Angiostatin

Angiogenesis: Biological Mechanisms and In Vitro Models

The translation of biomedical devices and drug research is an expensive and long process with a low probability of receiving FDA approval. Developing physiologically relevant in vitro models with human cells offers a solution to not only improving the odds of FDA approval but also to expand our ability to study complex in vivo systems in a simpler fashion. Animal models remain the standard for pre-clinical testing; however, the data from animal models is an unreliable extrapolation when anticipating a human response in clinical trials, thus contributing to the low rates of translation. In this review, we focus on in vitro vascular or angiogenic models because of the incremental role that the vascular system plays in the translation of biomedical research. The first section of this review discusses the most common angiogenic cytokines that are used in vitro to initiate angiogenesis, followed by angiogenic inhibitors where both initiators and inhibitors work to maintain vascular homeostasis. Next, we evaluate previously published in vitro models, where we evaluate capturing the physical environment for biomimetic in vitro modeling. These topics provide a foundation of parameters that must be considered to improve and achieve vascular biomimicry. Finally, we summarize these topics to suggest a path forward with the goal of engineering human in vitro models that emulate the in vivo environment and provide a platform for biomedical device and drug screening that produces data to support clinical translation.

Tumor angiogenesis and anti-angiogenic therapy

ABSTRACT

Anti-angiogenic drugs (AADs), which mainly target the vascular endothelial growth factor-A signaling pathway, have become a therapeutic option for cancer patients for two decades. During this period, tremendous clinical experience of anti-angiogenic therapy has been acquired, new AADs have been developed, and the clinical indications for AAD treatment of various cancers have been expanded using monotherapy and combination therapy. However, improvements in the therapeutic outcomes of clinically available AADs and the development of more effective next-generation AADs are still urgently required. This review aims to provide historical and perspective views on tumor angiogenesis to allow readers to gain mechanistic insights and learn new therapeutic development. We revisit the history of concept initiation and AAD discovery, and summarize the up-to-date clinical translation of anti-angiogenic cancer therapy in this field.

Identification and Validation of Cytotoxicity-Related Features to Predict Prognostic and Immunotherapy Response in Patients with Clear Cell Renal Cell Carcinoma

Background

Clear cell renal cell carcinoma (ccRCC) is a renal cortical malignancy with a complex pathogenesis. Identifying ideal biomarkers to establish more accurate promising prognostic models is crucial for the survival of kidney cancer patients.

Methods

Seurat R package was used for single-cell RNA-sequencing (scRNA-seq) data filtering, dimensionality reduction, clustering, and differentially expressed genes analysis. Gene coexpression network analysis (WGCNA) was performed to identify the cytotoxicity-related module. The independent cytotoxicity-related risk model was established by the survival R package, and Kaplan-Meier (KM) survival analysis and timeROC with area under the curve (AUC) were employed to confirm the prognosis and effectiveness of the risk model. The risk and prognosis in patients suffering from ccRCC were predicted by establishing a nomogram. A comparison of the level of immune infiltration in different risk groups and subtypes using the CIBERSORT, MCP-counter, and TIMER methods, as well as assessment of drug sensitivity to conventional chemotherapeutic agents in risk groups using the pRRophetic package, was made.

Results

Eleven ccRCC subpopulations were identified by single-cell sequencing data from the GSE224630 dataset. The identified cytotoxicity-related T-cell cluster and module genes defined three cytotoxicity-related molecular subtypes. Six key genes (SOWAHB, SLC16A12, IL20RB, SLC12A8, PLG, and HHLA2) affecting prognosis risk genes were selected for developing a risk model. A nomogram containing the RiskScore and stage revealed that the RiskScore contributed the most and exhibited excellent predicted performance for prognosis in the calibration plots and decision curve analysis (DCA). Notably, high-risk patients with ccRCC demonstrate a poorer prognosis with higher immune infiltration characteristics and TIDE scores, whereas low-risk patients are more likely to benefit from immunotherapy.

Conclusions

A ccRCC survival prognostic model was produced based on the cytotoxicity-related signature, which had important clinical significance and may provide guidance for ccRCC treatment.

Chemokines and receptors in the development and progression of malignant tumors

Cancer cells, endothelial cells, inflammatory cells and various cytokines form a part of the tumor microenvironment (TME). Chemokines constitute the largest family of cytokines, and are mainly secreted by tumor cells and inflammatory cells in the TME. They play an important role in tumor development and progression by promoting tumor growth and metastasis, angiogenesis, and targeting the chemoattraction of inflammatory cells. Currently, some chemokine receptor antagonists are being used in clinical trials as targeted anti-tumor drugs. In this article, we review the roles of chemokines in the development and progression of malignant tumors based on recently published papers, taking into consideration of the new anti-tumor therapeutic strategies targeting chemokines and receptors.

