Targeting uPAR with antagonistic recombinant human antibodies in aggressive breast cancer

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.

Clinical significance, molecular characterization, and immune microenvironment analysis of coagulation-related genes in clear cell renal cell carcinoma

Background

Numerous studies have revealed a tight connection between tumor development and the coagulation system. However, the effects of coagulation on the prognosis and tumor microenvironment (TME) of clear cell renal cell carcinoma (ccRCC) remain poorly understood.

Methods

We employed the consensus clustering method to characterize distinct molecular subtypes associated with coagulation patterns. Subsequently, we examined variations in the overall survival (OS), genomic profiles, and TME characteristics between these subtypes. To develop a prognostic coagulation-related risk score (CRRS) model, we utilized the least absolute shrinkage and selection operator Cox regression and stepwise multivariate Cox regression analyses. We also created a nomogram to aid in the clinical application of the risk score, evaluating the relationships between the CRRS and the immune microenvironment, responsiveness to immunotherapy, and targeted treatment. The clinical significance of PLAUR and its biological function in ccRCC were also further analyzed.

Results

There were significant differences in clinical features, prognostic stratification, genomic variation, and TME characteristics between the two coagulation-related subtypes. We established and validated a CRRS using six coagulation-related genes that can be employed as an effective indicator of risk stratification and prognosis estimation for ccRCC patients. Significant variations in survival outcomes were observed between the high- and low-risk groups. The nomogram was proficient in predicting the 1-, 3-, and 5-year OS. Additionally, the CRRS emerged as a novel tool for evaluating the clinical effectiveness of immunotherapy and targeted treatments in ccRCC. Moreover, we confirmed upregulated PLAUR expression in ccRCC samples that was significantly correlated with poor patient prognosis. PLAUR knockdown notably inhibited ccRCC cell proliferation and migration.

Conclusion

Our data suggested that CRRS may be employed as a reliable predictive biomarker that can provide therapeutic benefits for immunotherapy and targeted therapy in ccRCC.

YY1 regulates the proliferation and invasion of triple-negative breast cancer via activating PLAUR

It is well-established that breast cancer is a highly prevalent malignancy among women, emphasizing the need to investigate mechanisms underlying its pathogenesis and metastasis. In this study, the Gene Expression Omnibus (GEO) database was utilized to conduct differential expression analysis in breast cancer and adjacent tissues. Upregulated genes were selected for prognostic analysis of breast cancer. The expression of urokinase plasminogen activator receptor (uPAR), also known as PLAUR, was assessed using RT-qPCR and western blot. Immunofluorescence staining was employed to determine PLAUR localization. Various cellular processes were analyzed, including proliferation, migration, invasion, apoptosis, and cell cycle. Bioinformatics analysis was used to predict transcription factors of PLAUR, which were subsequently validated in a double luciferase reporter gene experiment. Rescue experiments confirmed the impact of PLAUR on the proliferation, apoptosis, and migration of MDA-MB-231 cells. Furthermore, the effects of PLAUR were evaluated in an orthotopic tumor transplantation and lung metastasis nude mouse model. Our findings substantiated the critical involvement of PLAUR in the progression of triple-negative breast cancer (TNBC) in vitro and among TNBC patients with a poor prognosis. Additionally, we demonstrated Yin Yang-1 (YY1) as a notable transcriptional regulator of PLAUR, whose activation could transcriptionally enhance the proliferation and invasion capabilities of TNBC cells. We also identified the downstream mechanism of PLAUR associated with PLAU, focal adhesion kinase (FAK), and AKT. Overall, these findings offer a novel perspective on PLAUR as a potential therapeutic target for TNBC.

Perturbations in podocyte transcriptome and biological pathways induced by FSGS associated circulating factors

Background

Focal segmental glomerulosclerosis (FSGS) is frequently associated with heavy proteinuria and progressive renal failure requiring dialysis or kidney transplantation. However, primary FSGS also has a ~40% risk of recurrence of disease in the transplanted kidney (rFSGS). Multiple circulating factors have been identified to contribute to the pathogenesis of primary and rFSGS including soluble urokinase-type plasminogen activator receptor (suPAR) and patient-derived CD40 autoantibody (CD40autoAb). However, the downstream effector pathways specific to individual factors require further study. The tumor necrosis factor, TNF pathway activation by one or more circulating factors present in the sera of patients with FSGS has been supported by multiple studies.

Methods

A human in vitro model was used to study podocyte injury measured as the loss of actin stress fibers. Anti-CD40 autoantibody was isolated from FSGS patients (recurrent and non-recurrent) and control patients with ESRD due to non-FSGS related causes. Two novel human antibodies-anti-uPAR (2G10) and anti-CD40 antibody (Bristol Meyer Squibb, 986090) were tested for their ability to rescue podocyte injury. Podocytes treated with patient derived antibody were transcriptionally profiled using whole human genome microarray.

Results

Here we show that podocyte injury caused by sera from FSGS patients is mediated by CD40 and suPAR and can be blocked by human anti-uPAR and anti-CD40 antibodies. Transcriptomic studies to compare the molecules and pathways activated in response to CD40 autoantibody from rFSGS patients (rFSGS/CD40autoAb) and suPAR, identified unique inflammatory pathways associated with FSGS injury.

Conclusions

We identified several novel and previously described genes associated with FSGS progression. Targeted blockade of suPAR and CD40 pathways with novel human antibodies showed inhibition of podocyte injury in FSGS.

Multi-Targeted and On-Demand Non-Coding RNA Regulation Nanoplatform against Metastasis and Recurrence of Triple-Negative Breast Cancer

Dysregulation of microRNAs (miRs) is the hallmark of triple-negative breast cancer (TNBC), which is closely involved with its growth, metastasis, and recurrence. Dysregulated miRs are promising targets for TNBC therapy, however, targeted and accurate regulation of multiple disordered miRs in tumors is still a great challenge. Here, a multi-targeting and on-demand non-coding RNA regulation nanoplatform (MTOR) is reported to precisely regulate disordered miRs, leading to dramatical suppression of TNBC growth, metastasis, and recurrence. With the assistance of long blood circulation, ligands of urokinase-type plasminogen activator peptide and hyaluronan located in multi-functional shells enable MTOR to actively target TNBC cells and breast cancer stem cell-like cells (BrCSCs). After entering TNBC cells and BrCSCs, MTOR is subjected to lysosomal hyaluronidase-induced shell detachment, leading to an explosion of the TAT-enriched core, thereby enhancing nuclear targeting. Subsequently, MTOR could precisely and simultaneously downregulate microRNA-21 expression and upregulate microRNA-205 expression in TNBC. In subcutaneous xenograft, orthotopic xenograft, pulmonary metastasis, and recurrence TNBC mouse models, MTOR shows remarkably synergetic effects on the inhibition of tumor growth, metastasis, and recurrence due to its on-demand regulation of disordered miRs. This MTOR system opens a new avenue for on-demand regulation of disordered miRs against growth, metastasis, and recurrence of TNBC.

Effects of PEG-Linker Chain Length of Folate-Linked Liposomal Formulations on Targeting Ability and Antitumor Activity of Encapsulated Drug

Introduction

Ligand-conjugated liposomes are promising for the treatment of specific receptor-overexpressing cancers. However, previous studies have shown inconsistent results because of the varying properties of the ligand, presence of a polyethylene glycol (PEG) coating on the liposome, length of the linker, and density of the ligand.

