Significant overexpression of urokinase-type plasminogen activator in pancreatic adenocarcinoma using real-time quantitative reverse transcription polymerase chain reaction

Liposomal drug delivery systems for organ-specific cancer targeting: early promises, subsequent problems, and recent breakthroughs

INTRODUCTION

Targeted liposomal systems for cancer intention have been recognized as a specific and robust approach compared to conventional liposomal delivery systems. Cancer cells have a unique microenvironment with special over-expressed receptors on their surface, providing opportunities for discovering novel and effective drug delivery systems using active targeting.

AREAS COVERED

Smartly targeted liposomes, responsive to internal or external stimulations, enhance the delivery efficiency by increasing accumulation of the encapsulated anti-cancer agent in the tumor site. The application of antibodies and aptamers against the prevalent cell surface receptors is a potent and ever-growing field. Moreover, immuno-liposomes and cancer vaccines as adjuvant chemotherapy are also amenable to favorable immune modulation. Combinational and multi-functional systems are also attractive in this regard. However, potentially active targeted liposomal drug delivery systems have a long path to clinical acceptance, chiefly due to cross-interference and biocompatibility affairs of the functionalized moieties.

EXPERT OPINION

Engineered liposomal formulations have to be designed based on tissue properties, including surface chemistry, charge, and microvasculature. In this paper, we aimed to investigate the updated targeted liposomal systems for common cancer therapy worldwide.

Cellular Components Contributing to the Development of Venous Thrombosis in Patients with Pancreatic Cancer

Pancreatic ductal adenocarcinoma (PDAC) is an aggressive type of cancer and has a poor prognosis. Patients with PDAC are at high risk of developing thromboembolic events, which is a leading cause of morbidity and mortality following cancer progression. Plasma-derived coagulation is the most studied process in cancer-associated thrombosis. Other blood components, such as platelets, red blood cells, and white blood cells, have been gaining less attention. This narrative review addresses the literature on the role of cellular components in the development of venous thromboembolism (VTE) in patients with PDAC. Blood cells seem to play an important role in the development of VTE. Altered blood cell counts, i.e., leukocytosis, thrombocytosis, and anemia, have been found to associate with VTE risk. Tumor-related activation of leukocytes leads to the release of tissue factor-expressing microvesicles and the formation of neutrophil extracellular traps, initiating coagulation and forming a scaffold for thrombi. Tissue factor-expressing microvesicles are also thought to be released by PDAC cells. PDAC cells have been shown to stimulate platelet activation and aggregation, proposedly via the secretion of podoplanin and mucins. Hypofibrinolysis, partially explained by increased plasminogen activator inhibitor-1 activity, is observed in PDAC. In short, PDAC-associated hypercoagulability is a complex and multifactorial process. A better understanding of cellular contributions to hypercoagulability might lead to the improvement of diagnostic tests to identify PDAC patients at highest risk of VTE.

Metastatic phenotype and immunosuppressive tumour microenvironment in pancreatic ductal adenocarcinoma: Key role of the urokinase plasminogen activator (PLAU)

Background

Previous studies have revealed the role of dysregulated urokinase plasminogen activator (encoded by PLAU) expression and activity in several pathways associated with cancer progression. However, systematic investigation into the association of PLAU expression with factors that modulate PDAC (pancreatic ductal adenocarcinoma) progression is lacking, such as those affecting stromal (pancreatic stellate cell, PSC)-cancer cell interactions, tumour immunity, PDAC subtypes and clinical outcomes from potential PLAU inhibition.

Methods

This study used an integrated bioinformatics approach to identify prognostic markers correlated with PLAU expression using different transcriptomics, proteomics, and clinical data sets. We then determined the association of dysregulated PLAU and correlated signatures with oncogenic pathways, metastatic phenotypes, stroma, immunosuppressive tumour microenvironment (TME) and clinical outcome. Finally, using an in vivo orthotopic model of pancreatic cancer, we confirmed the predicted effect of inhibiting PLAU on tumour growth and metastasis.

Results

Our analyses revealed that PLAU upregulation is not only associated with numerous other prognostic markers but also associated with the activation of various oncogenic signalling pathways, aggressive phenotypes relevant to PDAC growth and metastasis, such as proliferation, epithelial-mesenchymal transition (EMT), stemness, hypoxia, extracellular cell matrix (ECM) degradation, upregulation of stromal signatures, and immune suppression in the tumour microenvironment (TME). Moreover, the upregulation of PLAU was directly connected with signalling pathways known to mediate PSC-cancer cell interactions. Furthermore, PLAU upregulation was associated with the aggressive basal/squamous phenotype of PDAC and significantly reduced overall survival, indicating that this subset of patients may benefit from therapeutic interventions to inhibit PLAU activity. Our studies with a clinically relevant orthotopic pancreatic model showed that even short-term PLAU inhibition is sufficient to significantly halt tumour growth and, importantly, eliminate visible metastasis.

Conclusion

Elevated PLAU correlates with increased aggressive phenotypes, stromal score, and immune suppression in PDAC. PLAU upregulation is also closely associated with the basal subtype type of PDAC; patients with this subtype are at high risk of mortality from the disease and may benefit from therapeutic targeting of PLAU.

Urokinase plasminogen activator induces epithelial-mesenchymal and metastasis of pancreatic cancer through plasmin/MMP14/TGF-β axis, which is inhibited by 4-acetyl-antroquinonol B treatment

BACKGROUND

The current standard therapy for metastatic pancreatic cancer is ineffective, necessitating a new treatment approach for prognosis improvement. The urokinase-plasmin activator (uPA) is a critical factor in epithelial-mesenchymal transition (EMT) and cancer metastasis, but its underlying mechanisms in pancreatic cancer remains elusive.

