Therapeutic strategies targeting uPAR potentiate anti-PD-1 efficacy in diffuse-type gastric cancer.

The diffuse-type gastric cancer (DGC) is a subtype of gastric cancer (GC) associated with low HER2 positivity rate and insensitivity to chemotherapy and immune checkpoint inhibitors. Here, we identify urokinase-type plasminogen activator receptor (uPAR) as a potential therapeutic target for DGC. We have developed a novel anti-uPAR monoclonal antibody, which targets the domains II and III of uPAR and blocks the binding of urokinase-type plasminogen activator to uPAR. We show that the combination of anti-uPAR and anti-Programmed cell death protein 1 (PD-1) remarkably inhibits tumor growth and prolongs survival via multiple mechanisms, using cell line-derived xenograft and patient-derived xenograft mouse models. Furthermore, uPAR chimeric antigen receptor-expressing T cells based on the novel anti-uPAR effectively kill DGC patient-derived organoids and exhibit impressive survival benefit in the established mouse models, especially when combined with PD-1 blockade therapy. Our study provides a new possibility of DGC treatment by targeting uPAR in a unique manner.

Anti-ETAR and suPAR as markers of disease activity in renal ANCA-associated vasculitis.

PURPOSE: In anti-neutrophil cytoplasmic antibody (ANCA)-associated vasculitis (AAV), there is a lack of reliable biomarkers of disease activity. The aim of the study was to evaluate soluble urokinase plasminogen activator receptor (suPAR) and anti-endothelin-1 type A receptor (anti-ETAR) antibodies levels in active phase and remission of AAV. PATIENTS AND METHODS: We enrolled 60 patients (median age 63.0 years) with renal AAV into this study. Plasma suPAR, urine suPAR (expressed as urine suPAR/creatinine ratio) and serum anti-ETAR antibodies were assayed by ELISA. Disease activity was assessed using Birmingham Vasculitis Activity Score (BVAS) and patients were divided into 2 subgroups based on their BVAS scores, namely: active AAV subgroup (BVAS≥1) and remission subgroup (BVAS â€‹= â€‹0). Median follow-up was 12 months. RESULTS: Patients with active AAV had higher levels of all candidate biomarkers in comparison to those in remission (p â€‹< â€‹0.05). C-statistics for plasma suPAR, urine suPAR/creatinine ratio and serum anti-ETAR were 0.807, 0.713 and 0.783, respectively. In multivariable analysis, no clear associations were found between serum anti-ETAR and BVAS, while both plasma suPAR and serum anti-ETAR were independently influenced by estimated glomerular filtration rate (eGFR). CONCLUSIONS: Plasma suPAR better discriminated between active AAV and remission in comparison to urine suPAR/creatinine ratio and serum anti-ETAR antibodies.

Soluble Urokinase Plasminogen Activator Receptor (suPAR) as a Biomarker of Systemic Chronic Inflammation.

Systemic chronic inflammation (SCI) is persistent, health-damaging, low-grade inflammation that plays a major role in immunosenescence and in development and progression of many diseases. But currently, there are no recognized standard biomarkers to assess SCI levels alone, and SCI is typically measured by combining biomarkers of acute inflammation and infection, e.g., CRP, IL-6, and TNFα. In this review, we highlight 10 properties and characteristics that are shared by the blood protein soluble urokinase plasminogen activator receptor (suPAR) and SCI, supporting the argument that suPAR is a biomarker of SCI: (1) Expression and release of suPAR is upregulated by immune activation; (2) uPAR and suPAR exert pro-inflammatory functions; (3) suPAR is associated with the amount of circulating immune cells; (4) Blood suPAR levels correlate with the levels of established inflammatory biomarkers; (5) suPAR is minimally affected by acute changes and short-term influences, in contrast to many currently used markers of systemic inflammation; (6) Like SCI, suPAR is non-specifically associated with multiple diseases; (7) suPAR and SCI both predict morbidity and mortality; (8) suPAR and SCI share the same risk factors; (9) suPAR is associated with risk factors and outcomes of inflammation above and beyond other inflammatory biomarkers; (10) The suPAR level can be reduced by anti-inflammatory interventions and treatment of disease. Assessing SCI has the potential to inform risk for morbidity and mortality. Blood suPAR is a newer biomarker which may, in fact, be a biomarker of SCI since it is stably associated with inflammation and immune activation; shares the same risk factors as many age-related diseases; is both elevated by and predicts age-related diseases. There is strong evidence that suPAR is a prognostic marker of adverse events, morbidity, and mortality. It is associated with immune activity and prognosis across diverse conditions, including kidney disease, cardiovascular disease, cancer, diabetes, and inflammatory disorders. Thus, we think it likely represents a common underlying disease-process shared by many diseases; that is, SCI. We review the supporting literature and propose a research agenda that can help test the hypothesis that suPAR indexes SCI, with the potential of becoming the new gold standard for measuring SCI.