Methods

Here, we prepared PEGylated liposomes using PEG-linkers of various lengths conjugated with folate and evaluated the effect of the PEG-linker length on the nanoparticle distribution and pharmacological efficacy of the encapsulated drug both in vitro and in vivo.

Results

When folate was conjugated to the liposome surface, the cellular uptake efficiency in folate receptor overexpressed KB cells dramatically increased compared to that of the normal liposome. However, when comparing the effect of the PEG-linker length in vitro, no significant difference between the formulations was observed. In contrast, the level of tumor accumulation of particles in vivo significantly increased when the length of the PEG-linker was increased. The tumor size was reduced by >40% in the Dox/FL-10K-treated group compared to that in the Dox/FL-2K- or 5K-treated groups.

Discussion

Our study suggests that as the length of PEG-linker increases, the tumor-targeting ability can be enhanced under in vivo conditions, which can lead to an increase in the antitumor activity of the encapsulated drug.

High-throughput optofluidic screening of single B cells identifies novel cross-reactive antibodies as inhibitors of uPAR with antibody-dependent effector functions

The urokinase-type plasminogen activator receptor (uPAR) is an essential regulator for cell signaling in tumor cell proliferation, adhesion, and metastasis. The ubiquitous nature of uPAR in many aggressive cancer types makes uPAR an attractive target for immunotherapy. Here, we present a rapid and successful workflow for developing cross-reactive anti-uPAR recombinant antibodies (rAbs) using high-throughput optofluidic screening of single B-cells from human uPAR-immunized mice. A total of 80 human and cynomolgus uPAR cross-reactive plasma cells were identified, and selected mouse VH/VL domains were linked to the trastuzumab (Herceptin®) constant domains for the expression of mouse-human chimeric antibodies. The resulting rAbs were characterized by their tumor-cell recognition, binding activity, and cell adhesion inhibition on triple-negative breast cancer cells. In addition, the rAbs were shown to enact antibody-dependent cellular cytotoxicity (ADCC) in the presence of either human natural killer cells or peripheral blood mononuclear cells, and were evaluated for the potential use of uPAR-targeting antibody-drug conjugates (ADCs). Three lead antibodies (11857, 8163, and 3159) were evaluated for their therapeutic efficacy in vivo and were shown to suppress tumor growth. Finally, the binding epitopes of the lead antibodies were characterized, providing information on their unique binding modes to uPAR. Altogether, the strategy identified unique cross-reactive antibodies with ADCC, ADC, and functional inhibitory effects by targeting cell-surface uPAR, that can be tested in safety studies and serve as potential immunotherapeutics.

Comprehensive analysis of the importance of PLAUR in the progression and immune microenvironment of renal clear cell carcinoma

Clear cell renal cell carcinoma (ccRCC) is a common type of kidney cancer with a high mortality rate, and the discovery of new therapeutic markers is essential to improve patient survival. The plasminogen activator urokinase receptor (PLAUR) plays key roles in tissue remodeling and extracellular matrix degradation, which contribute to invasion and metastasis, a major feature of tumor malignancy. The role of PLAUR in ccRCC pathology has not been deeply studied. In this study, we collected the mRNA expression data of 33 tumor types, each derived from human patients obtained from TCGA database, and comprehensively analyzed the correlation between the expression of PLAUR in tumors and prognosis. Then, we studied the relationship between PLAUR expression in ccRCC and specific clinical features of ccRCC patients. In addition, we analyzed the function and mechanism of PLAUR in ccRCC. Our results showed that PLAUR was significantly overexpressed in ccRCC and that both PLAUR levels and PLAUR methylation levels significantly correlated with poor prognosis. Our results also suggest that PLAUR is involved in the progression of ccRCC. The results of functional and mechanistic analysis of PLAUR showed that PLAUR is involved in inflammatory and immune-related pathways in ccRCC; other data showed that PLAUR expression may affect the infiltration of multiple immune cell types in ccRCC and that PLAUR levels were significantly and positively correlated with the expression of immune checkpoints. In conclusion, our findings suggest that high PLAUR expression can promote the progression of ccRCC to poor prognosis, and thus PLAUR may serve as both a potential marker for predicting macrophage infiltration and immune microenvironment status and as an important immunotherapy target for ccRCC.

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.

Urokinase-type plasminogen activator receptor (uPAR) as a therapeutic target in cancer

Urokinase-type plasminogen activator receptor (uPAR) is an attractive target for the treatment of cancer, because it is expressed at low levels in healthy tissues but at high levels in malignant tumours. uPAR is closely related to the invasion and metastasis of malignant tumours, plays important roles in the degradation of extracellular matrix (ECM), tumour angiogenesis, cell proliferation and apoptosis, and is associated with the multidrug resistance (MDR) of tumour cells, which has important guiding significance for the judgement of tumor malignancy and prognosis. Several uPAR-targeted antitumour therapeutic agents have been developed to suppress tumour growth, metastatic processes and drug resistance. Here, we review the recent advances in the development of uPAR-targeted antitumor therapeutic strategies, including nanoplatforms carrying therapeutic agents, photodynamic therapy (PDT)/photothermal therapy (PTT) platforms, oncolytic virotherapy, gene therapy technologies, monoclonal antibody therapy and tumour immunotherapy, to promote the translation of these therapeutic agents to clinical applications.

Comprehensive Analysis of Prognostic Microenvironment-Related Genes in Invasive Breast Cancer

Recent studies reveal that tumor microenvironment contributes to breast cancer (BRCA) development, progression, and therapeutic response. However, the contribution of the tumor microenvironment-related genes in routine diagnostic testing or therapeutic decision making for BRCA remains elusive. Immune/stromal/ESTIMATE scores calculated by the ESTIMATE algorithm quantify immune and stromal components in a tumor, and thus can reflect tumor microenvironment. To investigate the association of the tumor microenvironment-related genes with invasive BRCA prognosis, here we analyzed the immune/stromal/ESTIMATE scores in combination with The Cancer Genome Atlas (TCGA) database in invasive BRCA. We found that immune/stromal/ESTIMATE scores were significantly correlated with the invasive BRCA clinicopathological factors. Based on the immune/stromal/ESTIMATE scores, we extracted a series of differential expression genes (DEGs) related to the tumor microenvironment. Survival analysis was further performed to identify a list of high-frequency DEGs (HF-DEGs), which exhibited prognostic value in invasive BRCA. Importantly, consistent with the results of bioinformatics analysis, immunohistochemistry results showed that high SASH3 expression was associated with a good prognosis in invasive BRCA patients. Our findings suggest that the tumor microenvironment-related HF-DEGs identified in this study have prognostic values and may serve as potential biomarkers and therapeutic targets for invasive BRCA.