METHODS

We investigated uPA expression in our pancreatic cancer cohort. A bioinformatics approach was used to further determine the role of uPA in pancreatic cancer. We employed MiaPaCa-2 and PANC-1 cell lines to investigate how uPA regulates EMT and metastasis in pancreatic cancer and present a novel approach aimed at inhibiting uPA in pancreatic cancer.

RESULTS

We observed that higher uPA mRNA expression was significantly associated with overall-poor survival and progression-free survival in pancreatic cancer. uPA was highly expressed in tumor tissue. Gene set enrichment analysis revealed a positive association between uPA mRNA expression and EMT and transforming growth factor β (TGF-β) signaling pathways. Moreover, shRNA-mediated uPA gene knockdown reduced plasmin, MMP14, and TGF-β activation, leading to the inhibition of PANC-1 cells' EMT marker expression, migration, invasion, and cell viability. Notably, 4-acetyl-antroquinonol B (4-AAQB) treatment suppressed MiaPaCa-2 and PANC-1 cell migratory and invasive abilities by inhibiting the uPA/MMP14/TGF-β axis through upregulation of miR-181d-5p. In the xenograft mouse model of orthotropic pancreatic cancer, 4-AAQB treatment has reduced tumor growth and metastasis rate by deactivating uPA and improving the survival of the mice model.

CONCLUSION

Accordingly, to extent of our knowledge and previous studies, we demonstrated that 4-AAQB is an anti Pan-Cancer drug, and may inhibit pancreatic cancer EMT and metastasis and serve as a new therapeutic approach for patients with late-stage pancreatic cancer.

The Urokinase Plasminogen Activation System in Pancreatic Cancer: Prospective Diagnostic and Therapeutic Targets

Pancreatic cancer is a highly aggressive malignancy that features high recurrence rates and the poorest prognosis of all solid cancers. The urokinase plasminogen activation system (uPAS) is strongly implicated in the pathophysiology and clinical outcomes of patients with pancreatic ductal adenocarcinoma (PDAC), which accounts for more than 90% of all pancreatic cancers. Overexpression of the urokinase-type plasminogen activator (uPA) or its cell surface receptor uPAR is a key step in the acquisition of a metastatic phenotype via multiple mechanisms, including the increased activation of cell surface localised plasminogen which generates the serine protease plasmin. This triggers multiple downstream processes that promote tumour cell migration and invasion. Increasing clinical evidence shows that the overexpression of uPA, uPAR, or of both is strongly associated with worse clinicopathological features and poor prognosis in PDAC patients. This review provides an overview of the current understanding of the uPAS in the pathogenesis and progression of pancreatic cancer, with a focus on PDAC, and summarises the substantial body of evidence that supports the role of uPAS components, including plasminogen receptors, in this disease. The review further outlines the clinical utility of uPAS components as prospective diagnostic and prognostic biomarkers for PDAC, as well as a rationale for the development of novel uPAS-targeted therapeutics.

Aberrant Factors of Fibrinolysis and Coagulation in Pancreatic Cancer

Aberrant factors associated with fibrinolysis and thrombosis are found in many cancer patients, which can promote metastasis and are associated with poor prognosis. The relationship between tumor-associated fibrinolysis and thrombosis is poorly understood in pancreatic cancer. This review provides a brief highlight of existing studies that the fibrinolysis and coagulation systems were activated in pancreatic cancer patients, along with aberrant high concentrations of tissue plasminogen activator (t-PA), urine plasminogen activator (u-PA), D-dimer, fibrinogen, or platelets. These factors cooperate with each other, propelling tumor cell shedding, localization, adhesion to distant metastasis. The relationship between thrombosis or fibrinolysis and cancer immune escape is also investigated. In addition, the potential prevention and therapy strategies of pancreatic cancer targeting factors in fibrinolysis and coagulation systems are also been discussed, in which we highlight two effective agents aspirin and low-molecular weight heparin (LMWH). Summarily, this review provides new directions for the research and treatment of pancreatic cancer.

Ab locks for improving the selectivity and safety of antibody drugs

Monoclonal antibodies (mAbs) are a major targeted therapy for malignancies, infectious diseases, autoimmune diseases, transplant rejection and chronic inflammatory diseases due to their antigen specificity and longer half-life than conventional drugs. However, long-term systemic antigen neutralization by mAbs may cause severe adverse events. Improving the selectivity of mAbs to distinguish target antigens at the disease site from normal healthy tissue and reducing severe adverse events caused by the mechanisms-of-action of mAbs is still a pressing need. Development of pro-antibodies (pro-Abs) by installing a protease-cleavable Ab lock is a novel and advanced recombinant Ab-based strategy that efficiently masks the antigen binding ability of mAbs in the normal state and selectively "turns on" the mAb activity when the pro-Ab reaches the proteolytic protease-overexpressed diseased tissue. In this review, we discuss the design and advantages/disadvantages of different Ab lock strategies, focusing particularly on spatial-hindrance-based and affinity peptide-based approaches. We expect that the development of different masking strategies for mAbs will benefit the local reactivity of mAbs at the disease site, increase the therapeutic efficacy and safety of long-term treatment with mAbs in chronic diseases and even permit scientists to develop Ab drugs for formerly undruggable targets and satisfy the unmet medical needs of mAb therapy.

