cDNA transfection of amino-terminal fragment of urokinase efficiently inhibits cancer cell invasion and metastasis

Inhibition of Human Urokinase-Type Plasminogen Activator (uPA) Enzyme Activity and Receptor Binding by DNA Aptamers as Potential Therapeutics through Binding to the Different Forms of uPA

Urokinase-type plasminogen activator is widely discussed as a marker for cancer prognosis and diagnosis and as a target for cancer therapies. Together with its receptor, uPA plays an important role in tumorigenesis, tumor progression and metastasis. In the present study, systematic evolution of ligands by exponential enrichment (SELEX) was used to select single-stranded DNA aptamers targeting different forms of human uPA. Selected aptamers allowed the distinction between HMW-uPA and LMW-uPA, and therefore, presumably, have different binding regions. Here, uPAapt-02-FR showed highly affine binding with a K_D of 0.7 nM for HMW-uPA and 21 nM for LMW-uPA and was also able to bind to pro-uPA with a K_D of 14 nM. Furthermore, no cross-reactivity to mouse uPA or tissue-type plasminogen activator (tPA) was measured, demonstrating high specificity. Suppression of the catalytic activity of uPA and inhibition of uPAR-binding could be demonstrated through binding with different aptamers and several of their truncated variants. Since RNA aptamers are already known to inhibit uPA-uPAR binding and other pathological functions of the uPA system, these aptamers represent a novel, promising tool not only for detection of uPA but also for interfering with the pathological functions of the uPA system by additionally inhibiting uPA activity.

Spontaneous lung and lymph node metastasis in transgenic breast cancer is independent of the urokinase receptor uPAR

Urokinase-type plasminogen activator (uPA) is an extracellular protease that plays a pivotal role in tumor progression. uPA activity is spatially restricted by its anchorage to high-affinity uPA receptors (uPAR) at the cell surface. High tumor tissue expression of uPA and uPAR is associated with poor prognosis in lung, breast, and colon cancer patients in clinical studies. Genetic deficiency of uPA leads to a significant reduction in metastases in the murine transgenic MMTV-PyMT breast cancer model, demonstrating a causal role for uPA in cancer dissemination. To investigate the role of uPAR in cancer progression, we analyze the effect of uPAR deficiency in the same cancer model. uPAR is predominantly expressed in stromal cells in the mouse primary tumors, similar to human breast cancer. In a cohort of MMTV-PyMT mice [uPAR-deficient (n = 31) or wild type controls (n = 33)], tumorigenesis, tumor growth, and tumor histopathology were not significantly affected by uPAR deficiency. Lung and lymph node metastases were also not significantly affected by uPAR deficiency, in contrast to the significant reduction seen in uPA-deficient mice. Taken together, our data show that the genetic absence of uPAR does not influence the outcome of the MMTV-PyMT cancer model.

Herbal compound triptolide synergistically enhanced antitumor activity of amino-terminal fragment of urokinase

Background

Urokinase (uPA) and its receptor (uPAR) play an important role in tumour growth and metastasis, and overexpression of these molecules is strongly correlated with poor prognosis in a variety of malignant tumours. Targeting the excessive activation of this system as well as the proliferation of the tumour vascular endothelial cell would be expected to prevent tumour neovasculature and halt tumour development. The amino terminal fragment (ATF) of urokinase has been confirmed effective to inhibit the proliferation, migration and invasiveness of cancer cells via interrupting the interaction of uPA and uPAR. Triptolide (TPL) is a purified diterpenoid isolated from the Chinese herb Tripterygium wilfordii Hook F that has shown antitumor activities in various cancer cell types. However, its therapeutic application is limited by its toxicity in normal tissues and complications caused in patients. In this study, we attempted to investigate the synergistic anticancer activity of TPL and ATF in various solid tumour cells.

Methods

Using in vitro and in vivo experiments, we investigated the combined effect of TPL and ATF at a low dosage on cell proliferation, cell apoptosis, cell cycle distribution, cell migration, signalling pathways, xenograft tumour growth and angiogenesis.

Results

Our data showed that the sensitivity of a combined therapy using TPL and ATF was higher than that of TPL or ATF alone. Suppression of NF-κB transcriptional activity, activation of caspase-9/caspase-3, cell cycle arrest, and inhibition of uPAR-mediated signalling pathway contributed to the synergistic effects of this combination therapy. Furthermore, using a mouse xenograft model, we demonstrated that the combined treatment completely suppressed tumour growth by inhibiting angiogenesis as compared with ATF or TPL treatment alone.

Conclusions

Our study suggests that lower concentration of ATF and TPL used in combination may produce a synergistic anticancer efficacy that warrants further investigation for its potential clinical applications.