Immunostimulatory bacterial antigen-armed oncolytic measles virotherapy significantly increases the potency of anti-PD1 checkpoint therapy.

Clinical immunotherapy approaches are lacking efficacy in the treatment of glioblastoma (GBM). In this study, we sought to reverse local and systemic GBM-induced immunosuppression using the Helicobacter pylori neutrophil-activating protein (NAP), a potent TLR2 agonist, as an immunostimulatory transgene expressed in an oncolytic measles virus (MV) platform, retargeted to allow viral entry through the urokinase-type plasminogen activator receptor (uPAR). While single-agent murine anti-PD1 treatment or repeat in situ immunization with MV-s-NAP-uPA provided modest survival benefit in MV-resistant syngeneic GBM models, the combination treatment led to synergy with a cure rate of 80% in mice bearing intracranial GL261 tumors and 72% in mice with CT-2A tumors. Combination NAP-immunovirotherapy induced massive influx of lymphoid cells in mouse brain, with CD8+ T cell predominance; therapeutic efficacy was CD8+ T cell dependent. Inhibition of the IFN response pathway using the JAK1/JAK2 inhibitor ruxolitinib decreased PD-L1 expression on myeloid-derived suppressor cells in the brain and further potentiated the therapeutic effect of MV-s-NAP-uPA and anti-PD1. Our findings support the notion that MV strains armed with bacterial immunostimulatory antigens represent an effective strategy to overcome the limited efficacy of immune checkpoint inhibitor-based therapies in GBM, creating a promising translational strategy for this lethal brain tumor.

A multimodal molecular imaging approach targeting urokinase plasminogen activator receptor for the diagnosis, resection and surveillance of urothelial cell carcinoma.

With a 5-year recurrence rate of 30-78%, urothelial cell carcinoma (UCC) rates amongst the highest of all solid malignancies. Consequently, after transurethral resection, patients are subjugated to life-long endoscopic surveillance. A multimodal near-infrared (NIR) fluorescence-based imaging strategy can improve diagnosis, resection and surveillance, hence increasing quality of life. METHODS: Expression of urokinase plasminogen activator receptor (uPAR) and epithelial cell adhesion molecule (EpCAM) are determined on paraffin-embedded human UCC using immunohistochemistry and on UCC cell lines by flow cytometry. MNPR-101, a humanised monoclonal antibody targeting uPAR is conjugated to IRDye800CW and binding is validated in vitro using surface plasmon resonance and cell-based binding assays. In vivo NIR fluorescence and photoacoustic three-dimensional (3D) imaging are performed with subcutaneously growing human UM-UC-3luc2 cells in BALB/c-nude mice. The translational potential is confirmed in a metastasising UM-UC-3luc2 orthotopic mouse model. Infliximab-IRDye800CW and rituximab-IRDye800CW are used as controls. RESULTS: UCCs show prominent uPAR expression at the tumour-stroma interface and EpCAM on epithelial cells. uPAR and EpCAM are expressed by 6/7 and 4/7 UCC cell lines, respectively. In vitro, MNPR-101-IRDye800CW has a picomolar affinity for domain 2-3 of uPAR. In vivo fluorescence imaging with MNPR-101-IRDye800CW, specifically delineates both subcutaneous and orthotopic tumours with tumour-to-background ratios reaching as high as 6.8, differing significantly from controls (p < 0.0001). Photoacoustic 3D in depth imaging confirms the homogenous distribution of MNPR-101-IRDye800CW through the tumour. CONCLUSIONS: MNPR-101-IRDye800CW is suitable for multimodal imaging of UCC, awaiting clinical translation.

Serum level of soluble urokinase plasminogen activator receptor (suPAR) as a disease severity marker of myasthenia gravis: a pilot study.

