Expression of plasminogen activator inhibitor type 1 by human prostate carcinoma cells inhibits primary tumor growth, tumor-associated angiogenesis, and metastasis to lung and liver in an athymic mouse model

Identification of blood protein biomarkers associated with prostate cancer risk using genetic prediction models: analysis of over 140,000 subjects

Prostate cancer (PCa) brings huge public health burden in men. A growing number of conventional observational studies report associations of multiple circulating proteins with PCa risk. However, the existing findings may be subject to incoherent biases of conventional epidemiologic studies. To better characterize their associations, herein, we evaluated associations of genetically predicted concentrations of plasma proteins with PCa risk. We developed comprehensive genetic prediction models for protein levels in plasma. After testing 1308 proteins in 79 194 cases and 61 112 controls of European ancestry included in the consortia of BPC3, CAPS, CRUK, PEGASUS, and PRACTICAL, 24 proteins showed significant associations with PCa risk, including 16 previously reported proteins and eight novel proteins. Of them, 14 proteins showed negative associations and 10 showed positive associations with PCa risk. For 18 of the identified proteins, potential functional somatic changes of encoding genes were detected in PCa patients in The Cancer Genome Atlas (TCGA). Genes encoding these proteins were significantly involved in cancer-related pathways. We further identified drugs targeting the identified proteins, which may serve as candidates for drug repurposing for treating PCa. In conclusion, this study identifies novel protein biomarker candidates for PCa risk, which may provide new perspectives on the etiology of PCa and improve its therapeutic strategies.

Naa10p promotes cell invasiveness of esophageal cancer by coordinating the c-Myc and PAI1 regulatory axis

N-α-acetyltransferase 10 protein, Naa10p, is involved in various cellular functions impacting tumor progression. Due to its capacity to acetylate a large spectrum of proteins, both oncogenic and tumor-suppressive roles of Naa10p have been documented. Here, we report an oncogenic role of Naa10p in promoting metastasis of esophageal cancer. NAA10 is more highly expressed in esophageal cancer tissues compared to normal tissues. Higher NAA10 expression also correlates with poorer survival of esophageal cancer patients. We found that NAA10 expression was transcriptionally regulated by the critical oncogene c-Myc in esophageal cancer. Furthermore, activation of the c-Myc-Naa10p axis resulted in upregulated cell invasiveness of esophageal cancer. This increased cell invasiveness was also elucidated to depend on the enzymatic activity of Naa10p. Moreover, Naa10p cooperated with Naa15p to interact with the protease inhibitor, PAI1, and prevent its secretion. This inhibition of PAI1 secretion may derive from the N-terminal acetylation effect of the Naa10p/Naa15p complex. Our results establish the significance of Naa10p in driving metastasis in esophageal cancer by coordinating the c-Myc-PAI1 axis, with implications for its potential use as a prognostic biomarker and therapeutic target for esophageal cancer.

The Role of Fibrinolytic System in Health and Disease

The fibrinolytic system is composed of the protease plasmin, its precursor plasminogen and their respective activators, tissue-type plasminogen activator (tPA) and urokinase-type plasminogen activator (uPA), counteracted by their inhibitors, plasminogen activator inhibitor type 1 (PAI-1), plasminogen activator inhibitor type 2 (PAI-2), protein C inhibitor (PCI), thrombin activable fibrinolysis inhibitor (TAFI), protease nexin 1 (PN-1) and neuroserpin. The action of plasmin is counteracted by α2-antiplasmin, α2-macroglobulin, TAFI, and other serine protease inhibitors (antithrombin and α2-antitrypsin) and PN-1 (protease nexin 1). These components are essential regulators of many physiologic processes. They are also involved in the pathogenesis of many disorders. Recent advancements in our understanding of these processes enable the opportunity of drug development in treating many of these disorders.

The Plasminogen-Activator Plasmin System in Physiological and Pathophysiological Angiogenesis

Angiogenesis is a process associated with the migration and proliferation of endothelial cells (EC) to form new blood vessels. It is involved in various physiological and pathophysiological conditions and is controlled by a wide range of proangiogenic and antiangiogenic molecules. The plasminogen activator–plasmin system plays a major role in the extracellular matrix remodeling process necessary for angiogenesis. Urokinase/tissue-type plasminogen activators (uPA/tPA) convert plasminogen into the active enzyme plasmin, which in turn activates matrix metalloproteinases and degrades the extracellular matrix releasing growth factors and proangiogenic molecules such as the vascular endothelial growth factor (VEGF-A). The plasminogen activator inhibitor-1 (PAI-1) is the main inhibitor of uPA and tPA, thereby an inhibitor of pericellular proteolysis and intravascular fibrinolysis, respectively. Paradoxically, PAI-1, which is expressed by EC during angiogenesis, is elevated in several cancers and is found to promote angiogenesis by regulating plasmin-mediated proteolysis and by promoting cellular migration through vitronectin. The urokinase-type plasminogen activator receptor (uPAR) also induces EC cellular migration during angiogenesis via interacting with signaling partners. Understanding the molecular functions of the plasminogen activator plasmin system and targeting angiogenesis via blocking serine proteases or their interactions with other molecules is one of the major therapeutic strategies scientists have been attracted to in controlling tumor growth and other pathological conditions characterized by neovascularization.

A curcumin analog CA-5f inhibits urokinase-type plasminogen activator and invasive phenotype of triple-negative breast cancer cells

Triple-negative breast cancer (TNBC) is one of the most aggressive types of breast cancer with poor outcomes. Patients with TNBC cannot benefit from targeted therapies such as Tamoxifen and Herceptin. The aim of the present study was to seek a preventive or therapeutic agent with a potential inhibitory effect on aggressive progression of TNBC. Anticancer effect of a natural compound curcumin have been demonstrated, however, development of more effective curcumin analogs with better bioavailability is needed. We investigated if a curcumin analog CA-5f could inhibit the invasive phenotype of TNBC cell lines in the present study. Treatment with CA-5f inhibited the viability of MDA‑MB‑231 and Hs578T TNBC cells, possible by inducing apoptosis. The invasive phenotypes of these cells were inhibited by CA-5f in a concentration-dependent manner. Protein expression of urokinase-type plasminogen activator (uPA), a serine protease known to degrade the extracellular matrix and lead to invasion, was markedly decreased by CA-5f in Hs578T cells. However, mRNA level of uPA was not altered by CA-5f, implicating that the effect of CA-5f was not through transcriptional regulation. Of note, CA-5f upregulated plasminogen activator inhibitor type (PAI)-1, which is known to inhibit uPA by interacting with urokinase-type plasminogen receptor, in TNBC cells. Taken together, these results demonstrated that CA-5f significantly inhibited the invasive phenotype of TNBC cells, possibly by decreasing the protein level of uPA through upregulating PAI-1. Our results may provide useful information on developing CA-5f as a potential therapeutic agent against malignant progression of TNBC.