Immunotargeting of Nanocrystals by SpyCatcher Conjugation of Engineered Antibodies

Inorganic nanocrystals such as quantum dots (QDs) and upconverting nanoparticles (UCNPs) are uniquely suited for quantitative live-cell imaging and are typically functionalized with ligands to study specific receptors or cellular targets. Antibodies (Ab) are among the most useful targeting reagents owing to their high affinities and specificities, but common nanocrystal labeling methods may orient Ab incorrectly, be reversible or denaturing, or lead to Ab-NP complexes too large for some applications. Here, we show that SpyCatcher proteins, which bind and spontaneously form covalent isopeptide bonds with cognate SpyTag peptides, can conjugate engineered Ab to nanoparticle surfaces with control over stability, orientation, and stoichiometry. Compact SpyCatcher-functionalized QDs and UCNPs may be labeled with short-chain variable fragment Ab (scFv) engineered to bind urokinase-type plasminogen activator receptors (uPAR) that are overexpressed in many human cancers. Confocal imaging of anti-uPAR scFv-QD conjugates shows the antibody mediates specific binding and internalization by breast cancer cells expressing uPAR. Time-lapse imaging of photostable scFv-UCNP conjugates shows that Ab binding causes uPAR internalization with a ∼20 min half-life on the cell surface, and uPAR is internalized to endolysosomal compartments distinct from general membrane stains and without significant recycling to the cell surface. The controlled and stable conjugation of engineered Ab to NPs enables targeting of diverse receptors for live-cell study of their distribution, trafficking, and physiology.

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.

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

The interaction between the serine protease urokinase-type plasminogen activator (uPA) and its glycolipid-anchored receptor (uPAR) focalizes plasminogen activation to cell surfaces, thereby regulating extravascular fibrinolysis, cell adhesion, and migration. uPAR belongs to the Ly6/uPAR (LU) gene superfamily and the high-affinity binding site for uPA is assembled by a dynamic association of its three consecutive LU domains. In most human solid cancers, uPAR is expressed at the invasive areas of the tumor-stromal microenvironment. High levels of uPAR in resected tumors or shed to the plasma of cancer patients are robustly associated with poor prognosis and increased risk of relapse and metastasis. Over the years, a plethora of different strategies to inhibit uPA and uPAR function have been designed and investigated in vitro and in vivo in mouse models, but so far none have been implemented in the clinics. In recent years, uPAR-targeting with the intent of cytotoxic eradication of uPAR-expressing cells have nonetheless gained increasing momentum. Another avenue that is currently being explored is non-invasive imaging with specific uPAR-targeted reporter-molecules containing positron emitting radionuclides or near-infrared (NIR) florescence probes with the overarching aim of being able to: (i) localize disease dissemination using positron emission tomography (PET) and (ii) assist fluorescence guided surgery using optical imaging. In this review, we will discuss these advancements with special emphasis on applications using a small 9-mer peptide antagonist that targets uPAR with high affinity.

Development of AE147 Peptide-Conjugated Nanocarriers for Targeting uPAR-Overexpressing Cancer Cells

Purpose

An AE147 peptide-conjugated nanocarrier based on PEGylated liposomes was developed in order to target the metastatic tumors overexpressing urokinase-type plasminogen activator receptor (uPAR), which cancer progression via uPA signaling. Therefore, the AE147 peptide-conjugated nanocarrier system may hold the potential for active targeting of metastatic tumors.

Methods

The AE147 peptide, an antagonist of uPAR, was conjugated to the PEGylated liposomes for targeting metastatic tumors overexpressing uPAR. Docetaxel (DTX), an anticancer drug, was incorporated into the nanocarriers. The structure of the AE147-conjugated nanocarrier, its physicochemical properties, and in vivo biodistribution were evaluated.

Results

The DTX-loaded nanocarrier showed a spherical structure, a high drug-loading capacity, and a high colloidal stability. Drug carrying AE147 conjugates were actively taken up by the uPAR-overexpressing MDA-MB-231 cancer cells. In vivo animal imaging confirmed that the AE147-conjugated nanoparticles effectively accumulated at the sites of tumor metastasis.

Conclusion

The AE147-nanocarrier showed potential for targeting metastatic tumor cells overexpressing uPAR and as a nanomedicine platform for theragnosis applications. These results suggest that this novel nano-platform will facilitate further advancements in cancer therapy.

Phosphorylation of OGFOD1 by Cell Cycle-Dependent Kinase 7/9 Enhances the Transcriptional Activity of RNA Polymerase II in Breast Cancer Cells

Simple Summary

Among the causes of accelerating cancer properties, dysregulated transcription is considerably prominent in many cancers. However, it is difficult to target transcriptional machineries due to their fundamental importance. Compared to breast cancer cell lines, we found that OGFOD1 aggravates cancers by enhancing RNA polymerase II transcriptional activity and it is improved by cell cycle-dependent kinases. Overall, we uncovered the novel mechanism for how OGFOD1 maliciously functions in breast cancers, suggesting it as a rational cancer treatment target protein.

Abstract

2-oxoglutarate and iron-dependent oxygenase domain-containing protein 1 (OGFOD1) expression is upregulated in a variety of cancers and has been related to poor prognosis. However, despite this significance to cancer progression, the precise oncogenic mechanism of OGFOD1 is not understood. We demonstrated that OGFOD1 plays a role in enhancing the transcriptional activity of RNA polymerase II in breast cancer cells. OGFOD1 directly binds to the C-terminal domain of RNA polymerase II to alter phosphorylation status. The elimination of OGFOD1 resulted in decreased tumor development. Additionally, cell cycle-dependent kinase 7 and cell cycle-dependent kinase 9, critical enzymes for activating RNA polymerase II, phosphorylated serine 256 of OGFOD1, whereas a non-phosphorylated mutant OGFOD1 failed to enhance transcriptional activation and tumor growth. Consequently, OGFOD1 helps promote tumor growth by enhancing RNA polymerase II, whereas simultaneous phosphorylation of OGFOD1 by CDK enzymes is essential in stimulating RNA polymerase II-mediated transcription both in vitro and in vivo, and expression of target genes.

The use of a uPAR-targeted probe for photothermal cancer therapy prolongs survival in a xenograft mouse model of glioblastoma

The development of tumor-targeted probes that can efficiently reach cancerous tissue is an important focus of preclinical research. Photothermal cancer therapy (PTT) relies on light-absorbing molecules, which are directed towards tumor tissue and irradiated with an external source of light. This light is transformed into heat, causing localized hyperthermia and tumor death. The fluorescent probe indocyanine green (ICG) is already used as an imaging agent both preclinically and in clinical settings, but its use for PTT is yet to be fully exploited due to its short retention time and non-specific tumor targeting. Therefore, increasing ICG tumor uptake is necessary to improve treatment outcome. The urokinase-type plasminogen activator receptor, uPAR, is overexpressed in multiple tumor types. ICG-Glu-Glu-AE105, consisting of the uPAR-targeting peptide AE105 conjugated to ICG, has shown great potential for fluorescence-guided surgery. In this study, ICG-Glu-Glu-AE105 was evaluated as photothermal agent in a subcutaneous mouse model of human glioblastoma. We observed that the photothermal abilities of ICG-Glu-Glu-AE105 triggered high temperatures in the tumor during PTT, leading to tumor death and prolonged survival. This confirms the potential of ICG-Glu-Glu-AE105 as photothermal agent and indicates that it could be used as an add-on to the application of the probe for fluorescence-guided surgery.

