Urokinase mediates endothelial cell survival via induction of the X-linked inhibitor of apoptosis protein

Urokinase prophylactic anticoagulation in children with nephrotic syndrome: a multicenter retrospective cohort study

OBJECTIVE

To analyze the clinical effect of urokinase on the prevention of thrombosis in children with primary nephrotic syndrome.

METHODS

A total of 370 children diagnosed with primary nephrotic syndrome (PNS) in the Children's Hospital of Soochow University and Zibo Maternal and Child Health Hospital from January 2018 to December 2022 were selected as the research objects. The patients were divided into a urokinase adjuvant therapy group and non-urokinase adjuvant therapy group according to the application of drugs. The clinical data of the children were collected, including sex, age, drug application, bleeding during treatment, and telephone follow-up, to record whether thromboembolism occurred in the acute stage and remission stage. The clinical pattern of PNS, renal biopsy, histopathological type, and related laboratory indexes before and after treatment were recorded.

RESULTS

A total of 313 patients were treated with urokinase and 57 patients were not. More thrombotic events was observed in non-urokinase group compared to the urokinase group(2 versus 0 episodes, p = 0.02). The thrombotic events observed included one patient had pulmonary embolism combined with right ventricular thrombosis, and another had intracranial venous thrombosis. More minor bleeding events occurred in urokinase group compared to the non-urokinase group(7 versus 1 episodes, p = 1.0). No major bleeding events occurred in either group.

CONCLUSION

The rational prophylactic use of urokinase anticoagulation in children with PNS can prevent the formation of thromboembolism and has good safety.

uPA deficiency aggravates cBSA-induced membranous nephropathy through Th2-prone immune response in mice

Urokinase plasminogen activator (uPA) is a crucial activator of the fibrinolytic system that modulates tissue remodeling, cancer progression, and inflammation. However, its role in membranous nephropathy (MN) remains unclear. To clarify this issue, an established mouse model mimicking human MN induced by cationic bovine serum albumin (cBSA) in BALB/c mice was used, which have a Th2-prone genetic background. To induce MN, cBSA was injected into Plau knockout (Plau-/-) and wild-type (WT) mice. The blood and urine samples were collected to measure biochemical parameters, including serum concentrations of IgG1 and IgG2a, using enzyme-linked immunoassay. The kidneys were histologically examined for the presence of glomerular polyanions, reactive oxygen species (ROS), and apoptosis, and transmission electron microscopy was used to examine subepithelial deposits. Lymphocyte subsets were determined by flow cytometry. Four weeks post-cBSA administration, Plau-/- mice exhibited a significantly high urine protein/creatine ratio, hypoalbuminemia, and hypercholesterolemia compared with WT mice. Histologically, compared with WT mice, Plau-/- mice showed more severe glomerular basement thickening, mesangial expansion, IgG granular deposition, intensified podocyte effacement, irregular thickening of glomerular basement membrane and subepithelial deposits, and abolishment of the glycocalyx. Moreover, increased renal ROS and apoptosis were observed in Plau-/- mice with MN. B lymphocyte subsets and the IgG1/IgG2a ratio were significantly higher in Plau-/- mice after MN induction. Thus, uPA deficiency induces a Th2-dominant immune response, leading to increased subepithelial deposits, ROS, and apoptosis in the kidneys, subsequently exacerbating MN progression in mice. This study provides a novel insight into the role of uPA in MN progression.

The uPA/uPAR System Orchestrates the Inflammatory Response, Vascular Homeostasis, and Immune System in Fibrosis Progression

Fibrotic diseases, such as systemic sclerosis (SSc), idiopathic pulmonary fibrosis, renal fibrosis and liver cirrhosis are characterized by tissue overgrowth due to excessive extracellular matrix (ECM) deposition. Fibrosis progression is caused by ECM overproduction and the inhibition of ECM degradation due to several events, including inflammation, vascular endothelial dysfunction, and immune abnormalities. Recently, it has been reported that urokinase plasminogen activator (uPA) and its receptor (uPAR), known to be fibrinolytic factors, orchestrate the inflammatory response, vascular homeostasis, and immune homeostasis system. The uPA/uPAR system may show promise as a potential therapeutic target for fibrotic diseases. This review considers the role of the uPA/uPAR system in the progression of fibrotic diseases.

Keeping abreast about ashwagandha in breast cancer

ETHNOPHARMACOLOGICAL RELEVANCE

Ashwagandha has been used as an ayurvedic medicine in the form of 'Rasayana' (as a tonic) even before 3000 BCE in India. As per Ayurveda, it has long been used traditionally for the treatment of inflammation, weakness, impotence, pulmonary tuberculosis. This plant is also beneficial in lumbago and leucorrhea in the female. In the recent past, Withania has shown its anti-cancerous activity in various experimental models. In addition, Withania also possesses many other properties such as anti-oxidant, anti-stress, adaptogenic, and regenerative which will eventually be beneficial and safe in treating cancer patients.

AIM OF THE STUDY

This review aims to provide experimental evidence along with a deeper insight into molecular mechanisms of Ashwagandha (Withania somnifera (L.) Dunal) through which it acts as a chemotherapeutic agent against different types of breast cancer.

MATERIALS AND METHODS

Literature searches with the help of electronic online databases (Elsevier, Google Scholar, Scopus, Springer Link, ScienceDirect, ResearchGate, PubMed) were carried out. The timeline for collection of data for the review article was from 2000 to 2019. The plant name was validated from The Plant List (2013). Version 1.1. Published on http://www.theplantlist.org/(accessed 21st March 2020).

RESULTS

Various forms of Withania somnifera were used and several in vitro, in vivo, and clinical studies were reported by researchers. They found ashwagandha to exhibit anti-apoptotic, anti-metastatic, anti-invasive and anti-inflammatory properties and gave the evidence that ashwagandha has a capability for averting and treating breast cancer.

CONCLUSION

Various in vitro and in vivo studies suggested Ashwagandha may possess a potential for treating breast cancer, especially ER/PR positive breast cancer and triple-negative breast cancer. A clinical trial has also been conducted in the past that suggested its potential in refining quality of life in breast cancer patients. Studies directed towards molecular pathways have helped in unravelling the key mechanisms of ashwagandha. Future research should be directed towards translational studies involving breast cancer patients. These will reinforce the ancient power of our Ayurvedic medicine.

Fibrinolytic Serine Proteases, Therapeutic Serpins and Inflammation: Fire Dancers and Firestorms

The making and breaking of clots orchestrated by the thrombotic and thrombolytic serine protease cascades are critical determinants of morbidity and mortality during infection and with vascular or tissue injury. Both the clot forming (thrombotic) and the clot dissolving (thrombolytic or fibrinolytic) cascades are composed of a highly sensitive and complex relationship of sequentially activated serine proteases and their regulatory inhibitors in the circulating blood. The proteases and inhibitors interact continuously throughout all branches of the cardiovascular system in the human body, representing one of the most abundant groups of proteins in the blood. There is an intricate interaction of the coagulation cascades with endothelial cell surface receptors lining the vascular tree, circulating immune cells, platelets and connective tissue encasing the arterial layers. Beyond their role in control of bleeding and clotting, the thrombotic and thrombolytic cascades initiate immune cell responses, representing a front line, "off-the-shelf" system for inducing inflammatory responses. These hemostatic pathways are one of the first response systems after injury with the fibrinolytic cascade being one of the earliest to evolve in primordial immune responses. An equally important contributor and parallel ancient component of these thrombotic and thrombolytic serine protease cascades are the serine protease inhibitors, termed serpins. Serpins are metastable suicide inhibitors with ubiquitous roles in coagulation and fibrinolysis as well as multiple central regulatory pathways throughout the body. Serpins are now known to also modulate the immune response, either via control of thrombotic and thrombolytic cascades or via direct effects on cellular phenotypes, among many other functions. Here we review the co-evolution of the thrombolytic cascade and the immune response in disease and in treatment. We will focus on the relevance of these recent advances in the context of the ongoing COVID-19 pandemic. SARS-CoV-2 is a "respiratory" coronavirus that causes extensive cardiovascular pathogenesis, with microthrombi throughout the vascular tree, resulting in severe and potentially fatal coagulopathies.

