Targeting the Urokinase-Type Plasminogen Activator Receptor (uPAR) in Human Diseases With a View to Non-invasive Imaging and Therapeutic Intervention

In silico screening of natural products as uPAR inhibitors via multiple structure-based docking and molecular dynamics simulations

Cancer remains one of the most pressing challenges to global healthcare, exerting a significant impact on patient life expectancy. Cancer metastasis is a critical determinant of the lethality and treatment resistance of cancer. The urokinase-type plasminogen activator receptor (uPAR) shows great potential as a target for anticancer and antimetastatic therapies. In this work, we aimed to identify potential uPAR inhibitors by structural dynamics-based virtual screenings against a natural product library on four representative apo-uPAR structural models recently derived from long-timescale molecular dynamics (MD) simulations. Fifteen potential inhibitors (NP1-NP15) were initially identified through molecular docking, consensus scoring, and visual inspection. Subsequently, we employed MD-based molecular mechanics-generalized Born surface area (MM-GBSA) calculations to evaluate their binding affinities to uPAR. Structural dynamics analyses further indicated that all of the top 6 compounds exhibited stable binding to uPAR and interacted with the critical residues in the binding interface between uPAR and its endogenous ligand uPA, suggesting their potential as uPAR inhibitors by interrupting the uPAR-uPA interaction. We finally predicted the ADMET properties of these compounds. The natural products NP5, NP12, and NP14 with better binding affinities to uPAR than the uPAR inhibitors previously discovered by us were proven to be potentially orally active in humans. This work offers potential uPAR inhibitors that may contribute to the development of novel effective anticancer and antimetastatic therapeutics.

Dual modified ferritin nanocages for tumor-targeted and microenvironment-responsive drug delivery

Human heavy-chain ferritin (HFn) possesses a stable and uniform cage-like structure, tumor-targeting properties, self-assembly capabilities, and biocompatibility, rendering it an ideal candidate for drug delivery. Here, we developed a dual modified HFn-based nanocage (DFn) that targets the urokinase-type plasminogen activator receptor (uPAR) and, at the same time, is responsive to the tumor microenvironment for controlled extracellular drug release. This DFn was used to co-encapsulate a photosensitizer (CPZ) and a hypoxia-activated prodrug (TPZ), creating the multifunctional nanoparticles C/T@DFn. In vitro cellular assays demonstrated that C/T@DFn significantly outperformed both unmodified HFn-based nanoparticles and its counterpart without the uPAR-targeting motif in inhibiting tumor cell survival, proliferation, and migration, and showed enhanced tumor cell spheroids penetration. In vivo studies further demonstrated the improved tumor-specific accumulation and antitumor efficacy of the loaded cargo in the DFn nanocages in comparison with wild-type HFn. This improved therapeutic effect is achieved through receptor-mediated targeting and tumor microenvironment-responsive release of the cargo from the DFn nanocages, resulting in synergistic action of CPZ and TPZ within the tumor tissue. Overall, this study introduces an ideal ferritin-based nanoplatform for the efficient co-delivery of therapeutic agents, offering a promising strategy for targeted tumor therapy.

Interface-driven structural evolution on diltiazem as novel uPAR inhibitors: from in silico design to in vitro evaluation

The urokinase-type plasminogen activator receptor (uPAR) emerges as a key target for anti-metastasis owing to its pivotal role in facilitating the invasive and migratory processes of cancer cells. Recently, we identified the uPAR-targeting anti-metastatic ability of diltiazem (22), a commonly used antihypertensive agent. Fine-tuning the chemical structures of known hits represents a vital branch of drug development. To develop novel anti-metastatic drugs, we performed an interface-driven structural evolution strategy on 22. The uPAR-targeting and anti-cancer abilities of this antihypertensive drug wereidentified by us recently. Based on in silico strategy, including extensive molecular dynamics (MD) simulations, hierarchical binding free energy predictions, and ADMET profilings, we designed, synthesized, and identified three new diltiazem derivatives (221-8, 221-57, and 221-68) as uPAR inhibitors. Indeed, all of these three derivatives exhibited uPAR-depending inhibitory activity against PC-3 cell line invasion at micromolar level. Particularly, derivatives 221-68 and 221-8 showed enhanced uPAR-dependent inhibitory activity against the tumor cell invasion compared to the original compound. Microsecond timesclae MD simulations demonstrated the optimized moiety of 221-68 and 221-8 forming more comprehensive interactions with the uPAR, highlighting the reasonability of our strategy. This work introduces three novel uPAR inhibitors, which not only pave the way for the development of effective anti-metastatic therapeutics, but also emphasize the efficacy and robustness of an in silico-based lead compound optimization strategy in drug design.