Myasthenia gravis (MG) is an autoantibody-mediated inflammatory disease of the neuromuscular junction. Biomarkers indicating disease activity in MG are warranted. Recently, the soluble urokinase plasminogen activator receptor (suPAR) has been reported to be associated with inflammation, tissue damage, disease activity and prognosis in various diseases, including autoimmune diseases. In this study, serum suPAR levels were measured in 40 patients with anti-acetylcholine receptor antibody-positive MG and 30 controls, and their correlations with clinical variables and severity scale scores were investigated. We identified that serum suPAR levels significantly correlated with MG activities of daily living scale (Spearman's ρ = 0·45; P = 0·004) and MG Foundation of America classification (Spearman's ρ = 0·37; P = 0·02) at serum sampling, but not with anti-acetylcholine receptor antibody titers. In conclusion, serum suPAR levels can be a candidate for a novel biomarker of disease activity in anti-acetylcholine receptor antibody-positive MG.

Further Evidence That the Soluble Urokinase Plasminogen Activator Receptor Does Not Directly Injure Mice or Human Podocytes.

BACKGROUND: The role of the soluble urokinase plasminogen activator receptor (suPAR) in focal segmental glomerulosclerosis (FSGS) as the circulating factor or as a predictor of recurrence after transplantation remains controversial. Previously published studies in mice and isolated podocytes produced conflicting results on the effect of suPAR on podocyte injury, effacement of foot processes, and proteinuria. These discordant results were in part due to diverse experimental designs and different strains of mice. The aim of our study was to determine the reasons for the inconsistencies of the previous studies results with suPAR by using uniform methods and studies in different strains of mice. METHODS: We utilized a primary culture of human podocytes and 2 mouse models, the wild type (WT) and the urokinase plasminogen activator receptor (uPAR) KO (uPAR), in an attempt to resolve the reported conflicting results. RESULTS: In both WT and uPAR mouse models, injection of recombinant uPAR, even at a high dose (100 µg), did not induce proteinuria, effacement of podocytes, or disruption of the cytoskeleton. Injection of suPAR resulted in its deposition exclusively in the glomerular endothelial cells and not in the podocytes of WT mice and was not detected at the uPAR KO mice. Kidneys from patients with recurrent FSGS had negative immunostaining for uPAR. We also evaluated the effect of recombinant uPAR on primary culture of human podocytes. uPAR did not result in podocytes damage. CONCLUSIONS: suPAR by itself is not the cause for direct podocyte injury, in vitro or in vivo. These findings suggest a more complex and still poorly understood role of suPAR in FSGS.

[Expression of CD44, CD87 and CD123 in Acute Leukemia and Its Correlation with Cellular Immunity].

OBJECTIVE: To investigate the expression of CD44, CD87 and CD123 in acute leukemia and its correlation with cellular immune markers. METHODS: A total of 166 patients with acute leukemia (AL) admitted from May 2014 to February 2017 were enrolled in AL groups. Among these patients, 100 patients suffered from acute myeloid leukemia, 50 patients suffered from acute lymphoid leukemia, and 16 patients showed B/medullary phenotype. At the same time 50 patients with non-acute leukemia were enrolled in the control group. 5 ml of fasting venous blood collected from the patients in each group, and the percentage of CD44, CD87 and CD123 cells was determined by three-color flow cytometry. Symptomatic chemotherapy was given to the patients with confirmed acute leukemia, and the remission was evaluated after 2 treatmen courses. The Complete remission (CR) was recorded and the percentage of CD44, CD87 and CD123 cells under different curative efficacy were recorded. The correlation of the prognosis patients with CD44, CD87 and CD123 was analyzed by SPSS Pearson correlation analysis software. RESULTS: The positive rates of CD44, CD87 and CD123 in AL group were all higher than those in the control group (P＜0. 05). The positive rates of CD44 and CD123 in acute myeloid leukemia group were higher than those in acute lymphoblastic leukemia group and B/myeloid phenotype group (P＜0. 05). The positive rate of CD44 in acute lymphoid leukemia group was higher than that in B/medullary double phenotype group (P＜0.05). The treatment in the patients of AL group was successfully completed. 132 patients reachel to CR and 34 patients to PR+NR after 2 courses. The positive rates of CD44, CD87 and CD123 in CR patients were lower than those in PR+NR patients (P＜0.05). The results of SPSS Pearson correlation analysis showed that the prognosis of patients with acute leukemia negatively correlated with CD44 and CD87 (P＜0.05). CONCLUSION: The expression of CD44, CD87 and CD123 in different phenotype of acute leukemia are different, which correlateds with prognosis. The determination of CD44, CD87 and CD123 can be used to evaluate the prognosis of patients for the reference of clinical treatment.