Therapeutics targeting the fibrinolytic system

The function of the fibrinolytic system was first identified to dissolve fibrin to maintain vascular patency. Connections between the fibrinolytic system and many other physiological and pathological processes have been well established. Dysregulation of the fibrinolytic system is closely associated with multiple pathological conditions, including thrombosis, inflammation, cancer progression, and neuropathies. Thus, molecules in the fibrinolytic system are potent therapeutic and diagnostic targets. This review summarizes the currently used agents targeting this system and the development of novel therapeutic strategies in experimental studies. Future directions for the development of modulators of the fibrinolytic system are also discussed.

The fibrinolytic system was originally identified to dissolve blood clots, and is shown to have important roles in other pathological processes, including cancer progression, inflammation, and thrombosis. Molecules or therapeutics targeting fibrinolytic system have been successfully used in the clinical treatments of cancer and thrombotic diseases. The clinical studies and experimental models targeting fibrinolytic system are reviewed by Haili Lin at Sanming First Hosipital, Mingdong Huang at Fuzhou University in China, and Peng Xu at A*STAR in Singapore to demonstrate fibrinolytic system as novel therapeutic targets. As an example, the inhibition of fibrinolytic system protein can be used to suppress cancer prolifieration and metastasis. This review also discusses the potential therapeutic effects of inhibitiors of fibrinolytic system on inflammatory disorders.

Suppression of Tumor Growth and Metastases by Targeted Intervention in Urokinase Activity with Cyclic Peptides

Urokinase-type plasminogen activator (uPA) is a diagnostic marker for breast and prostate cancers recommended by American Society for Clinical Oncology and German Breast Cancer Society. Inhibition of uPA was proposed as an efficient strategy for cancer treatments. In this study, we report peptide-based uPA inhibitors with high potency and specificity comparable to monoclonal antibodies. We revealed the binding and inhibitory mechanisms by combining crystallography, molecular dynamic simulation, and other biophysical and biochemical approaches. Besides, we showed that our peptides efficiently inhibited the invasion of cancer cells via intervening with the processes of the degradation of extracellular matrices. Furthermore, our peptides significantly suppressed the tumor growth and the cancer metastases in tumor-bearing mice. This study demonstrates that these uPA peptides are highly potent anticancer agents and reveals the mechanistic insights of these uPA inhibitors, which can be useful for developing other serine protease inhibitors.

The anti-cancer effect of amygdalin on human cancer cell lines

Derived from rosaceous plant seed, amygdalin belongs to aromatic cyanogenic glycoside group, and its anticancer effects have been supported by mounting evidence. In this study, we objected to investigate amygdalin effect on two antiapoptotic genes (Survivin, XIAP) and two lncRNAs (GAS5, MALAT1) in human cancer cells (A549, MCF7, AGS). Employing RT-qPCR analysis, we compared the mRNA levels of the genes related to apoptosis in A549, MCF7, and AGS cancer cells between amygdalin-treated (24, 48 and 72 h) and un-treated groups. RNA was extracted from both cell groups and then cDNAs were synthesized. The changes in the gene expression levels were specified using ΔΔCt method. RT-qPCR analysis has revealed that the expression of Survivin, XIAP, GAS5 and MALAT1 in amygdala-treated cancer cells were significantly different, compared to the un-treated cells. However, these expressions were different depending on the treatment time. According to the results, amygdalin significantly inhibited the expression level of Survivin, and XIAP genes in treated via untreated group. Our findings suggest that amygdalin might have an anticancer effect due to the various gene expressions in A549, MCF7, and AGS human cancer cells, showing it's potential as a natural therapeutic anticancer drug.

The Role of Fibrinolytic Regulators in Vascular Dysfunction of Systemic Sclerosis

Systemic sclerosis (SSc) is a connective tissue disease of autoimmune origin characterized by vascular dysfunction and extensive fibrosis of the skin and visceral organs. Vascular dysfunction is caused by endothelial cell (EC) apoptosis, defective angiogenesis, defective vasculogenesis, endothelial-to-mesenchymal transition (EndoMT), and coagulation abnormalities, and exacerbates the disease. Fibrinolytic regulators, such as plasminogen (Plg), plasmin, α2-antiplasmin (α2AP), tissue-type plasminogen activator (tPA), urokinase-type plasminogen activator (uPA) and its receptor (uPAR), plasminogen activator inhibitor 1 (PAI-1), and angiostatin, are considered to play an important role in the maintenance of endothelial homeostasis, and are associated with the endothelial dysfunction of SSc. This review considers the roles of fibrinolytic factors in vascular dysfunction of SSc.

The urokinase plasminogen activator system components are regulated by vascular endothelial growth factor D in bovine oviduct

SummaryThe mammalian oviduct plays a pivotal role in the success of early reproductive events. The urokinase plasminogen activator system (uPAS) is present in the bovine oviduct and is involved in extracellular matrix remodelling through plasmin generation. This system can be regulated by several members of the vascular endothelial growth factors (VEGF) and their receptors. In this study, the VEGF-D effect on the regulation of uPAS was evaluated. First, RT-polymerase chain reaction (PCR) analyses were used to evidence the expression of VEGF-D and its receptors in oviductal epithelial cells (BOEC). VEGF-D, VEGFR2 and VEGFR3 transcripts were found in ex vivo and in vitro BOEC, while only VEGFR2 mRNA was present after in vitro conditions. VEGF-D showed a regulatory effect on uPAS gene expression in a dose-dependent manner, inducing an increase in the expression of both uPA and its receptor (uPAR) at 24 h post-induction and decreases in the expression of its inhibitor (PAI-1). In addition, the regulation of cell migration induced by VEGF-D and uPA in BOEC monolayer cultures was analyzed. The wound areas of monolayer cultures incubated with VEGF-D 10 ng/ml or uPA 10 nM were modified and significant differences were found at 24 h for both stimulations. These results indicated that uPAS and VEGF-D systems can modify the arrangement of the bovine oviductal epithelium and contribute to the correct maintenance of the oviductal microenvironment.

Urokinase plasminogen activator protects cardiac myocytes from oxidative damage and apoptosis via hOGG1 induction

The role of uPA in tissue remodeling and cell migration is already well established. In addition, uPA was reported to stabilize p53, a key cell cycle control, DNA repair and apoptosis initiation protein. We aimed to determine the role of uPA-uPAR signaling towards cell survival or apoptosis in human adult cardiac myocytes (HACM). HACM were stimulated with uPA and DNA damage was inflicted by incubating cells with 200 µM H₂O₂. To analyze for apoptotic cells we applied TUNEL staining. Oxidative damage foci were analyzed by staining for 8-oxoguanine base pairs. In vivo qPCR analysis from RNA extracted from failing human hearts demonstrated a close relation of uPA with apoptosis and the p53 pathway. Furthermore, we observed a close correlation of uPA and p53 protein in homogenized tissue lysates. In vitro studies revealed that uPA preincubation protected HACM from oxidative damage induced cell death and reduced oxidative damage foci. uPA protection is independent of its catalytic activity, as the amino terminal fragment of uPA showed similar protection. A key enzyme for repairing oxidative DNA damage is the p53 target hOGG1. We found a significant increase of hOGG1 after pretreatment of HACM with uPA. Knockdown of hOGG1 completely abrogated the protective effect of uPA. We conclude that uPA might have a tissue protective role in human hearts besides its role in tissue remodeling. Tissue protection is mediated by the DNA repair protein hOGG1. This might be beneficial during tissue remodeling and thus could be a target for therapeutic approaches in the diseased heart.