Fibrinolytic System and Cancer: Diagnostic and Therapeutic Applications

Fibrinolysis is a crucial physiological process that helps to maintain a hemostatic balance by counteracting excessive thrombosis. The components of the fibrinolytic system are well established and are associated with a wide array of physiological and pathophysiological processes. The aberrant expression of several components, especially urokinase-type plasminogen activator (uPA), its cognate receptor uPAR, and plasminogen activator inhibitor-1 (PAI-1), has shown a direct correlation with increased tumor growth, invasiveness, and metastasis. As a result, targeting the fibrinolytic system has been of great interest in the field of cancer biology. Even though there is a plethora of encouraging preclinical evidence on the potential therapeutic benefits of targeting the key oncogenic components of the fibrinolytic system, none of them made it from “bench to bedside” due to a limited number of clinical trials on them. This review summarizes our existing understanding of the various diagnostic and therapeutic strategies targeting the fibrinolytic system during cancer.

Global Protease Activity Profiling Identifies HER2-Driven Proteolysis in Breast Cancer

Differential expression of extracellular proteases and endogenous protease inhibitors has been associated with distinct molecular subtypes of breast cancer. However, due to the tight post-translational regulation of protease activity, protease expression-level data alone are not sufficient to understand the role of proteases in malignant transformation. Therefore, we hypothesized that global profiles of extracellular protease activity could more completely reflect differences observed at the transcriptional level in breast cancer and that subtype-associated protease activity may be leveraged to identify specific proteases that play a functional role in cancer signaling. Here, we used a global peptide library-based approach to profile the activities of proteases within distinct breast cancer subtypes. Analysis of 3651 total peptide cleavages from a panel of well-characterized breast cancer cell lines demonstrated differences in proteolytic signatures between cell lines. Cell line clustering based on protease cleavages within the peptide library expanded upon the expected classification derived from transcriptional profiling. An isogenic cell line model developed to further interrogate proteolysis in the HER2 subtype revealed a proteolytic signature consistent with activation of TGF-β signaling. Specifically, we determined that a metalloprotease involved in TGF-β signaling, BMP1, was upregulated at both the protein (2-fold, P = 0.001) and activity (P = 0.0599) levels. Inhibition of BMP1 and HER2 suppressed invasion of HER2-expressing cells by 35% (P < 0.0001), compared to 15% (P = 0.0086) observed in cells where only HER2 was inhibited. In summary, through global identification of extracellular proteolysis in breast cancer cell lines, we demonstrate subtype-specific differences in protease activity and elucidate proteolysis associated with HER2-mediated signaling.

Development of inhibitors for uPAR: blocking the interaction of uPAR with its partners

Urokinase-type plasminogen activator receptor (uPAR) mediates a multitude of biological activities, has key roles in several clinical indications, including malignancies and inflammation, and, thus, has attracted intensive research over the past few decades. The pleiotropic functions of uPAR can be attributed to its interaction with an array of partners. Many inhibitors have been developed to intervene with the interaction of uPAR with these partners. Here, we review the development of these classes of uPAR inhibitor and their inhibitory mechanisms to promote the translation of these inhibitors to clinical applications.

Molecular imaging of the urokinase plasminogen activator receptor: opportunities beyond cancer

The urokinase plasminogen activator receptor (uPAR) plays a multifaceted role in almost any process where migration of cells and tissue-remodeling is involved such as inflammation, but also in diseases as arthritis and cancer. Normally, uPAR is absent in healthy tissues. By its carefully orchestrated interaction with the protease urokinase plasminogen activator and its inhibitor (plasminogen activator inhibitor-1), uPAR localizes a cascade of proteolytic activities, enabling (patho)physiologic cell migration. Moreover, via the interaction with a broad range of cell membrane proteins, like vitronectin and various integrins, uPAR plays a significant, but not yet completely understood, role in differentiation and proliferation of cells, affecting also disease progression. The implications of these processes, either for diagnostics or therapeutics, have received much attention in oncology, but only limited beyond. Nonetheless, the role of uPAR in different diseases provides ample opportunity to exploit new applications for targeting. Especially in the fields of oncology, cardiology, rheumatology, neurology, and infectious diseases, uPAR-targeted molecular imaging could offer insights for new directions in diagnosis, surveillance, or treatment options.

Tranexamic acid is an active site inhibitor of urokinase plasminogen activator

TXA is an active-site inhibitor of uPA. TXA attenuates MDA-MB-231 BAG cell migration and inhibits endogenous uPA activity.

The anti-tumoral potential of the saporin-based uPAR-targeting chimera ATF-SAP

The development of personalized therapies represents an urgent need owing to the high rate of cancer recurrence and systemic toxicity of conventional drugs. So far, targeted toxins have shown promising results as potential therapeutic compounds. Specifically, toxins conjugated to antibodies or fused to growth factors/enzymes have been largely demonstrated to selectively address and kill cancer cells. We investigated the anti-tumor potential of a chimeric recombinant fusion protein formed by the Ribosome Inactivating Protein saporin (SAP) and the amino-terminal fragment (ATF) of the urokinase-type plasminogen activator (uPA), whose receptor has been shown to be over-expressed on the surface of aggressive tumors. ATF-SAP was recombinantly produced by the P. pastoris yeast and its activity was assessed on a panel of bladder and breast cancer cell lines. ATF-SAP resulted to be highly active in vitro, as nano-molar concentrations were sufficient to impair viability on tumor cell lines. In contrast to untargeted toxins, the chimeric fusion protein displayed a significantly improved toxic effect in uPAR-expressing cells, demonstrating that the selective activity was due to the presence of the targeting moiety. Fibroblasts were not sensitive to ATF-SAP despite uPAR expression, indicating that cell-specific receptor-mediated internalization pathway(s) might be considered. The in vivo anti-tumor effect of the chimera was shown in a bladder cancer xenograft model. Current findings indicate ATF-SAP as a suitable anti-tumoral therapeutic option to cope with cancer aggressiveness, as a single treatment or in combination with traditional therapeutic approaches, to appropriately address the intra- and inter- tumor heterogeneity.

Exploitation of CD133 for the Targeted Imaging of Lethal Prostate Cancer

PURPOSE

Aggressive variant prostate cancer (AVPC) is a nonandrogen receptor-driven form of disease that arises in men in whom standard-of-care therapies have failed. Therapeutic options for AVPC are limited, and the development of novel therapeutics is significantly hindered by the inability to accurately quantify patient response to therapy by imaging. Imaging modalities that accurately and sensitively detect the bone and visceral metastases associated with AVPC do not exist.

EXPERIMENTAL DESIGN

This study investigated the transmembrane protein CD133 as a targetable cell surface antigen in AVPC. We evaluated the expression of CD133 by microarray and IHC analysis. The imaging potential of the CD133-targeted IgG (HA10 IgG) was evaluated in preclinical prostate cancer models using two different imaging modalities: near-infrared and PET imaging.

RESULTS

Evaluation of the patient data demonstrated that CD133 is overexpressed in a specific phenotype of AVPC that is androgen receptor indifferent and neuroendocrine differentiated. In addition, HA10 IgG was selective for CD133-expressing tumors in all preclinical imaging studies. PET imaging with [⁸⁹Zr]Zr-HA10 IgG revealed a mean %ID/g of 24.30 ± 3.19 in CD133-positive metastatic lesions as compared with 11.82 ± 0.57 in CD133-negative lesions after 72 hours (P = 0.0069). Ex vivo biodistribution showed similar trends as signals were increased by nearly 3-fold in CD133-positive tumors (P < 0.0001).

CONCLUSIONS

To our knowledge, this is the first study to define CD133 as a targetable marker of AVPC. Similarly, we have developed a novel imaging agent, which is selective for CD133-expressing tumors, resulting in a noninvasive PET imaging approach to more effectively detect and monitor AVPC.

