Increased levels of syndecan-1 in serum during acute graft-versus-host disease

Galectin-3 predicts acute GvHD and overall mortality post reduced intensity allo-HCT: a BMT-CTN biorepository study

Identifying plasma biomarkers early after allo-HCT may become crucial to prevent and treat severe aGvHD. We utilized samples from 203 allo-HCT patients selected from the Blood & Marrow Transplant Clinical Trials Network (BMT CTN) to identify new biomarker models to predict aGvHD and overall mortality. Two new biomarkers (Gal-3 and LAG-3), and previously identified biomarkers (ST2/IL33R, IL6, Reg3A, PD-1, TIM-3, TNFR1) were screened. Increased Gal-3 levels measured at Day +7 post-transplant predicted the development of aGvHD (grade 2-4) in the total population [AUC: 0.602; P = 0.045] while higher Day +14 levels predicted overall mortality due to toxicity among patients receiving reduced intensity conditioning [P = 0.028] but not myeloablative conditioning. Elevated LAG-3 levels (Day +21) were associated with less severe aGvHD [159.1 ng/mL vs 222.0 ng/mL; P = 0.046]. We developed a model utilizing Gal-3, LAG-3, and PD-1 levels at Days +14 and +21 with an improved performance to predict aGvHD and overall non-relapse mortality. We confirmed four informative biomarkers (Reg3A, ST2, TIM-3, and TNFR1) predict severe aGvHD at day +14 and day +21 (grade 3-4). In conclusion, the combination of Gal-3 alone or in combination with LAG-3, and PD-1 is a new informative model to predict aGvHD development and overall non-relapse mortality after allo-HCT.

Soluble vascular endothelial glycocalyx proteoglycans as potential therapeutic targets in inflammatory diseases

Reducing the activity of cytokines and leukocyte extravasation is an emerging therapeutic strategy to limit tissue-damaging inflammatory responses and restore immune homeostasis in inflammatory diseases. Proteoglycans embedded in the vascular endothelial glycocalyx, which regulate the activity of cytokines to restrict the inflammatory response in physiological conditions, are proteolytically cleaved in inflammatory diseases. Here we critically review the potential of proteolytically shed, soluble vascular endothelial glycocalyx proteoglycans to modulate pathological inflammatory responses. Soluble forms of the proteoglycans syndecan-1, syndecan-3 and biglycan exert beneficial anti-inflammatory effects by the removal of chemokines, suppression of proinflammatory cytokine expression and leukocyte migration, and induction of autophagy of proinflammatory M1 macrophages. By contrast, soluble versikine and decorin enhance proinflammatory responses by increasing inflammatory cytokine synthesis and leukocyte migration. Endogenous syndecan-2 and mimecan exert proinflammatory effects, syndecan-4 and perlecan mediate beneficial anti-inflammatory effects and glypican regulates Hh and Wnt signaling pathways involved in systemic inflammatory responses. Taken together, targeting the vascular endothelial glycocalyx-derived, soluble syndecan-1, syndecan-2, syndecan-3, syndecan-4, biglycan, versikine, mimecan, perlecan, glypican and decorin might be a potential therapeutic strategy to suppress overstimulated cytokine and leukocyte responses in inflammatory diseases.

The level of Tim-3+CD8+ T cells can serve as a potential marker for evaluating the severity of acute graft-versus-host disease after haplo-PBSCT

Early and accurate diagnosis of acute graft-versus-host disease (aGVHD) after allogeneic hematopoietic stem cell transplantation is crucial for the prognosis of patients. This study identified a potential biomarker for the severity of aGVHD after human leukocyte antigen (HLA)-haploidentical peripheral blood hematopoietic stem cell transplantation (haplo-PBSCT). We included 20 healthy subjects and 57 patients who underwent haplo-PBSCT. Of these patients, 22 developed aGVHD after haplo-PBSCT. The results showed that patients with aGVHD had significantly increased levels of Tim-3+/Perforin+/Granzyme B+CD8+ T cells, but significantly decreased Galectin-9. The differences in Galectin-9 and Tim-3+/Granzyme B+CD8+ T cells between grade I-II aGVHD and III-IV aGVHD were also significant. In vitro, the apoptosis of CD8+ T cells from aGVHD patients was significantly increased after Tim-3/Galectin-9 pathway activation, which decreased Granzyme B secretion. As revealed by univariate analysis, the level of Tim-3+CD8+ T cells was a risk factor for severe aGVHD. ROC analysis demonstrated that high levels of Tim-3+CD8+ T cells had a significant diagnostic value for severe aGVHD, with an area under the curve of 0.854 and cut-off value of 14.155%. In conclusion, the binding of Tim-3 with exogenous Galectin-9 can promote apoptosis of CD8+ T cells and affect the secretion of Granzyme B. Tim-3+CD8+ T cells have the potential to serve as immunological markers for assessing the severity of aGVHD after haplo-PBSCT and identifying patients at a higher risk for severe aGVHD.

Combination of ST2 With Organ-Specific Biomarker is More Sensitive and Specific for the Diagnosis of Acute Graft-vs-Host Disease

BACKGROUND

Diagnosis of acute graft-vs-host disease (aGVHD) based on clinical symptoms and biopsy of involved organ was not satisfactory; reliable plasma biomarkers or their panels would be of great value to increase the sensitivity and specificity for such a fatal complication.

METHOD

One hundred two patients who received allogeneic hematopoietic stem cell transplantation in our center were included in this study. Systemic biomarkers of ST2, IP10, IL-2Rα, TNFR1, and organ-specific biomarkers of Elafin, REG-3α, and KRT-18F in plasma were tested by ELISA. The correlation of each biomarker or selected panel of some systemic and organ-specific biomarker with aGVHD was investigated.

