposomes decorated only with the Furin (FuFu) domains of RSPO3 are taken up by cells in a highly specific, LGR5-dependent manner. Moreover, encapsulating doxorubicin in FuFuRSPO3 liposomes allowed us to selectively inhibit the growth of LGR5-high cells. Thus, FuFuRSPO3-coated liposomes allow for the selective detection and ablation of LGR5-high cells, providing a potential drug delivery system for LGR5-targeted anti-cancer strategies.

Screening and characterisation of a novel efficient tumour cell-targeting peptide derived from insulin-like growth factor binding proteins

Targeted delivery of antitumor drugs is particularly important in tumour treatment. Tumour-targeted peptide is a very effective drug carrier for tumour therapy. Here, we screened and characterised a highly efficient targeted peptide named IHP5, which was derived from insulin-like growth factor binding proteins (IGFBPs). IHP5 exhibited preferential binding to the tested tumour cell lines. The delivery efficiency of IHP5 was higher in various tested tumour cells than in normal cells, especially in the human cervical cancer cell line HeLa, which was 11.7-fold higher than in normal human embryonic kidney cells HEK293. Moreover, the penetration efficiency of IHP5 was 13 times higher than that of the classical cell penetrating peptide TAT in HeLa cells. Detail analysis revealed that IHP5 endocytosis was possibly correlated with acetylated heparan sulphate proteoglycans including phosphatidylinositol proteoglycan 3 (GPC3), phosphatidylinositol proteoglycan 5 (GPC5) and syndecan 2 (SDC2). Subsequently, the introduction of IHP5 enhanced the inhibitory effect of trichosanthin (TCS) on tumour cells, resulting in at least 19-fold increase in tumour cells without enhanced cytotoxicity in normal cells HEK293. These results suggested that IHP5, as a novel tumour cell-targeting penetrating peptide with the ability to target tumour cells, has great potential in drug delivery applications.

Neuroprotective Effects of Lactoferrin in Alzheimer's and Parkinson's Diseases: A Narrative Review.

Recent advancements in lactoferrin research have uncovered that lactoferrin does function not only as an antimicrobial protein but also as an immunomodulatory, anticancer, and neuroprotective agent. Focusing on neuroprotection, this literature review delineates how lactoferrin interacts in the brain, specifically its neuroprotective effects and mechanisms against Alzheimer's and Parkinson's diseases (AD and PD), the two most common neurodegenerative diseases. The neuroprotective pathways involving surface receptors (heparan sulfate proteoglycan (HSPG) and lactoferrin receptor (LfR)), signaling pathways (extracellular regulated protein kinase-cAMP response element-binding protein (ERK-CREB) and phosphoinositide 3-kinase/Akt (PI3K/Akt)), and effector proteins (A disintegrin and metalloprotease10 (ADAM10) and hypoxia-inducible factor 1α (HIF-1α)) in cortical/hippocampal and dopaminergic neurons are described. These cellular effects of lactoferrin are likely responsible for attenuating cognitive and motor deficits, amyloid-β and α-synuclein accumulation, and neurodegeneration in animal and cellular models of AD and PD. This review also discusses the inconsistent findings related to the neuroprotective effects of lactoferrin against AD. Overall, this review contributes to the existing literature by clarifying the potential neuroprotective effects and mechanisms of lactoferrin in the context of AD and PD neuropathology.

Site-Specifically Conjugated Single-Domain Antibody Successfully Identifies Glypican-3-Expressing Liver Cancer by Immuno-PET.

Primary liver cancer is the third leading cause of cancer-related deaths, and its incidence and mortality are increasing worldwide. Hepatocellular carcinoma (HCC) accounts for 80% of primary liver cancer cases. Glypican-3 (GPC3) is a heparan sulfate proteoglycan that histopathologically defines HCC and represents an attractive tumor-selective marker for radiopharmaceutical imaging and therapy for this disease. Single-domain antibodies are a promising scaffold for imaging because of their favorable pharmacokinetic properties, good tumor penetration, and renal clearance. Although conventional lysine-directed bioconjugation can be used to yield conjugates for radiolabeling full-length antibodies, this stochastic approach risks negatively affecting target binding of the smaller single-domain antibodies. To address this challenge, site-specific approaches have been explored. Here, we used conventional and sortase-based site-specific conjugation methods to engineer GPC3-specific human single-domain antibody (HN3) PET probes. Methods: Bifunctional deferoxamine (DFO) isothiocyanate was used to synthesize native HN3 (nHN3)-DFO. Site-specifically modified HN3 (ssHN3)-DFO was engineered using sortase-mediated conjugation of triglycine-DFO chelator and HN3 containing an LPETG C-terminal tag. Both conjugates were radiolabeled with 89Zr, and their binding affinity invitro and target engagement of GPC3-positive (GPC3+) tumors invivo were determined. Results: Both 89Zr-ssHN3 and 89Zr-nHN3 displayed nanomolar affinity for GPC3 invitro. Biodistribution and PET/CT image analysis in mice bearing isogenic A431 and A431-GPC3+ xenografts, as well as in HepG2 liver cancer xenografts, showed that both conjugates specifically identify GPC3+ tumors. 89Zr-ssHN3 exhibited more favorable biodistribution and pharmacokinetic properties, including higher tumor uptake and lower liver accumulation. Comparative PET/CT studies on mice imaged with both 18F-FDG and 89Zr-ssHN3 showed more consistent tumor accumulation for the single-domain antibody conjugate, further establishing its potential for PET imaging. Conclusion: 89Zr-ssHN3 showed clear advantages in tumor uptake and tumor-to-liver signal ratio over the conventionally modified 89Zr-nHN3 in xenograft models. Our results establish the potential of HN3-based single-domain antibody probes for GPC3-directed PET imaging of liver cancers.