Antibody-Drug Conjugates Targeting the Urokinase Receptor (uPAR) as a Possible Treatment of Aggressive Breast Cancer

A promising molecular target for aggressive cancers is the urokinase receptor (uPAR). A fully human, recombinant antibody that binds uPAR to form a stable complex that blocks uPA-uPAR interactions (2G10) and is internalized primarily through endocytosis showed efficacy in a mouse xenograft model of highly aggressive, triple negative breast cancer (TNBC). Antibody-drug conjugates (ADCs) of 2G10 were designed and produced bearing tubulin inhibitor payloads ligated through seven different linkers. Aldehyde tag technology was employed for linking, and either one or two tags were inserted into the antibody heavy chain, to produce site-specifically conjugated ADCs with drug-to-antibody ratios of either two or four. Both cleavable and non-cleavable linkers were combined with two different antimitotic toxins—MMAE (monomethylauristatin E) and maytansine. Nine different 2G10 ADCs were produced and tested for their ability to target uPAR in cell-based assays and a mouse model. The anti-uPAR ADC that resulted in tumor regression comprised an MMAE payload with a cathepsin B cleavable linker, 2G10-RED-244-MMAE. This work demonstrates in vitro activity of the 2G10-RED-244-MMAE in TNBC cell lines and validates uPAR as a therapeutic target for TNBC.

The multifaceted roles of tumor-associated proteases and harnessing their activity for prodrug activation

The role of proteases in cancer was originally thought to be limited to the breakdown of basement membranes and extracellular matrix (ECM), thereby promoting cancer cell invasion into surrounding normal tissues. It is now well understood that proteases play a much more complicated role in all stages of cancer progression and that not only tumor cells, but also stromal cells are an important source of proteases in the tumor microenvironment. Among all the proteolytic enzymes potentially associated with cancer, some proteases have taken on heightened importance due to their significant up-regulation and ability to participate at multiple stages of cancer progression and metastasis. In this review, we discuss some of the advances in understanding of the roles of several key proteases from different classes in the development and progression of cancer and the potential to leverage their upregulated activity for the development of novel targeted treatment strategies.

Knockdown of Notch1 inhibits nasopharyngeal carcinoma cell growth and metastasis via downregulation of CCL2, CXCL16, and uPA

Notch pathway is a highly conserved cell signaling system that plays very important roles in controlling multiple cell differentiation processes during embryonic and adult life. Multiple lines of evidence support the oncogenic role of Notch signaling in several human solid cancers; however, the pleiotropic effects and molecular mechanisms of Notch signaling inhibition on nasopharyngeal carcinoma (NPC) remain unclear. In this study, we evaluated Notch1 expression in NPC cell lines (CNE1, CNE2, SUNE1, HONE1, and HK1) by real-time quantitative PCR and Western blot analysis, and we found that CNE1 and CNE2 cells expressed a higher level of Notch1 compared with HONE1, SUNE1, and HK1 cells. Then Notch1 expression was specifically knocked down in CNE1 and CNE2 cells by Notch1 short hairpin RNA (shRNA). In Notch1 knockdown cells, cell proliferation, migration, and invasion were significantly inhibited. The epithelial-mesenchymal transition of tumor cells was reversed in Notch1-shRNA-transfected cells, accompanied by epithelioid-like morphology changes, increased protein levels of E-cadherin, and decreased expression of vimentin. In addition, knockdown of Notch1 markedly inhibited the expression of urokinase plasminogen activator (uPA) and its receptor uPAR, and chemokines C-C motif chemokine ligand 2 and C-X-C motif chemokine ligand 16, indicating that these factors are downstream targets of Notch1. Furthermore, deleting uPA expression had similar effects as Notch1. Finally, knockdown of Notch1 significantly diminished CNE1 cell growth in a murine model concomitant with inhibition of cell proliferation and induction of apoptosis. These results suggest that Notch1 may become a novel therapeutic target for the clinical treatment of NPC.

Surface-enhanced Raman spectroscopy (SERS) nanoprobes for ratiometric detection of cancer cells

A surface-enhanced Raman spectroscopic strategy is developed for ratiometric detection of cancer cells by quantifying the expression ratio of extracellular biomarkers.

An Exploratory Search for Potential Molecular Targets Responsive to the Probiotic Lactobacillus salivarius PS2 in Women With Mastitis: Gene Expression Profiling vs. Interindividual Variability

Probiotics constitute an attractive alternative in the battle against microbial infections. Oral administration of certain strains of lactobacilli isolated from human milk has resulted in an effective reduction of the bacterial load as well as an improvement of the mastitis-associated symptoms. Nevertheless, little is yet known about the potential molecular mechanisms and specific targets implicated in these effects. Transcriptomic profiling has been used to search for disease-associated and therapy-responsive molecules in different disorders and experimental models. We have applied for the first time a gene expression-based molecular approach to explore for potential targets responsive to intervention with a probiotic in: (i) breast milk somatic cells (n = 17) and (ii) blood leukocytes (n = 19). Women with mastitis ingested a new strain of lactobacilli, Lactobacillus salivarius PS2 (3 × capsules per day, each capsule contained ~9.5 log10 CFU) for 21 days. We applied Affymetrix microarrays and Taqman one-step quantitative reverse transcription PCR (RT-qPCR) to analyze and compare gene expression changes between samples pre- and post-treatment. Our results substantiate the involvement of inflammatory and cell-growth related pathways and genes in the breast milk somatic cells following the intake of L. salivarius PS2. Individual analyses of selected genes: (1) supported the upregulation of STC1 and IL19 and the downregulation of PLAUR and IFNGR1 in the somatic cells of the patients as potential targets responsive to the probiotic, (2) detected a lack of a relationship between the gene expression responses in the two types of cells, and (3) evidenced a substantial interindividual variability in the gene expression changes in both types of cells. Our study provides an insight into the essentiality of incorporating the study of tissue-specific interindividual molecular responsivity into future clinical intervention trials to further understand the complexity of human gene expression responses to therapy and the potentiality of selecting appropriate responsive targets.

Towards clinical translation of ligand-functionalized liposomes in targeted cancer therapy: Challenges and opportunities

The development of therapeutic resistance to targeted anticancer therapies remains a significant clinical problem, with intratumoral heterogeneity playing a key role. In this context, improving the therapeutic outcome through simultaneous targeting of multiple tumor cell subtypes within a heterogeneous tumor is a promising approach. Liposomes have emerged as useful drug carriers that can reduce systemic toxicity and increase drug delivery to the tumor site. While clinically used liposomal drug formulations show marked therapeutic advantages over free drug formulations, ligand-functionalized liposomes that can target multiple tumor cell subtypes may further improve the therapeutic efficacy by facilitating drug delivery to a broader population of tumor cells making up the heterogeneous tumor tissue. Ligand-directed liposomes enable the so-called active targeting of cell receptors via surface-attached ligands that direct drug uptake into tumor cells or tumor-associated stromal cells, and so can increase the selectivity of drug delivery. Despite promising preclinical results demonstrating improved targeting and anti-tumor effects of ligand-directed liposomes, there has been limited translation of this approach to the clinic. Key challenges for translation include the lack of established methods to scale up production and comprehensively characterize ligand-functionalized liposome formulations, as well as the inadequate recapitulation of in vivo tumors in the preclinical models currently used to evaluate their performance. Herein, we discuss the utility of recent ligand-directed liposome approaches, with a focus on dual-ligand liposomes, for the treatment of solid tumors and examine the drawbacks limiting their progression to clinical adoption.