RESULTS

The level of each systemic biomarker in aGVHD patients was significantly higher than that in patients without aGVHD. Organ-specific biomarker of Elafin, REG-3α, and KRT-18F also had predictive value for aGVHD of skin, gastrointestinal tract, and liver, respectively. Combination of ST2 with one of the 3 organ-specific biomarkers could provide more accurate prediction for aGVHD with skin, gastrointestinal tract, and liver, respectively.

CONCLUSIONS

All the biomarkers tested in our study correlated with the severity and clinical course of aGVHD. Combination of each systemic biomarker with organ-specific biomarker could increase the sensitivity and specificity for the diagnosis of aGVHD, whereas ST2 with organ-specific biomarker is more sensitive for the diagnosis of organ-specific aGVHD.

Endothelial dysfunction triggers acute respiratory distress syndrome in patients with sepsis: a narrative review

Acute respiratory distress syndrome (ARDS) is a severe organ failure occurring mainly in critically ill patients as a result of different types of insults such as sepsis, trauma or aspiration. Sepsis is the main cause of ARDS, and it contributes to a high mortality and resources consumption both in hospital setting and in the community. ARDS develops mainly an acute respiratory failure with severe and often refractory hypoxemia. ARDS also has long term implications and sequelae. Endothelial damage plays an important role in the pathogenesis of ARDS. Understanding the mechanisms of ARDS presents opportunities for novel diagnostic and therapeutic targets. Biochemical signals can be used in concert to identify and classify patients into ARDS phenotypes allowing earlier effective treatment with personalised therapies. This is a narrative review where we aimed to flesh out the pathogenetic mechanisms and heterogeneity of ARDS. We examine the links between endothelium damage and its contribution to organ failure. We have also investigated future strategies for treatment with a special emphasis in endothelial damage.

Endothelial Damage and the Microcirculation in Critical Illness

Endothelial integrity maintains microcirculatory flow and tissue oxygen delivery. The endothelial glycocalyx is involved in cell signalling, coagulation and inflammation. Our ability to treat critically ill and septic patients effectively is determined by understanding the underpinning biological mechanisms. Many mechanisms govern the development of sepsis and many large trials for new treatments have failed to show a benefit. Endothelial dysfunction is possibly one of these biological mechanisms. Glycocalyx damage is measured biochemically. Novel microscopy techniques now mean the glycocalyx can be indirectly visualised, using sidestream dark field imaging. How the clinical visualisation of microcirculation changes relate to biochemical laboratory measurements of glycocalyx damage is not clear. This article reviews the evidence for a relationship between clinically evaluable microcirculation and biological signal of glycocalyx disruption in various diseases in ICU. Microcirculation changes relate to biochemical evidence of glycocalyx damage in some disease states, but results are highly variable. Better understanding and larger studies of this relationship could improve phenotyping and personalised medicine in the future. Damage to the glycocalyx could underpin many critical illness pathologies and having real-time information on the glycocalyx and microcirculation in the future could improve patient stratification, diagnosis and treatment.

Elevated Serum and Cerebrospinal Fluid CD138 in Patients With Anti-N-Methyl-d-Aspartate Receptor Encephalitis

Background

CD138 (also known as syndecan-1) is an important component of endothelial cell glycocalyx, and it is reportedly involved in negative regulation of various inflammatory processes. The clinical implications of circulating and cerebrospinal fluid (CSF) soluble CD138 (sCD138) in patients with Anti-N-methyl-d-aspartate receptor (NMDAR) encephalitis remain unclear.

Objective

The aim of the current study was to investigate associations between serum and CSF sCD138 levels in anti-NMDAR encephalitis patients.

Methods

The participants enrolled in the study included 27 with anti-NMDAR encephalitis, 11 with viral meningoencephalitis, and 22 controls. At acute stage and 3 to 6-month follow-up time-points, sCD138, tumor necrosis factor-α, matrix metalloproteinase-2, and matrix metalloproteinase-9 in serum and CSF were measured in all participants via enzyme-linked immunosorbent assays.

Results

Serum and CSF levels of sCD138 were significantly increased in patients with anti-NMDAR encephalitis. Furthermore, after 3–6 months of follow-up CSF sCD138 levels were significantly decreased in anti-NMDAR encephalitis patients. Changes in sCD138 levels were significantly associated with amelioration of modified Rankin Scale scores in patients with anti-NMDAR encephalitis.

Conclusion

In anti-NMDAR encephalitis patients, high circulating, and CSF sCD138 is associated with inflammation and poor clinical prognosis. The present study suggests that sCD138 may be an informative biomarker of inflammation in anti-NMDAR encephalitis.

Syndecan-1 Shedding Inhibition to Protect Against Ischemic Acute Kidney Injury Through HGF Target Signaling Pathway

BACKGROUND

The hepatocyte growth factor (HGF) target pathway plays pivotal renoprotective roles after acute kidney injury. Syndecan-1 (SDC-1) serves as the coreceptor for HGF. Shedding of SDC-1 is involved in various pathological processes. Thus, we hypothesized that ischemia/reperfusion injury induced SDC-1 shedding, and inhibiting SDC-1 shedding would protect against kidney injury by potentiating activation of the HGF receptor mesenchymal epithelial transition factor (c-Met).