The Role of the Plasminogen/Plasmin System in Inflammation of the Oral Cavity

The oral cavity is a unique environment that consists of teeth surrounded by periodontal tissues, oral mucosae with minor salivary glands, and terminal parts of major salivary glands that open into the oral cavity. The cavity is constantly exposed to viral and microbial pathogens. Recent studies indicate that components of the plasminogen (Plg)/plasmin (Pm) system are expressed in tissues of the oral cavity, such as the salivary gland, and contribute to microbial infection and inflammation, such as periodontitis. The Plg/Pm system fulfills two major functions: (a) the destruction of fibrin deposits in the bloodstream or damaged tissues, a process called fibrinolysis, and (b) non-fibrinolytic actions that include the proteolytic modulation of proteins. One can observe both functions during inflammation. The virus that causes the coronavirus disease 2019 (COVID-19) exploits the fibrinolytic and non-fibrinolytic functions of the Plg/Pm system in the oral cavity. During COVID-19, well-established coagulopathy with the development of microthrombi requires constant activation of the fibrinolytic function. Furthermore, viral entry is modulated by receptors such as TMPRSS2, which is necessary in the oral cavity, leading to a derailed immune response that peaks in cytokine storm syndrome. This paper outlines the significance of the Plg/Pm system for infectious and inflammatory diseases that start in the oral cavity.

Obesity: The Fat Tissue Disease Version of Cancer

Obesity is a disease with high potential for fatality. It perfectly fits the disease definition, as cancer does. This is because it damages body structure and functions, both mechanically and biologically, and alters physical, mental, and social health. In addition, it shares many common morbid characteristics with the most feared disease, cancer. For example, it is influenced by a sophisticated interaction between a person’s genetics, the environment, and an increasing number of other backgrounds. Furthermore, it displays abnormal cell growth and proliferation events, only limited to white fat, resulting in adipose tissue taking up an increasing amount of space within the body. This occurs through fat “metastases” and via altered signaling that further aggravates the pathology of obesity by inducing ubiquitous dishomeostasis. These metastases can be made graver by angiogenesis, which might boost diseased tissue growth. More common features with cancer include its progressive escalation through different levels of severity and its possibility of re-onset after recovery. Despite all these similarities with cancer, obesity is substantially less agitating for most people. Thus, the ideas proposed herein could have utility to sensitize the public opinion about the hard reality of obesity. This is increasingly needed, as the obesity pandemic has waged a fierce war against our bodies and society in general, while there is still doubt about whether it is a real disease or not. Hence, raising public consciousness to properly face health issues is crucial to improving our health instead of gaining weight unhealthily. It is obviously illogical to fight cancer extremely seriously on the one hand and to consider dying with obesity as self-inflicted on the other. In fact, obesity merits a top position among the most lethal diseases besides cancer.

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.

Defueling the cancer: ATP synthase as an emerging target in cancer therapy

Reprogramming of cellular metabolism is a hallmark of cancer. Mitochondrial ATP synthase (MAS) produces most of the ATP that drives the cell. High expression of the MAS-composing proteins is found during cancer and is linked to a poor prognosis in glioblastoma, ovarian cancer, prostate cancer, breast cancer, and clear cell renal cell carcinoma. Cell surface-expressed ATP synthase, translocated from mitochondrion to cell membrane, involves the angiogenesis, tumorigenesis, and metastasis of cancer. ATP synthase has therefore been considered a therapeutic target. We review recent various ATP synthase inhibitors that suppress tumor growth and are being tested for the clinic.

Recent Advances in the Mechanism Research and Clinical Treatment of Anti-Angiogenesis in Biliary Tract Cancer

Biliary tract cancers (BTCs), including cholangiocarcinoma (CCA) and gallbladder cancer (GC), are malignancies originating from the biliary tract with poor prognosis. In the early stage of BTCs, surgery is the only choice for cure. Unfortunately, most patients with BTC are diagnosed at an advanced stage and lose the opportunity for surgery. For many advanced solid tumors, antiangiogenic therapy has achieved encouraging results. While most clinical studies on antiangiogenic therapy in advanced BTCs have shown an excellent disease control rate (DCR), the improvement in overall survival (OS) is controversial. Understanding how the relevant signaling molecules influence the angiogenic response and the functional interaction is necessary for the formulation of new treatment regimens and the selection of enrolled patients. In this review, we aim to summarize and discuss the latest advances in antiangeogenesis for BTCs, mainly focusing on the molecular mechanism of angiogenesis in BTCs and the therapeutic effects from clinical trials. Furthermore, the horizon of antiangiogenesis for BTCs is highlighted.