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.

Urokinase plasminogen activator receptor (uPAR) and plasminogen activator inhibitor-1 (PAI-1) are potential predictive biomarkers in early stage oral squamous cell carcinomas (OSCC)

Oral squamous cell carcinoma (OSCC) is often associated with metastatic disease and a poor 5 year survival rate. Patients diagnosed with small tumours generally have a more favourable outcome, but some of these small tumours are aggressive and lead to early death. To avoid harmful overtreatment of patients with favourable prognosis, there is a need for predictive biomarkers that can be used for treatment stratification. In this study we assessed the possibility to use components of the plasminogen activator (PA) system as prognostic markers for OSCC outcome and compared this to the commonly used biomarker Ki-67. A tissue-micro-array (TMA) based immunohistochemical analysis of primary tumour tissue obtained from a North Norwegian cohort of 115 patients diagnosed with OSCC was conducted. The expression of the biomarkers was compared with clinicopathological variables and disease specific death. The statistical analyses revealed that low expression of uPAR (p = 0.031) and PAI-1 (p = 0.021) in the tumour cells was significantly associated with low disease specific death in patients with small tumours and no lymph node metastasis (T1N0). The commonly used biomarker, Ki-67, was not associated with disease specific death in any of the groups of patients analysed. The conclusion is that uPAR and PAI-1 are potential predictive biomarkers in early stage tumours and that this warrants further studies on a larger cohort of patients.

Plasma Levels of Plasminogen Activator Inhibitor Type 1 and Vitronectin in Children With Cancer

BACKGROUND

The plasminogen activator system controls intravascular fibrin deposition; besides, it also participates in a wide variety of physiologic and pathologic processes, including cancer.

PROCEDURE

In this study, we examined the levels of plasminogen activator inhibitor 1 (PAI-1) and vitronectin in 32 newly diagnosed pediatric patients with malignancies, determined by enzyme-linked immunosorbent assay between January 2009 and January 2010 and compared them to 35 age-matched healthy children, using SPSS 16.0 software.

RESULTS

The mean level of PAI-1 was 23.02 ± 15 (8.2-71.19) ng/mL and vitronectin was 83.10% ± 23.77% (12%-126%) in the tumor group. Thirty-five healthy children in the same age range were enrolled in the control group. The levels of PAI-1 and vitronectin were 23.63 ± 10.44 (11.67-58.85) ng/mL and 85% ± 20.85% (39%-126%), respectively. No significant difference was found between the 2 groups by independent sample t-test (P = .86 and P = .69).

CONCLUSIONS

This is a preliminary study done in children with malignancies, investigating PAI-1 and vitronectin. Further study is needed, including larger trials and tumor tissue with histopathological examination as in adults.

Involvement of urokinase-type plasminogen activator system in cancer: an overview

Currently, there are several studies supporting the role of urokinase-type plasminogen activator (uPA) system in cancer. The association of uPA to its receptor triggers the conversion of plasminogen into plasmin. This process is regulated by the uPA inhibitors (PAI-1 and PAI-2). Plasmin promotes degradation of basement membrane and extracellular matrix (ECM) components as well as activation of ECM latent matrix metalloproteases. Degradation and remodeling of the surrounding tissues is crucial in the early steps of tumor progression by facilitating expansion of the tumor mass, release of tumor growth factors, activation of cytokines as well as induction of tumor cell proliferation, migration, and invasion. Hence, many tumors showed a correlation between uPA system component levels and tumor aggressiveness and survival. Therefore, this review summarizes the structure of the uPA system, its contribution to cancer progression, and the clinical relevance of uPA family members in cancer diagnosis. In addition, the review evaluates the significance of uPA system in the development of cancer-targeted therapies.

High level of urokinase plasminogen activator contributes to cholangiocarcinoma invasion and metastasis

AIM

To investigate the role of urokinase plasminogen activator (uPA) in cholangiocarcinoma (CCA) invasion and its correlation with clinicopathological parameters.

METHODS

uPA expression in CCA tissue was determined by immunohistochemistry. The level of uPA from two CCA cell lines (HuCCA-1 and KKU-M213) and a non-cancer immortalized cholangiocyte cell line (H69) was monitored by plasminogen-gelatin zymography and western blotting, whereas that of plasminogen activator inhibitor type 1 (PAI-1) protein and uPA receptor (uPAR) mRNA was monitored by western blotting and quantitative real-time reverse transcriptase polymerase chain reaction, respectively. Two independent methods were employed to suppress uPA function: a synthetic uPA inhibitor (B428) and silencing of uPA gene expression using siRNA. In vitro invasion of the uPA-disrupted cells was assessed by Matrigel-coated Transwell assay.

RESULTS

The immunohistochemical study showed that 75.3% (131/174) of CCA tissues expressed uPA. High uPA expression was correlated with lymphatic invasion and metastasis of CCA patients. Plasminogen-gelatin zymography of the conditioned media and cell-surface eluates showed that both CCA cell lines, but not H69, expressed both secreted and membrane-bound forms of uPA. Although the two CCA cell lines, HuCCA-1 and KKU-M213, expressed a relatively high level of uPA and uPAR, the latter exhibited a much lower degree of in vitro invasiveness, correlating with a high expression of PAI-1 in the latter, but not in the former. Suppressing uPA function with a specific uPA inhibitor, B428, or with siRNA against uPA reduced in vitro invasiveness of KKU-M213 cells, demonstrating the requirement for uPA in the invasiveness of CCA cells. Therefore, our in vivo and in vitro studies suggest that uPA is an important requirement for the invasion process of CCA.