Chemotherapy-induced metastasis: mechanisms and translational opportunities

Tumors often overcome the cytotoxic effects of chemotherapy through either acquired or environment-mediated drug resistance. In addition, signals from the microenvironment obfuscate the beneficial effects of chemotherapy and may facilitate progression and metastatic dissemination. Seminal mediators in chemotherapy-induced metastasis appear to be a wide range of hematopoietic, mesenchymal and immune progenitor cells, originating from the bone marrow. The actual purpose of these cells is to orchestrate the repair response to the cytotoxic damage of chemotherapy. However, these repair responses are exploited by tumor cells at every step of the metastatic cascade, ranging from tumor cell invasion, intravasation and hematogenous dissemination to extravasation and effective colonization at the metastatic site. A better understanding of the mechanistic underpinnings of chemotherapy-induced metastasis will allow us to better predict which patients are more likely to exhibit pro-metastatic responses to chemotherapy and will help develop new therapeutic strategies to neutralize chemotherapy-driven prometastatic changes.

Transcriptomic pathway analysis of urokinase receptor silenced breast cancer cells: a microarray study

Urokinase plasminogen activator receptor (PLAUR) has been implicated in a variety of physiological and pathological conditions. The multi-functionality of PLAUR is due to its capacity to interact with many co-receptors to regulate extracellular proteolysis and intracellular signaling. Recent reports are identifying novel functions of PLAUR which were not evident in the past; however, the molecular mechanisms of PLAUR signaling are not completely understood. Here, we have compared the transcriptomes of silencing control (sicon) and PLAUR silenced (PLAURsi) MDA-MB-231 breast cancer cells on treatment with radiation. We isolated RNA from the cells, synthesized cDNA and measured the gene expression changes by microarray. We identified 24 downregulated and 53 upregulated genes, which were significantly (P-value < 0.005) affected by PLAUR silencing. Our analysis revealed 415 canonical pathways and 743 causal disease networks affected on silencing PLAUR. Transcriptomic changes and predicted pathways supported and consolidated some of the earlier understanding in the context of PLAUR signaling; including our recent observations in DNA damage and repair process. In addition, we have identified several novel pathways where PLAUR is implicated.

Negative regulation of urokinase receptor activity by a GPI-specific phospholipase C in breast cancer cells

The urokinase receptor (uPAR) is a glycosylphosphatidylinositol (GPI)-anchored protein that promotes tissue remodeling, tumor cell adhesion, migration and invasion. uPAR mediates degradation of the extracellular matrix through protease recruitment and enhances cell adhesion, migration and signaling through vitronectin binding and interactions with integrins. Full-length uPAR is released from the cell surface, but the mechanism and significance of uPAR shedding remain obscure. Here we identify transmembrane glycerophosphodiesterase GDE3 as a GPI-specific phospholipase C that cleaves and releases uPAR with consequent loss of function, whereas its homologue GDE2 fails to attack uPAR. GDE3 overexpression depletes uPAR from distinct basolateral membrane domains in breast cancer cells, resulting in a less transformed phenotype, it slows tumor growth in a xenograft model and correlates with prolonged survival in patients. Our results establish GDE3 as a negative regulator of the uPAR signaling network and, furthermore, highlight GPI-anchor hydrolysis as a cell-intrinsic mechanism to alter cell behavior.

Every process in the body, from how cells divide to how they move around, is tightly regulated. For example, cells only migrate when they receive the correct signals from their environment. These signals are recognised by receptor proteins that sit on the cell surface and connect the outside signal with the cell’s response. However, in cancer cells, these processes are out of control, which is why cancer cells can grow very quickly or spread to many different parts of the body.

One important receptor protein is the urokinase receptor, which helps to reorganize the tissue, for example, when wounds heal, but also enables cancer cells to grow and spread. A special feature of urokinase receptor is the way it is connected to the cell surface, namely through a molecule that acts as an anchor, called the GPI anchor. The urokinase receptor and some other GPI-anchored proteins can be released from their anchor. However, until now it was not clear why and how the urokinase receptor is released from cells, or how losing the receptor affects the cell.

Now, van Veen, Matas-Rico et al. studied breast cancer cells, and discovered that an enzyme called GDE3 cuts the urokinase receptor off its GPI anchor to release the receptor from the cells. However, when breast cancer cells shed the urokinase receptor, they also lost the receptor from the cell surface in specific areas. As a result, the receptor could not work anymore. When breast cancer cells were experimentally modified to produce high levels of GDE3, the cancer cells became less mobile and aggressive.

Van Veen, Matas-Rico et al. then implanted ‘normal’ breast cancer cells, and breast cancer cells with extra GDE3 into mice, and observed that the tumors of mice with additional GDE3 grew less quickly. Moreover, breast cancer patients with high levels of GDE3 tend to live longer than patients with low levels of GDE3. These results suggest that the enzyme GDE3 can suppress tumor growth.

These findings uncover a new way how cells can alter their behavior, namely by cleaving GPI anchors at the cell surface. Future experiments will need to address how GDE3 itself is controlled, and if it releases other GPI-anchored proteins from cells. Once we know how to increase GDE3 activity in tumor cells, the new knowledge could one day lead to therapies to help patients with cancer.

Urokinase-type plasminogen activator receptor inhibits apoptosis in triple-negative breast cancer through miR-17/20a suppression of death receptors 4 and 5

Dissection and understanding of the molecular pathways driving triple-negative breast cancer (TNBC) are urgently needed to develop efficient tailored therapies. Aside from cell invasion and metastasis, the urokinase-type plasminogen activator receptor (uPAR) has been linked to apoptosis resistance in breast tumors. We explored the mechanism of uPAR-disrupted apoptosis in breast cancer. We found that depletion of uPAR by RNAi increases death receptor 4 (DR4) and death receptor 5 (DR5) expression and triggers TRAIL-induced apoptosis in TNBC cells. The microRNAs miR-17-5p and miR-20a inhibit cell apoptosis via suppression of DR4/DR5. We provide evidence that uPAR enhances miR-17-5p/20a expression through upregulation of c-myc. Blocking miR-17-5p/20a with antagomiRNA suppressed the growth of uPAR-overexpressing breast tumor xenografts in mice. These results indicate that uPAR suppresses cell apoptosis by inhibiting the c-myc-miR-17/5p/20a-DR4/DR5 pathway. Therapy directed at uPAR-induced miR-17/20a is a potential option for breast cancer and TNBC.

Be Active or Not: the Relative Contribution of Active and Passive Tumor Targeting of Nanomaterials

Malignant tumor (cancer) remains as one of the deadliest diseases throughout the world, despite its overall mortality drops. Nanomaterials (NMs) have been widely studied as diagnostic and/or therapeutic agents for tumors. A feature of NMs, compared to small molecules, is that NMs can be concentrated passively in tumors through enhanced permeability and retention (EPR) effect. In the meantime, NMs can be engineered to target toward tumor specific markers in an active manner, e.g., receptor-mediated targeting. The relative contribution of the EPR effect and the receptor-mediated targeting to NM accumulation in tumor tissues has not been clearly defined yet. Here, we tackle this fundamental issue by reviewing previous studies. First, we summarize the current knowledge on these two tumor targeting strategies of NMs, and on how NMs arrive to tumors from blood circulation. We then demonstrate that contribution of the active and passive effects to total accumulation of NMs in tumors varies with time. Over time, the receptor-mediated targeting contributes more than the EPR effect with a ratio of 3 in the case of urokinase-type plasminogen activator receptor (uPAR)-mediated targeting and human serum albumin (HSA)-mediated EPR effect. Therefore, this review highlights the dynamics of active and passive targeting of NMs on their accumulation at tumor sites, and is valuable for future design of NMs in cancer diagnosis and treatment.