Protective, repairing and fibrinolytic effects of rivaroxaban on vascular endothelium

AIMS

Rivaroxaban, a direct inhibitor of activated factor X (FXa), is the only new oral anticoagulant approved for secondary prevention after acute coronary syndrome. Our objective was to identify the possible molecular mechanisms of rivaroxaban that contribute to endothelial function.

METHODS

Cell viability and growth of human umbilical vein endothelial cells (HUVEC) were registered. Gene expression studies comparing the effects of rivaroxaban and FXa were conducted by a selective RNA array and confirmed by protein quantification. Wound-healing experiments on HUVEC, platelet adhesion, enzymatic activity, and cell-based assays for fibrin formation were performed with rivaroxaban.

RESULTS

Rivaroxaban (50 nM) only altered (>2 fold change) the expression of matrix metallopeptidase 2 and urokinase plasminogen activator (u-PA), but counteracted the FXa (9 nM)-induced upregulation of several pro-inflammatory genes (P < 0.05) and FXa-enhanced platelet adhesion over HUVEC. Rivaroxaban increased u-PA protein expression in HUVEC supernatants and enhanced u-PA activity (up to 4 IU ng^-1 of u-PA). Rivaroxaban (1 nM-1 μM) showed a significant and dose-dependent positive effect on HUVEC growth that was inhibited by BC-11-hydroxibromide, an inhibitor of u-PA. Healing properties after a wound on HUVEC cultures, and fibrinolytic properties were also shown by rivaroxaban. Both effects were reversed by BC-11-hydroxibromide.

CONCLUSIONS

Rivaroxaban enhanced viability, growth and migration of HUVEC, mainly by u-PA activation and upregulation, which also participate in the rivaroxaban-induced fibrinolytic activity at endothelial level. Rivaroxaban also protected from the pro-inflammatory effects of FXa on HUVEC. Altogether may improve endothelial functionality and could contribute to the cardiovascular benefits of rivaroxaban.

Quercetin Has Antimetastatic Effects on Gastric Cancer Cells via the Interruption of uPA/uPAR Function by Modulating NF-κb, PKC-δ, ERK1/2, and AMPKα

Gastric cancer (GC) is a malignancy with few effective treatment options after metastasis occurs. Quercetin (Qu) intake has been associated with reduced incidence and slow development of GC, probably due to its anti-proliferative and apoptotic effects, but it is unclear whether Qu can inhibit the metastatic activity. The urokinase plasminogen activator (uPA)/uPA receptor (uPAR) system plays an important role in cancer metastasis. In this study, we measured both uPA activity and uPAR expression in GC and pericarcinous tissues, and we investigated the correlation between uPAR expression and the migratory and invasive activities of various GC cell lines. GC BGC823 and AGS cells were subjected to treatment with 10 μM Qu for 72 hours and uPAR knockdown, alone or in combination, before evaluating cell metastasis. The results showed that uPA activity and uPAR expression were higher in GC tissues than in pericarcinous tissues. Migratory and invasive activities of GC cell lines positively correlated with uPAR expression. Qu treatment decreased BGC823 and AGS cell migration and invasion, accompanied by reduced uPA and uPAR protein expression. Both Qu treatment and uPAR knockdown decreased matrix metalloproteinase-2 and -9 activity and blocked Pak1-Limk1-cofilin signaling. Qu treatment was associated with inhibition of NF-κb, PKC-δ, and ERK1/2, and with AMPKα activation. Specific inhibitors of NF-κb, PKC, and ERK1/2, and an AMPKα activator suppressed uPA and uPAR expression in GC cells. Collectively, Qu showed an antimetastatic effect on GC cells via the interruption of uPA/uPAR function and modulation of NF-κb, PKC-δ, ERK1/2, and AMPKα. This suggests that Qu is a promising agent against GC metastasis.

SERPINE2/Protease Nexin-1 in vivo multiple functions: Does the puzzle make sense?

Cultures of glial cells and fibroblasts allowed and lead to the identification SERPINE2/Protease Nexin-1 (SERPINE2/PN-1). Cellular, biochemical, immunological and molecular characterization substantiated its variable expression in many organs as a function of development, adult stages, pathological situations or following injury. It is not a circulating serpin, but as other members of the family, its target specificity is influenced by components of the extracellular matrix. The challenges are to identify where and when SERPINE2/PN-1 modulatory action becomes crucial or even possibly specific in a mosaic of feasible in vivo impacts. Data providing correlations are not sufficient to satisfy this aim. Genetically modified mice, or tissue derived thereof, provide interesting in vivo models to identify and study the relevance of this serpin. This review will highlight sometimes-intriguing results indicating a crucial impact of SERPINE2/PN-1, especially in the vasculature, the nervous system or the behavior of cancer cells in vivo. Data presently available will be discussed in an attempt to define general trends in the diversity of SERPINE2/PN-1 modes of action in vivo.

Urokinase-type Plasminogen Activator (uPA) Promotes Angiogenesis by Attenuating Proline-rich Homeodomain Protein (PRH) Transcription Factor Activity and De-repressing Vascular Endothelial Growth Factor (VEGF) Receptor Expression

Urokinase-type plasminogen activator (uPA) regulates angiogenesis and vascular permeability through proteolytic degradation of extracellular matrix and intracellular signaling initiated upon its binding to uPAR/CD87 and other cell surface receptors. Here, we describe an additional mechanism by which uPA regulates angiogenesis. Ex vivo VEGF-induced vascular sprouting from Matrigel-embedded aortic rings isolated from uPA knock-out (uPA(-/-)) mice was impaired compared with vessels emanating from wild-type mice. Endothelial cells isolated from uPA(-/-) mice show less proliferation and migration in response to VEGF than their wild type counterparts or uPA(-/-) endothelial cells in which expression of wild type uPA had been restored. We reported previously that uPA is transported from cell surface receptors to nuclei through a mechanism that requires its kringle domain. Intranuclear uPA modulates gene transcription by binding to a subset of transcription factors. Here we report that wild type single-chain uPA, but not uPA variants incapable of nuclear transport, increases the expression of cell surface VEGF receptor 1 (VEGFR1) and VEGF receptor 2 (VEGFR2) by translocating to the nuclei of ECs. Intranuclear single-chain uPA binds directly to and interferes with the function of the transcription factor hematopoietically expressed homeodomain protein or proline-rich homeodomain protein (HHEX/PRH), which thereby lose their physiologic capacity to repress the activity of vehgr1 and vegfr2 gene promoters. These studies identify uPA-dependent de-repression of vegfr1 and vegfr2 gene transcription through binding to HHEX/PRH as a novel mechanism by which uPA mediates the pro-angiogenic effects of VEGF and identifies a potential new target for control of pathologic angiogenesis.

Systemic sclerosis-like histopathological features in the myocardium of uPAR-deficient mice

OBJECTIVE

Cardiomyopathy is among the leading causes of death from systemic sclerosis (SSc). Urokinase-type plasminogen activator receptor (uPAR)-deficient mice have been recently reported to display important histopathological hallmarks of SSc, including dermal fibrosis, reduced dermal capillary density, and pulmonary fibrosis. Here, we investigated whether uPAR-deficient mice could display the histopathological features of SSc-related cardiomyopathy.