The plasminogen activator inhibitor-1 paradox in cancer: a mechanistic understanding

The paradoxical pro-tumorigenic function of plasminogen activator inhibitor 1 (PAI-1, aka Serpin E1) in cancer progression and metastasis has been the subject of an abundant scientific literature that has pointed to a pro-angiogenic role, a growth and migration stimulatory function, and an anti-apoptotic activity, all directed toward promoting tumor growth, cancer cell survival, and metastasis. With uPA, PAI-1 is among the most reliable biomarkers and prognosticators in many cancer types. More recently, a novel pro-tumorigenic function of PAI-1 in cancer-related inflammation has been demonstrated. These multifaceted activities of PAI-1 in cancer progression are explained by the complex structure of PAI-1 and its multiple functions that go beyond its anti-fibrinolytic and anti-plasminogen activation activities. However, despite the multiple evidences supporting a pro-tumorigenic role of PAI-1 in cancer, and the development of several inhibitors, targeting PAI-1, has remained elusive. In this article, the various mechanisms responsible for the pro-tumorigenic functions of PAI-1 are reviewed with emphasis on its more recently described contribution to cancer inflammation. The challenges of targeting PAI-1 in cancer therapy are then discussed.

Plasminogen activator inhibitor-1 in cancer research

[Despite as a major inhibitor of urokinase (uPA), paradoxically,] Plasminogen activator inhibitor-1 (PAI-1) has been validated to be highly expressed in various types of tumor biopsy tissues or plasma compared with controls based on huge clinical data bases analysis, more importantly, PAI-1 alone or in conjunction with uPA have been identified as prognostic for disease progression and relapse in certain cancer types. particularly in breast cancer. In addition to play important roles in cell adhesion, migration and invasion, PAI-1 has been reported to induce tumor vascularization and thus promote cell dissemination and tumor metastasis. Furthermore, there are many tumor promoting factors involved in the modulation of PAI-1 expression and activity, which will strengthen the pro-tumorigenic roles of PAI-1. Undoubtedly, PAI-1 may be a promising target for therapeutic intervention of specific cancer treatment. In fact, some PAI-1 inhibitors are currently being evaluated in cancer therapy, which may be developed to new antitumor agents in the future.

Overexpression of Rab11-FIP2 in colorectal cancer cells promotes tumor migration and angiogenesis through increasing secretion of PAI-1

Background

Rab11 family-interacting protein 2 (Rab11-FIP2) can interact with MYO5B and plays an important role in regulating plasma membrane recycling. However, little is known about the clinical significance of DUSP2 in colorectal cancer (CRC).

Methods

In this study, we investigated Rab11-FIP2 expression by immunohistochemistry in 125 patients with colorectal cancer. Conditioned media containing all secreted factors was harvested. Chemokine secretion and expression were analyzed by Chemi-array.

Results

We found that the expression level of Rab11-FIP2 was significantly increased in colorectal cancer tissues and high expression of Rab11-FIP2 was closely correlated with nodal metastasis in colorectal cancer patients. Rab11-FIP2 overexpression promoted colorectal cancer metastasis in vitro and in vivo. Finally, we demonstrated that Rab11-FIP2 overexpression may contribute to increased secretion of PAI-1 in human colorectal cancer cells.

Conclusions

Our findings reveal a novel mechanism underlying the role of Rab11-FIP2 in colorectal cancer dissemination, suggesting that targeting Rab11-FIP2 might be a promising therapeutic strategy for CRC.

Electronic supplementary material

The online version of this article (10.1186/s12935-018-0532-0) contains supplementary material, which is available to authorized users.

Intracellular Expression of PAI-1 Specific Aptamers Alters Breast Cancer Cell Migration, Invasion and Angiogenesis

Plasminogen activator inhibitor-1 (PAI-1) is elevated in various cancers, where it has been shown to effect cell migration and invasion and angiogenesis. While, PAI-1 is a secreted protein, its intercellular levels are increased in cancer cells. Consequently, intracellular PAI-1 could contribute to cancer progression. While various small molecule inhibitors of PAI-1 are currently being investigated, none specifically target intracellular PAI-1. A class of inhibitors, termed aptamers, has been used effectively in several clinical applications. We previously generated RNA aptamers that target PAI-1 and demonstrated their ability to inhibit extracellular PAI-1. In the current study we explored the effect of these aptamers on intracellular PAI-1. We transiently transfected the PAI-1 specific aptamers into both MDA-MB-231 human breast cancer cells, and human umbilical vein endothelial cells (HUVECs) and studied their effects on cell migration, invasion and angiogenesis. Aptamer expressing MDA-MB-231 cells exhibited a decrease in cell migration and invasion. Additionally, intracellular PAI-1 and urokinase plasminogen activator (uPA) protein levels decreased, while the PAI-1/uPA complex increased. Moreover, a significant decrease in endothelial tube formation in HUVECs transfected with the aptamers was observed. In contrast, conditioned media from aptamer transfected MDA-MB-231 cells displayed a slight pro-angiogenic effect. Collectively, our study shows that expressing functional aptamers inside breast and endothelial cells is feasible and may exhibit therapeutic potential.

Angiogenesis: Basic Mechanisms and Clinical Applications

The development and maintenance of an adequate vascular supply is critical for the viability of normal and neoplastic tissues. Angiogenesis, the development of new blood vessels from preexisting capillary networks, plays an important role in a number of physiologic and pathologic processes, including reproduction, wound repair, inflammatory diseases, and tumor growth. Angiogenesis involves sequential steps that are triggered in response to angiogenic growth factors released by inflammatory, mesenchymal, or tumor cells that act as ligands for endothelial cell receptor tyrosine kinases. Stimulated endothelial cells detach from neighboring cells and migrate, proliferate, and form tubes. The immature tubes are subsequently invested and stabilized by pericytes or smooth muscle cells. Angiogenesis depends upon complex interactions among various classes of molecules, including adhesion molecules, proteases, structural proteins, cell surface receptors, and growth factors. The therapeutic manipulation of angiogenesis targeted against ischemic and neoplastic diseases has been investigated in preclinical animal models and in clinical trials. Proangiogenic trials that have stimulated vessel growth in ischemic coronary or peripheral tissues through expression, delivery, or stimulated release of growth factors have shown efficacy in animal models and mixed results in human clinical trials. Antiangiogenic trials have used strategies to block the function of molecules critical for new vessel growth or maturation in the treatment of a variety of malignancies, mostly with results less encouraging than those seen in preclinical models. Pro-and antiangiogenic clinical trials demonstrate that strategies for optimal drug delivery, dosing schedules, patient selection, and endpoint measurements need further investigation and refinement before the therapeutic manipulation of angiogenesis will realize its full clinical potential.