Genetic variants of TRAF6 modulate peritoneal immunity and the risk of spontaneous bacterial peritonitis in cirrhosis: A combined prospective-retrospective study.

Alterations of the innate immunity contribute to the development of spontaneous bacterial peritonitis (SBP) in liver cirrhosis. Given its role in immune signaling, antimicrobial function, and macrophage differentiation, we hypothesized that genetic polymorphisms of TRAF6 modulate the risk of SBP. Thus, we determined theTRAF6 haplotype in 432 patients with cirrhosis and ascites using the haplotype-tagging single nucleotide polymorphisms rs331457 and rs5030419. In addition, peritoneal macrophages were immunomagnetically isolated and characterized. Overall, 122 (28%) patients had an episode of SBP. In the combined prospective-retrospective analysis the frequency of SBP differed between the four haplotypes (P = 0.014) and was the highest in 102 patients carrying the rs331457 but not the rs5030419 variant, when compared to other haplotypes (odds ratio 1.95 [1.22-3.12]) or to the wild-type (odds ratio 1.71 [1.04-2.82]). This association was confirmed in multivariate logistic regression (adjusted odds ratio 2.00 [1.24-3.22]) and in prospective sensitivity analysis (hazard ratio 2.09 [1.08-4.07]; P = 0.03). The risk haplotype was associated with lower concentrations of the immune activation marker soluble CD87 in ascitic fluid and with a decreased expression of IL-6 and CXCL8 in isolated peritoneal macrophages. In conclusion, genetic polymorphisms of TRAF6 are associated with decreased peritoneal immune activation and an increased risk of SBP.

Reduced monocyte adhesion to aortae of diabetic plasminogen activator inhibitor-1 knockout mice.

OBJECTIVE AND DESIGN: To determine the requirement of plasminogen activator inhibitor-1-knockout (PAI-1) for monocyte adhesion in animals and cells under diabetic conditions. METHODS AND SUBJECTS: Monocyte adhesion assay, enzyme-linked immunosorbent assay, and Western blotting were used in analyzing samples from PAI-1-knockout (PAI-1-KO) mice or cultured human umbilical vein endothelial cells (HUVEC). TREATMENTS: Diabetes in PAI-1-KO and wild-type mice was induced by intraperitoneal injection of streptozotocin (STZ). HUVEC was transfected with short interference RNA (siRNA) against PAI-1, tumor necrosis factor-α (TNFα), or toll-like receptor (TLR4), and then was treated with glycated low-density lipoproteins (glyLDL). RESULTS: The adhesion of monocytes to aortic intima was reduced in PAI-1-KO mice, which was associated with decreased levels of TNFα and monocyte chemotactic protein-1 (MCP-1) in plasma and cardiovascular tissue, and increased abundances of urokinase plasminogen activator (uPA) and uPA receptor (uPAR) in cardiovascular tissue compared to wild-type mice. Significant reductions in monocyte adhesion, inflammatory, and fibrinolytic regulators were detected in cardiovascular tissue or plasma in diabetic PAI-1-KO mice compared to wild-type diabetic mice. Transfection of PAI-1, TNFα or TLR4 siRNA to HUVEC inhibited glyLDL-induced monocyte adhesion to EC. PAI-1 siRNA inhibited the abundances of TLR4 and TNFα in EC. CONCLUSION: The findings suggest that PAI-1 is required for diabetes-induced monocyte adhesion via interactions with uPA/uPAR, and it also regulates TLR4 and TNFα expression in vascular EC. Inhibition of PAI-1 potentially reduces vascular inflammation under diabetic condition.

An ELISA method detecting the active form of suPAR.