METHODS

Expression of SDC-1 and its sheddases were observed in kidneys of sham and ischemia/reperfusion (I/R) mice. To inhibit SDC-1 shedding, mice were injected with the sheddase inhibitor GM6001 before I/R surgery, and then, renal inflammation, tubular apoptosis, and activation of the c-Met/AKT/glycogen synthase kinase-3β (GSK-3β) pathway were analyzed. In vitro, human proximal tubular cell lines were pretreated with GM6001 under hypoxia/reperfusion conditions. The apoptosis and viability of cells and expression of c-Met/AKT/GSK-3β pathway components were evaluated. The relationship was further confirmed by treatment with SU11274, a specific inhibitor of phospho-c-Met.

RESULTS

Shedding of SDC-1 was induced after ischemia/reperfusion injury both in vivo and in vitro. GM6001 pretreatment suppressed SDC-1 shedding, alleviated renal inflammation and tubular apoptosis, and upregulated phosphorylation of the c-Met/AKT/GSK-3β pathway. In vitro, pretreatment with GM6001 also decreased hypoxia/reperfusion-induced cell apoptosis and promoted activation of the c-Met pathway. In addition, the cytoprotective role of GM6001 was attenuated by suppressing c-Met phosphorylation with SU11274.

CONCLUSIONS

Our findings suggest that inhibiting I/R-induced SDC-1 shedding protected against ischemic acute kidney injury by potentiating the c-Met/AKT/GSK-3β pathway.

Plasma syndecan-1 in hemodialysis patients associates with survival and lower markers of volume status

Syndecan-1, a transmembrane heparan sulfate proteoglycan, associates with renal and cardiovascular functioning. We earlier reported syndecan-1 to be involved in renal tubular regeneration. We now examined plasma values of syndecan-1 in a hemodialysis cohort and its association with volume and inflammatory and endothelial markers in addition to outcome. Eighty-four prevalent hemodialysis patients were evaluated for their plasma syndecan-1 levels by ELISA before the start of hemodialysis, as well as 60, 180, and 240 min after start of dialysis. Patients were divided into sex-stratified tertiles based on predialysis plasma syndecan-1 levels. We studied the association between plasma levels of syndecan-1 and volume, inflammation, and endothelial markers and its association with cardiovascular events and all-cause mortality using Kaplan-Meier curves and Cox regression analyses with adjustments for gender, age, diabetes, and dialysis vintage. Predialysis syndecan-1 levels were twofold higher in men compared with women ( P = 0.0003). Patients in the highest predialysis plasma syndecan-1 tertile had a significantly higher ultrafiltration rate ( P = 0.034) and lower plasma values of BNP ( P = 0.019), pro-ANP ( P = 0.024), and endothelin ( P < 0.0001) compared with the two lower predialysis syndecan-1 tertiles. No significant associations with inflammatory markers were found. Cox regression analysis showed that patients in the highest syndecan-1 tertile had significantly less cardiovascular events and better survival compared with the lowest syndecan-1 tertile ( P = 0.02 and P = 0.005, respectively). In hemodialysis patients, higher plasma syndecan-1 levels were associated with lower concentrations of BNP, pro-ANP, and endothelin and with better patient survival. This may suggest that control of volume status in hemodialysis patients allows an adaptive tissue regenerative response as reflected by higher plasma syndecan-1 levels.

Soluble syndecans: biomarkers for diseases and therapeutic options

Syndecans are important mediators of signalling by transmitting external stimuli into the cells. This role in signal transduction has been attributed mainly to the membrane-bound syndecans. In the last years, however, the soluble ectodomain of syndecans generated by shedding has come into the focus of research as this process has been show to modulate the syndecan-dependent signalling pathways, as well as other pathways. This review summarizes the current knowledge about the induction of syndecan shedding and the different pathways modulated by shed syndecan proteins. This review summarizes the known and putative sheddases for each syndecan and describes the exemplary conditions of sheddase activity for some syndecans. This review summarizes the proposed use of shed syndecans as biomarkers for various diseases, as the shedding process of syndecans depends crucially on tissue- and disease-specific activation of the sheddases. Furthermore, the potential use of soluble syndecans as a therapeutic option is discussed, on the basis of the current literature. LINKED ARTICLES: This article is part of a themed section on Translating the Matrix. To view the other articles in this section visit http://onlinelibrary.wiley.com/doi/10.1111/bph.v176.1/issuetoc.

Danger Signals and Graft-versus-host Disease: Current Understanding and Future Perspectives

Graft-versus-host response after allogeneic hematopoietic stem cell transplantation (allo-HCT) represents one of the most intense inflammatory responses observed in humans. Host conditioning facilitates engraftment of donor cells, but the tissue injury caused from it primes the critical first steps in the development of acute graft-versus-host disease (GVHD). Tissue injuries release pro-inflammatory cytokines (such as TNF-α, IL-1β, and IL-6) through widespread stimulation of pattern recognition receptors (PRRs) by the release of danger stimuli, such as damage-associated molecular patterns (DAMPs) and pathogen-associated molecular patterns (PAMPs). DAMPs and PAMPs function as potent stimulators for host and donor-derived antigen presenting cells (APCs) that in turn activate and amplify the responses of alloreactive donor T cells. Emerging data also point towards a role for suppression of DAMP induced inflammation by the APCs and donor T cells in mitigating GVHD severity. In this review, we summarize the current understanding on the role of danger stimuli, such as the DAMPs and PAMPs, in GVHD.