CONCLUSION

uPA expression correlates with lymphatic invasion and metastasis in vivo and is required for CCA cell invasion in vitro, suggesting its potential as a therapeutic target.

Carbon-ion radiation enhances migration ability and invasiveness of the pancreatic cancer cell, PANC-1, in vitro

Pancreatic cancer is an aggressive disease that responds poorly to conventional photon radiotherapy. Carbon-ion (C-ion) radiation has advantages compared with conventional radiotherapy, because it enables more accurate dose distribution and more efficient tumor cell killing. To elucidate the effects of local radiotherapy on the characteristics of metastatic tumors, it is necessary to understand the nature of motility in irradiated tumor cells; this will, in turn, facilitate the development of effective strategies to counter tumor cell motility, which can be used in combination with radiotherapy. The aim of the present study was to examine the invasiveness of pancreatic cancer cells exposed to C-ion irradiation. We found that C-ion irradiation suppressed the migration of MIAPaCa-2, BxPC-3 and AsPC-1; diminished the invasiveness of MIAPaCa-2; and tended to reduce the invasion of BxPC-3 and AsPC-1. However, C-ion irradiation increased the invasiveness of PANC-1 through the activation of plasmin and urokinase-type plasiminogen activator. Administration of serine protease inhibitor (SerPI) alone failed to reduce C-ion-induced PANC-1 invasiveness, whereas the combination of SerPI and Rho-associated coiled-coil forming protein kinase (ROCK) inhibitor suppressed it. Furthermore, PANC-1 showed mesenchymal-amoeboid transition when we treated with SerPI alone. In conclusion, C-ion irradiation is effective in suppressing the invasive potential of several pancreatic tumor cell lines, but not PANC-1; this is the first study showing that C-ion irradiation induces the invasive potential of a tumor cell line. Further in vivo studies are required to examine the therapeutic effectiveness of radiotherapy combined with inhibitors of both mesenchymal and amoeboid modes of tumor cell motility.

Invasive markers identified by gene expression profiling in pancreatic cancer

BACKGROUND

Molecular profiling has proven utility as a diagnostic and predictive tool in clinical oncology. However, a clinically relevant gene expression profile in pancreatic cancer remains elusive.

METHODS

Primary and metastatic pancreatic cancer cell lines (BxPC-3 and AsPC-1), were stimulated with phorbol-12-myristate 13-acetate (PMA), a known inducer of cell invasion. Affymetrix gene expression microarray analysis was performed, comparing gene expression to unstimulated controls. Differential expression was identified using ArrayAssist, and confirmed using quantitative real-time PCR. Bioinformatic analysis was performed using Pathway Studio and GOstat. The derived gene expression was further validated in fresh frozen pancreatic tumour samples. The ability of the derived 3 gene expression markersto differentiate between pancreatic adenocarcinoma (PDAC) and other neoplasms, and its association with clinicopathological variables was examined.

RESULTS

PMA-induced significant changes in cell line gene expression, from which distinctive 3 potential invasive markers were derived. Expression of these genes, uPA, MMP-1 and IL1-R1 was confirmed in human pancreatic tumours, and was found to differentiate PDAC from other pancreatic neoplasms. The expression of IL1-R1 in PDAC is a novel finding. We found that the expression of MMP-1 was associated with high-grade PDAC (p = 0.035, Wilcoxon rank sum).

CONCLUSION

We have identified three potential invasive markers, uPA, MMP-1 and IL1-R1, whose gene expression may differentiate PDAC from other pancreatic neoplasms, and potentially reflect a more invasive phenotype.

Gene expression signature of advanced pancreatic ductal adenocarcinoma using low density array on endoscopic ultrasound-guided fine needle aspiration samples

AIMS

The purpose of this study was to investigate the clinical feasibility and utility of low-density array analysis on samples obtained from endoscopic ultrasound-guided fine needle aspiration biopsy in locally advanced and/or metastatic pancreatic ductal adenocarcinoma and chronic pancreatitis.

PATIENTS AND METHODS

In this prospective multicenter study, we quantified candidate gene expression in biopsies sampled from 44 locally advanced and/or metastatic pancreatic carcinoma and from 17 pseudotumoural chronic pancreatitis using dedicated low-density array microfluidic plates.

RESULTS

We first demonstrated that 18S gene expression is stable and comparable in normal pancreas and pancreatic cancer tissues. Next, we found that eight genes (S100P, PLAT, PLAU, MSLN, MMP-11, MMP-7, KRT7, KRT17) were significantly over expressed in pancreatic cancer samples when compared to pseudotumoural chronic pancreatitis (p value ranging from 0.0007 to 0.0215): Linear discriminative analysis identified S100P, PLAT, MSLN, MMP-7, KRT7 as highly explicative variables. The area under receiver operating curve establishes the clinical validity of the potential diagnostic markers identified in this study (values ranging from 0.69 to 0.76). In addition, combination of S100P and KRT7 gave better diagnosis performances (Area Under Receiver Operating Curve 0.81, sensitivity 81%, specificity 77%).

CONCLUSION

We demonstrate that molecular studies on EUS-guided FNA material are feasible for the identification and quantification of markers in PDAC patients diagnosed with non-resectable tumours. Using low-density array, we isolated a molecular signature of advanced pancreatic carcinoma including mostly cancer invasion-related genes. This work stems for the use of novel biomarkers for the molecular diagnosis of patient with solid pancreatic masses.