METHODS

Ventricular myocardial specimens from uPAR-deficient and wild-type mice at 12 and 24 weeks of age were analysed by both light microscopy and transmission electron microscopy. Picrosirius red staining and hydroxyproline content of myocardial specimens were quantified. Myofibroblast and microvessel counts were determined by immunofluorescence for α-smooth muscle actin and CD31, respectively. Endothelial cell apoptosis was assessed by a combined TUNEL/CD31 immunofluorescence assay. Expression of uPAR in human SSc and control ventricular myocardial autopsy specimens was determined by immunohistochemistry.

RESULTS

The myocardium of 24-week-old uPAR-deficient mice displayed focal ischaemic lesions with cardiomyocyte hypertrophy, myofibril rarefaction and contraction band necrosis. At 24 weeks of age, interstitial and perivascular collagen deposition and myofibroblast counts were significantly greater in myocardial tissue of uPAR-deficient mice than in wild-type mice. In uPAR-deficient mice, myocardial fibrosis was paralleled by microvascular endothelial cell apoptosis and reduced capillary density. uPAR expression was significantly downregulated in the myocardium of patients with SSc.

CONCLUSIONS

Typical histopathological features of SSc-related cardiomyopathy are mimicked by uPAR-deficient mice. The downregulation of uPAR in the myocardium of patients with SSc may suggest similar underlying pathogenetic mechanisms. uPAR-deficient mice could be used as a preclinical model to study the mechanisms and therapeutic approaches of myocardial involvement in SSc.

The interaction of uPAR with VEGFR2 promotes VEGF-induced angiogenesis

In endothelial cells, binding of vascular endothelial growth factor (VEGF) to the receptor VEGFR2 activates multiple signaling pathways that trigger processes such as proliferation, survival, and migration that are necessary for angiogenesis. VEGF-bound VEGFR2 becomes internalized, which is a key step in the proangiogenic signal. We showed that the urokinase plasminogen activator receptor (uPAR) interacted with VEGFR2 and described the mechanism by which this interaction mediated VEGF signaling and promoted angiogenesis. Knockdown of uPAR in human umbilical vein endothelial cells (HUVECs) impaired VEGFR2 signaling, and uPAR deficiency in mice prevented VEGF-induced angiogenesis. Upon exposure of HUVECs to VEGF, uPAR recruited the low-density lipoprotein receptor-related protein 1 (LRP-1) to VEGFR2, which induced VEGFR2 internalization. Thus, the uPAR-VEGFR2 interaction is crucial for VEGF signaling in endothelial cells.

The TNF-α/NF-κB signaling pathway has a key role in methamphetamine-induced blood-brain barrier dysfunction

Methamphetamine (METH) is a psychostimulant that causes neurologic and psychiatric abnormalities. Recent studies have suggested that its neurotoxicity may also result from its ability to compromise the blood-brain barrier (BBB). Herein, we show that METH rapidly increased the vesicular transport across endothelial cells (ECs), followed by an increase of paracellular transport. Moreover, METH triggered the release of tumor necrosis factor-alpha (TNF-α), and the blockade of this cytokine or the inhibition of nuclear factor-kappa B (NF-κB) pathway prevented endothelial dysfunction. Since astrocytes have a crucial role in modulating BBB function, we further showed that conditioned medium obtained from astrocytes previously exposed to METH had a negative impact on barrier properties also via TNF-α/NF-κB pathway. Animal studies corroborated the in vitro results. Overall, we show that METH directly interferes with EC properties or indirectly via astrocytes through the release of TNF-α and subsequent activation of NF-κB pathway culminating in barrier dysfunction.

PTEN expression in endothelial cells is down-regulated by uPAR to promote angiogenesis

The tumour suppressor phosphatase and tensin homologue (PTEN), mutated or lost in many human cancers, is a major regulator of angiogenesis. However, the cellular mechanism of PTEN regulation in endothelial cells so far remains elusive. Here, we characterise the urokinase receptor (uPAR, CD87) and its tumour-derived soluble form, suPAR, as a key molecule of regulating PTEN in endothelial cells. We observed uPAR-deficient endothelial cells to express enhanced PTEN mRNA- and protein levels. Consistently, uPAR expression in endogenous negative uPAR cells, down-regulated PTEN and activated the PI3K/Akt pathway. Additionally, we found that integrin adhesion receptors act as trans-membrane signaling partners for uPAR to repress PTEN transcription in a NF-κB-dependent manner. Functional in vitro assays with endothelial cells, derived from uPAR-deficient and PTEN heterozygous crossbred mice, demonstrated the impact of uPAR-dependent PTEN regulation on cell motility and survival. In an in vivo murine angiogenesis model uPAR-deficient PTEN heterozygous animals increased the impaired angiogenic phenotype of uPAR knockout mice and were able to reverse the high invasive potential of PTEN heterozygots. Our data provide first evidence that endogenous as well as exogenous soluble uPAR down-regulated PTEN in endothelial cells to support angiogenesis. The uPAR-induced PTEN regulation might represent a novel target for drug interference, and may lead to the development of new therapeutic strategies in anti-angiogenic treatment.

Protease nexin 1 induces apoptosis of prostate tumor cells through inhibition of X-chromosome-linked inhibitor of apoptosis protein

Protease nexin 1 (PN1) is an endogenous serine protease inhibitor (SERPIN), expressed at high levels in the prostate, and capable of inhibiting the proliferation of prostate cancer cells. We previously showed that PN1-uPA complexes inhibited Sonic Hedgehog (SHH) signalling through engagement of the LRP receptor. Here, we describe an alternative anti-proliferative mechanism through which PN1 expression leads to apoptosis. In prostate cancer cells, increased expression of PN1 led to substantial reduction of XIAP levels and apoptosis mediated through the uPAR, but not the LRP receptor. The alterations in XIAP were effected in two ways 1) via alteration in the NF-κB pathway, a pathway known to signal XIAP transcription and 2) by promoting XIAP instability. The AKT pathway is known to phosphorylate XIAP at serine 87 leading to protein stability and PN1 expression is shown to interfere with this process. As a result of both mechanisms, programmed cell death is substantially increased. Consistent with these observations, reduced PN1 protein correlated with elevated p65/XIAP expression and with higher Gleason scores in human prostate tissue arrays. Thus, PN1 expression appears to differentially down-regulate distinct oncogenic pathways depending upon the cell surface receptor engaged by its complexes and demonstrates a novel molecular mechanism by which the protein can promote tumor cell apoptosis.

Bisphenol A promotes X-linked inhibitor of apoptosis protein-dependent angiogenesis via G protein-coupled estrogen receptor pathway

Bisphenol A (BPA), one of the high-volume chemicals worldwide, has a core structure resembling that of natural estradiol. Recent evidence has demonstrated that exposure to BPA has a relationship with the risk of cancer. The objective of our study is to investigate the mechanisms underlying the pro-angiogenic effects of BPA. We demonstrated that BPA markedly induces endothelial cell proliferation, migration and tube formation by activating endothelial nitric oxide synthase. BPA-induced nitric oxide generation appeared to be associated with the X-linked inhibitor of apoptosis protein (XIAP), which competes with endothelial nitric oxide synthase for caveolin-1. BPA was shown to exert its pro-angiogenic effect by upregulating XIAP expression via G protein-coupled estrogen receptor (ER) activation but not via ERα or ERβ. Our data suggest that 100 nM BPA promote angiogenesis in a G protein-coupled ER-dependent genomic pathway, and provide a novel insight into the potential role of XIAP in mediating the pro-angiogenic effects of BPA in endothelial cells.