Urokinase-type plasminogen activator receptor promotes proliferation and invasion with reduced cisplatin sensitivity in malignant mesothelioma

Malignant mesothelioma (MM) is a rare neoplasm associated with asbestos exposure. The prognosis of MM is poor because it is aggressive and highly resistant to chemotherapy. Using a rat model of asbestos-induced MM, we found elevated urokinase-type plasminogen activator receptor (uPAR; Plaur) expression in rat tissues, which was associated with poor prognosis. The proliferation, migration and invasion of MM cells were suppressed by uPAR knockdown and increased by overexpression experiments, irrespective of urokinase-type plasminogen activator (uPA; Plau) levels. More importantly, we found that uPAR expression is associated with sensitivity to cisplatin in MM through the PI3K/AKT pathway, which was demonstrated with specific inhibitors, LY294002 and Akti-1/2. uPAR knockdown significantly increased sensitivity to cisplatin whereas its overexpression significantly decreased cisplatin sensitivity. Furthermore, sera and tissues from MM patients showed significantly high uPAR levels, which suggested the pathogenic role of uPAR in the tumor biology of human MM. In conclusion, our findings indicate that uPAR levels are associated with malignant characteristics and cisplatin sensitivity of MM. In addition to the potential use of uPAR as a prognostic marker, the combination of uPAR abrogation and cisplatin may reveal a promising therapeutic approach for MM.

Site-Specific Radiofluorination of Biomolecules with 8-[(18)F]-Fluorooctanoic Acid Catalyzed by Lipoic Acid Ligase

New methodologies for site-specifically radiolabeling proteins with (18)F are required to generate high quality radiotracers for preclinical and clinical applications with positron emission tomography. Herein, we report an approach by which we use lipoic acid ligase (LplA) to conjugate [(18)F]-fluorooctanoic acid to an antibody fragment bearing the peptide substrate of LplA. The mild conditions of the reaction preserve antibody immunoreactivity, and the efficiency of LplA allows for >90% yield even with very small amounts of peptidic precursor (1-10 nmol). These features are advantageous compared to the current gold standard in the field. Moreover, the methodology introduces a new application for an important tool in chemical biology.

Serum uPAR as Biomarker in Breast Cancer Recurrence: A Mathematical Model

There are currently over 2.5 million breast cancer survivors in the United States and, according to the American Cancer Society, 10 to 20 percent of these women will develop recurrent breast cancer. Early detection of recurrence can avoid unnecessary radical treatment. However, self-examination or mammography screening may not discover a recurring cancer if the number of surviving cancer cells is small, while biopsy is too invasive and cannot be frequently repeated. It is therefore important to identify non-invasive biomarkers that can detect early recurrence. The present paper develops a mathematical model of cancer recurrence. The model, based on a system of partial differential equations, focuses on tissue biomarkers that include the plasminogen system. Among them, only uPAR is known to have significant correlation to its concentration in serum and could therefore be a good candidate for serum biomarker. The model includes uPAR and other associated cytokines and cells. It is assumed that the residual cancer cells that survived primary cancer therapy are concentrated in the same location within a region with a very small diameter. Model simulations establish a quantitative relation between the diameter of the growing cancer and the total uPAR mass in the cancer. This relation is used to identify uPAR as a potential serum biomarker for breast cancer recurrence.

Induction of a Tumor-Metastasis-Receptive Microenvironment as an Unwanted Side Effect After Radio/Chemotherapy and In Vitro and In Vivo Assays to Study this Phenomenon

Besides surgical removal of tumor tissue, chemotherapy and radiotherapy are the most important and efficient treatment modalities employed to treat therapy-susceptible malignancies. The main aim of this treatment-to destroy tumor cells-is unfortunately usually associated with toxicity to nontumor cells and different degrees of tissue and organ damage. In damaged tissues several chemoattractants are upregulated and released that may attract tumor cells. Moreover, highly migratory radio/chemotherapy treatment may endow cells with several properties of cancer stem cells which survive and respond to these chemoattractants upregulated in collateral tissues. Based on this, one of the unwanted and underappreciated side effects of chemotherapy or radiotherapy is the creation of a metastasis-receptive microenvironment in bones as well as in other organs of the body. Herein we describe methods and assays that can be employed to study migratory properties of cancer cells in in vitro (chemotaxis) and in vivo (seeding efficiency assay) conditions in response to the induction of pro-metastatic microenvironments in various organs and tissues.

Vectors for the delivery of radiopharmaceuticals in cancer therapeutics

Internal radiation using radiopharmaceuticals promises efficient cancer therapeutics. The specificity and selectivity required for screening and pinpointing tumor cells for cell-kill has been made possible by targeted ligands based on 'magic bullet' and tracer principle- theories nearing a century. Overexpression of certain receptors has been exploited using biomolecules for targeting. The pragmatic analysis, however, is not as promising compared with the theoretical knowledge of available gamut of vectors and targets. The complex interplay of in vitro and in vivo parameters, and the effect of radionuclides involve a systematic assessment of radiopharmaceuticals as diagnostic and therapeutic agent. This review presents different vectors with their pros and cons, present status and recent design variations followed by a future perspective based on novel approaches.

Cytotoxicity of the Urokinase-Plasminogen Activator Inhibitor Carbamimidothioic Acid (4-Boronophenyl) Methyl Ester Hydrobromide (BC-11) on Triple-Negative MDA-MB231 Breast Cancer Cells

BC-11 is an easily synthesized simple thiouronium-substituted phenylboronic acid, which has been shown to be cytotoxic on triple negative MDA-MB231 breast cancer cells by inducing a perturbation of cell cycle when administered at a concentration equal to its ED₅₀ at 72 h (117 μM). Exposure of cells to BC-11, either pre-absorbed with a soluble preparation of the N-terminal fragment of urokinase-plasminogen activator (uPa), or in co-treatment with two different EGFR inhibitors, indicated that: (i) BC-11 acts via binding to the N-terminus of the enzyme where uPa- and EGF receptor-recognizing sites are present, thereby abrogating the growth-sustaining effect resulting from receptor binding; and (ii) the co-presence of the EGFR inhibitor PD153035 potentiates BC-11’s cytotoxicity. Exposure of cells to a higher concentration of BC-11 corresponding to its ED₇₅ at 72 h (250 μM) caused additional impairment of mitochondrial activity, the production of reactive oxygen species and promotion of apoptosis. Therefore, BC-11 treatment appears to show potential for the development of this class of compounds in the prevention and/or therapy of “aggressive” breast carcinoma.