Combined mRNA expression levels of members of the urokinase plasminogen activator (uPA) system correlate with disease-associated survival of soft-tissue sarcoma patients

Background

Members of the urokinase-type plasminogen activator (uPA) system are up-regulated in various solid malignant tumors. High antigen levels of uPA, its inhibitor PAI-1 and its receptor uPAR have recently been shown to be associated with poor prognosis in soft-tissue sarcoma (STS) patients. However, the mRNA expression of uPA system components has not yet been comprehensively investigated in STS patients.

Methods

The mRNA expression level of uPA, PAI-1, uPAR and an uPAR splice variant, uPAR-del4/5, was analyzed in tumor tissue from 78 STS patients by quantitative PCR.

Results

Elevated mRNA expression levels of PAI-1 and uPAR-del4/5 were significantly associated with clinical parameters such as histological subtype (P = 0.037 and P < 0.001, respectively) and higher tumor grade (P = 0.017 and P = 0.003, respectively). In addition, high uPAR-del4/5 mRNA values were significantly related to higher tumor stage of STS patients (P = 0.031). On the other hand, mRNA expression of uPA system components was not significantly associated with patients' survival. However, in STS patients with complete tumor resection (R0), high PAI-1 and uPAR-del4/5 mRNA levels were associated with a distinctly increased risk of tumor-related death (RR = 6.55, P = 0.054 and RR = 6.00, P = 0.088, respectively). Strikingly, R0 patients with both high PAI-1 and uPAR-del4/5 mRNA expression levels showed a significant, 19-fold increased risk of tumor-related death (P = 0.044) compared to the low expression group.

Conclusion

Our results suggest that PAI-1 and uPAR-del4/5 mRNA levels may add prognostic information in STS patients with R0 status and distinguish a subgroup of R0 patients with low PAI-1 and/or low uPAR-del4/5 values who have a better outcome compared to patients with high marker levels.

Targeted alpha therapy approach to the management of pancreatic cancer

Evidence for the efficacy of targeted alpha therapy for the control of pancreatic cancer in preclinical models is reviewed. Results are given for in vitro pancreatic cancer cells and clusters and micro-metastatic cancer lesions in vivo. Two complementary targeting vectors are examined. These are the C595 monoclonal antibody that targets the MUC1 antigen and the PAI2 ligand that targets the uPA receptor. The expression of the tumor-associated antigen MUC-1 and the uPA receptor on three pancreatic cancer cell lines is reported for cell clusters, human mouse xenografts and lymph node metastases, as well as for human pancreatic cancer tissues, using immuno-histochemistry, confocal microscopy and flow cytometry. The targeting vectors C595 and PAI2 were labeled with the alpha emitting radioisotope 213Bi using the chelators cDTPA and CHX-A″ to form the alpha-conjugates (AC). Cell clusters were incubated with the AC and examined at 48 hours. Apoptosis was documented using the TUNEL assay. In vivo, the anti-proliferative effect for tumors was tested at two days post-subcutaneous cell inoculation. Mice were injected with different concentrations of AC by local or systemic administration. Changes in tumor progression were assessed by tumor size. MUC-1 and uPA are strongly expressed on CFPAC-1, PANC-1 and moderate expression was found CAPAN-1 cell clusters and tumor xenografts. The ACs can target pancreatic cells and regress cell clusters (~100 µm diameter), causing apoptosis in some 70-90 % of cells. At two days post-cell inoculation in mice, a single local injection of 74 MBq/kg of AC causes complete inhibition of tumor growth. Systemic injections of 111, 222 and 333 MBq/kg of alpha-conjugate caused significant tumor growth delay in a dose dependent manner after 16 weeks, compared with the non-specific control at 333 MBq/kg. Cytotoxicity was assessed by the MTS and TUNEL assays. The C595 and PAI2-alpha conjugates are indicated for the treatment of micro-metastatic pancreatic cancer with over-expression of MUC1 and uPA receptors in post-surgical patients with minimal residual disease. The observation of tumor regression in a Phase I clinical trial of targeted alpha therapy for metastatic melanoma indicates that alpha therapy can regress tumors by a process called tumor anti-vascular alpha therapy (TAVAT). As a consequence, this therapy could be indicated for the management of non-surgical pancreatic cancer tumors.

A pilot study of urokinase-type plasminogen activator (uPA) overexpression in the brush cytology of patients with malignant pancreatic or biliary strictures

We have previously demonstrated that uPA is overexpressed in pancreatic tumors. In an attempt to diagnose these tumors earlier, we sought to determine whether uPA could be identified in endoscopic retrograde cholangiopancreatography obtained brushings in patients with malignant pancreatic and biliary strictures. Secondarily, uPA was measured in the serum of this patient population. uPA overexpression was identified in the cytologic tissue in 8 of 11 patients (72.7%). Serum analysis demonstrated a 2-fold higher concentration of uPA in the pancreaticobiliary cancer patients (1.27 versus 0.56 ng/mL; P = .0182). Also, uPA overexpression correlated with serum levels (P < .0001). This study confirms that uPA can be detected in the ERCP cytologically obtained tissue and is frequently present in a higher concentration in the serum of pancreaticobiliary cancer patients. A larger sample size will be required to address its value as a sensitive marker for the diagnosis of pancreatic or biliary cancers.