Urokinase plasminogen activator receptor (uPAR) exists in a number of formats in human plasma, including soluble uPAR (suPAR) and uPAR fragments. We developed an ELISA method to detect specifically the active form suPAR, which binds to its natural ligand uPA. The intra CV and inter CV of this ELISA assay is 8.5% and 9.6% respectively, and the assay can recover 99.74% of added recombinant suPAR from 10% plasma. This assay is quite sensitive, capable of detecting down to 15pg/ml of suPAR, and can measure suPAR concentrations in the range of 0.031-8ng/ml with high linear relationship. Plasma samples from pregnant women were also measured for the active form of suPAR with this assay, giving an averaged level of 1.39ng/ml, slightly higher than the level of pooled plasma from healthy donors (0.96ng/ml). This study demonstrates the feasibility to measure the active form of suPAR, which will likely have value in clinical applications.

Urokinase receptor-deficient mice mount an innate immune response to and clarify respiratory viruses as efficiently as wild-type mice.

The plasminogen activator receptor (uPAR) is required for lung infiltration by innate immune cells in respiratory bacterial infections. In order to verify if this held true for respiratory viruses, wild type (WT) and uPAR knockout (uPAR(-/-)) mice were inoculated intranasally with the human respiratory syncytial virus (HRSV) and the influenza A virus. At several days post-infection (dpi), viral titers in the lungs were determined while cell infiltrates in the bronchoalveolar lavage (BAL) were analyzed by flow cytometry. In the case of influenza A, body weight loss and mortality were also monitored. Only minor differences were observed between infected WT and uPAR(-/-) mice, primarily in influenza virus replication and pathology. These results indicate that uPAR does not play a major role in limiting virus replication or in orchestrating the innate immune response against HRSV or influenza infections in mice. This suggests that there are fundamental differences in the immune control of the viral infections studied here and those caused by bacteria.

uPAR-targeted multimodal tracer for pre- and intraoperative imaging in cancer surgery.

Pre- and intraoperative diagnostic techniques facilitating tumor staging are of paramount importance in colorectal cancer surgery. The urokinase receptor (uPAR) plays an important role in the development of cancer, tumor invasion, angiogenesis, and metastasis and over-expression is found in the majority of carcinomas. This study aims to develop the first clinically relevant anti-uPAR antibody-based imaging agent that combines nuclear (111In) and real-time near-infrared (NIR) fluorescent imaging (ZW800-1). Conjugation and binding capacities were investigated and validated in vitro using spectrophotometry and cell-based assays. In vivo, three human colorectal xenograft models were used including an orthotopic peritoneal carcinomatosis model to image small tumors. Nuclear and NIR fluorescent signals showed clear tumor delineation between 24h and 72h post-injection, with highest tumor-to-background ratios of 5.0 ± 1.3 at 72h using fluorescence and 4.2 ± 0.1 at 24h with radioactivity. 1-2 mm sized tumors could be clearly recognized by their fluorescent rim. This study showed the feasibility of an uPAR-recognizing multimodal agent to visualize tumors during image-guided resections using NIR fluorescence, whereas its nuclear component assisted in the pre-operative non-invasive recognition of tumors using SPECT imaging. This strategy can assist in surgical planning and subsequent precision surgery to reduce the number of incomplete resections.

Stabilizing a flexible interdomain hinge region harboring the SMB binding site drives uPAR into its closed conformation.

The urokinase-type plasminogen activator receptor (uPAR) is a multidomain glycolipid-anchored membrane protein, which facilitates extracellular matrix remodeling by focalizing plasminogen activation to cell surfaces via its high-affinity interaction with uPA. The modular assembly of its three LU (Ly6/uPAR-like) domains is inherently flexible and binding of uPA drives uPAR into its closed conformation, which presents the higher-affinity state for vitronectin thus providing an allosteric regulatory mechanism. Using a new class of epitope-mapped anti-uPAR monoclonal antibodies (mAbs), we now demonstrate that the reciprocal stabilization is indeed also possible. By surface plasmon resonance studies, we show that these mAbs and vitronectin have overlapping binding sites on uPAR and that they share Arg91 as hotspot residue in their binding interfaces. The crystal structure solved for one of these uPAR·mAb complexes at 3.0Å clearly shows that this mAb preselects the closed uPAR conformation with an empty but correctly assembled large hydrophobic binding cavity for uPA. Accordingly, these mAbs inhibit the uPAR-dependent lamellipodia formation and migration on vitronectin-coated matrices irrespective of the conformational status of uPAR and its occupancy with uPA. This is the first study to the best of our knowledge, showing that the dynamic assembly of the three LU domains in uPARwt can be driven toward the closed form by an external ligand, which is not engaging the hydrophobic uPA binding cavity. As this binding interface is also exploited by the somatomedin B domain of vitronectin, therefore, this relationship should be taken into consideration when exploring uPAR-dependent cell adhesion and migration in vitronectin-rich environments.