Targeting uPAR with an antibody-drug conjugate suppresses tumor growth and reshapes the immune landscape in pancreatic cancer models

Antibody-drug conjugates (ADCs) hold promise to advance targeted therapy of pancreatic ductal adenocarcinoma (PDAC), where the desmoplastic tumor stroma challenges effective treatment. Here, we explored the urokinase plasminogen activator receptor (uPAR) as a candidate ADC target in PDAC, harnessing its massive tumoral and stromal expression in this stroma-dense tumor. We generated a site-specific ADC offering high-affinity, cross-species reactivity, and efficient internalization of the anti-uPAR monoclonal antibody, FL1, carrying a potent anthracycline derivative (PNU-158692). In vitro, FL1-PNU exhibited potent and specific cytotoxicity against uPAR-expressing PDAC cell lines, stromal and immune cells, and bystander killing of uPAR-negative cells. In vivo, the ADC induced remission or sustained tumor regression and extended survival in xenograft models. In syngeneic orthotopic models, the antitumor effect promoted immunomodulation by enhancing infiltrating immune effectors and decreasing immunosuppressive cells. This study lays grounds for further exploring FL1-PNU as a putative clinical ADC candidate, potentially providing a promising therapeutic avenue for PDAC as a monotherapy or in combinatorial regimens.

Urokinase-Type Plasminogen Activator Receptor (uPAR) in Inflammation and Disease: A Unique Inflammatory Pathway Activator

The urokinase-type plasminogen activator receptor (uPAR) is a unique protease binding receptor, now recognized as a key regulator of inflammation. Initially, uPA/uPAR was considered thrombolytic (clot-dissolving); however, recent studies have demonstrated its predominant immunomodulatory functions in inflammation and cancer. The uPA/uPAR complex has a multifaceted central role in both normal physiological and also pathological responses. uPAR is expressed as a glycophosphatidylinositol (GPI)-linked receptor interacting with vitronectin, integrins, G protein-coupled receptors, and growth factor receptors within a large lipid raft. Through protein-to-protein interactions, cell surface uPAR modulates intracellular signaling, altering cellular adhesion and migration. The uPA/uPAR also modifies extracellular activity, activating plasminogen to form plasmin, which breaks down fibrin, dissolving clots and activating matrix metalloproteinases that lyse connective tissue, allowing immune and cancer cell invasion and releasing growth factors. uPAR is now recognized as a biomarker for inflammatory diseases and cancer; uPAR and soluble uPAR fragments (suPAR) are increased in viral sepsis (COVID-19), inflammatory bowel disease, and metastasis. Here, we provide a comprehensive overview of the structure, function, and current studies examining uPAR and suPAR as diagnostic markers and therapeutic targets. Understanding uPAR is central to developing diagnostic markers and the ongoing development of antibody, small-molecule, nanogel, and virus-derived immune-modulating treatments that target uPAR.

Gene Association Study of the Urokinase Plasminogen Activator and Its Receptor Gene in Alzheimer's Disease

Background

The role of the innate immune system has long been associated with Alzheimer's disease (AD). There is now accumulating evidence that the soluble Urokinase Plasminogen Activator Receptor pathway, and its genes, PLAU and PLAUR may be important in AD, and yet there have been few genetic association studies to explore this.

Objective

This study utilizes the DNA bank of the Brains for Dementia Research cohort to investigate the genetic association of common polymorphisms across the PLAU and PLAUR genes with AD.

Methods

TaqMan genotyping assays were used with standard procedures followed by association analysis in PLINK.

Results

No association was observed between the PLAU gene and AD; however, two SNPs located in the PLAUR gene were indicative of a trend towards association but did not surpass multiple testing significance thresholds.

Conclusions

Further genotyping studies and exploration of the consequences of these SNPs on gene expression and alternative splicing are warranted to fully uncover the role this system may have in AD.