Role of heparin and non heparin binding serpins in coagulation and angiogenesis: A complex interplay

Pro-coagulant, anti-coagulant and fibrinolytic pathways are responsible for maintaining hemostatic balance under physiological conditions. Any deviation from these pathways would result in hypercoagulability leading to life threatening diseases like myocardial infarction, stroke, portal vein thrombosis, deep vein thrombosis (DVT) and pulmonary embolism (PE). Angiogenesis is the process of sprouting of new blood vessels from pre-existing ones and plays a critical role in vascular repair, diabetic retinopathy, chronic inflammation and cancer progression. Serpins; a superfamily of protease inhibitors, play a key role in regulating both angiogenesis and coagulation. They are characterized by the presence of highly conserved secondary structure comprising of 3 β-sheets and 7-9 α-helices. Inhibitory role of serpins is modulated by binding to cofactors, specially heparin and heparan sulfate proteoglycans (HSPGs) present on cell surfaces and extracellular matrix. Heparin and HSPGs are the mainstay of anti-coagulant therapy and also have therapeutic potential as anti-angiogenic inhibitors. Many of the heparin binding serpins that regulate coagulation cascade are also potent inhibitors of angiogenesis. Understanding the molecular mechanism of the switch between their specific anti-coagulant and anti-angiogenic role during inflammation, stress and regular hemostasis is important. In this review, we have tried to integrate the role of different serpins, their interaction with cofactors and their interplay in regulating coagulation and angiogenesis.

High Expression of Urokinase-Type Plasminogen Activator Is Associated with Lymph Node Metastasis of Invasive Ductal Carcinoma of the Breast

Purpose

In the present study, we evaluated the levels of urokinase-type plasminogen activator (uPA) and plasminogen activator inhibitor 1 (PAI-1) by performing immunohistochemical staining to determine whether they were reliable prognostic markers in patients with breast cancer.

Methods

Demographic and clinicopathological parameters of 214 patients with invasive ductal carcinoma (IDC) and 80 patients with ductal carcinoma in situ (DCIS) who were diagnosed and treated from 2006 to 2010 were analyzed. Tissue microarray was constructed and immunohistochemical staining was performed for each specimen.

Results

Univariate analyses showed that age at diagnosis, history of hormone replacement therapy, radiation therapy, skin and chest wall invasion, Paget disease, lymphovascular invasion, estrogen receptor positivity, and triple-negative subtype were significantly associated with patient prognosis (p<0.005). Patients with DCIS showed higher PAI-1 expression than patients with IDC (82.5% and 36.2%, respectively; p=0.012). Lymph node metastasis was more frequent in patients with high uPA levels than in patients with low uPA levels (p=0.001).

Conclusion

Our results suggested that PAI-1 was involved in tumor progression in the early stages of breast cancer, such as DCIS. In addition, our results suggested that high uPA levels were associated with the lymph node metastasis of IDC.

Is there a role for urokinase-type plasminogen activator inhibitors as maintenance therapy in patients with ovarian cancer?

There is abundant evidence that the urokinase-type plasminogen activator (uPA), its inhibitors PAI-1 and PAI-2 (plasminogen activator inhibitor type-1 and type-2) and its cells surface receptor (uPA-R, CD87) play a fundamental role in tumor invasion and metastasis and are of significant prognostic significance for many tumor types. We performed a systematic Med-line search on uPA, PAI, uPA-R and (epithelial) ovarian cancer (EOC). The majority of malignant EOC specimens show moderate to strong immunostating of tumor and stromal cells. Overexpression of u-PA and PAI-1 can be found in more the 75% of primary ovarian carcinomas, in most metastatic EOC samples and all examined epithelial ovarian cancer cell lines. uPA overexpression in primary specimens was significantly associated with tumor stage, grade, residual disease status after cytoreductive surgery, and poor clinical outcome. This may be explained by increased chemoresistance, a lower resectability and more aggressive tumor biology and tumor dissemination in patients with high uPA and PAI-1. Several therapeutical approaches aimed at inhibiting the uPA/uPAR functions have shown to possess anti-tumor effects in vitro and in animal models. When treating a patient with advanced ovarian cancer it may to be assumed that inhibiting the progression of established (micro) metastases may be more therapeutically relevant than trying to destroy all tumor cells which is not possible in most cases with current systemic treatment modalities. Taking into account the role of uPA and PAI in cell detachment, formation of new stroma, tumor cell reimplantation and metastasis uPA inhibition should be further investigated as maintenance treatment in patients with advanced EOC.

Diabetes-associated dysregulated cytokines and cancer

Epidemiological data demonstrate that patients with diabetes have an augmented risk of developing various types of cancers, accompanied by higher mortality. A number of mechanisms for this connection have been hypothesized, such as insulin resistance, hyperinsulinemia, hyperglycemia, and increased inflammatory processes. Apart from these potential mechanisms, several diabetes-associated dysregulated cytokines might be implicated in the link between diabetes and cancer. In fact, some inflammatory cytokines, e.g. TNF-α, IL-6 and leptin, have been revealed to play important roles in both initiation and progression of tumor. Here, we depict the role of these cytokines in key events of carcinogenesis and cancer development, including their capability to induce oxidative stress, inflammation, their participation in epithelial mesenchymal transition (EMT), angiogenesis, and metastasis. Finally, we will also highlight the existing knowledge in terms of the involvement of these cytokines in different cancer types and comment on potential significances for future clinical applications.

Components of the Plasminogen-Plasmin System as Biologic Markers for Cancer

Members of the plasminogen-plasmin (PP) system participate in many physiologic functions. In particular, uPA, its receptor (uPAR) and its inhibitor PAI-1 play an important role in cell migration, cell proliferation and tissue remodeling. Through a number of interactions, these components of the PP system are also involved in the pathogenesis of many diseases. In cancer, they modulate the essential processes of tumor development, growth, invasion and metastasis as well as angiogenesis and fibrosis. Thus, quantification of uPA, uPAR and PAI-1 in tumors and, in some cases in the circulating blood, became of potential value in the prognostication of many types of cancer. These include cancer of the breast, stomach, colon and rectum, esophagus, pancreas, glioma, lung, kidney, prostate, uterine cervix, ovary, liver and bone. Published data are reviewed in this chapter. Clinical validation of the prognostic value has also been made, particularly in cancer of the breast. Inclusion of these biomarkers in the risk assessment of cancer patients is now considered in the risk-adapted management in carcinoma of the breast. Factors limiting its broader use are discussed with suggestions how these can be overcome. Hopefully the use of these biomarkers will be applied to other types of cancer in the near future.

Plasminogen activator inhibitor-1 regulates infiltration of macrophages into melanoma via phosphorylation of FAK-Tyr⁹²⁵

Tumor-infiltrating macrophages are potential candidates for cancer immunotherapy. However, the detailed molecular mechanism underlying macrophage infiltration into tumors is poorly understood. Based on our previous finding that plasminogen activator inhibitor-1 (PAI-1) enhances vitronectin-dependent migration of macrophages, we investigated the potential role of PAI-1 in macrophage invasion into melanoma. Experimental evidence obtained from spheroid confrontation assay clearly showed that PAI-1 overexpression significantly enhanced the invasion of RAW 264.7 cells into B16F10 melanoma. We further demonstrated that PAI-1 induces phosphorylation of focal adhesion kinase (FAK) at Tyr(925), which, in turn, mediated the invasion of macrophages into the melanoma. This work further illustrates that low-density lipoprotein receptor related-protein 1 (LRP1) is essential for PAI-1-mediated FAK phosphorylation and macrophage invasion into melanoma. In conclusion, our study demonstrates a novel role of PAI-1 in macrophage invasion into melanoma and provides insights into the underlying molecular mechanism.