Incipient renal transplant dysfunction associates with tubular syndecan-1 expression and shedding

Syndecan-1 is a transmembrane heparan sulfate proteoglycan involved in regenerative growth and cellular adhesion. We hypothesized that the induction of tubular syndecan-1 is a repair response to incipient renal damage in apparently stable, uncomplicated renal transplant recipients. We quantified tubular syndecan-1 in unselected renal protocol biopsies taken 1 yr after transplantation. Spearman rank correlation analysis revealed an inverse correlation between tubular syndecan-1 expression and creatinine clearance at the time of biopsy ( r = −0.483, P < 0.03). In a larger panel of protocol and indication biopsies from renal transplant recipients, tubular syndecan-1 correlated with tubular proliferation marker Ki67 ( r = 0.518, P < 0.0001). In a rat renal transplantation model, 2 mo after transplantation, mRNA expression of syndecan-1 and its major sheddase, A disintegrin and metalloproteinase-17, were upregulated (both P < 0.03). Since shed syndecan-1 might end up in the circulation, in a stable cross-sectional human renal transplant population ( n = 510), we measured plasma syndecan-1. By multivariate regression analysis, we showed robust independent associations of plasma syndecan-1 with renal (plasma creatinine and plasma urea) and endothelial function parameters (plasma VEGF-A, all P < 0.01). By various approaches, we were not able to localize syndecan-1 in vessel wall or endothelial cells, which makes shedding of syndecan-1 from the endothelial glycocalyx unlikely. Our data suggest that early damage in transplanted kidneys induces repair mechanisms within the graft, namely, tubular syndecan-1 expression for tubular regeneration and VEGF production for endothelial repair. Elevated plasma syndecan-1 levels in renal transplantation patients might be interpreted as repair/survival factor related to loss of tubular and endothelial function in transplanted kidneys.

Wnt Signaling Cascades and the Roles of Syndecan Proteoglycans

Wnt signaling comprises a group of pathways emanating from the extracellular environment through cell-surface receptors into the intracellular milieu. Wnt signaling cascades can be divided into two main branches, the canonical/β-catenin pathway and the non-canonical pathways containing the Wnt/planar cell polarity and Wnt/calcium signaling. Syndecans are type I transmembrane proteoglycans with a long evolutionary history, being expressed in all Bilateria and in almost all cell types. Both Wnt pathways have been extensively studied over the past 30 years and shown to have roles during development and in a multitude of diseases. Although the first evidence for interactions between syndecans and Wnts dates back to 1997, the number of studies connecting these pathways is low, and many open questions remained unanswered. In this review, syndecan's involvement in Wnt signaling pathways as well as some of the pathologies resulting from dysregulation of the components of these pathways are summarized.

Elevated Serum Levels of Syndecan-1 Are Associated with Renal Involvement in Patients with Systemic Lupus Erythematosus

Objective.

Syndecan-1 (SDC-1) is a major constituent of the endothelial glycocalyx, which plays a role in maintaining vascular homeostasis and functions as a glomerular filtration barrier. SDC-1 is readily shed into the blood under various conditions, but the clinical implication of circulating SDC-1 in patients with systemic lupus erythematosus (SLE) remains unclear. We aimed to investigate the association of serum SDC-1 level with certain clinical manifestations of SLE.

Methods.

We measured serum SDC-1 levels by ELISA in 111 patients with SLE, 18 with rheumatoid arthritis (RA), and 20 healthy subjects, and investigated its association with clinical manifestations and laboratory variables.

Results.

Serum SDC-1 levels were higher in patients with SLE than in those with RA and healthy controls (both p < 0.001) and were positively correlated with SLE Disease Activity Index (SLEDAI; r = 0.367, p < 0.001) and anti-dsDNA antibody level (r = 0.259, p = 0.007), but inversely correlated with serum C3 and CH50 levels (r = −0.305, p = 0.001 and r = −0.244, p = 0.012). Patients with active nephritis had higher serum SDC-1 levels than patients with inactive nephritis and those without nephritis (both p < 0.001). In addition, serum SDC-1 levels were correlated with renal SLEDAI score (r = 0.540, p < 0.001) and excretion of proteinuria as measured by spot urine protein/creatinine ratio (r = 0.538, p < 0.001). In 14 patients with lupus nephritis (LN) whose serum samples were obtained at the time of renal biopsy, there was a positive correlation between serum SDC-1 levels and activity index (r = 0.632, p = 0.015).

Conclusion.

Serum SDC-1 levels are increased in SLE patients with nephritis, indicating that SDC-1 might be a useful serum biomarker for active LN.

Opportunities and challenges of proteomics in pediatric patients: circulating biomarkers after hematopoietic stem cell transplantation as a successful example

Biomarkers have the potential to improve diagnosis and prognosis, facilitate-targeted treatment, and reduce health care costs. Thus, there is great hope that biomarkers will be integrated in all clinical decisions in the near future. A decade ago, the biomarker field was launched with great enthusiasm because MS revealed that blood contains a rich library of candidate biomarkers. However, biomarker research has not yet delivered on its promise due to several limitations: (i) improper sample handling and tracking as well as limited sample availability in the pediatric population, (ii) omission of appropriate controls in original study designs, (iii) lability and low abundance of interesting biomarkers in blood, and (iv) the inability to mechanistically tie biomarker presence to disease biology. These limitations as well as successful strategies to overcome them are discussed in this review. Several advances in biomarker discovery and validation have been made in hematopoietic stem cell transplantation, the current most effective tumor immunotherapy, and these could serve as examples for other conditions. This review provides fresh optimism that biomarkers clinically relevant in pediatrics are closer to being realized based on: (i) a uniform protocol for low-volume blood collection and preservation, (ii) inclusion of well-controlled independent cohorts, (iii) novel technologies and instrumentation with low analytical sensitivity, and (iv) integrated animal models for exploring potential biomarkers and targeted therapies.