Regulation of Peptidase Activity beyond the Active Site in Human Health and Disease

This comprehensive review addresses the intricate and multifaceted regulation of peptidase activity in human health and disease, providing a comprehensive investigation that extends well beyond the boundaries of the active site. Our review focuses on multiple mechanisms and highlights the important role of exosites, allosteric sites, and processes involved in zymogen activation. These mechanisms play a central role in shaping the complex world of peptidase function and are promising potential targets for the development of innovative drugs and therapeutic interventions. The review also briefly discusses the influence of glycosaminoglycans and non-inhibitory binding proteins on enzyme activities. Understanding their role may be a crucial factor in the development of therapeutic strategies. By elucidating the intricate web of regulatory mechanisms that control peptidase activity, this review deepens our understanding in this field and provides a roadmap for various strategies to influence and modulate peptidase activity.

Systemically Administered Anti-uPAR Antibody Plasma and Lung ELF Pharmacokinetics Characterized by Minimal Lung PBPK Model

Antibody-based therapeutics have recently gained keen attention for the treatment of pulmonary indications. However, systemically administered antibody exposure in the lungs needs to be better understood and remains a topic of interest. In this study, we evaluated the exposure of two different uPAR (urokinase-type plasminogen activator receptor) targeting full-length monoclonal IgGs in plasma and lung epithelial lining fluid (ELF) of mice after IP and IV administration. Antibody AK17 exhibited linear pharmacokinetics (PK) in plasma and ELF at 3 and 30 mg/kg single IV dose. The average plasma and ELF half-lives for AK17 and AK21 ranged between ~321-411 h and ~230-345 h, respectively, indicating sustained systemic and lung exposure of antibodies. The average ELF to the plasma concentration ratio of antibodies was ~0.01 and ~0.03 with IP and IV dosing, respectively, over 2 weeks post single dose. We simultaneously characterized plasma and ELF PK of antibody in mice by developing a minimal lung PBPK model for antibody. This model reasonably captured the plasma and ELF PK data while estimating three parameters. The model accounts for the convective transport of antibody into the tissues via blood and lymph flow. FcRn-mediated transcytosis was incorporated into the model for antibody distribution across the lung epithelial barrier. This model serves as a platform to predict the pulmonary PK of systemically administered antibodies and to support optimal dose selection for desired exposure in the lungs as the site of action.

Targeted imaging of uPAR expression in vivo with cyclic AE105 variants

A comprehensive literature reports on the correlation between elevated levels of urokinase-type plasminogen activator receptor (uPAR) and the severity of diseases with chronic inflammation including solid cancers. Molecular imaging is widely used as a non-invasive method to locate disease dissemination via full body scans and to stratify patients for targeted treatment. To date, the only imaging probe targeting uPAR that has reached clinical phase-II testing relies on a high-affinity 9-mer peptide (AE105), and several studies by positron emission tomography (PET) scanning or near-infra red (NIR) fluorescence imaging have validated its utility and specificity in vivo. While our previous studies focused on applying various reporter groups, the current study aims to improve uPAR-targeting properties of AE105. We successfully stabilized the small uPAR-targeting core of AE105 by constraining its conformational landscape by disulfide-mediated cyclization. Importantly, this modification mitigated the penalty on uPAR-affinity typically observed after conjugation to macrocyclic chelators. Cyclization did not impair tumor targeting efficiency of AE105 in vivo as assessed by PET imaging and a trend towards increased tracer uptake was observed. In future studies, we predict that this knowledge will aid development of new fluorescent AE105 derivatives with a view to optical imaging of uPAR to assist precision guided cancer surgery.

Plasminogen activator urokinase receptor as a diagnostic and prognostic biomarker in type 2 diabetic patients with cardiovascular disease

Introduction

Cardiovascular diseases are the main cause of death among type 2 diabetic patients. Higher levels of plasminogen activator urokinase receptor have been found to predict morbidity and mortality across acute and chronic diseases in the common populace. This study aims to explore the role of serum plasminogen activator urokinase receptor levels as a cardiometabolic risk factor among type 2 diabetic Iraqi patients.

Methods

Seventy type 2 diabetic patients (40 male and 30 female) (mean age: 46.20±7.56 years) participated in this study; 35 patients were with cardiovascular disease and 35 were without cardiovascular disease; their ages range was 40-55 years. In addition, 30 individuals who apparently healthy were selected as the control group.