PAI-1 leads to G1-phase cell-cycle progression through cyclin D3/cdk4/6 upregulation

The canonical function of plasminogen activator inhibitor-1 (PAI-1/SERPINE1) is as an inhibitor of urokinase-type plasminogen activator for blood clot maintenance, but it is now also considered a pleiotropic factor that can exert diverse cellular and tumorigenic effects. However, the mechanism controlling its pleiotropic effects is far from being understood. To elucidate the tumorigenic role of PAI-1, we tested the effects of PAI-1 after manipulation of its expression or through the use of a small-molecule inhibitor, tiplaxtinin. Downregulation of PAI-1 significantly reduced cellular proliferation through an inability to progress from the G(0-G1) phase of the cell cycle. Accordingly, overexpression of PAI-1 augmented proliferation by encouraging S-phase entry. Biochemically, cell-cycle arrest was associated with the depletion of the G(1)-phase transition complexes, cyclin D3/cdk4/6 and cyclin E/cdk2, in parallel with the upregulation of the cell-cycle inhibitors p53, p21Cip1/Waf1, and p27Kip1. PAI-1 depletion significantly decreased the tumor size of urothelial T24 and UM-UC-14 xenografts, and overexpression of PAI-1 substantially increased the tumor size of HeLa xenografts. Finally, immunohistochemical analysis of human bladder and cervical tumor tissue microarrays revealed increased expression of PAI-1 in cancerous tissue, specifically in aggressive tumors, supporting the relevance of this molecule in human tumor biology.

IMPLICATIONS

Targeting PAI-1 has beneficial antitumoral effects and should be further investigated clinically.

Targeting plasminogen activator inhibitor-1 inhibits angiogenesis and tumor growth in a human cancer xenograft model

Cancers of the urinary bladder result in aggressive and highly angiogenic tumors for which standard treatments have only limited success. Patients with advanced disease have a 5-year survival rate of less than 20%, and no new anticancer agent has been successfully introduced into the clinic armamentarium for the treatment of bladder cancer in more than 20 years. Investigations have identified plasminogen activator inhibitor-1 (PAI-1), a serine protease inhibitor, as being highly expressed in several malignancies, including bladder cancer, in which high expression is associated with a poor prognosis. In this study, we evaluated PAI-1 as a potential therapeutic target for bladder cancer. PAI-1 expression was manipulated in a panel of cell lines and functional inhibition was achieved using the small molecule tiplaxtinin. Reduction or inhibition of PAI-1 resulted in the reduction of cellular proliferation, cell adhesion, and colony formation, and the induction of apoptosis and anoikis in vitro. Treatment of T24 xenografts with tiplaxtinin resulted in inhibition of angiogenesis and induction of apoptosis, leading to a significant reduction in tumor growth. Similar results were obtained through evaluation of the human cervical cancer HeLa cell line, showing that PAI-1-mediated effects are not restricted to tumor cells of bladder origin. Collectively, these data show that targeting PAI-1 may be beneficial and support the notion that novel drugs such as tiplaxtinin could be investigated as anticancer agents.

Thrombospondin-1 in urological cancer: pathological role, clinical significance, and therapeutic prospects

Angiogenesis is an important process for tumor growth and progression of various solid tumors including urological cancers. Thrombospondins (TSPs), especially TSP-1, are representative “anti”-angiogenic molecules and many studies have clarified their pathological role and clinical significance in vivo and in vitro. In fact, TSP-1 expression is associated with clinicopathological features and prognosis in many types of cancers. However, TSP-1 is a multi-functional protein and its biological activities vary according to the specific tumor environments. Consequently, there is no general agreement on its cancer-related function in urological cancers, and detailed information regarding regulative mechanisms is essential for a better understanding of its therapeutic effects and prognostic values. Various “suppressor genes” and “oncogenes” are known to be regulators and TSP-1-related factors under physiological and pathological conditions. In addition, various types of fragments derived from TSP-1 exist in a given tissue microenvironment and TSP-1 derived-peptides have specific activities. However, a detailed pathological function in human cancer tissues is not still understood. This review will focus on the pathological roles and clinical significance of TSP-1 in urological cancers, including prostate cancer, renal cell carcinoma, and urothelial cancer. In addition, special attention is paid to TSP-1-derived peptide and TSP-1-based therapy for malignancies.

Signal-dependent Elk-1 target genes involved in transcript processing and cell migration

Elk-1 was regarded as a transcription factor engaged mainly in the regulation of cell growth, differentiation, and survival. Recent findings show the engagement of Elk-1 in the control of expression of genes encoding proteins involved in transcript turnover, such as MCPIP1/ZC3H12A and tristetraprolin (TTP/ZFP36). Thus, Elk-1 plays an important role in the control of gene expression not only through the stimulation of expression of transcription factors, but also through regulation of transcript half-live. Moreover, Elk-1 is engaged in the regulation of expression of genes encoding proteins that control proteolytic activity, such as inhibitor of plasminogen activator-1 (PAI-1) and metalloproteinases-2 and -9 (MMP-2 and MMP-9). This review summarizes the biological roles of proteins with expression regulated by Elk-1, involved in transcripts turnover or in cell migration. The broad range of function of these proteins illustrates the complex role of Elk-1 in the regulation of cancer and inflammation.

ZEB1 Promotes invasiveness of colorectal carcinoma cells through the opposing regulation of uPA and PAI-1

PURPOSE

Carcinoma cells enhance their invasive capacity through dedifferentiation and dissolution of intercellular adhesions. A key activator of this process is the ZEB1 transcription factor, which is induced in invading cancer cells by canonical Wnt signaling (β-catenin/TCF4). Tumor invasiveness also entails proteolytic remodeling of the peritumoral stroma. This study aimed to investigate the potential regulation by ZEB1 of the plasminogen proteolytic system constituted by the urokinase plasminogen activator (uPA), and its inhibitor, plasminogen activator inhibitor-1 (PAI-1).

EXPERIMENTAL DESIGN

Through multiple experimental approaches, colorectal carcinoma (CRC) cell lines and samples from human primary CRC and ZEB1 (-/-) mice were used to examine ZEB1-mediated regulation of uPA and PAI-1 at the protein, mRNA, and transcriptional level.

RESULTS

ZEB1 regulates uPA and PAI-1 in opposite directions: induces uPA and inhibits PAI-1. In vivo expression of uPA depends on ZEB1 as it is severely reduced in the developing intestine of ZEB1 null (-/-) mice. Optimal induction of uPA by Wnt signaling requires ZEB1 expression. ZEB1 binds to the uPA promoter and activates its transcription through a mechanism implicating the histone acetyltransferase p300. In contrast, inhibition of PAI-1 by ZEB1 does not involve transcriptional repression but rather downregulation of mRNA stability. ZEB1-mediated tumor cell migration and invasion depend on its induction of uPA. ZEB1 coexpresses with uPA in cancer cells at the invasive front of CRCs.