Components of the plasminogen activation system promote engraftment of porous polyethylene biomaterial via common and distinct effects

Rapid fibrovascularization is a prerequisite for successful biomaterial engraftment. In addition to their well-known roles in fibrinolysis, urokinase-type plasminogen activator (uPA) and tissue plasminogen activator (tPA) or their inhibitor plasminogen activator inhibitor-1 (PAI-1) have recently been implicated as individual mediators in non-fibrinolytic processes, including cell adhesion, migration, and proliferation. Since these events are critical for fibrovascularization of biomaterial, we hypothesized that the components of the plasminogen activation system contribute to biomaterial engraftment. Employing in vivo and ex vivo microscopy techniques, vessel and collagen network formation within porous polyethylene (PPE) implants engrafted into dorsal skinfold chambers were found to be significantly impaired in uPA-, tPA-, or PAI-1-deficient mice. Consequently, the force required for mechanical disintegration of the implants out of the host tissue was significantly lower in the mutant mice than in wild-type controls. Conversely, surface coating with recombinant uPA, tPA, non-catalytic uPA, or PAI-1, but not with non-catalytic tPA, accelerated implant vascularization in wild-type mice. Thus, uPA, tPA, and PAI-1 contribute to the fibrovascularization of PPE implants through common and distinct effects. As clinical perspective, surface coating with recombinant uPA, tPA, or PAI-1 might provide a novel strategy for accelerating the vascularization of this biomaterial.

Inactivation of urokinase-type plasminogen activator receptor (uPAR) gene induces dermal and pulmonary fibrosis and peripheral microvasculopathy in mice: a new model of experimental scleroderma?

OBJECTIVE

Urokinase-type plasminogen activator receptor (uPAR) is a key component of the fibrinolytic system involved in extracellular matrix remodelling and angiogenesis. The cleavage/inactivation of uPAR is a crucial step in fibroblast-to-myofibroblast transition and has been implicated in systemic sclerosis (SSc) microvasculopathy. In the present study, we investigated whether uPAR gene inactivation in mice could result in tissue fibrosis and peripheral microvasculopathy resembling human SSc.

METHODS

The expression of the native full-length form of uPAR in human skin biopsies was determined by immunohistochemistry. Skin and lung sections from uPAR-deficient (uPAR(-/-)) and wild-type (uPAR(+/+)) mice at 12 and 24 weeks of age were stained with haematoxylin-eosin, Masson's trichrome and Picrosirius red. Dermal thickness and hydroxyproline content in skin and lungs were quantified. Dermal myofibroblast and microvessel counts were determined by immunohistochemistry for α-smooth muscle actin and CD31, respectively. Endothelial cell apoptosis was assessed by TUNEL/CD31 immunofluorescence assay.

RESULTS

Full-length uPAR expression was significantly downregulated in SSc dermis, especially in fibroblasts and endothelial cells. Dermal thickness, collagen content and myofibroblast counts were significantly greater in uPAR(-/-) than in uPAR(+/+) mice. In uPAR(-/-) mice, dermal fibrosis was paralleled by endothelial cell apoptosis and severe loss of microvessels. Lungs from uPAR(-/-) mice displayed non-specific interstitial pneumonia-like pathological features, both with inflammation and collagen deposition. Pulmonary pathology worsened significantly from 12 to 24 weeks, as shown by a significant increase in alveolar septal width and collagen content.

CONCLUSIONS

uPAR(-/-) mice are a new animal model closely mimicking the histopathological features of SSc. This model warrants future studies.

Regulation of epithelial sodium channels in urokinase plasminogen activator deficiency

Epithelial sodium channels (ENaC) govern transepithelial salt and fluid homeostasis. ENaC contributes to polarization, apoptosis, epithelial-mesenchymal transformation, etc. Fibrinolytic proteases play a crucial role in virtually all of these processes and are elaborated by the airway epithelium. We hypothesized that urokinase-like plasminogen activator (uPA) regulates ENaC function in airway epithelial cells and tested that possibility in primary murine tracheal epithelial cells (MTE). Both basal and cAMP-activated Na(+) flow through ENaC were significantly reduced in monolayers of uPA-deficient cells. The reduction in ENaC activity was further confirmed in basolateral membrane-permeabilized cells. A decrease in the Na(+)-K(+)-ATPase activity in the basolateral membrane could contribute to the attenuation of ENaC function in intact monolayer cells. Dysfunctional fluid resolution was seen in uPA-disrupted cells. Administration of uPA and plasmin partially restores ENaC activity and fluid reabsorption by MTEs. ERK1/2, but not Akt, phosphorylation was observed in the cells and lungs of uPA-deficient mice. On the other hand, cleavage of γ ENaC is significantly depressed in the lungs of uPA knockout mice vs. those of wild-type controls. Expression of caspase 8, however, did not differ between wild-type and uPA(-/-) mice. In addition, uPA deficiency did not alter transepithelial resistance. Taken together, the mechanisms for the regulation of ENaC by uPA in MTEs include augmentation of Na(+)-K(+)-ATPase, proteolysis, and restriction of ERK1/2 phosphorylation. We demonstrate for the first time that ENaC may serve as a downstream signaling target by which uPA controls the biophysical profiles of airway fluid and epithelial function.

Metastasis review: from bench to bedside

Cancer is the final result of uninhibited cell growth that involves an enormous group of associated diseases. One major aspect of cancer is when cells attack adjacent components of the body and spread to other organs, named metastasis, which is the major cause of cancer-related mortality. In developing this process, metastatic cells must successfully negotiate a series of complex steps, including dissociation, invasion, intravasation, extravasation, and dormancy regulated by various signaling pathways. In this review, we will focus on the recent studies and collect a comprehensive encyclopedia in molecular basis of metastasis, and then we will discuss some new potential therapeutics which target the metastasis pathways. Understanding the new aspects on molecular mechanisms and signaling pathways controlling tumor cell metastasis is critical for the development of therapeutic strategies for cancer patients that would be valuable for researchers in both fields of molecular and clinical oncology.

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.

Disruption of the endothelial barrier by proteases from the bacterial pathogen Pseudomonas aeruginosa: implication of matrilysis and receptor cleavage

Within the vasculature, uncontrolled pericellular proteolysis can lead to disruption of cell-to-cell and cell-to-matrix interactions and subsequent detachment-induced cell apoptosis, or anoikis, contributing to inflammatory vascular diseases, with the endothelium as the major target. Most studies so far have focused on endogenous proteinases. However, during bloodstream infections, bacterial proteinases may also trigger endothelial anoikis. We thus investigated the potential apoptotic activity of the proteinases secreted by the haematotropic opportunistic pathogen, Pseudomonas aeruginosa, and particularly its predominant metalloproteinase, LasB. For this, we used the secretome of the LasB-expressing pseudomonal strain, PAO1, and compared it with that from the isogenic, LasB-deficient strain (PAO1∆lasB), as well as with purified LasB. Secretomes were tested for apoptotic activity on cultured human endothelial cells derived from the umbilical vein or from the cerebral microvasculature. We found that the PAO1 secretome readily induced endothelial cell anoikis, as did secretomes of LasB-positive clinical pseudomonal isolates, while the PAO1∆lasB secretome had only a limited impact on endothelial adherence and viability. Notably, purified LasB reproduced most of the effects of the LasB-containing secretomes, and these were drastically reduced in the presence of the LasB-selective inhibitor, phosphoramidon. A precocious and extensive LasB-dependent degradation of several proteins associated with the endothelial extracellular matrix, fibronectin and von Willebrand factor, was observed by immunofluorescence and/or immunoblotting analysis of cell cultures. Moreover, the PAO1 secretome, but not that from PAO1∆lasB, specifically induced rapid endoproteolysis of two major interendothelial junction components, VE-cadherin and occludin, as well as of the anti-anoikis, integrin-associated urokinase receptor, uPAR. Taken as a prototype for exogenous haemorrhagic proteinases, pseudomonal LasB thus appears to induce endothelial anoikis not only via matrilysis, as observed for many pro-apoptotic proteinases, but also via cleavage of some essential cell-to-cell and cell-to-matrix adhesion receptors implicated in the maintenance of the endothelial barrier.