HAX1 Augments Cell Proliferation, Migration, Adhesion, and Invasion Induced by Urokinase-Type Plasminogen Activator Receptor

The urokinase-type plasminogen activator receptor (uPAR) is a cell surface receptor which has a multifunctional task in the process of tumorigenesis including cell proliferation, adhesion, migration, and invasion. Many of the biological functions of uPAR necessitate interactions with other proteins. We have shown previously that uPAR interacts with HAX1 protein (HS-1-associated protein X-1). In the current study, to gain insight into the possible role of HAX1 overexpression in regulation of uPAR signal transduction pathway, several function assays were used. We found that, upon stimulation of uPAR, HAX1 colocalizes with uPAR suggesting a physiological role for HAX1 in the regulation of uPAR signal transduction. HAX1 overexpression augments cell proliferation and migration in uPAR-stimulated cells. Moreover, HAX1 over-expression augmented uPAR-induced cell adhesion to vitronectin as well as cellular invasion. Our results suggest that HAX1 over-expression may underlay a novel mechanism to regulate uPAR-induced functions in cancer cells.

Modulators of the urokinase-type plasminogen activation system for cancer

IMPORTANCE OF THE FIELD

The serine protease urokinase-type plasminogen activator (uPA) and its receptor uPAR as well as two specific inhibitors, the plasminogen activator inhibitor type-1 (PAI-1) and type-2 (PAI-2), are involved in the control of extracellular matrix turnover and tumor growth. Data accumulating over the past 20 years have made increasingly clear that the uPA system has a multifunctional role in neoplastic evolution, affecting cancer cell proliferation, tumor angiogenesis, adhesion and migration.

AREAS COVERED IN THIS REVIEW

Several therapeutic strategies inhibiting the uPA system have been or are currently being developed for suppression of tumor growth. This review examines the role of the uPA system in tumor progression and assesses the various therapeutic strategies developed to selectively exploit this system.

WHAT WILL THE READER GAIN

We focus on the therapeutic developments of the last 15 years. In addition to antibodies and recombinant uPA- or uPAR-derived proteins, various antagonistic peptides as well as small molecules have been designed and synthesized that inhibit the uPA system, leading to reduced tumor progression.

TAKE HOME MESSAGE

The multifunctional potential of the uPA system in cancer has rendered this system an attractive novel target for anticancer therapy. A few novel tumor biology-based therapeutic strategies reported here, opening new ways for patient-optimized and individualized cancer therapy. It may be the right time to evaluate the hypothesis that the uPA system plays a pivotal role in cancer progression and that targeting this system will lead to clinical benefit in cancer patients.

Urokinase plasminogen activator system as a potential target for cancer therapy

Proteolysis of extracellular matrix (ECM) and basement membrane is an essential mechanism used by cancer cells for their invasion and metastasis. The ECM proteinases are divided into three groups: metalloproteinases, cysteine proteinases and serine proteinases. The urokinase plasminogen activator (uPA) system is one of the serine proteinase systems involved in ECM degradation. Members of this system, including uPA and its receptor (uPAR), are overexpressed in several malignant tumors. This system plays a major role in adhesion, migration, invasion and metastasis of cancer cells, thus making it an important target for anticancer drug therapy. Several strategies, including the use of antisense oligodeoxynucleotides, ribozymes, DNAzyme, RNAi, uPA inhibitors, soluble uPAR, catalytically inactive uPA fragments, synthetic peptides and synthetic hybrids are under study, as they interfere with the expression and/or activity of uPA or uPAR in tumor cells. Herein, we discuss the various pharmaceutical strategies under investigation to combat the uPA activity in cancer.

The roles of proteolytic enzymes in the development of tumour-induced bone disease in breast and prostate cancer

Tumour-induced bone disease is a common clinical feature of advanced breast and prostate cancer and is associated with considerable morbidity for the affected patients. Our understanding of the molecular mechanisms underlying the development of bone metastases is incomplete, but proteolytic enzymes are implicated in a number of processes involved in both bone metastasis and in normal bone turnover, including matrix degradation, cell migration, angiogenesis, tumour promotion and growth factor activation. Malignant as well as non-malignant cells in the primary and secondary sites express these enzymes, the activity of which may be regulated by soluble factors, cell- or matrix-associated components, as well as a number of cell signalling pathways. A number of secreted and cell surface-associated proteolytic enzymes are implicated in tumour-induced bone disease, including the matrix metalloproteinases, lysosomal cysteine proteinases and plasminogen activators. This review will introduce the role of proteolytic enzymes in normal bone turnover and give an overview of the studies in which their involvement and regulation in the development of bone metastases in breast and prostate cancer has been described. The results from trials involving protease inhibitors in clinical development will also be briefly discussed.