CONCLUSIONS

ZEB1 promotes tumor invasiveness not only via induction in cancer cells of a motile dedifferentiated phenotype but also by differential regulation of genes involved in stroma remodeling.

Plasmin-driven fibrinolysis facilitates skin tumor growth in a gender-dependent manner

Rearrangement of the skin during wound healing depends on plasmin and plasminogen, which serve to degrade fibrin depositions in the provisional matrix and thereby facilitate keratinocyte migration. In the current study, we investigated whether plasmin and plasminogen likewise played a role during the development of skin cancer. To test this, we set up a chemically induced skin tumor model in a cohort of mice and found that skin tumor growth in Plg(-/-) male mice was reduced by 52% compared with wild-type controls. Histological analyses suggested that the growth-restricting effect of plasminogen deficiency was due to thrombosis and lost patency of the tumor vasculature, resulting in tumor necrosis. The connection between plasmin-dependent fibrinolysis, vascular patency, and tumor growth was further substantiated as the effect of plasminogen deficiency on tumor growth could be reverted by superimposing heterozygous fibrinogen deficiency on Plg(-/-) mice. Tumors derived from these Fib(-/+);Plg(-/-) mice displayed a significantly decreased level of tumor thrombosis compared with Plg(-/-) mice. In summary, these data indicate that plasmin-driven fibrinolysis facilitates tumor growth by maintaining patency of the tumor vasculature.

PAI-1-dependent endothelial cell death determines severity of radiation-induced intestinal injury

Normal tissue toxicity still remains a dose-limiting factor in clinical radiation therapy. Recently, plasminogen activator inhibitor type 1 (SERPINE1/PAI-1) was reported as an essential mediator of late radiation-induced intestinal injury. However, it is not clear whether PAI-1 plays a role in acute radiation-induced intestinal damage and we hypothesized that PAI-1 may play a role in the endothelium radiosensitivity. In vivo, in a model of radiation enteropathy in PAI-1 −/− mice, apoptosis of radiosensitive compartments, epithelial and microvascular endothelium was quantified. In vitro, the role of PAI-1 in the radiation-induced endothelial cells (ECs) death was investigated. The level of apoptotic ECs is lower in PAI-1 −/− compared with Wt mice after irradiation. This is associated with a conserved microvascular density and consequently with a better mucosal integrity in PAI-1 −/− mice. In vitro, irradiation rapidly stimulates PAI-1 expression in ECs and radiation sensitivity is increased in ECs that stably overexpress PAI-1, whereas PAI-1 knockdown increases EC survival after irradiation. Moreover, ECs prepared from PAI-1 −/− mice are more resistant to radiation-induced cell death than Wt ECs and this is associated with activation of the Akt pathway. This study demonstrates that PAI-1 plays a key role in radiation-induced EC death in the intestine and suggests that this contributes strongly to the progression of radiation-induced intestinal injury.

Plasminogen activator inhibitor 1 RNAi suppresses gastric cancer metastasis in vivo

Cancer metastasis remains the primary cause of pain, suffering, and death in cancer patients, and even the most current therapeutic strategies have not been highly successful in preventing or inhibiting metastasis. In most patients with scirrhous gastric cancer (one of the most aggressive of diffuse-type gastric cancer), recurrence occurs even after potentially curative resection, most frequently in the form of peritoneal metastasis. Given that the occurrence of diffuse-type gastric cancers has been increasing, the development of new strategies to combat metastasis of this disease is critically important. Plasminogen activator inhibitor-1 (PAI-1) is a critical factor in cancer progression; thus, PAI-1 RNAi may be an effective therapy against cancer metastasis. In the present study, we used an RNAi technique to reduce PAI-1 expression in an in vivo model system for gastric cancer metastasis. Ex vivo plasmid transfection and adenovirus infection were tested as mechanisms to incorporate specific PAI-1 RNAi vectors into human gastric carcinoma cells. Both approaches significantly decreased peritoneal tumor growth and the formation of bloody ascites in the mouse model, suggesting that this approach may provide a new, effective strategy for inhibiting cancer metastasis.

Novel regulatory mechanism and functional implication of plasminogen activator inhibitor-1 (PAI-1) expression in CpG-ODN-stimulated macrophages

Macrophages are activated by recognizing bacterial DNA and CpG-oligodeoxynucleotides (CpG-ODNs) through Toll-like receptor-9 (TLR-9). Plasminogen activator inhibitor-1 (PAI-1) has been shown to be an important factor in inflammation-induced macrophage migration which is essential for defense functions. The aim of this study was to demonstrate the molecular mechanism associated with the regulation of PAI-1 expression and its biological significance in CpG-ODN-stimulated mouse macrophages. Our results clearly show that PAI-1 expression in macrophages was highly up-regulated by CpG-ODN-stimulation in vitro and in vivo. The TLR-9-mediated stimulation of PAI-1 expression was independent of the NF-κB pathway and involved the synergistic activation of Sp1 and Elk-1 by the MEK1/2-ERK and JNK signaling pathways. The elevated PAI-1 expression resulted in significantly enhanced transmigration of RAW264.7 cells through vitronectin but not through fibronectin. We suggest that CpG-ODN plays a role in regulating macrophage migration by stimulating the expression of PAI-1, and the migration is modulated depending on the microenvironmental extracellular matrix components.

Matrix remodeling stimulates stromal autophagy, "fueling" cancer cell mitochondrial metabolism and metastasis

We have previously demonstrated that loss of stromal caveolin-1 (Cav-1) in cancer-associated fibroblasts is a strong and independent predictor of poor clinical outcome in human breast cancer patients. However, the signaling mechanism(s) by which Cav-1 downregulation leads to this tumor-promoting microenvironment are not well understood. To address this issue, we performed an unbiased comparative proteomic analysis of wild-type (WT) and Cav-1(-/-) null mammary stromal fibroblasts (MSFs). Our results show that plasminogen activator inhibitor type 1 and type 2 (PAI-1 and PAI-2) expression is significantly increased in Cav-1(-/-) MSFs. To establish a direct cause-effect relationship, we next generated immortalized human fibroblast lines stably overexpressing either PAI-1 or PAI-2. Importantly, PAI-1/2(+) fibroblasts promote the growth of MDA-MB-231 tumors (a human breast cancer cell line) in a murine xenograft model, without any increases in angiogenesis. Similarly, PAI-1/2(+) fibroblasts stimulate experimental metastasis of MDA-MB-231 cells using an in vivo lung colonization assay. Further mechanistic studies revealed that fibroblasts overexpressing PAI-1 or PAI-2 display increased autophagy ("self-eating") and are sufficient to induce mitochondrial biogenesis/activity in adjacent cancer cells, in co-culture experiments. In xenografts, PAI-1/2(+) fibroblasts significantly reduce the apoptosis of MDA-MB-231 tumor cells. The current study provides further support for the "Autophagic Tumor Stroma Model of Cancer" and identifies a novel "extracellular matrix"-based signaling mechanism, by which a loss of stromal Cav-1 generates a metastatic phenotype. Thus, the secretion and remodeling of extracellular matrix components (such as PAI-1/2) can directly regulate both (1) autophagy in stromal fibroblasts and (2) epithelial tumor cell mitochondrial metabolism.