Suppression of urokinase plasminogen activator receptor inhibits proliferation and migration of pancreatic adenocarcinoma cells via regulation of ERK/p38 signaling

Pancreatic ductal adenocarcinoma (PDAC) expresses high levels of urokinase-type plasminogen activator (uPA), its receptor (uPAR) and plasminogen activator inhibitor (PAI)-2, which may play an important role in PDAC progression. The overexpression of uPAR predicted short survival in PDAC patients. In this study, two different PDAC cell lines were used to examine the effect of small interfering (si) RNAs to uPAR, uPA and PAI-2 on proliferation, apoptosis, migration and MAP kinase activation. In both PDAC cell lines, siRNA to uPAR significantly inhibited cell proliferation and migration and stimulated apoptosis, to a greater extent than uPA siRNA. When either PDAC cell line was treated with uPAR siRNA, the level of phosphorylated ERK (p-ERK) decreased substantially, whereas phosphorylated p38 (p-p38) increased when compared to non-silencing control, uPA siRNA or PAI-2 siRNA treatment. This resulted in enhancement of the p-p38/p-ERK ratio which favors cancer cell arrest. Interestingly, uPAR protein expression was suppressed by p-ERK inhibition and stimulated with p-p38 inhibition, suggesting the presence of a positive feedback loop between uPAR and ERK. In summary, our data indicate that, of the uPA system, uPAR exerts the strongest effects on PDAC cells, by acting through the ERK signaling pathway via a positive feedback loop. Disruption of this loop with uPAR siRNA or inhibitor of p-ERK, inhibits PDAC proliferation and migration and promotes apoptosis. These findings suggest that uPAR strongly contributes to PDAC progression and may be considered as a potential anti-pancreatic cancer target.

Prognostic significance of growth factors and the urokinase-type plasminogen activator system in pancreatic ductal adenocarcinoma

OBJECTIVES

To determine the diagnostic and prognostic significance of growth factors and the urokinase-type plasminogen activator (uPA) system in pancreatic ductal adenocarcinoma (PDAC) using a multigene assay.

METHODS

Messenger RNA (mRNA) expression of 15 genes from epidermal growth factor receptor, insulin-like growth factor (IGF), and uPA families were measured in 46 PDAC tissue samples using quantitative real-time reverse transcription-polymerase chain reaction. These results were compared with those of the uninvolved adjacent (AP) tissue and benign mucinous cystadenomas (BMC). The mRNA expression was evaluated using logistic regression and receiver operating characteristic area under the curve (ROC AUC) analyses. Their relationship with prognosis was tested by Cox regression multivariate analysis.

RESULTS

All genes were overexpressed in most of the PDAC tissue. When compared with AP tissue, the median expression values for IGF-binding protein 3 (IGFBP-3) and uPA receptor (uPAR) was 9.8- and 9.6-fold, respectively. Expression levels of uPA, uPAR, IGF-I, and IGFBP-3 mRNA were significantly greater in PDAC than in BMC. The IGFBP-3 mRNA expression demonstrated greatest ROC AUC values for PDAC versus AP tissue (ROC AUC, 0.745; 95% confidence interval [CI], 0.65-0.86); whereas ROC AUC values were greatest for uPAR when PDAC was compared with BMC (ROC AUC, 0.846; 95% CI, 0.76-0.94). The combination of uPA, uPAR, and IGF-I significantly improved discriminatory power (ROC AUC, 0.965; 95% CI, 0.93-1.00). The IGFBP-3, uPA, plasminogen activator inhibitor-2, and International Union Against Cancer stage had a significant influence on survival, but the effect of IGFBP-3 was lost after multivariate stepwise analysis.

CONCLUSIONS

These results indicate that there is an influence of IGF system in tumor progression from BMC to PDAC, whereas the uPA/uPAR system has the greater influence on survival in PDAC.

Evolving role of uPA/uPAR system in human cancers

Recent advancements in cancer research have led to some major breakthroughs; however, the impact on overall cancer-related death rate remains unacceptable, suggesting that further insight into tumor markers and development of targeted therapies is urgently needed. The urokinase plasminogen activator (uPA) system represents a family of serine proteases that are involved in the degradation of basement membrane and the extracellular matrix, leading to tumor cell invasion and metastasis. In this review, we have provided an overview of emerging data, from basic research as well as clinical studies, highlighting the evolving role of uPA/uPAR system in tumor progression. It is currently believed that the expression and activation of uPA plays an important role in tumorigenicity, and high endogenous levels of uPA and uPAR are associated with advanced metastatic cancers. The endogenous inhibitors of this system, PAI-1 and PAI-2, regulate uPA-uPAR activity by either direct inhibition or affecting cell surface expression and internalization. PAI-1's role in cancers is rather unusual; on one hand, it inhibits uPA-uPAR leading to inhibition of invasion and metastasis and on the other it has been reported to facilitate tumor growth and angiogenesis. Individual components of uPA/uPAR system are reported to be differentially expressed in cancer tissues compared to normal tissues and, thus, have the potential to be developed as prognostic and/or therapeutic targets. Therefore, this system represents a highly attractive target that warrants further in-depth studies. Such studies are likely to contribute towards the development of molecularly-driven targeted therapies in the near future.

High expression of plasminogen activator inhibitor-2 (PAI-2) is a predictor of improved survival in patients with pancreatic adenocarcinoma

OBJECTIVE

Recent findings suggest that the urokinase-type plasminogen activator (uPA), its receptor (uPAR), plasminogen activator inhibitor-1 (PAI-1), and -2 (PAI-2) play key roles in cancer invasion. The prognostic value of components of this system is well established in breast cancer. However, little is known of its involvement in pancreatic cancer (PC).