Systemic Effects of Hemorrhagic Snake Venom Metalloproteinases: Untargeted Peptidomics to Explore the Pathodegradome of Plasma Proteins

Hemorrhage induced by snake venom metalloproteinases (SVMPs) is a complex phenomenon that involves capillary disruption and blood extravasation. HF3 (hemorrhagic factor 3) is an extremely hemorrhagic SVMP of Bothrops jararaca venom. Studies using proteomic approaches revealed targets of HF3 among intracellular and extracellular proteins. However, the role of the cleavage of plasma proteins in the context of the hemorrhage remains not fully understood. The main goal of this study was to analyze the degradome of HF3 in human plasma. For this purpose, approaches for the depletion of the most abundant proteins, and for the enrichment of low abundant proteins of human plasma, were used to minimize the dynamic range of protein concentration, in order to assess the proteolytic activity of HF3 on a wide spectrum of proteins, and to detect the degradation products using mass spectrometry-based untargeted peptidomics. The results revealed the hydrolysis products generated by HF3 and allowed the identification of cleavage sites. A total of 61 plasma proteins were identified as cleaved by HF3. Some of these proteins corroborate previous studies, and others are new HF3 targets, including proteins of the coagulation cascade, of the complement system, proteins acting on the modulation of inflammation, and plasma proteinase inhibitors. Overall, the data indicate that HF3 escapes inhibition and sculpts the plasma proteome by degrading key proteins and generating peptides that may act synergistically in the hemorrhagic process.

Plasmin and Plasminogen System in the Tumor Microenvironment: Implications for Cancer Diagnosis, Prognosis, and Therapy

Simple Summary

In this review, we present a detailed discussion of how the plasminogen-activation system is utilized by tumor cells in their unrelenting attack on the tissues surrounding them. Plasmin is an enzyme which is responsible for digesting several proteins that hold the tissues surrounding solid tumors together. In this process tumor cells utilize the activity of plasmin to digest tissue barriers in order to leave the tumour site and spread to other parts of the body. We specifically focus on the role of plasminogen receptor—p11 which is an important regulatory protein that facilitates the conversion of plasminogen to plasmin and by this means promotes the attack by the tumour cells on their surrounding tissues.

Abstract

The tumor microenvironment (TME) is now being widely accepted as the key contributor to a range of processes involved in cancer progression from tumor growth to metastasis and chemoresistance. The extracellular matrix (ECM) and the proteases that mediate the remodeling of the ECM form an integral part of the TME. Plasmin is a broad-spectrum, highly potent, serine protease whose activation from its precursor plasminogen is tightly regulated by the activators (uPA, uPAR, and tPA), the inhibitors (PAI-1, PAI-2), and plasminogen receptors. Collectively, this system is called the plasminogen activation system. The expression of the components of the plasminogen activation system by malignant cells and the surrounding stromal cells modulates the TME resulting in sustained cancer progression signals. In this review, we provide a detailed discussion of the roles of plasminogen activation system in tumor growth, invasion, metastasis, and chemoresistance with specific emphasis on their role in the TME. We particularly review the recent highlights of the plasminogen receptor S100A10 (p11), which is a pivotal component of the plasminogen activation system.

Development of a four-gene prognostic model for clear cell renal cell carcinoma based on transcriptome analysis

This study aimed to develop a prognostic model for clear cell renal cell carcinoma (ccRCC) based on transcriptome analysis. We screened Gene Expression Omnibus (GEO) database and the Cancer Genome Atlas (TCGA) database for gene expression data and clinical characteristics of ccRCC. After differentially expression analysis, we identified 533 key genes of the development of ccRCC. Next, a weighted gene co-expression network analysis (WGCNA) was executed to investigate the association between differentially expressed genes and clinical characteristics. Then, based on protein-protein interaction (PPI) network, least absolute shrinkage and selection operator (LASSO) regression and Cox regression, a four-gene (COL4A5, ABCB1, NR3C2 and PLG) prognostic model has been constructed in TCGA training cohort. Finally, we examined the predictive power of this model with survival analysis and receiver operating characteristic (ROC) curve both in training cohort and in validation cohorts. And we found this model was significantly correlated with infiltrating immune cells. The four-gene prognosis model could be a potential prediction tool with high accuracy and reliability for ccRCC patients.