Results

There were significant increases (P<0.05) in glycemic and lipid profiles in diabetic patients with cardiovascular disease as compared to those without cardiovascular disease and control group. The present results reveal high levels of plasminogen activator urokinase receptor (2500.72±12.36 ρg/mL versus 2255.32±10.15 ρg/mL) with OR=1.80, 95%CI 1.2, and P=0.0001 in type 2 diabetic patients with and without cardiovascular disease respectively as compared to healthy control (229.00±14.48 ρg/mL).

Conclusion

It has been concluded that serum plasminogen activator urokinase receptor showed higher levels among type 2 diabetic patients with cardiovascular disease, this revealed it's critical role in cardiac disease. Therefore, it could be considered a more sensitive biomarker for the detection of cardiovascular events among type 2 diabetic patients who were at high-risk.

Recent Advances in Targeting the Urokinase Plasminogen Activator with Nanotherapeutics

The aberrant proteolytic landscape of the tumor microenvironment is a key contributor of cancer progression. Overexpression of urokinase plasminogen activator (uPA) and/or its associated cell-surface receptor (uPAR) in tumor versus normal tissue is significantly associated with worse clinicopathological features and poorer patient survival across multiple cancer types. This is linked to mechanisms that facilitate tumor cell invasion and migration, via direct and downstream activation of various proteolytic processes that degrade the extracellular matrix─ultimately leading to metastasis. Targeting uPA has thus long been considered an attractive anticancer strategy. However, poor bioavailability of several uPA-selective small-molecule inhibitors has limited early clinical progress. Nanodelivery systems have emerged as an exciting method to enhance the pharmacokinetic (PK) profile of existing chemotherapeutics, allowing increased circulation time, improved bioavailability, and targeted delivery to tumor tissue. Combining uPA inhibitors with nanoparticle-based delivery systems thus offers a remarkable opportunity to overcome existing PK challenges associated with conventional uPA inhibitors, while leveraging potent candidates into novel targeted nanotherapeutics for an improved anticancer response in uPA positive tumors.

PLAUR splicing pattern in hereditary angioedema patients' monocytes and macrophages

BACKGROUND

The PLAUR gene encodes the urokinase-like plasminogen activator receptor (uPAR) and may undergo alternative splicing. Excluding cassette exons 3, 5 and 6 from the transcript results in truncated protein variants whose precise functions have not been elucidated yet. The PLAUR gene is one of several expressed in myeloid cells, where uPAR participates in different cellular processes, including the contact activation system and kallikrein-kinin system, which play an important role in hereditary angioedema (HAE) pathogenesis. A hypothesis about the PLAUR splicing pattern impact on HAE severity was tested.

METHODS AND RESULTS

The RT-PCR quantified by capillary electrophoresis was used. Although no significant difference in alternative transcript frequency was observed between healthy volunteers and HAE patients, a significant increase in all cassette exon inclusion variants was revealed during monocyte-to-macrophage differentiation.

CONCLUSIONS

PLAUR alternative splicing in monocytes and macrophages neither was different between HAE patients and healthy controls, nor reflected disease severity. However, the results showed an PLAUR splicing pattern was changing during monocyte-to-macrophage differentiation, but the significance of these changes is unknown and awaits future clarification.

Structural Dynamics-Driven Discovery of Anticancer and Antimetastatic Effects of Diltiazem and Glibenclamide Targeting Urokinase Receptor

Diltiazem and glibenclamide are commonly used hypotensive and antidiabetic drugs. This study reports the discovery of the potential antitumor and antimetastatic effects of these two drugs using a structural dynamics-driven virtual screening targeting urokinase receptor (uPAR). Owing to uPAR's high flexibility, currently resolved crystal structures of uPAR, all in ligand-bound states, provide limited representations of its physiological conformation. To improve the accuracy of screening, we performed a long-timescale molecular dynamics simulation and obtained the representative conformations of apo-uPAR as the targets for our screening. Experimentally, we demonstrated that diltiazem and glibenclamide bound uPAR with K_D values in the micromolar range. In addition, both compounds effectively suppressed tumor growth and metastasis in a uPAR-dependent manner in vitro and in vivo. This work not only provides two potent uPAR inhibitors but also reports a proof-of-concept study on the potential off-label antitumor and antimetastatic uses of diltiazem and glibenclamide.