Hepatic syndecan-1 changes associate with dyslipidemia after renal transplantation

Syndecan-1 is a transmembrane heparan sulfate (HS) proteoglycan present on hepatocytes and involved in uptake of triglyceride-rich lipoproteins via its HS polysaccharide side chains. We hypothesized that altered hepatic syndecan-1 metabolism could be involved in dyslipidemia related to renal transplantation. In a rat renal transplantation model elevated plasma triglycerides were associated with fivefold increased expression of hepatic syndecan-1 mRNA (p < 0.01), but not protein. Expression of syndecan-1 sheddases (ADAM17, MMP9) and heparanase was significantly up-regulated after renal transplantation (all p < 0.05). Profiling of HS side chains revealed loss of hepatic HS upon renal transplantation accompanied by significant decreased functional capacity for VLDL binding (p = 0.02). In a human renal transplantation cohort (n = 510), plasma levels of shed syndecan-1 were measured. Multivariate analysis showed plasma syndecan-1 to be independently associated with triglycerides (p < 0.0001) and inversely with HDL cholesterol (p < 0.0001). Last, we show a physical association of syndecan-1 to HDL from renal transplant recipients (RTRs), but not to HDL from healthy controls. Our data suggest that after renal transplantation loss of hepatic HS together with increased syndecan-1 shedding hampers lipoprotein binding and uptake by the liver contributing to dyslipidemia. Our data open perspectives toward improvement of lipid profiles by targeted inhibition of syndecan-1 catabolism in renal transplantation.

Graft-versus-host disease biomarkers: omics and personalized medicine

Allogeneic hematopoietic stem cell transplantation (allo-HSCT) is the most effective form of tumor immunotherapy available to date and the frequency of transplants continues to increase worldwide. However, while allo-HSCT usually induces a beneficial graft-versus leukemia effect, a major source of morbidity and mortality following allo-HSCT is graft-versus-host disease (GVHD). Currently available diagnostic and staging tools frequently fail to identify those at higher risk for GVHD morbidity, treatment unresponsiveness, and death. Furthermore, there are shortcomings in the risk stratification of patients before GVHD clinical signs develop. In parallel, recent years have been characterized by an explosive evolution of omics technologies, largely due to technological advancements in chemistry, engineering, and bioinformatics. Building on these opportunities, plasma biomarkers have been identified and validated as promising diagnostic and prognostic tools for acute GVHD. This review summarizes current information on the types of GVHD biomarkers, the omics tools used to identify them, the biomarkers currently validated as acute GVHD markers, and future recommendations for incorporating biomarkers into new grading algorithms for risk-stratifying patients and creating more personalized treatment courses. Future directions will include randomized evaluations of these biomarkers in multicenter prospective studies while extending on the need for biomarkers of chronic GVHD.

Interleukin-1α promotes extracellular shedding of syndecan-2 via induction of matrix metalloproteinase-7 expression

The cell surface heparan sulfate proteoglycan, syndecan-2, is known to play an important role in the tumorigenic activity of colon cancer cells. In addition, the extracellular domain of syndecan-2 is cleaved by matrix metalloproteinase-7 (MMP-7) in various colon cancer cells, but factors involved in regulating this process remain unknown. Here, we demonstrate a role for interleukin-1α (IL-1α) in syndecan-2 shedding in colon cancer cells. Treatment of low metastatic (HT-29) and highly metastatic (HCT-116) colon cancer cells with various soluble growth factors and cytokines revealed that IL-1α specifically increased extracellular shedding of syndecan-2 in a concentration- and time-dependent manner. IL-1α did not affect the expression of syndecan-2, but did significantly reduce its cell surface levels. Notably, IL-1α increased the mRNA expression and subsequent secreted levels of MMP-7 protein and enhanced the phosphorylation of p38 and ERK mitogen-activated protein kinases. Furthermore, increased syndecan-2 shedding was dependent on the mitogen-activated protein kinase-mediated MMP-7 expression. Taken together, these data suggest that IL-1α regulates extracellular domain shedding of syndecan-2 through regulation of the MAP kinase-mediated MMP-7 expression in colon cancer cells.

Potential biomarkers for early detection of acute graft-versus-host disease

Acute graft-versus-host disease (aGVHD) is the main complication of allogeneic hematopoietic stem cell transplantation (HCT), resulting in considerable morbidity and mortality. Currently, the diagnosis of aGVHD is largely made based on clinical parameters and invasive biopsies. For the past 20 years, researchers have been trying to find reliable biomarkers to enable early and accurate diagnosis of aGVHD. Although a number of potential aGVHD biomarkers have been published, as yet, no validated diagnostic test is available. Proteomics encompasses a broad range of rapidly developing technologies, which have shown tremendous promise for early detection of aGVHD. In this article, we review the current state of aGVHD biomarker discovery, provide a summary of the key proteins of interest and the most common analytical procedures for the clinic, as well as outlining the significant challenges faced in their use.

Discovery and validation of graft-versus-host disease biomarkers

Allogeneic hematopoietic stem cell transplantation (allo-HSCT) is the most effective tumor immunotherapy available. Although allo-HSCT provides beneficial graft-versus-tumor effects, acute GVHD (aGVHD) is the primary source of morbidity and mortality after HSCT. Diagnosis of aGVHD is typically based on clinical symptoms in one or more of the main target organs (skin, liver, gastrointestinal tract) and confirmed by biopsy. However, currently available diagnostic and staging tools often fail to identify patients at higher risk of GVHD progression, unresponsiveness to therapy, or death. In addition, there are shortcomings in the prediction of GVHD before clinical signs develop, indicating the urgent need for noninvasive and reliable laboratory tests. Through the continuing evolution of proteomics technologies seen in recent years, plasma biomarkers have been identified and validated as promising diagnostic tools for GVHD and prognostic tools for nonrelapse mortality. These biomarkers may facilitate timely and selective therapeutic intervention but should be more widely validated and incorporated into a new grading system for risk stratification of patients and better-customized treatment. This review identifies biomarkers for detecting GVHD, summarizes current information on aGVHD biomarkers, proposes future prospects for the blinded evaluation of these biomarkers, and discusses the need for biomarkers of chronic GVHD.