Inactivation of DNA-dependent protein kinase promotes heat-induced apoptosis independently of heat-shock protein induction in human cancer cell lines

The inhibition of DNA damage response pathway seems to be an attractive strategy for cancer therapy. It was previously reported that in rodent cells exposed to heat stress, cell growth was promoted by the activity of DNA-dependent protein kinase (DNA-PK), an enzyme involved in DNA non-homologous end joining (NHEJ) required for double-strand break repair. The absence of a functioning DNA-PK was associated with down regulation of heat shock protein 70 (HSP70). The objective of this study is thus to investigate the role of DNA-PK inhibition in heat-induced apoptosis in human cell lines. The inhibitors of phosphorylation of the DNA-PK catalytic subunit (DNA-PKcs) at Ser2056, such as NU7026 and NU7441, were utilized. Furthermore, knock down of DNA-PKcs was carried out using small interfering RNA (siDNA-PKcs). For heat exposure, cells were placed in water bath at 44°C for 60 min. Apoptosis was evaluated after 24 h incubation flow cytometrically. Proteins were extracted after 24 h and analyzed for HSP70 and HSP40 expression by Western blotting. Total RNA was extracted 6 h after treatment and analyzed using a GeneChip® microarray system to identify and select the up-regulated genes (≥1.5 fold). The results showed an enhancement in heat-induced apoptosis in absence of functioning DNA-PKcs. Interestingly, the expression levels of HSP70 and HSP40 were elevated in the absence of DNA-PKcs under heat stress. The results of genetic network analysis showed that HSPs and JUN genes were up-regulated independently of DNA-PKcs in exposed parent and knock out cells. In the presence of functioning DNA-PKcs, there was an observed up-regulation of anti-apoptotic genes, such as NR1D1, whereas in the absence of DNA-PKcs the pro-apoptotic genes, such as EGR2, were preferentially up-regulated. From these findings, we concluded that in human cells, the inactivation of DNA-PKcs can promote heat-induced apoptosis independently of heat-shock proteins.

H-RN, a peptide derived from hepatocyte growth factor, inhibits corneal neovascularization by inducing endothelial apoptosis and arresting the cell cycle

BACKGROUND

The goal of this study was to investigate the anti-angiogenic activity of a novel peptide H-RN, derived from the hepatocyte growth factor kringle 1 domain (HGF K1), in a mouse model of corneal neovascularization. The anti-angiogenic effect of H-RN on vascular endothelial growth factor (VEGF)-stimulated cell proliferation, cell migration and endothelial cell tube formation was assessed in vitro using Human Umbilical Vein Endothelial Cells (HUVECs) and in vivo using a mouse cornea micropocket assay. Apoptosis and cell cycle arrest were assessed by flow cytometry. A scrambled peptide was used as a negative control.

RESULTS

H-RN effectively inhibited VEGF-stimulated HUVEC proliferation, migration and tube formation on Matrigel, while a scrambled peptide exerted no effect. In the mouse model of corneal angiogenesis, VEGF-stimulated angiogenesis was significantly inhibited by H-RN compared to a scrambled peptide that had no such activity. VEGF protected HUVECs from apoptosis, while H-RN inhibited this protective effect of VEGF. VEGF significantly increased the proportion of cells in the S phase compared to control treated cells (p<0.05). Treatment with H-RN (1.5 mM) induced the accumulation of cells in G0/G1 phase, while the proportion of cells in the S phase and G2/M phase decreased significantly compared to control group (p<0.05).

CONCLUSIONS

H-RN has anti-angiogenic activity in HUVECs and in a mouse model of VEGF-induced corneal neovascularization. The anti-angiogenic activity of H-RN was related to apoptosis and cell cycle arrest, indicating a potential strategy for anti-angiogenic treatment in the cornea.

Role of vegetation-associated protease activity in valve destruction in human infective endocarditis

AIMS

Infective endocarditis (IE) is characterized by septic thrombi (vegetations) attached on heart valves, consisting of microbial colonization of the valvular endocardium, that may eventually lead to congestive heart failure or stroke subsequent to systemic embolism. We hypothesized that host defense activation may be directly involved in tissue proteolytic aggression, in addition to pathogenic effects of bacterial colonization.

METHODS AND RESULTS

IE valve samples collected during surgery (n = 39) were dissected macroscopically by separating vegetations (VG) and the surrounding damaged part of the valve from the adjacent, apparently normal (N) valvular tissue. Corresponding conditioned media were prepared separately by incubation in culture medium. Histological analysis showed an accumulation of platelets and polymorphonuclear neutrophils (PMNs) at the interface between the VG and the underlying tissue. Apoptotic cells (PMNs and valvular cells) were abundantly detected in this area. Plasminogen activators (PA), including urokinase (uPA) and tissue (tPA) types were also associated with the VG. Secreted matrix metalloproteinase (MMP) 9 was also increased in VG, as was leukocyte elastase and myeloperoxidase (MPO). The presence of neutrophil extracellular traps (NETs) associating MPO and externalized nucleosomes, was shown by immunostaining in the VG. Both MPO and cell-free DNA were released in larger amounts by VG than N samples, suggesting bacterial activation of PMNs within the vegetation. Finally, evidence of proteolytic tissue damage was obtained by the release of fragments of extracellular matrix components such as fibrinogen and fibronectin, as well as protease-sensitive receptors such as the uPA receptor.

CONCLUSION

Our data obtained using human IE valves suggest that septic vegetations represent an important source of proteases originating from massive leukocyte recruitment and activation of the host plasminergic system. The latter forms a potential therapeutic target to minimize valvular tissue degradation independently from that induced by bacterial proteases.

The urokinase receptor (CD87) represents a central mediator of growth factor-induced endothelial cell migration

Angiogenesis, the sprouting of blood vessels form pre-existing vasculature after injury or in neoplastic diseases, is initiated by growth factor-induced endothelial cell migration. Recently, the major angiogenic growth factor VEGF165 has become the target of therapeutic interventions. However, this approach has been clinically proven to be of limited efficacy, which might be due to the fact that tumour angiogenesis is not only induced by VEGF, but also by a variety of other growth factors. Thus, the identification of a common downstream mediator of growth-factor-induced endothelial cell migration is mandatory to effectively interfere with (tumour-) angiogenesis. We found that the urokinase-type plasminogen activator (uPA)-system, which affects proteolytic as well as adhesive capacities, represents an essential regulatory mechanism in growth factor-induced endothelial cell migration and invasion. This mechanism was not limited to VEGF165, but mediated pro-angiogenic endothelial cell behaviour induced by various growth factors. Thus, VEGF165, VEGF-E, FGF-2, EGF as well as HGF induced a PI3k-dependent activation of pro-uPA when bound to uPAR, which led to an increase in cell surface fibrinolytic activity. As a consequence, uPAR became internalised and redistributed via LDLR-proteins. Interference with these events led to a reduced migratory response of endothelial cells towards VEGF in vitro as well as endothelial cell invasion in vivo. These data give first evidence that the uPA-system, which represents the only level-of-evidence-1 cancer biomarker system for prognosis and/or prediction in node negative breast cancer, might directly affect (tumour-) angiogenesis.

The interferon stimulated gene 12 inactivates vasculoprotective functions of NR4A nuclear receptors

RATIONALE

Innate and adaptive immune responses alter numerous homeostatic processes that are controlled by nuclear hormone receptors. NR4A1 is a nuclear receptor that is induced in vascular pathologies, where it mediates protection.

OBJECTIVE

The underlying mechanisms that regulate the activity of NR4A1 during vascular injury are not clear. We therefore searched for modulators of NR4A1 function that are present during vascular inflammation.