Plasminogen activator, urokinase enhances the migration, invasion, and proliferation of colorectal cancer cells by activating the Src/ERK pathway

Background

This paper aims to explore the effects of plasminogen activator, urokinase (PLAU) expression on the migration, invasion, and proliferation of colorectal cancer (CRC) cells and to preliminarily analyze its possible mechanism, thereby laying a foundation for the research on potential biological targets of CRC.

Methods

CRC-related mRNA was screened in Gene Expression Omnibus (GEO) database (https://www.ncbi.nlm.nih.gov/gds/). Differentially expressed genes (DEGs) were obtained for functional enrichment analysis. The enriched pathway and key involved functional gene were screened for further in vitro and in vivo analysis CRC cells were transfected with PLAU-NC (negative control), PLAU-mimic, and PLAU-inhibitor for 48 h and divided into the above groups for later studies. The migration, invasion, and proliferation capacities of CRC cells were detected using wound healing, Transwell, and colony formation assays, respectively. The Src inhibitor saracatinib (AZD0530) was added to the PLAU-NC and PLAU-mimic groups, and the expression levels of Src/extracellular signal-regulated kinase (ERK) pathway-, migration-, invasion-, and proliferation-related proteins were detected by Western blotting.

Results

The results showed that after upregulation of PLAU, the number of CRC cells (SW480) that migrated to the center of the wound significantly increased, the number of cells that migrated and invaded through the basement membrane increased in the PLAU-mimic group, and the number of colonies also increased. These results suggest that increasing PLAU expression promotes the migration, invasion, and proliferation of CRC cells. At the same time, the molecular mechanism of PLAU in CRC cells was investigated by downregulating the protein expression of Src combined with the results of the bioinformatics analysis. Western blotting revealed that the protein expressions of phosphorylated Src (p-Src) and phosphorylated ERK (p-ERK) in SW480 and SW620 cells increased significantly in the PLAU-mimic group compared with the PLAU-NC group, while the results were the opposite in the PLAU-inhibitor group. After being treated with saracatinib, we observed significantly decreased protein levels of p-ERK, matrix metallopeptidase 2 (MMP-2), MMP-3, MMP-9, Cyclin D1, and Cyclin A2 in the SW480 cells.

Conclusions

In conclusion, PLAU affects the migration, invasion, and proliferation of CRC cells by activating the Src/ERK pathway.

Urokinase-type plasminogen activator receptor (uPAR) assessed by liquid biopsies and PET/CT for prognostication in head and neck cancer patients

Strong prognostic biomarkers are lacking regarding the stratification of treatment and surveillance regimens in head and neck squamous cell carcinoma (HNSCC). The study aimed to assess the prognostic value of soluble urokinase-type plasminogen activator receptor in plasma (suPAR) compared to evaluation by uPAR-positron-emission-tomography (PET) in HNSCC patients. Plasma from 19 controls and 49 HNSCC patients referred to curatively intended radiotherapy (2017-2021) was collected pre-treatment and post-treatment (n = 37). Information on uPAR-PET was available from previous evaluation. Patient median suPAR was significantly higher pre- and post-treatment compared to controls (p = 0.013, p = 0.003) and increased significantly during radiotherapy (p = 0.003). Pre-treatment suPAR did not predict survival outcomes. Post-treatment suPAR significantly predicted RFS (HR = 6.67 (95% CI 1.44-30.9) p = 0.015), but not OS (HR = 3.29 (95% CI 0.882-12.3) p = 0.076) in univariate analysis. RFS prediction was maintained for post-treatment suPAR in multivariate analysis, including TNM-stage (HR = 6.62 (95% CI 1.40-31.4) p = 0.017). Pre-treatment uPAR-PET/CT and post-treatment suPAR was available in 24 patients. High uPAR-estimates on both modalities was significantly associated with poor RFS compared to patients with low uPAR-estimates (log-rank, p = 0.008). Patients with discordant uPAR-estimates (one-low/one-high) were at intermediate risk, although non-significant (p = 0.131). In conclusion, pre-treatment suPAR did not predict RFS or OS. Pre-treatment uPAR-PET and post-treatment suPAR predicted RFS.

Clinical Efficacy of Xueshuantong plus Urokinase in the Treatment of Sudden Deafness

Objective

To investigate the clinical effect of Xueshuantong combined with urokinase in the treatment of sudden deafness.