Biomarkers for acute GVHD: can we predict the unpredictable?

Acute GVHD remains an important complication after allogeneic hematopoietic cell transplantation (HCT). Many efforts have been devoted to identifying potential noninvasive peripheral blood biomarkers to help improve the diagnosis or management of acute GVHD while avoiding invasive tissue biopsies. Early attempts to identify biomarkers focused on inflammatory cytokines, especially IL-2 or TNF-α, however, both of these and others were not specific for GVHD, often being elevated in the setting of generalized inflammation, accompanying other major complications of HCT as well. More recent efforts have focused on additional cytokines and other cell-surface molecules, which function in leukocyte trafficking and activation with the hope that these can also serve as targets for novel therapeutic approaches. Modern proteomic methods have allowed the screening of large numbers of patient samples and yielded several novel candidate biomarkers, including elafin and reg3α, which may not be directly involved in the immunological pathogenesis of GVHD, but may be unique biomarkers for end-organ injury. Combining these new molecules with traditionally identified cytokines to form an acute GVHD biomarker panel has recently shown the ability to predict outcomes in patients who develop acute GVHD. The ultimate goals of identifying a specific biomarker are to refine diagnosis, guide therapy and develop risk-adapted approaches in order to better treat patients and improve outcomes after allogeneic HCT. These approaches include differential treatment for patients who develop acute GVHD with a high-risk biomarker profile as well as pre-emptive therapy in patients after HCT prior to the development of symptoms. With the recent progress summarized below, these goals may soon be realized.

Heparan sulfate, an endogenous TLR4 agonist, promotes acute GVHD after allogeneic stem cell transplantation

Graft-versus-host disease (GVHD) remains the most common cause of nonrelapse-related morbidity and mortality after allogeneic hematopoietic stem cell transplantation (allo-HSCT). Although T-cell depletion and intensive immunosuppression are effective in the control of GVHD, they are often associated with higher rates of infection and tumor recurrence. In this study, we showed that heparan sulfate (HS), an extracellular matrix component, can activate Toll-like receptor 4 on dendritic cells in vitro, leading to the enhancement of dendritic cell maturation and alloreactive T-cell responses. We further demonstrated in vivo that serum HS levels were acutely elevated at the onset of clinical GVHD in mice after allo-HSCT. Treatment with the serine protease inhibitor α1-antitrypsin decreased serum levels of HS, leading to a reduction in alloreactive T-cell responses and GVHD severity. Conversely, an HS mimetic that increased serum HS levels accelerated GVHD. In addition, in patients undergoing allo-HSCT for hematologic malignancies, serum HS levels were elevated and correlated with the severity of GVHD. These results identify a critical role for HS in promoting acute GVHD after allo-HSCT, and they suggest that modulation of HS release may have therapeutic potential for the control of clinical GVHD.

Shedding of cell membrane-bound proteoglycans

Membrane-bound proteoglycans function primarily as coreceptors for many glycosaminoglycan (GAG)-binding ligands at the cell surface. The majority of membrane-bound proteoglycans can also function as soluble autocrine or paracrine effectors as their extracellular domains, replete with all GAG chains, are enzymatically cleaved and released from the cell surface by ectodomain shedding. In particular, the ectodomain shedding of syndecans, a major family of cell surface heparan sulfate proteoglycans, is an important posttranslational mechanism that modulates diverse pathophysiological processes. Syndecan shedding is a tightly controlled process that regulates the onset, progression, and resolution of various infectious and noninfectious inflammatory diseases. This review describes methods to induce and measure the shedding of cell membrane-bound proteoglycans, focusing on syndecan shedding as a prototypic example.

Syndecan-1 shedding facilitates the resolution of neutrophilic inflammation by removing sequestered CXC chemokines

Heparan sulfate binds to and regulates many inflammatory mediators in vitro, suggesting that it serves an important role in directing the progression and outcome of inflammatory responses in vivo. Here, we evaluated the role of syndecan-1, a major heparan sulfate proteoglycan, in modulating multiorgan host injury responses in murine endotoxemia. The extent of systemic inflammation was similar between endotoxemic syndecan-1-null and wild-type mice. However, high levels of CXC chemokines (KC and MIP-2), particularly at later times after LPS, were specifically sustained in multiple organs in syndecan-1-null mice and associated with exaggerated neutrophilic inflammation, organ damage, and lethality. Syndecan-1 shedding was activated in several organs of endotoxemic wild-type mice, and this associated closely with the removal of tissue-bound CXC chemokines and resolution of accumulated neutrophils. Moreover, administration of a shedding inhibitor exacerbated disease by impeding the removal of CXC chemokines and neutrophils, whereas administration of heparan sulfate inhibited the accumulation of CXC chemokines and neutrophils in tissues and attenuated multiorgan injury and lethality. These data show that syndecan-1 shedding is a critical endogenous mechanism that facilitates the resolution of neutrophilic inflammation by aiding the clearance of proinflammatory chemokines in a heparan sulfate-dependent manner.

Plasma biomarkers in graft-versus-host disease: a new era?

Acute graft versus host disease (GVHD) remains a major complication of allogeneic hematopoietic cell transplantation (HCT). The diagnosis of acute GVHD is based on strictly clinical criteria and its severity also determined by these criteria. Currently, there is no validated diagnostic blood test for acute GVHD. This review will summarize proteomics approaches to identify biomarkers for GVHD in the plasma with diagnostic, prognostic and predictive value. If successful, these studies could establish a novel biomarker panel that will contribute important information including long term survival, and that may eventually facilitate therapeutic decisions for allogeneic HCT patients.