METHODS AND RESULTS

We report that the protein encoded by interferon stimulated gene 12 (ISG12), is a novel interaction partner of NR4A1 that inhibits the transcriptional activities of NR4A1 by mediating its Crm1-dependent nuclear export. Using 2 models of vascular injury, we show that ISG12-deficient mice are protected from neointima formation. This effect is dependent on the presence of NR4A1, as mice deficient for both ISG12 and NR4A1 exhibit neointima formation similar to wild-type mice.

CONCLUSIONS

These findings identify a previously unrecognized feedback loop activated by interferons that inhibits the vasculoprotective functions of NR4A nuclear receptors, providing a potential new therapeutic target for interferon-driven pathologies.

VEGF-induced endothelial cell migration requires urokinase receptor (uPAR)-dependent integrin redistribution

AIMS

Vascular endothelial growth factor (VEGF)-initiated angiogenesis requires coordinated proteolytic degradation of extracellular matrix provided by the urokinase plasminogen activator/urokinase receptor (uPA/uPAR) system and regulation of cell migration provided by integrin-matrix interaction. In this study, we investigated the mechanisms underlying the uPAR-dependent modulation of VEGF-induced endothelial migration.

METHODS AND RESULTS

We used flow cytometry to quantify integrins at the cell surface. Stimulation of human and murine endothelial cells with VEGF resulted in internalization of α5β1-integrins. Micropatterning and immunocytochemistry revealed co-clustering of uPAR and α5β1-integrins and retrieval via clathrin-coated vesicles. It was also contingent on receptors of the low-density lipoprotein receptor (LDL-R) family. VEGF-induced integrin redistribution was inhibited by elimination of uPAR from the endothelial cell surface or by inhibitory peptides that block the uPAR-integrin interaction. Under these conditions, the migratory response of endothelial cells upon VEGF stimulation was impaired both in vitro and in vivo.

CONCLUSIONS

The observations indicate that uPAR is an essential component of the network through which VEGF controls endothelial cell migration. uPAR is a bottleneck through which the VEGF-induced signal must be funnelled for both focused proteolytic activity at the leading edge and for redistribution of integrins.

uPA and PAI-1-Related Signaling Pathways Differ between Primary Breast Cancers and Lymph Node Metastases

The supporting role of urokinase-type plasminogen activator (uPA) and its inhibitor plasminogen activator inhibitor 1 (PAI-1) in migration and invasion is well known. In addition, both factors are key components in cancer cell-related signaling. However, little information is available for uPA and PAI-1-associated signaling pathways in primary cancers and corresponding lymph node metastases. The aim of this study was to compare the expression of uPA and PAI-1-associated signaling proteins in 52 primary breast cancers and corresponding metastases. Proteins were extracted from formalin-fixed paraffin-embedded tissue samples of the primary tumors and metastases. Protein lysates were subsequently analyzed by reverse phase protein array for the expression of members of the PI3K/AKT (FAK, GSK3-β, ILK, pGSK3-β, PI3K, and ROCK) and the MAPK pathways (pp38, pSTAT3, and p38). A solid correlation of uPA expression existed between primary tumors and metastases, whereas PAI-1 expression did not significantly correlate between them. The correlations of uPA and PAI-1 with signaling pathways found in primary tumors did not persist in metastases. Analysis of single molecules revealed that some correlated well between tumors and metastases (FAK, pGSK3-β, ILK, Met, PI3K, ROCK, uPA, p38, and pp38), whereas others did not (PAI-1 and GSK3-β). Whether the expression of a protein correlated between tumor and metastasis or not was independent of the pathway the protein is related to. These findings hint at a complete deregulation of uPA and PAI-1-related signaling in metastases, which might be the reason why uPA and PAI-1 reached clinical relevance only for lymph node-negative breast cancer tissues.

Angiogenesis in cancer: Anti-VEGF escape mechanisms

It is now widely accepted that tumor-angiogenesis plays a crucial role in tumor growth, tumor propagation and metastasis formation. Among several angiogenic activators, the vascular endothelial growth factor (VEGF) and its receptors represent one of the major inducers of tumor angiogenesis. Thus, this system has become the focus of therapeutic interventions, which led to the approval of the anti-VEGF blocking antibody bevacizumab and the VEGFR-2 pathway inhibitors pazopanib, sorafenib and sunitinib. However, not every cancer patient benefits from such treatment or finally becomes resistant to anti-VEGF approaches; others are suffering from adverse effects. Thus, there is an urgent need for a better understanding of VEGF-independent mechanisms leading to angiogenesis in cancer. This review focuses on anti-VEGF escape mechanisms of tumor cells and its microenvironment.

Vitronectin inhibits neutrophil apoptosis through activation of integrin-associated signaling pathways

Vitronectin is present in large concentrations in serum and the extracellular matrix. Although vitronectin is known to modulate neutrophil adhesion and chemotaxis, and to contribute to neutrophil-associated proinflammatory processes, a role in apoptosis has not been demonstrated. In the present studies, we found that neutrophils demonstrated more rapid progression to spontaneous or TNF-related apoptosis-inducing ligand-induced apoptosis when incubated under vitronectin-free conditions than when vitronectin was present. The ability of native vitronectin to delay neutrophil apoptosis was not recapitulated by the vitronectin somatomedin B domain. In contrast, inclusion of the cyclo[Arg-Gly-Asp-D-Phe-Val] peptide in cultures containing vitronectin resulted in enhanced neutrophil apoptosis, showing that the vitronectin RGD motif (Arg-Gly-Asp motif) was responsible for the antiapoptotic effects of vitronectin. Addition of antibodies to β(1), β(3), or β(5), but not to β(2) or β(4) integrins, reversed the ability of vitronectin to diminish neutrophil apoptosis. The ability of vitronectin to enhance neutrophil viability was dependent on activation of phosphatidylinositol 3-kinase and extracellular signal-regulated kinase 1/2 kinases, but not on the p38 kinase. Increased numbers of apoptotic neutrophils were present in the lungs of LPS-treated transgenic vitronectin-deficient mice, as compared with control mice. These results demonstrate a novel antiapoptotic function for vitronectin.

Overexpression of VEGF189 in breast cancer cells induces apoptosis via NRP1 under stress conditions

The existence of multiple VEGF-A isoforms raised the possibility that they may have distinct functions in tumor growth. We have previously published that VEGF189 and VEGF165 contribute to breast cancer progression and angiogenesis, but VEGF165 induced the most rapid tumor uptake. Since VEGF165 has been described as a survival factor for breast tumor cells, we questioned here the effects of VEGF189 on the survival/apoptosis of MDA-MB-231 cells. We used clones which overexpress VEGF189 (V189) or VEGF165 (V165) isoforms and compared them to a control one (cV). Overexpression of VEGF189 resulted in increased cell apoptosis, as determined by Annexin-V apoptosis assay, under serum starvation and doxorubicin treatment, while VEGF 165 was confirmed to be a survival factor. Since MDA-MB-231 highly express NRP1 (a co-receptor for VEGF-A), we used short hairpin RNA (shRNA) to knockdown NRP1 expression. V189shNRP1 clones were characterized by reduced apoptosis and higher necrosis, as compared to V189shCtl, under stress conditions. Unexpectedly, NRP1 knock-down had no effect on the survival or apoptosis of V165 cells. VEGF189 showed greater affinity towards NRP1 than VEGF165 using a BIAcore binding assay. Finally, since endogenously produced urokinase-type plasminogen (uPA) has been found to prevent apoptosis in breast cancers, we analyzed the level of uPA activity in our clones. An inhibition of uPA activity was observed in V189shNRP1 clones. Altogether, these results suggest a major role of NRP1 in apoptosis induced by VEGF189 in stress conditions and confirm VEGF165 as a survival factor.