Targeting urokinase-type plasminogen activator and its receptor for cancer therapy

Cancer invasion and metastasis are highly complex processes and a serine protease urokinase-type plasminogen activator/urokinase-type plasminogen activator receptor system has been postulated to play a central role in the mediation of cancer progression. Of note, malignant tumor urokinase-type plasminogen activator and urokinase-type plasminogen activator receptor levels have been found to vary considerably, and to be related to patient prognosis. In mouse models, the urokinase-type plasminogen activator/urokinase-type plasminogen activator receptor system has been studied extensively as a target for anticancer therapy using a variety of approaches. In this review, we discuss the advances in the various modalities that have been used to target the urokinase-type plasminogen activator/urokinase-type plasminogen activator receptor system, including protein-based and peptide-based drugs, antisense therapy, and RNA interference technology. In particular, preclinical mouse model studies that used human tumor xenografts are reviewed.

The protease inhibitor bikunin, a novel anti-metastatic agent

Bikunin is a Kunitz-type protease inhibitor predominantly found in human amniotic fluid. In cancers, administration of bikunin may block tumor cell invasion by a direct inhibition of tumor cell-associated plasmin activity as well as by inhibiting urokinase-type plasminogen activator (uPA) expression at the gene and protein levels, possibly through suppression of CD44 dimerization and/or the MAP kinase signaling cascade. Treatment of cancer patients with bikunin may be beneficial in the adjuvant setting to delay the onset of metastasis development and/or in combination with cytotoxic agents to improve treatment efficacy in patients with advanced ovarian cancer.

Suppression of invasion and peritoneal carcinomatosis of ovarian cancer cell line by overexpression of bikunin

Bikunin (bik), a Kunitz-type protease inhibitor, also known as urinary trypsin inhibitor, is proposed as a main participant in the inhibition of tumor cell invasion and metastasis, possibly through the direct inhibition of cell-associated plasmin activity and suppression of urokinase-type plasminogen activator (uPA) mRNA expression. In the present study, we transfected the human ovarian carcinoma cell line HRA, highly invasive cells, with an expression vector harboring a cDNA encoding for human bik. Our study was designed to investigate the effect of bik overexpression and changes in tumor cell phenotype and invasiveness in the stably transfected clones. Bik gene transfection of HRA gave the following results: 1) transfection of HRA with the bik cDNA resulted in 5 variants stably expressing functional bik; 2) bik(+) clones exhibited a significantly reduced uPA mRNA expression as compared to the parental cells; 3) bikunin negatively regulates the ERK1/2 activity; 4) secretion-blocking treatments of bik(+) clones abrogated bik-mediated suppression of ERK1/2 activation and uPA expression; 5) the regulation of invasion seen in the HRA cells is mainly mediated by the uPA-plasmin-MMP-2 system; 6) transfection of HRA with the bik gene significantly reduced invasion, but not proliferation, adhesion, or migration relative to the parental cells; and 7) animals with bik(+) clones induced reduced peritoneal dissemination and long term survival. We conclude that transfection of HRA cells with the bik cDNA constitutively suppresses ERK1/2 activation, which results in inhibition of uPA expression and subsequently reduces dissemination of bik(+) clones.

The role of the plasminogen activation cascade in glioma cell invasion: a review

Tumour cell invasion is a dynamic process that depends on a co-ordinated series of biochemical events. This review discusses the role of the proteolytic enzyme system, the plasminogen activation cascade, in glioma cell invasion.

Modulation of invasive properties of human glioblastoma cells stably expressing amino-terminal fragment of urokinase-type plasminogen activator

The binding of urokinase-type plasminogen activator (uPA) to its receptor (uPAR) on the surface of tumor cells is involved in the activation of proteolytic cascades responsible for the invasiveness of those cells. The diffuse, extensive infiltration of glioblastomas into the surrounding normal brain tissue is believed to rely on modifications of the proteolysis of extracellular matrix components; blocking the interaction between uPA and uPAR might be a suitable approach for inhibiting glioma tumorigenesis. We assessed how expression of an amino-terminal fragment (ATF) of uPA that contains binding site to uPAR affects the invasiveness of SNB19 human glioblastoma cells. SNB19 cells were transfected with an expression plasmid (pcDNA3-ATF) containing a cDNA sequence of ATF-uPA. The resulting ATF-uPA-expressing clones showed markedly less cell adhesion, spreading, and clonogenicity than did control cells. Endogenous ATF expression also significantly decreased the invasive capacity of transfected glioblastoma cells in Matrigel and spheroid-rat brain cell aggregate models. ATF-uPA transfectants were also markedly less invasive than parental SNB19 cells after injection into the brains of nude mice, suggesting that competitive inhibition of the uPA-uPAR interaction on SNB19 cells by means of transfection with ATF cDNA could be a useful therapeutic strategy for inhibiting tumor progression.