METHODS

Quantitative real-time polymerase chain reaction (Q-RT-PCR) was used on tissue-banked specimens and immunohistochemistry (IHC) on paraffin specimens was used to measure expression of uPA, uPAR, PAI-1, and PAI-2 proteins in 46 PC and 12 cystadenoma specimens. Results were related to survival using Cox's proportional hazards testing.

RESULTS

Increased expression of uPA, uPAR, and PAI-1 in PC tissue were independently associated with a higher Union Internationale Contre le Cancer [International Union Against Cancer (UICC)] tumor stage (P < 0.001) and were intercorrelated (P < 0.001). Overexpression of uPAR indicated reduced survival (P = 0.03). Conversely, PAI-2 messenger ribonucleic acid (mRNA) overexpression, which occurred in 21 of 46 tumors, negatively correlated with tumor size (P = 0.008) and survival (P < 0.007) but not with uPA, uPAR, or tumor stage. There was good agreement between PAI-2 mRNA value and IHC score (P < 0.001). Using Cox's stepwise analysis, PAI-2 mRNA value (HR = 0.24; P = 0.001) and UICC tumor stage (HR = 2.014; P = 0.001) independently predicted survival. An IHC score for PAI-2 of 3+ or 4+ also independently predicted improved survival (HR = 2.72; P = 0.025).

CONCLUSIONS

The uPA/uPAR/PAI-1 system is activated in advanced pancreatic cancer and may account for the tumor's aggressive behavior, whereas PAI-2 expression appears to be independent of uPA/uPAR/PAI-1 and is associated with improved prognosis. Because of its intercorrelation with mRNA expression, PAI-2 IHC may be used as an indicator of survival.

Identification of a novel inhibitor of urokinase-type plasminogen activator

Urokinase-type plasminogen activator (uPA), a highly restricted serine protease, plays an important role in the regulation of diverse physiologic and pathologic processes. Strong clinical and experimental evidence has shown that elevated uPA expression is associated with cancer progression, metastasis, and shortened survival in patients. uPA has been considered as a promising molecular target for development of anticancer drugs. Here, we report the identification of several new uPA inhibitors using a high-throughput screen from a chemical library. From these uPA inhibitors, molecular modeling and docking studies identified 4-oxazolidinone as a novel lead pharmacophore. Optimization of the 4-oxazolidinone pharmacophore resulted in a series of structurally modified compounds with improved potency and selectivity. One of the 4-oxazolidinone analogues, UK122, showed the highest inhibition of uPA activity. The IC(50) of UK122 in a cell-free indirect uPA assay is 0.2 micromol/L. This compound also showed no or little inhibition of other serine proteases such as thrombin, trypsin, plasmin, and the tissue-type plasminogen activator, indicating its high specificity against uPA. Moreover, UK122 showed little cytotoxicity against CFPAC-1 cells (IC(50) >100 micromol/L) but significantly inhibited the migration and invasion of this pancreatic cancer cell line. Our data show that UK122 could potentially be developed as a new anticancer agent that prevents the invasion and metastasis of pancreatic cancer.

Activation of peroxisome proliferator-activated receptor-gamma decreases pancreatic cancer cell invasion through modulation of the plasminogen activator system

Cancer cell invasion and metastasis require the concerted action of several proteases that degrade extracellular matrix proteins and basement membranes. Recent reports suggest the plasminogen activator system plays a critical role in pancreatic cancer biology. In the present study, we determined the contribution of the plasminogen activator system to pancreatic cancer cell invasion in vitro. Moreover, the effect of peroxisome proliferator-activated receptor (PPAR)-gamma ligands, which are currently in clinical use as antidiabetic drugs and interestingly seem to display antitumor activities, on pancreatic cancer cell invasion and the plasminogen activator system was assessed. Expression of components of the plasminogen activator system [i.e., urokinase-type plasminogen activator (uPA), plasminogen activator inhibitor-1, and uPA receptor] was detected in six human pancreatic cancer cell lines. Inhibition of urokinase activity by specific synthetic compounds reduced baseline pancreatic cancer cell invasion. The PPAR-gamma ligands 15-deoxy-Delta12,14-prostaglandin J2 and ciglitazone also attenuated pancreatic cancer cell invasion. This effect was abrogated by dominant-negative PPAR-gamma receptors and pharmacologic PPAR-gamma inhibitors. Moreover, activation of PPAR-gamma by ligands increased plasminogen activator inhibitor-1 and decreased uPA levels in pancreatic cancer cells, and this was accompanied by a reduction in total urokinase activity. The present study shows that the plasminogen activator system plays an integral role in pancreatic cancer cell invasion in vitro. Activation of the nuclear receptor PPAR-gamma by ligands reduced pancreatic cancer cell invasion, which was largely mediated by modulation of the plasminogen activator system. These findings further underscore the potential role of PPAR-gamma ligands as therapeutic agents in pancreatic cancer.

Interleukin-1alpha enhances the aggressive behavior of pancreatic cancer cells by regulating the alpha6beta1-integrin and urokinase plasminogen activator receptor expression

Background

In human pancreatic cancer progression, the α₆β₁-integrin is expressed on cancer cell surface during invasion and metastasis formation. In this study, we investigated whether interleukin (IL)-1α induces the alterations of integrin subunits and urokinase plasminogen activator/urokinase plasminogen activator receptor (uPA/uPAR) expression in pancreatic cancer cells. We hypothesize that the alterations of integrin subunits and uPA/uPAR expression make an important role in signaling pathways responsible for biological behavior of pancreatic cancer cells.