Host response biomarker in sepsis: suPAR detection.

Recent studies of our group have shown that suPAR may complement APACHE II score for risk assessment in sepsis. suPAR may be measured in serum of patients by an enzyme immunosorbent assay developed by Virogates (suPARnostic™). Production of suPAR from circulating neutrophils and monocytes may be assessed after isolation of neutrophils and monocytes and ex vivo culture. This is followed by measurement of suPAR in culture supernatants.

TGF-ß1, but not bone morphogenetic proteins, activates Smad1/5 pathway in primary human macrophages and induces expression of proatherogenic genes.

Macrophages are responsible for the control of inflammation and healing, and their malfunction results in cardiometabolic disorders. TGF-ß is a pleiotropic growth factor with dual (protective and detrimental) roles in atherogenesis. We have previously shown that in human macrophages, TGF-ß1 activates Smad2/3 signaling and induces a complex gene expression program. However, activated genes were not limited to known Smad2/3-dependent ones, which prompted us to study TGF-ß1-induced signaling in macrophages in detail. Analysis of Id3 regulatory sequences revealed a novel enhancer, located between +4517 and 4662 bp, but the luciferase reporter assay demonstrated that this enhancer is not Smad2/3 dependent. Because Id3 expression is regulated by Smad1/5 in endothelial cells, we analyzed activation of Smad1/5 in macrophages. We demonstrate here for the first time, to our knowledge, that TGF-ß1, but not BMPs, activates Smad1/5 in macrophages. We show that an ALK5/ALK1 heterodimer is responsible for the induction of Smad1/5 signaling by TGF-ß1 in mature human macrophages. Activation of Smad1/5 by TGF-ß1 induces not only Id3, but also HAMP and PLAUR, which contribute to atherosclerotic plaque vulnerability. We suggest that the balance between Smad1/5- and Smad2/3-dependent signaling defines the outcome of the effect of TGF-ß on atherosclerosis where Smad1/5 is responsible for proatherogenic effects, whereas Smad2/3 regulate atheroprotective effects of TGF-ß.

Prognostic impact of urokinase-type plasminogen activator system components in clear cell renal cell carcinoma patients without distant metastasis.

BACKGROUND: Members of the urokinase-type plasminogen activator (uPA) system including uPA, its receptor uPAR and the plasminogen activator inhibitor 1 (PAI-1) play an important role in tumour invasion and progression in a variety of tumour types. Since the majority of clear cell renal cell carcinoma (ccRCC) shows distant metastasis at time of diagnosis or later, the interplay of uPA, uPAR and PAI-1 might be of importance in this process determining the patients' outcome. METHODS: Corresponding pairs of malignant and non-malignant renal tissue specimens were obtained from 112 ccRCC patients without distant metastasis who underwent tumour nephrectomy. Tissue extracts prepared from fresh-frozen tissue samples by detergent extraction were used for the determination of antigen levels of uPA, uPAR and PAI-1 by ELISA. Antigen levels were normalised to protein concentrations and expressed as ng per mg of total protein. RESULTS: Antigen levels of uPA, uPAR, and PAI-1 correlated with each other in the malignant tissue specimens (rs=0.51-0.65; all P<0.001). Antigen levels of uPA system components were significantly higher in tissue extracts of non-organ confined tumours (pT3+4) compared to organ-confined tumours (pT1+2; all P<0.05). Significantly elevated levels of uPAR and PAI-1 were also observed in high grade ccRCC. When using median antigen levels as cut-off points, all three uPA system factors were significant predictors for disease-specific survival (DSS) in univariate Cox's regression analyses. High levels of uPA and uPAR remained independent predictors for DSS with HR=2.86 (95% CI 1.07-7.67, P=0.037) and HR=4.70 (95% CI 1.51-14.6, P=0.008), respectively, in multivariate Cox's regression analyses. A combination of high antigen levels of uPA and/or uPAR further improved the prediction of DSS in multivariate analysis (HR=14.5, 95% CI 1.88-111.1, P=0.010). Moreover, high uPA and/or uPAR levels defined a patient subgroup of high risk for tumour-related death in ccRCC patients with organ-confined disease (pT1+2) (HR=9.83, 95% CI 1.21-79.6, P=0.032). CONCLUSIONS: High levels of uPA and uPAR in tumour tissue extracts are associated with a significantly shorter DSS of ccRCC patients without distant metastases.