Use of mouse models to study plasminogen activator inhibitor-1

Plasminogen activator inhibitor-1 (PAI-1) is the main inhibitor of tissue-type plasminogen activator (t-PA) and urokinase-type plasminogen activator (u-PA) and therefore plays an important role in the plasminogen/plasmin system. PAI-1 is involved in a variety of cardiovascular diseases (mainly through inhibition of t-PA) as well as in cell migration and tumor development (mainly through inhibition of u-PA and interaction with vitronectin). PAI-1 is a unique member of the serpin superfamily, exhibiting particular unique conformational and functional properties. Since its involvement in various biological and pathophysiological processes PAI-1 has been the subject of many in vivo studies in mouse models. We briefly discuss structural and physiological differences between human and mouse PAI-1 that should be taken into account prior to extrapolation of data obtained in mouse models to the human situation. The current review provides an overview of the various models, with a focus on cardiovascular disease and cancer, using wild-type mice or genetically modified mice, either deficient in PAI-1 or overexpressing different variants of PAI-1.

Plasminogen activator inhibitor type 1 interacts with alpha3 subunit of proteasome and modulates its activity

Plasminogen activator inhibitor type-1 (PAI-1), a multifunctional protein, is an important physiological regulator of fibrinolysis, extracellular matrix homeostasis, and cell motility. Recent observations show that PAI-1 may also be implicated in maintaining integrity of cells, especially with respect to cellular proliferation or apoptosis. In the present study we provide evidence that PAI-1 interacts with proteasome and affects its activity. First, by using the yeast two-hybrid system, we found that the α3 subunit of proteasome directly interacts with PAI-1. Then, to ensure that the PAI-1-proteasome complex is formed in vivo, both proteins were coimmunoprecipitated from endothelial cells and identified with specific antibodies. The specificity of this interaction was evidenced after transfection of HeLa cells with pCMV-PAI-1 and coimmunoprecipitation of both proteins with anti-PAI-1 antibodies. Subsequently, cellular distribution of the PAI-1-proteasome complexes was established by immunogold staining and electron microscopy analyses. Both proteins appeared in a diffuse cytosolic pattern but also could be found in a dense perinuclear and nuclear location. Furthermore, PAI-1 induced formation of aggresomes freely located in endothelial cytoplasm. Increased PAI-1 expression abrogated degradation of degron analyzed after cotransfection of HeLa cells with pCMV-PAI-1 and pd2EGFP-N1 and prevented degradation of p53 as well as IκBα, as evidenced both by confocal microscopy and Western immunoblotting.

Type 1 plasminogen activator inhibitor (PAI-1) in clear cell renal cell carcinoma (CCRCC) and its impact on angiogenesis, progression and patient survival after radical nephrectomy

Background

To examine the expression of type 1 plasminogen inhibitor (PAI-1) in clear cell renal cell carcinoma (CCRCC), and its possible association with microvessel density (MVD), the expression of thrombospondin-1 (TSP-1), nuclear grade, tumour stage, continuously coded tumour size (CCTS) and to assess the value of PAI as a prognostic marker in 162 patients with CCRCC treated with radical nephrectomy.

Methods

A total of 172 consecutive patients with CCRCC treated with radical nephrectomy were enrolled in the study. The expression of PAI-1, TSP-1 and factor VIII were analysed on formalin-fixed, paraffin-embedded tissues without knowledge of the clinical outcome. Ten cases, where PAI-1 immunohistochemistry was not possible due to technical problems and lack of material, were excluded. Sixty-nine patients (43%) died of RCC, while 47 patients (29%) died of other diseases. Median follow-up was 13.8 years for the surviving 46 patients (28%).

Results

Nine percent of the tumours showed PAI-1 positivity. High expression of PAI-1 was significantly inversely correlated with TSP-1 (p = 0.046) and directly with advanced stage (p = 0.008), high NG (3+4) (p = 0.002), tumour size (p = 0.011), microvessel density (p = 0.049) and disease progression (p = 0.002). In univariate analysis PAI-1 was a significant prognosticator of cancer-specific survival (CSS) (p < 0.001). Multivariate analysis revealed that TNM stage (p < 0.001), PAI-1 (p = 0.020), TSP-1 (p < 0.001) and MVD (p = 0.007) were independent predictors of CSS.

Conclusions

PAI-1 was found to be an independently significant prognosticator of CSS and a promoter of tumour angiogenesis, aggressiveness and progression in CCRCC.

Decrease of plasminogen activator inhibitor-1 may contribute to the anti-invasive action of cannabidiol on human lung cancer cells

PURPOSE

Using human lung cancer cells, we evaluated the involvement of plasminogen activator inhibitor-1 (PAI-1) in the anti-invasive action of cannabidiol, a non-psychoactive cannabinoid.

METHODS

Invasion was quantified by a modified Boyden chamber assay. PAI-1 protein in cell culture media and PAI-1 mRNA were determined by immunoblotting and RT-PCR, respectively.

RESULTS

Cannabidiol caused a profound inhibition of A549 cell invasion, accompanied by a decreased expression and secretion of PAI-1. Cannabidiol's effects on PAI-1 secretion and invasion were suppressed by antagonists to CB(1) and CB(2) receptors as well as to transient receptor potential vanilloid 1. Recombinant human PAI-1 and PAI-1 siRNA led to a concentration-dependent up- and down-regulation of invasiveness, respectively, suggesting a crucial role of PAI-1 in A549 invasiveness. Evidence for a causal link between cannabidiol's effects on PAI-1 and invasion was provided by experiments showing a reversal of its anti-invasive action by addition of recombinant PAI-1 at non-proinvasive concentrations. Key data were confirmed in two other human lung cancer cell lines (H460, H358). In vivo, a significant downregulation of PAI-1 protein by cannabidiol was demonstrated in A549 xenografts.

CONCLUSION

Our data provide evidence for a hitherto unknown mechanism underlying the anti-invasive action of cannabidiol on human lung cancer cells.

Molecular mediators of angiogenesis

Angiogenesis, or the formation of new blood vessels from the preexisting vasculature, is a key component in numerous physiologic and pathologic responses and has broad impact in many medical and surgical specialties. In this review, we discuss the key cellular steps that lead to the neovascularization of tissues and highlight the main molecular mechanisms and mediators in this process. We include discussions on proteolytic enzymes, cell-matrix interactions, and pertinent cell signaling pathways and end with a survey of the mechanisms that lead to the stabilization and maturation of neovasculatures.