Results

IL-1α upregulated the expression of α₆ and β₁ integrins without any alterations of α₅ and α_v integrins expression. IL-1α also induced enhancement in the expression of uPA/uPAR in pancreatic cancer cells. IL-1α enhanced the proliferation, adhesion, and migration in pancreatic cancer cells, and IL-1α-induced alterations of uPA/uPAR expression correlated with the increased the migration of pancreatic cancer cells. Upregulation of α₆ integrin subunit and uPA/uPAR correlated with the activation of Ras and downstream extracellular signal-regulated kinase (ERK) pathways. IL-1α-induced activation of Ras and downstream ERK can be inhibited by using inhibitory antibodies against α₆ and β₁ integrin and uPAR, consistent with the inhibition of proliferation, adhesion and migration of pancreatic cancer cells. Immunohistochemical analysis demonstrated a significant association between strong expressions of α₆ integrin with uPAR in pancreatic cancer specimens. Furthermore, the strong expression of α₆ integrin and uPAR was found to be independent prognosticator in pancreatic cancer patients.

Conclusion

Based on these findings, we conclude that IL-1α can induce selective upregulation of α₆β₁-integrin and uPA/uPAR in pancreatic cancer cells and these changes may modulate the aggressive functions of pancreatic cancer.

Epidermal growth factor promotes invasiveness of pancreatic cancer cells through NF-kappaB-mediated proteinase productions

OBJECTIVES

Overexpression of epidermal growth factor (EGF) and EGF receptor has been associated with progression and invasive phenotype in pancreatic cancer. However, the underlying molecular mechanism by which EGF worked in pancreatic cancer cells has been poorly understood. In this study, we determined the effect of EGF on the invasiveness and the related regulatory mechanism in two pancreatic cancer cell lines NOR-P1 and KP4.

METHODS

Invasion assay was performed to examine the invasiveness of tumor cells induced by EGF, and the expression of matrix metalloproteinase (MMP)-9, MMP-2, and plasminogen activator (uPA) was determined by reverse transcription-polymerase chain reaction and Western blot. Gelatin zymography was used to detect the activities of MMP-9 and MMP-2, and the nuclear factor-kappaB (NF-kappaB) binding activity was determined by electrophoretic mobility shift assay (EMSA).

RESULTS

EGF significantly increased the invasiveness of both cell lines but did not affect cell proliferation or adhesion. Increased invasiveness was associated with the induction of MMP-9 and uPA at both mRNA and protein levels. Furthermore, EGF stimulated NF-kappaB binding activity. Moreover, pretreatment of cells with NF-kappaB inhibitors, pyrrolidine dithiocarbamate or ibuprofen, markedly attenuated EGF-induced NF-kappaB activation. Subsequently, the EGF-induced MMP-9 and uPA expression and MMP-9 activity, as well as cell invasiveness, were also inhibited by these NF-kappaB inhibitors.

CONCLUSIONS

Our findings indicated that NF-kappaB-mediated MMP-9 and uPA induction was responsible for EGF-induced invasiveness in these pancreatic cancer cell lines and implicate that such anti-NF-kappaB therapy as the use of NF-kappaB inhibitors may contribute to the reduction of invasiveness of pancreatic cancer.

Assessment of HER-2 status in pancreatic adenocarcinoma: correlation of immunohistochemistry, quantitative real-time RT-PCR, and FISH with aneuploidy and survival

HER-2 is a transmembrane growth factor receptor recognized in overexpression as an independent adverse prognostic factor in several cancers. This study measured HER-2 overexpression in pancreatic adenocarcinoma at the genetic, transcriptional, and translational level. Expression was gauged with regard to stage, grade, and survival. Pancreatic adenocarcinoma samples (n = 30) were analyzed with immunohistochemical labeling for HER-2 protein, Quantitative real-time reverse transcriptase polymerase chain reaction (Q-RT-PCR) measurement of HER-2 mRNA and fluorescence in situ hybridization (FISH) analysis of HER-2 gene expression. HER-2 expression in benign pancreatic lesions (n = 10) provided a control. Five (17%) of the pancreatic adenocarcinomas scored maximal 3+ immunohistochemistry (IHC) labeling, seven (23%) had significantly increased expression of HER-2 mRNA, while only one (3%) exhibited low level HER-2 gene amplification. Ten (33%) tumors demonstrated aneuploidy. In general, concordance between methodologies was poor, but the best agreement was seen between FISH aneuploidy status and Q-RT-PCR mRNA overexpression (80% agreement), followed by IHC and Q-RT-PCR (73% agreement). The least agreement was seen between IHC and FISH aneuploidy status (67% agreement). Tumor stage was positively associated with HER-2 mRNA and protein expression, but tumor grade and other patient characteristics did not reach statistical significance. A poor survival outcome was demonstrated with positive HER-2 status in all three measures of overexpression (Kaplan-Meier log-rank score; P < 0.01 [IHC], P = 0.05 [Q-RT-PCR], P = 0.02 [FISH]). Discordance in expression at the nuclear, cytoplasmic, and cell surface levels highlights the limitations of immunohistochemical evaluation alone and stresses the need for further evaluation of response to anti-HER-2 targeted therapies in tumors displaying overexpression in gene copy, mRNA, and receptor protein.