Methods

A total of 90 patients with sudden deafness who were treated in South China Hospital affiliated to Shenzhen University from June 2019 to August 2020 were recruited and assigned (1 : 1) into the control group (n = 45, urokinase) and the experimental group (n = 45, Xueshuantong plus urokinase) according to the different treatment methods. The clinical treatment effect, the degree of tinnitus, the average auditory valve of the damaged frequency, and the changes in hemorheology (plasma viscosity, whole blood high-shear reduced viscosity, whole blood low-shear reduced viscosity, hematocrit, and fibrinogen) were compared between the two groups of patients.

Results

The treatment with urokinase and Xueshuangtong injection in the experimental group resulted in a significantly higher clinical treatment effect when compared with the treatment in the control group (P < 0.05). After treatment, the degree of tinnitus and the average auditory valve of the damaged frequency in the experimental group were significantly lower than those in the control group (P < 0.05). The levels of hemorheology (plasma viscosity, whole blood high-shear reduced viscosity, whole blood low-shear reduced viscosity, hematocrit, and fibrinogen) in the experimental group after treatment were significantly lower than those in the control group (P < 0.05).

Conclusion

The clinical effect of Xueshuantong combined with urokinase in the treatment of patients with sudden deafness is remarkable, and it can effectively improve the hearing level and hemorheology-related indexes of patients, and it thus merits clinical application.

Therapeutic Strategies Targeting Urokinase and Its Receptor in Cancer

Several studies have ascertained that uPA and uPAR do participate in tumor progression and metastasis and are involved in cell adhesion, migration, invasion and survival, as well as angiogenesis. Increased levels of uPA and uPAR in tumor tissues, stroma and biological fluids correlate with adverse clinic-pathologic features and poor patient outcomes. After binding to uPAR, uPA activates plasminogen to plasmin, a broad-spectrum matrix- and fibrin-degrading enzyme able to facilitate tumor cell invasion and dissemination to distant sites. Moreover, uPAR activated by uPA regulates most cancer cell activities by interacting with a broad range of cell membrane receptors. These findings make uPA and uPAR not only promising diagnostic and prognostic markers but also attractive targets for developing anticancer therapies. In this review, we debate the uPA/uPAR structure-function relationship as well as give an update on the molecules that interfere with or inhibit uPA/uPAR functions. Additionally, the possible clinical development of these compounds is discussed.

The Urokinase Receptor (uPAR) as a "Trojan Horse" in Targeted Cancer Therapy: Challenges and Opportunities

Simple Summary

Discovered more than three decades ago, the urokinase-type plasminogen activator receptor (uPAR) has now firmly established itself as a versatile molecular target holding promise for the treatment of aggressive malignancies. The copious abundance of uPAR in virtually all human cancerous tissues versus their healthy counterparts has fostered a gradual shift in the therapeutic landscape targeting this receptor from function inhibition to cytotoxic approaches to selectively eradicate the uPAR-expressing cells by delivering a targeted cytotoxic insult. Multiple avenues are being explored in a preclinical setting, including the more innovative immune- or stroma targeting therapies. This review discusses the current state of these strategies, their potentialities, and challenges, along with future directions in the field of uPAR targeting.

Abstract

One of the largest challenges to the implementation of precision oncology is identifying and validating selective tumor-driving targets to enhance the therapeutic efficacy while limiting off-target toxicity. In this context, the urokinase-type plasminogen activator receptor (uPAR) has progressively emerged as a promising therapeutic target in the management of aggressive malignancies. By focalizing the plasminogen activation cascade and subsequent extracellular proteolysis on the cell surface of migrating cells, uPAR endows malignant cells with a high proteolytic and migratory potential to dissolve the restraining extracellular matrix (ECM) barriers and metastasize to distant sites. uPAR is also assumed to choreograph multiple other neoplastic stages via a complex molecular interplay with distinct cancer-associated signaling pathways. Accordingly, high uPAR expression is observed in virtually all human cancers and is frequently associated with poor patient prognosis and survival. The promising therapeutic potential unveiled by the pleiotropic nature of this receptor has prompted the development of distinct targeted intervention strategies. The present review will focus on recently emerged cytotoxic approaches emphasizing the novel technologies and related limits hindering their application in the clinical setting. Finally, future research directions and emerging opportunities in the field of uPAR targeting are also discussed.