Imaging the urokinase plasminongen activator receptor in preclinical breast cancer models of acquired drug resistance.

Subtype-targeted therapies can have a dramatic impact on improving the quality and quantity of life for women suffering from breast cancer. Despite an initial therapeutic response, cancer recurrence and acquired drug-resistance are commonplace. Non-invasive imaging probes that identify drug-resistant lesions are urgently needed to aid in the development of novel drugs and the effective utilization of established therapies for breast cancer. The protease receptor urokinase plasminogen activator receptor (uPAR) is a target that can be exploited for non-invasive imaging. The expression of uPAR has been associated with phenotypically aggressive breast cancer and acquired drug-resistance. Acquired drug-resistance was modeled in cell lines from two different breast cancer subtypes, the uPAR negative luminal A subtype and the uPAR positive triple negative subtype cell line MDA-MB-231. MCF-7 cells, cultured to be resistant to tamoxifen (MCF-7 TamR), were found to significantly over-express uPAR compared to the parental cell line. uPAR expression was maintained when resistance was modeled in triple-negative breast cancer by generating doxorubicin and paclitaxel resistant MDA-MB-231 cells (MDA-MB-231 DoxR and MDA-MB-231 TaxR). Using the antagonistic uPAR antibody 2G10, uPAR was imaged in vivo by near-infrared (NIR) optical imaging and (111)In-single photon emission computed tomography (SPECT). Tumor uptake of the (111)In-SPECT probe was high in the three drug-resistant xenografts (> 46 %ID/g) and minimal in uPAR negative xenografts at 72 hours post-injection. This preclinical study demonstrates that uPAR can be targeted for imaging breast cancer models of acquired resistance leading to potential clinical applications.

Identification of a new epitope in uPAR as a target for the cancer therapeutic monoclonal antibody ATN-658, a structural homolog of the uPAR binding integrin CD11b (αM).

The urokinase plasminogen activator receptor (uPAR) plays a role in tumor progression and has been proposed as a target for the treatment of cancer. We recently described the development of a novel humanized monoclonal antibody that targets uPAR and has anti-tumor activity in multiple xenograft animal tumor models. This antibody, ATN-658, does not inhibit ligand binding (i.e. uPA and vitronectin) to uPAR and its mechanism of action remains unclear. As a first step in understanding the anti-tumor activity of ATN-658, we set out to identify the epitope on uPAR to which ATN-658 binds. Guided by comparisons between primate and human uPAR, epitope mapping studies were performed using several orthogonal techniques. Systematic site directed and alanine scanning mutagenesis identified the region of aa 268-275 of uPAR as the epitope for ATN-658. No known function has previously been attributed to this epitope Structural insights into epitope recognition were obtained from structural studies of the Fab fragment of ATN-658 bound to uPAR. The structure shows that the ATN-658 binds to the DIII domain of uPAR, close to the C-terminus of the receptor, corroborating the epitope mapping results. Intriguingly, when bound to uPAR, the complementarity determining region (CDR) regions of ATN-658 closely mimic the binding regions of the integrin CD11b (αM), a previously identified uPAR ligand thought to be involved in leukocyte rolling, migration and complement fixation with no known role in tumor progression of solid tumors. These studies reveal a new functional epitope on uPAR involved in tumor progression and demonstrate a previously unrecognized strategy for the therapeutic targeting of uPAR.

Role of epithelial mesenchymal transition (EMT) in chronic obstructive pulmonary disease (COPD).

Small airway fibrosis is the main contributor to physiological airway dysfunction in COPD. One potential mechanism contributing to small airway fibrosis is epithelial mesenchymal transition (EMT). When associated with angiogenesis (so called EMT-Type-3) it may well also be the link with the development of cancer, which is closely associated with COPD and predominantly in large airways. In a recent study published in Respiratory Research, Qin Wang and colleagues investigated the role of urokinase plasminogen activator receptor (uPAR) in EMT in small airway epithelium of COPD patients. However, there are some issues with the paper which we wish to comment on.