Syndecan-1 ectodomain shedding is regulated by the small GTPase Rab5

The ectodomain shedding of syndecan-1, a major cell surface heparan sulfate proteoglycan, modulates molecular and cellular processes central to the pathogenesis of inflammatory diseases. Syndecan-1 shedding is a highly regulated process in which outside-in signaling accelerates the proteolytic cleavage of syndecan-1 ectodomains at the cell surface. Several extracellular agonists that induce syndecan-1 shedding and metalloproteinases that cleave syndecan-1 ectodomains have been identified, but the intracellular mechanisms that regulate syndecan-1 shedding are largely unknown. Here we examined the role of the syndecan-1 cytoplasmic domain in the regulation of agonist-induced syndecan-1 shedding. Our results showed that the syndecan-1 cytoplasmic domain is essential because mutation of invariant cytoplasmic Tyr residues abrogates ectodomain shedding, but not because it is Tyr phosphorylated upon shedding stimulation. Instead, our data showed that the syndecan-1 cytoplasmic domain binds to Rab5, a small GTPase that regulates intracellular trafficking and signaling events, and this interaction controls the onset of syndecan-1 shedding. Syndecan-1 cytoplasmic domain bound specifically to Rab5 and preferentially to inactive GDP-Rab5 over active GTP-Rab5, and shedding stimulation induced the dissociation of Rab5 from the syndecan-1 cytoplasmic domain. Moreover, the expression of dominant-negative Rab5, unable to exchange GDP for GTP, interfered with the agonist-induced dissociation of Rab5 from the syndecan-1 cytoplasmic domain and significantly inhibited syndecan-1 shedding induced by several distinct agonists. Based on these data, we propose that Rab5 is a critical regulator of syndecan-1 shedding that serves as an on-off molecular switch through its alternation between the GDP-bound and GTP-bound forms.

A biomarker panel for acute graft-versus-host disease

No validated biomarkers exist for acute graft-versus-host disease (GVHD). We screened plasma with antibody microarrays for 120 proteins in a discovery set of 42 patients who underwent transplantation that revealed 8 potential biomarkers for diagnostic of GVHD. We then measured by enzyme-linked immunosorbent assay (ELISA) the levels of these biomarkers in samples from 424 patients who underwent transplantation randomly divided into training (n = 282) and validation (n = 142) sets. Logistic regression analysis of these 8 proteins determined a composite biomarker panel of 4 proteins (interleukin-2-receptor-alpha, tumor-necrosis-factor-receptor-1, interleukin-8, and hepatocyte growth factor) that optimally discriminated patients with and without GVHD. The area under the receiver operating characteristic curve distinguishing these 2 groups in the training set was 0.91 (95% confidence interval, 0.87-0.94) and 0.86 (95% confidence interval, 0.79-0.92) in the validation set. In patients with GVHD, Cox regression analysis revealed that the biomarker panel predicted survival independently of GVHD severity. A panel of 4 biomarkers can confirm the diagnosis of GVHD in patients at onset of clinical symptoms of GVHD and provide prognostic information independent of GVHD severity.

Syndecan-1 is an in vivo suppressor of Gram-positive toxic shock

Heparan sulfate proteoglycans bind to and regulate many inflammatory mediators in vitro, suggesting that they serve an important role in influencing inflammatory responses in vivo. Here we evaluated the role of syndecan-1, a major heparan sulfate proteoglycan, in modulating inflammatory responses in Gram-positive toxic shock, a systemic disease that is a significant cause of morbidity and mortality. Syndecan-1-null and wild-type mice were injected intraperitoneally with staphylococcal enterotoxin B, a pyrogenic superantigen, and their inflammatory responses were assessed. Syndecan-1-null mice showed significantly increased liver injury, vascular permeability, and death in response to staphylococcal enterotoxin B challenge compared with wild-type mice. Although serum levels of systemic IL-2 and IFNgamma were similar between the two backgrounds, those of TNFalpha and IL-6 were significantly increased in syndecan-1-null mice undergoing Gram-positive toxic shock. Furthermore, syndecan-1-null mice challenged with staphylococcal enterotoxin B showed enhanced T cell accumulation in tissues, whereas immunodepletion of T cells protected syndecan-1-null mice from the magnified systemic cytokine storm, inflammatory tissue injury, and death. Importantly, syndecan-1 shedding was induced in wild-type mice injected with staphylococcal enterotoxin B, and the administration of heparan sulfate, but not syndecan-1 core protein, rescued syndecan-1-null mice from lethal toxic shock by suppressing the production of TNFalpha and IL-6, and attenuating inflammatory tissue injury. Altogether, these data suggest that syndecan-1 shedding is a key endogenous mechanism that protects the host from Gram-positive toxic shock by inhibiting the dysregulation and amplification of the inflammatory response.

Increase in soluble CD138 in bronchoalveolar lavage fluid of multicentric Castleman's disease

Multicentric Castleman's disease (MCD) is a rare and often incurable lymphoproliferative disorder. It is typically a systemic illness, but occasionally manifests primarily as a pulmonary parenchymal disease with massive infiltration of CD138 (syndecan-1)-positive plasma cells. This is the first report to demonstrate a marked elevation of soluble CD138, despite the absence of plasma cells, in BAL fluid in an MCD patient with pulmonary involvement. This finding suggests that the quantitative measurement of soluble CD138 in BAL fluid may reflect plasma cell infiltration and disease activity in the lungs of patients with MCD.