The role of plasminogen-plasmin system in cancer

Components of the plasminogen-plasmin system participate in a wide variety of physiologic and pathologic processes, including tumor growth, invasion and metastasis, through their effect on angiogenesis and cell migration. These components are found in most tumors and their expression not only signifies their function but also carries a prognostic value. Their expression is in turn modulated by cytokines and growth factors, many of which are up-regulated in cancer. Though both tPA and uPA are expressed in tumor cells, uPA with its receptor (uPAR) is mostly involved in cellular functions, while tPA with its receptor Annexin II on endothelial surface, regulates intravascular fibrin deposition. Among the inhibitors of fibrinolysis, PAI-1 is a major player in the pathogenesis of many vascular diseases as well as in cancer. Therapeutic interventions, either using plasminogen activators or experimental inhibitor agents against PAI-1, have shown encouraging results in experimental tumors but not been verified clinically.

Plasminogen activator inhibitor-1: the double-edged sword in apoptosis

Plasminogen activator inhibitor type-1 (PAI-1) is a multi-functional protein. It is a fast-acting inhibitor of plasminogen activators; urokinase-plasminogen activator and tissue type plasminogen activator, and also plays an important role in regulating cell proliferation, adhesion, migration, and signal transduction pathways. These biological events are important processes during angiogenesis and restenosis. PAI-1 has been shown to regulate proliferation, migration, and apoptosis of vascular smooth muscle cells and endothelial cells. The ability of PAI-1 to regulate cellular proliferation and migration has been attributed to its ability to control plasmin production, modify signaling pathways, and its inherent multifactorial ability to bind to vitronectin and lipoprotein receptor-related protein. However, the mechanism by which PAI-1 regulates the apoptotic pathway is not well understood. Evidence from the literature suggests that PAI-1 or its deficiency alters key signalling pathways, such as the PI3-k/Akt and the Jak/STAT pathways, and is involved in maintaining endothelial cell integrity thereby regulating cell death. Other investigators have demonstrated that PAI-1 directly binds to caspases as a mechanism of PAI-1-mediated cellular apoptosis. Moreover, results from studies assessing the role of PAI-1 in apoptosis have suggested that PAI-1 can exert pathogenic or protective effects, which may be related to the disease model or type of injury employed.

Intravesical administration of plasminogen activator inhibitor type-1 inhibits in vivo bladder tumor invasion and progression

PURPOSE

The potent effects of PAI-1 on tumorigenesis and angiogenesis in various experimental models are complex, complicated and at times contradictory. We determined the therapeutic potential of PAI-1 for inhibiting bladder tumor invasion under conditions that closely mimic the clinical setting.

MATERIALS AND METHODS

An orthotopic rat bladder tumor model was established by implanting AY-27 rat transitional carcinoma cells into the bladder lumen of syngeneic Fischer F344 rats. Three weeks after implantation 1 microM PAI-1 was administrated directly into the bladder lumen twice weekly for 2 weeks. Two days after the final treatment tumor size, total bladder weight, tumor stage and angiogenesis were assessed. To assess the uPA axis the levels of active and total uPA, and active and total PAI-1 in tumor extracts were determined 0, 2, 24 and 48 hours after intravesical PAI-1 administration.

RESULTS

Intravesical PAI-1 bound and inactivated its molecular target, tumor uPA. There was significant inhibition of bladder tumor progression, as manifested by 53%, 37% and 57% reductions in tumor size, total bladder weight and angiogenesis, respectively. Only 22% of PAI-1 treated tumors invaded muscle vs 79% in controls. No PAI-1 toxicity was detected.

CONCLUSIONS

To our knowledge this study is the first to demonstrate that intravesical treatment with PAI-1 significantly inhibits tumor progression in an in vivo model of bladder cancer. Further clinical development is warranted for using PAI-1 directly or in combination with current standards, such as bacillus Calmette-Guerin or interferon.

The plasminogen activator inhibitor "paradox" in cancer

Proteolysis in general and specifically the plasminogen activating system regulated by urokinase (uPA) its specific receptor, the GPI membrane anchored urokinase receptor (uPAR) and the specific plasminogen activator inhibitor 1 (PAI-1) plays a major role in tumorigenesis, tumor progression, tumor invasion and metastasis formation. This is exemplified by a body of published work showing a positive correlation between the expression of uPA or uPAR in several tumors and their malignancy. It is generally assumed that such a "pro-malignant" effect of the uPA-uPAR system is mediated by increased local proteolysis thus favoring tumor invasion, by a pro-angiogenic effect of this system and also by uPA-uPAR signaling towards the tumor thereby shifting the tumor phenotype to a more "malignant" one. However, when tumor patients are analyzed for long term survival, those with high levels of the inhibitor of the system, PAI-1 have a much worse prognosis than those with lower PAI-1 levels. This indicates that increased overall proteolysis alone cannot be made responsible for the adverse effects of the plasminogen activating system in tumors. Moreover, it becomes increasingly evident that components of the fibrinolytic system secreted by the tumor cells themselves are not solely responsible for a correlation between the plasminogen activating system and tumor malignancy; components of the plasminogen activating system secreted by stroma cells or cells of the immune system such as macrophages contribute also to the impact of fibrinolysis on malignancy. This review summarizes the evidence for the role of plasminogen activator inhibitor-1 in mediating the malignant phenotype and possible mechanism thereby trying to explain the "PAI-1 paradox in cancer" on a molecular level.

Significant down-regulation of the plasminogen activator inhibitor 1 mRNA in pancreatic cancer

OBJECTIVES

We examined mRNA expression of the urokinase-type plasminogen activator (uPA), its receptor (uPAR), and the plasminogen activator inhibitor 1 (PAI-1) in a panel of adenocarcinomas of the pancreas (PC) and cancers of the papilla of Vater (CPV). Expression profiles were compared with paired uninvolved normal tissues to define a possible differential role of these genes in tumorigenesis of both tumor types.

METHODS

Urokinase-type plasminogen activator, uPAR, and PAI-1 mRNA expression was analyzed by real-time quantitative reverse-transcriptase polymerase chain reaction (TaqMan) in 25 PC, 7 CPV, and in the paired uninvolved normal tissues.

RESULTS

Uninvolved normal tissue probes from PC and CPV showed similar mRNA expression profiles of uPA, uPAR, and PAI-1. Whereas expression levels of uPA (P = 0.81) and uPAR (P = 0.75) were not statistically significant different between tumor and paired normal tissues, PAI-1 levels were significantly down-regulated in tumor compared with paired normal tissue samples (Wilcoxon test; P < 0.006). No differences in mRNA expression of uPA, uPAR, and PAI-1 between PC and CPV were observed. Expression levels of the 3 genes were not associated with tumor stage, grading, or survival.

CONCLUSIONS

Increased mRNA expression of uPA and uPAR could not be detected in PC and CPV; however, PAI-1 mRNA expression levels are significantly down-regulated in PC, which might lead to higher activity levels of uPA components. Our data are merely hypothesis generating and should be validated in larger translational studies.

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.