Targeted nanoparticles for image-guided treatment of triple-negative breast cancer: clinical significance and technological advances

Effective treatment of triple-negative breast cancer (TNBC) with its aggressive tumor biology, highly heterogeneous tumor cells, and poor prognosis requires an integrated therapeutic approach that addresses critical issues in cancer therapy. Multifunctional nanoparticles with the abilities of targeted drug delivery and noninvasive imaging for monitoring drug delivery and responses to therapy, such as theranostic nanoparticles, hold great promise toward the development of novel therapeutic approaches for the treatment of TNBC using a single therapeutic platform. The biological and pathological characteristics of TNBC provide insight into several potential molecular targets for current and future nanoparticle-based therapeutics. Extensive tumor stroma, highly proliferative cells, and a high rate of drug resistance are all barriers that must be appropriately addressed in order for these nanotherapeutic platforms to be effective. Utilization of the enhanced permeability and retention effect coupled with active targeting of cell surface receptors expressed by TNBC cells, and tumor-associated endothelial cells, stromal fibroblasts, and macrophages is likely to overcome such barriers to facilitate more effective drug delivery. An in-depth summary of current studies investigating targeted nanoparticles in preclinical TNBC mouse and human xenograft models is presented. This review aims to outline the current status of nanotherapeutic options for TNBC patients, identification of promising molecular targets, challenges associated with the development of targeted nanotherapeutics, the research done by our group as well as by others, and future perspectives on the nanomedicine field and ways to translate current preclinical studies into the clinic.

HER2 and uPAR cooperativity contribute to metastatic phenotype of HER2-positive breast cancer

Human epidermal growth factor receptor type 2 (HER2)-positive breast carcinoma is highly aggressive and mostly metastatic in nature though curable/manageable in part by molecular targeted therapy. Recent evidence suggests a subtype of cells within HER2-positive breast tumors that concomitantly expresses the urokinase plasminogen activator receptor (uPAR) with inherent stem cell/mesenchymal-like properties promoting tumor cell motility and a metastatic phenotype. This HER-positive/uPAR-positive subtype may be partially responsible for the failure of HER2-targeted treatment strategies. Herein we discuss and substantiate the cumulative preclinical and clinical evidence on HER2-uPAR cooperativity in terms of gene co-amplification and/or mRNA/protein co-overexpression. We then propose a regulatory signaling model that we hypothesize to maintain upregulation and cooperativity between HER2 and uPAR in aggressive breast cancer. An improved understanding of the HER2/uPAR interaction in breast cancer will provide critical biomolecular information that may help better predict disease course and response to therapy.

Imaging active urokinase plasminogen activator in prostate cancer

The increased proteolytic activity of membrane-bound and secreted proteases on the surface of cancer cells and in the transformed stroma is a common characteristic of aggressive metastatic prostate cancer. We describe here the development of an active site-specific probe for detecting a secreted peritumoral protease expressed by cancer cells and the surrounding tumor microenvironment. Using a human fragment antigen-binding phage display library, we identified a human antibody termed U33 that selectively inhibited the active form of the protease urokinase plasminogen activator (uPA, PLAU). In the full-length immunoglobulin form, U33 IgG labeled with near-infrared fluorophores or radionuclides allowed us to noninvasively detect active uPA in prostate cancer xenograft models using optical and single-photon emission computed tomography imaging modalities. U33 IgG labeled with (111)In had a remarkable tumor uptake of 43.2% injected dose per gram (%ID/g) 72 hours after tail vein injection of the radiolabeled probe in subcutaneous xenografts. In addition, U33 was able to image active uPA in small soft-tissue and osseous metastatic lesions using a cardiac dissemination prostate cancer model that recapitulated metastatic human cancer. The favorable imaging properties were the direct result of U33 IgG internalization through an uPA receptor-mediated mechanism in which U33 mimicked the function of the endogenous inhibitor of uPA to gain entry into the cancer cell. Overall, our imaging probe targets a prostate cancer-associated protease, through a unique mechanism, allowing for the noninvasive preclinical imaging of prostate cancer lesions.

In vivo anti-metastatic effects of uPAR retargeted measles virus in syngeneic and xenograft models of mammary cancer

The urokinase receptor (uPAR) plays a critical role in breast cancer (BC) progression and metastases and is a validated target for novel therapies. The current study investigates the effects of MV-uPA, an oncolytic measles virus fully retargeted against uPAR in syngeneic and xenograft BC metastases models. In vitro replication and cytotoxicity of MVs retargeted against human (MV-h-uPA) or mouse (MV-m-uPA) uPAR were assessed in human and murine cancer and non-cancer mammary epithelial cells. The in vivo effects of species-specific uPAR retargeted MVs were assessed in syngeneic and xenograft models of experimental metastases, established by intravenous administration of luciferase expressing 4T1 or MDA-MD-231 cells. Metastases progression was assessed by in vivo bioluminescence imaging. Tumor targeting was evaluated by qRT-PCR of MV-N, rescue of viable viral particles, and immunostaining of MV particles in lungs from tumor bearing mice. In vitro, MV-h-uPA and MV-m-uPA selectively infected, replicated, and induced cytotoxicity in cancer compared to non-cancer cells in a species-specific manner. In vivo, MV-m-uPA delayed 4T1 lung metastases progression and prolonged survival. These effects were associated with identification of viable viral particles, viral RNA, and detection of MV-N by immunostaining from lung tissues in treated mice. In the human MDA-MB-231 metastases model, intravenous administration of MV-h-uPA markedly inhibited metastases progression and significantly improved survival, compared to controls. No significant treatment-related toxicity was observed in treated mice. The above preclinical findings strongly suggest that uPAR retargeted measles virotherapy is a novel and feasible systemic therapy strategy against metastatic breast cancer.

The predictive value of soluble urokinase plasminogen activator receptor (SuPAR) regarding 90-day mortality and 12-month neurological outcome in critically ill patients after out-of-hospital cardiac arrest. Data from the prospective FINNRESUSCI study

AIM

The whole body ischaemia-reperfusion after cardiac arrest (CA) induces a systemic inflammation-reperfusion response. The expression of urokinase plasminogen activator receptor (uPAR) is known to be induced after hypoxia and increased levels of soluble form suPAR have been measured after hypoxia and ischaemia. Our aim was to evaluate, whether ischaemia/reperfusion injury after out-of-hospital cardiac arrest (OHCA) increases suPAR concentrations in serum and to evaluate the prognostic value of suPAR regarding 90-day mortality and 12-month neurological outcome.

METHODS

This is a pre-determined substudy of prospective FINNRESUSCI study. Total of 287 patients treated in the intensive care units after OHCA and with consent from the next-of-kin and serum samples between baseline and day 4 were included. Outcome and neurological outcome were evaluated according the Pittsburgh Cerebral Performance Categories (CPC). Kaplan-Meier survival curves, areas under receiver operational characteristics curves and positive likelihood ratios for mortality and poor neurological outcome were calculated.

RESULTS

Non-survivors had higher levels of suPAR after OHCA. Kaplan-Meier survival curves indicated high 90-day mortality in the highest concentration quintiles. LR+ for 1-year CPC 3-5 was 1.8-2.7 for the whole patient cohort and in shockable rhythms 2.0-2.4. In therapeutic hypothermia prognostic value remained.

CONCLUSIONS

We found that high SuPAR concentrations were associated with poor outcome in patients with OHCA admitted to critical care. However, suPAR alone had inadequate predictive value for poor outcome and did not associate with 12-month neurological outcome.