Proteomic patterns predict acute graft-versus-host disease after allogeneic hematopoietic stem cell transplantation

Acute graft-versus-host disease (aGvHD) contributes significantly to morbidity and mortality after allogeneic hematopoietic stem cell transplantation (allo-HSCT). Diagnosis of GvHD is mainly based on clinical features and tissue biopsies. A noninvasive, unbiased laboratory test for GvHD diagnosis does not exist. Here we describe the application of capillary electrophoresis coupled online with mass spectrometry (CE-MS) to 13 samples from 10 patients with aGvHD of grade II or more and 50 control samples from 23 patients without GvHD. About 170 GvHD-specific polypeptides were detected and a tentatively aGvHD-specific model consisting of 31 polypeptides was chosen, allowing correct classification of 13 of 13 (sensitivity 100.0% [95% confidence interval {CI} 75.1 to 100.0]) aGvHD samples and 49 of 50 (specificity 98.0% [95% CI 89.3 to 99.7]) control samples of the training set. The subsequent blinded evaluation of 599 samples enabled diagnosis of aGvHD greater than grade II, even prior to clinical diagnosis, with a sensitivity of 83.1% (95% CI 73.1 to 87.9) and a specificity of 75.6% (95% CI 71.6 to 79.4). Thus, high-resolution proteome analysis represents an unbiased laboratory-based screening method, enabling diagnosis, and possibly enabling preemptive therapy.

Effect of treatment of larynx and hypopharynx carcinomas on serum syndecan-1 concentrations

PURPOSE

Syndecan-1 is a multifunctional transmembrane heparan sulfate proteoglycan present on a variety of cell types that mediates basic fibroblast growth factor (bFGF) and other growth factor binding. High serum syndecan-1 (S-syndecan-1) ectodomain levels have been found to be associated with poor outcome in lung cancer and myeloma, but little is known about the effect of cancer treatment on S-syndecan-1 levels. We studied S-syndecan-1 levels longitudinally in a series of patients diagnosed with locoregional squamous cell larynx or hypopharynx carcinoma (n=44) and who we treated with surgery and/or radiation therapy.

METHODS

S-syndecan-1 and S-bFGF levels were measured with ELISA prior to, during, and following primary treatment of patients. Syndecan-1 expression was assessed from formalin-fixed and paraffin-embedded tumour samples using immunohistochemistry.

RESULTS

S-syndecan-1 levels tended to correlate positively with S-bFGF levels, and the pretreatment levels decreased from a median value of 75 to 58 ng/ml 3 months following treatment (P<0.0001). Patients treated with radiation therapy had a transient increase in S-syndecan-1 during the course of radiation therapy. Patients whose S-syndecan-1 decreased >or=10% from the pretreatment level had more favourable survival than those whose levels remained stable or increased (P=0.0069). Recurred cancer was associated with elevated S-syndecan-1 as compared to the levels measured 3 months following completion of primary therapy.

CONCLUSIONS

These findings suggest that a part of S-syndecan-1 originates from the cancerous tissue, and that S-syndecan-1 levels generally decrease following successful cancer treatment.

Value of proteomics applied to the follow-up in stem cell transplantation

Proteome analysis is now emerging as an important technology for deciphering biological processes and the discovery of biomarkers for diseases from tissues and body fluids. Polypeptides found in body fluids are responsible for the flow of information from cells and tissues, and the changes of the expression of these vehicles may give insight in different states of health and disease. Thus, body fluids obtained from patients are particularly interesting for monitoring of disease, disease progression, and responsiveness to therapy. The complexity and the wide dynamic range of protein expression pose an enormous challenge to both protein/peptide separation technologies and the following identification tools, mainly mass spectrometry (MS). In this paper, we review the application of proteomic screening to the early detection of acute graft vs host disease after allogeneic hematopoietic stem cell transplantation (allo-HSCT). We discuss proteomic screening of clinical samples focusing on the two most important methods, namely, "surface-enhanced laser desorption/ionization" (SELDI)-MS and "capillary zone electrophoresis" (CE)-MS, from an application point of view, evaluating its merits and vices with regard to biomarker discovery and the benefits in clinical application. As an example, we describe the use of CE-MS for the determination of protein patterns in urine. Finally, the benefits and limitations of CE-MS for the analysis of proteins in the follow up of patients after HSCT are discussed against the background of alternative technologies.

Proteomics applied to the clinical follow-up of patients after allogeneic hematopoietic stem cell transplantation

A phase 1 diagnostic study was performed to evaluate a novel technology for clinical proteomic research based on capillary electrophoresis and mass spectrometry. Urine from 40 patients after hematopoietic stem cell transplantation (HSCT; 35 allogeneic, 5 autologous) and 5 patients with sepsis was collected for a period of 100 days and analyzed. More than 1000 different polypeptides could be detected in individual samples. Polypeptide patterns excreted in the urine of patients were significantly different from those of healthy volunteers. No significant differences were detected comparing different conditioning regimens. The aim of this study was to identify polypeptide patterns functioning as early indicators of graft-versus-host disease (GVHD). Eighteen patients developed GVHD after allogeneic HSCT. Sixteen differentially excreted polypeptides formed a pattern of early GVHD markers, allowing discrimination of GVHD from patients without complications with 82% specificity and 100% sensitivity, cross-validated. Inclusion of 13 sepsis-specific polypeptides allowed us to distinguish sepsis from GVHD with a specificity of 97% and a sensitivity of 100%. Sequencing 2 prominent GVHD-indicative polypeptides led to the identification of a peptide from leukotriene A4 hydrolase and a peptide from serum albumin. The data reveal that capillary electrophoresis and mass spectrometry allow identification of biomarkers for a variety of diseases or related complications.