Plasminogen Activation Inhibitor-1 Improves the Predictive Accuracy of Prostate Cancer Nomograms

PURPOSE

We tested whether the addition of preoperative circulating plasminogen activator inhibitor type I levels improves the accuracy of standard preoperative and postoperative models for prediction of biochemical recurrence after radical prostatectomy.

MATERIALS AND METHODS

Preoperative plasma levels of plasminogen activator inhibitor type I were measured in 429 consecutive patients treated with radical prostatectomy for clinically localized prostate cancer. The patients were randomly divided into a development (67%, 286) and a split sample validation cohort (33%, 143). Cox regression analysis was used to develop prognostic nomograms for prediction of biochemical recurrence.

RESULTS

In standard univariate analyses categorically coded preoperative plasminogen activator inhibitor type I was significantly associated with biochemical recurrence (p <0.001). In standard preoperative and postoperative multivariate analyses preoperative plasminogen activator inhibitor type I was independently associated with biochemical recurrence (p <0.001 and p = 0.002, respectively). In the split sample validation cohort the addition of plasminogen activator inhibitor type I increased the predictive accuracy of the preoperative multivariate model by 1.2%, 7.7%, 10.3%, 6.7% and 5.4% at 1, 2, 3, 4 and 5 years, respectively (p values <0.001). Moreover, the addition of plasminogen activator inhibitor type I increased the predictive accuracy of the postoperative model by 0.5%, 1.1%, 4.0%, 2.4% and 3.6% at 1, 2, 3, 4 and 5 years, respectively (p values <0.001).

CONCLUSIONS

Preoperative circulating plasminogen activator inhibitor type I is a predictor of biochemical recurrence, and it enhances the accuracy of preoperative and postoperative nomograms. After external validation these nomograms may assist clinical decision making regarding treatment choice and followup as well as identification of patients at high risk for biochemical recurrence who may benefit from neoadjuvant and/or adjuvant treatment.

Adhesive and proteolytic phenotype of migrating endothelial cells induced by thymosin beta-4

The early stages of angiogenesis are usually accompanied by the occurrence of vascular leakage, and the deposition of fibrin in extravascular spaces. Initially, the fibrin network acts as a sealing matrix, but later on also as a scaffolding for invading endothelial cells. This process is induced by angiogenic growth factors, particularly by vascular endothelial growth factor (VEGF). Angiogenesis involves proteolytic activities, in particular cell-bound urokinase/plasmin and matrix metalloproteinase (MMPs) activities that modulate the fibrin structure and affect adhesion and migration of endothelial cells. Recent data show that formation of new vessels may be stimulated by thymosin beta-4 (Tbeta-4), but it is still not clear whether Tbeta-4 alone is angiogenic or the angiogenic potential of Tbeta-4 is mediated by VEGF. In this report to further characterize Tbeta-4 angiogenic activity, we produced its mutants that were deprived of the N-terminal tetrapeptide AcSDKP (Tbeta-4((AcSDKPT/4A))), the actin-binding sequence KLKKTET (Tbeta-4((KLKKTET/7A))) and with the nuclear localization sequence damaged by a point mutation Lys16Ala (Tbeta-4((K16A))). Then we tested their activity to induce expression and release of MMPs as well as plasminogen activators inhibitor type-1 (PAI-1). We also analyzed their effect on migration and proliferation of endothelial cells in three-dimensional (3D) fibrin matrix as well as on their ability to stimulate the outgrowth of human endothelial cells in capillary-like tubular structures. Our data demonstrate that increased intracellular expression of Tbeta-4 and its mutants is necessary and sufficient to induce PAI-1 gene expression in endothelial cells. Similarly, they stimulate expression and release of MMP-1, -2, and -3. As evaluated by using specific inhibitors to these MMPs, they modified specifically the structure of fibrin and thus facilitated migration of endothelial cells. To sum up, our data show that the mechanism by which Tbeta-4 induced transition of endothelial cells from quiescent to proangiogenic phenotype is characterized by increased expression of PAI-1 and MMPs did not require the presence of the N-terminal sequence AcSDKP, and depended only partially on its ability to bind G-actin or to enter the nucleus.

Inhibition of pulmonary metastasis of melanoma b16fo cells in C57BL/6 mice by a nutrient mixture consisting of ascorbic Acid, lysine, proline, arginine, and green tea extract

The authors investigated the effect of a nutrient mixture (NM) on lung metastasis by B16F0 melanoma cells in C57BL/6 female mice. Mice were divided into equal groups (1 to 6) and injected via tail vein with B16F0 cells (groups 1 to 4), B16FO cells pretreated with NM (group 5), or saline (group 6). Groups 1, 3, 4, 5, and 6 were fed the control diet and group 2 the 0.5% NM supplemented diet. Groups 3 and 4 received NM intraperitoneally (IP) and intravenously (IV), respectively. Two weeks later, pulmonary metastatic colonies were counted. Pulmonary colonization was reduced by 63% in mice supplemented with NM diet, by 86% in mice receiving NM by IP and IV injections, and completely inhibited in mice injected with melanoma cells pretreated with NM. These results show that NM is effective in inhibiting the metastasis of B16FO melanoma cells.

Plasminogen activator inhibitor type-1 (PAI-1) polymorphism 4G/5G is associated with prostate cancer among men with a positive family history

BACKGROUND

Variation in the expression of plasminogen activator inhibitor type-1 (PAI-1) is associated with many human diseases, including several types of cancer. In particular, tumor cell overexpression of PAI-1 has been found to inhibit prostate cancer tumor growth, angiogenesis, and metastasis in mouse models. Normal host cell expression of PAI-1 is influenced by the 4G/5G insertion/deletion polymorphism in the promoter region of the PAI-1 gene. To evaluate the effect of PAI-1 expression on cancer development, we examined the association of the 4G/5G polymorphism in a sibling-based case-control study of prostate cancer.

METHODS

One thousand one hundred thirty seven subjects, 655 cases, and 482 sibling controls from 526 families, were recruited from the major medical institutions in the greater Cleveland, OH area and from the Henry Ford Health System, Detroit, MI. A Cox age-of-onset model with robust variance estimation was used to evaluate the association between the PAI-1 4G/5G polymorphism and prostate cancer.

RESULTS

No association was observed between the PAI-1 4G/5G polymorphism and prostate cancer in the entire sample. We did, however, identify a statistically significant association between the PAI-1 4G/5G polymorphism and prostate cancer in subjects with a family history of this disease (OR = 1.28, 95% CI 1.02-1.61, P-value = 0.036). The PAI-1 5G/5G genotype, associated with lower PAI-1 expression, appears to drive this result as it was associated with an increased risk of prostate cancer and an earlier mean age of onset compared to those with the 4G/4G genotype (OR = 1.83, 95% CI 1.12-2.99) while the 4G/5G genotype group did not show a significant difference in prostate cancer risk compared to the 4G/4G genotype group (OR = 0.98, 95% CI 0.75-1.28).

CONCLUSIONS

These observations suggest that the 4G/5G polymorphism in PAI-1 may explain some of the increased risk and earlier mean age of onset of prostate cancer due to a positive family history.