Angiogenesis in cancer. Basic mechanisms and therapeutic advances

Etiological concepts on cancer development, malignant growth and tumour propagation have undergone a revolutionary development during recent years: Among other aspects, the discovery of angiogenesis - the growth of new blood vessels from pre-existing vasculature - as a key element in the pathogenesis of malignancy has opened an abundance of biologic insights and subsequent therapeutic options, which have led to improved prognosis in many cancers including those originating from colon, lung, breast and kidney. Thereby, targeting the major pro-angiogenic stimulus vascular endothelial growth factor (VEGF) became the focus for therapeutic interventions. However, the use of VEGF-targeting drugs has been shown to be of limited efficacy, which might lie in the fact that tumor angiogenesis is mediated by a variety of different subcellular systems. This review focuses on the basic mechanisms involved in angiogenesis, which potentially represent novel targets for pharmacological agents in the treatment of malignancies.

Density enhanced phosphatase-1 down-regulates urokinase receptor surface expression in confluent endothelial cells

VEGF(165), the major angiogenic growth factor, is known to activate various steps in proangiogenic endothelial cell behavior, such as endothelial cell migration and invasion, or endothelial cell survival. Thereby, the urokinase-type plasminogen activator (uPA) system has been shown to play an essential role not only by its proteolytic capacities, but also by induction of intracellular signal transduction. Therefore, expression of its cell surface receptor uPAR is thought to be an essential regulatory mechanism in angiogenesis. We found that uPAR expression on the surface of confluent endothelial cells was down-regulated compared with subconfluent proliferating endothelial cells. Regulation of uPAR expression was most probably affected by extracellular signal-regulated kinase 1/2 (ERK1/2) activation, a downstream signaling event of the VEGF/VEGF-receptor system. Consistently, the receptor-like protein tyrosine phosphatase DEP-1 (density enhanced phosphatase-1/CD148), which is abundantly expressed in confluent endothelial cells, inhibited the VEGF-dependent activation of ERK1/2, leading to down-regulation of uPAR expression. Overexpression of active ERK1 rescued the DEP-1 effect on uPAR. That DEP-1 plays a biologic role in angiogenic endothelial cell behavior was demonstrated in endothelial cell migration, proliferation, and capillary-like tube formation assays in vitro.

The soluble form of urokinase receptor promotes angiogenesis through its Ser⁸⁸-Arg-Ser-Arg-Tyr⁹² chemotactic sequence

BACKGROUND

The urokinase plasminogen activator receptor (u-PAR) focuses the proteolytic activity of the urokinase plasminogen activator (u-PA) on the endothelial cell surface, thus promoting angiogenesis in a protease-dependent manner. The u-PAR may exist in a glycophosphatidylinositol-anchored and in a soluble form (soluble u-PAR [Su-PAR]), both including the chemotactic Ser⁸⁸ -Arg-Ser-Arg-Tyr⁹² internal sequence.

OBJECTIVE

To investigate whether Su-PAR may trigger endothelial cell signaling leading to new vessel formation through its chemotactic Ser⁸⁸ -Arg-Ser-Arg-Tyr⁹² sequence.

METHODS AND RESULTS

In this study, the formation of vascular-like structures by human umbilical vein endothelial cells was assessed by using a matrigel basement membrane preparation. First, we found that Su-PAR protein promotes the formation of cord-like structures, and that this ability is retained by the isolated Ser(88) -Arg-Ser-Arg-Tyr⁹² chemotactic sequence, the maximal effect being reached at 10 nmol L⁻¹ SRSRY peptide (SRSRY). This effect is mediated by the α(v) β₃ vitronectin receptor, is independent of u-PA proteolytic activity, and involves the internalization of the G-protein-coupled formyl-peptide receptor in endothelial cells. Furthermore, exposure of human saphenous vein rings to Su-PAR or SRSRY leads to a remarkable degree of sprouting. Finally, we show that Su-PAR and SRSRY promote a marked response in angioreactors implanted into the dorsal flank of nude mice, retaining 91% and 66%, respectively, of the angiogenic response generated by a mixture of vascular endothelial growth factor and fibroblast growth factor type 2.

CONCLUSIONS

Our results show a new protease-independent activity of Su-PAR that stimulates in vivo angiogenesis through its Ser⁸⁸ -Arg-Ser-Arg-Tyr⁹² chemotactic sequence.

Signalling networks associated with urokinase-type plasminogen activator (uPA) and its inhibitor PAI-1 in breast cancer tissues: new insights from protein microarray analysis

The urokinase-type plasminogen activator (uPA) and the main uPA inhibitor PAI-1 play important roles in cell migration and invasion in both physiological and pathological contexts. Both factors are clinically applicable predictive markers in node-negative breast cancer patients that are used to stratify patients for adjuvant chemotherapy. In addition to their classical functions in plasmin regulation, both factors are key components in cancer-related cell signalling. Such signalling cascades are well described in cell culture systems, but a better understanding of uPA- and PAI-1-associated signalling networks in clinical tissues is needed. We examined the expression of uPA, PAI-1, and 21 signalling molecules in 201 primary breast cancer tissues using protein microarrays. Expression of uPA was significantly correlated with the expression of ERK and Stat3, while expression of PAI-1 was correlated with the uPA receptor and Akt activation, presumably via integrin and HER-receptor signalling. Analysis of uPA expression did not reveal any significant correlation with staging, grading or age of the patients. The PAI-1 expression was correlated with nodal stage. Network monitoring for uPA and PAI-1 in breast cancer reveals interactions with main signalling cascades and extends the findings from cell culture experiments. Our results reveal possible mechanisms underlying cancer development.

Molecular regulation of thyroid gland function

PURPOSE OF REVIEW

For de-novo thyroid hormone synthesis ex vivo, thyroid follicular cells require a serum-free medium supplying nutrients, iodide, thyroid-stimulating hormone and insulin-like growth factor I (IGF-I) (or insulin). Under these conditions, T3 and T4 are secreted but so are other factors such as growth factors, plasminogen activators, their inhibitors known as serpins, and so on. What is the function of these factors? Do thyroid cells respond to them or are these paracrine/endocrine factors? The purpose of this review is to highlight the current developments in the identification and role of the signalling pathways that regulate thyroid growth and function and the putative role of endogenous thyroid proteases in regulating this.

RECENT FINDINGS

The roles of the mitogen-activated protein kinases and phosphoinositol 3 kinases and integrins in mediating growth and function in thyroid cancer cells and the roles of plasminogen activators, their receptors and the downstream signalling pathways they modulate have been developed. Discoveries of novel proteases, expressed in thyroid cancers, may be useful in diagnosis.

SUMMARY

The signalling pathways regulating thyroid activity are examined and the roles of follicular cell products in maintaining thyroid homeostasis evaluated. The possibility that thyroid cell products other than T3 and T4 may circulate and have extrathyroidal effects is proposed.

Targeting of VEGF-dependent transendothelial migration of cancer cells by bevacizumab

Cancer progression is often associated with the formation of malignant effusions. Vascular endothelial growth factor (VEGF) is a major regulator of vascular permeability and has been implicated as mediator of tumor progression. We examined the production and secretion of VEGF(165) in various primary cancer cells derived from malignant effusions, and the role of exogenous VEGF(165) as a mediator of effusion formation. VEGF(165) was constantly secreted by all cultured tumor cells in an mTOR-dependent manner, as it was inhibited by the mTOR inhibitor rapamycin. Secreted VEGF(165) showed functional activity by inducing endothelial leakiness and tumor cell-transendothelial migration in vitro, effects which could be reverted by the anti-VEGF antibody bevacizumab. Thus, mTOR inhibitors as well as bevacizumab should be considered as potential agents in cancer patients suffering from malignant effusions.