PRODUCTION AND APPLICATION OF ANGIOSTATINS FOR THE TREATMENT OF OCULAR NEOVASCULAR DISEASES

Angiostatins comprise a group of kringle-containing proteolytically-derived fragments of plasminogen/plasmin, which act as potent inhibitory mediators of endothelial cells proliferation and migration. Angiostatins are involved in modulation of vessel growth in healthy tissues and various pathological conditions associated with aberrant neovascularization. The aim of the present paper was to summarize available information, including our own experimental data, on prospects of angiostatin application for treatment of ocular neovascular diseases (OND), focusing on retinal pathologies and corneal injury. In particular, literature data on prospective and retrospective studies, clinical trials and animal models relating to the pathophysiology, investigation and management of OND are described. Special emphasis was made on the laboratory approaches of production of different angiostatin isoforms, as well as comparison of antiangiogenic capacities of native and recombinant angiostatin polypeptides. Several studies reported that angiostatins may completely abolish pathologic angiogenesis in diabetic proliferative retinopathy without affecting normal retinal vessel development and without exhibiting adverse side effects. Angiostatins have been tested as a tool for corneal antiangiogenesis target therapy in order to manage diverse ocular surface pathological conditions induced by traumas, chemical burns, previous surgery, chronic contact lens wear, autoimmune diseases, keratitis and viral infections (herpes, COVID-19), corneal graft rejection, etc. Among all known angiostatin species, isolated K5 plasminogen fragment was shown to display the most potent inhibitory activity against proliferation of endothelial cells via triggering multiple signaling pathways, which lead to cell death and resulting angiogenesis suppression. Application of adenoviral genetic construct encoding angiostatin K5 as a promising tool for OND treatment illustrates a vivid example of upcoming revolution in local gene therapy. Further comprehensive studies are necessary to elucidate the clinical potential and optimal regimes of angiostatinbased intervention modalities for treating ocular neovascularization.

The multifaceted role of plasminogen in inflammation

A fine-tuned activation and deactivation of proteases and their inhibitors are involved in the execution of the inflammatory response. The zymogen/proenzyme plasminogen is converted to the serine protease plasmin, a key fibrinolytic factor by plasminogen activators including tissue-type plasminogen activator (tPA). Plasmin is part of an intricate protease network controlling proteins of initial hemostasis/coagulation, fibrinolytic and complement system. Activation of these protease cascades is required to mount a proper inflammatory response. Although best known for its ability to dissolve clots and cleave fibrin, recent studies point to the importance of fibrin-independent functions of plasmin during acute inflammation and inflammation resolution. In this review, we provide an up-to-date overview of the current knowledge of the enzymatic and cytokine-like effects of tPA and describe the role of tPA and plasminogen receptors in the regulation of the inflammatory response with emphasis on the cytokine storm syndrome such as observed during coronavirus disease 2019 or macrophage activation syndrome. We discuss tPA as a modulator of Toll like receptor signaling, plasmin as an activator of NFkB signaling, and summarize recent studies on the role of plasminogen receptors as controllers of the macrophage conversion into the M2 type and as mediators of efferocytosis during inflammation resolution.

Cleavage of proteoglycans, plasma proteins and the platelet-derived growth factor receptor in the hemorrhagic process induced by snake venom metalloproteinases

Envenoming by viperid snakes results in a complex pattern of tissue damage, including hemorrhage, which in severe cases may lead to permanent sequelae. Snake venom metalloproteinases (SVMPs) are main players in this pathogenesis, acting synergistically upon different mammalian proteomes. Hemorrhagic Factor 3 (HF3), a P-III class SVMP from Bothrops jararaca, induces severe local hemorrhage at pmol doses in a murine model. Our hypothesis is that in a complex scenario of tissue damage, HF3 triggers proteolytic cascades by acting on a partially known substrate repertoire. Here, we focused on the hypothesis that different proteoglycans, plasma proteins, and the platelet derived growth factor receptor (PDGFR) could be involved in the HF3-induced hemorrhagic process. In surface plasmon resonance assays, various proteoglycans were demonstrated to interact with HF3, and their incubation with HF3 showed degradation or limited proteolysis. Likewise, Western blot analysis showed in vivo degradation of biglycan, decorin, glypican, lumican and syndecan in the HF3-induced hemorrhagic process. Moreover, antithrombin III, complement components C3 and C4, factor II and plasminogen were cleaved in vitro by HF3. Notably, HF3 cleaved PDGFR (alpha and beta) and PDGF in vitro, while both receptor forms were detected as cleaved in vivo in the hemorrhagic process induced by HF3. These findings outline the multifactorial character of SVMP-induced tissue damage, including the transient activation of tissue proteinases, and underscore for the first time that endothelial glycocalyx proteoglycans and PDGFR are targets of SVMPs in the disruption of microvasculature integrity and generation of hemorrhage.

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.

Construction of a novel gene-based model for prognosis prediction of clear cell renal cell carcinoma

BACKGROUND

Clear cell renal cell carcinoma (ccRCC) comprises the majority of kidney cancer death worldwide, whose incidence and mortality are not promising. Identifying ideal biomarkers to construct a more accurate prognostic model than conventional clinical parameters is crucial.

METHODS

Raw count of RNA-sequencing data and clinicopathological data were acquired from The Cancer Genome Atlas (TCGA). Tumor samples were divided into two sets. Differentially expressed genes (DEGs) were screened in the whole set and prognosis-related genes were identified from the training set. Their common genes were used in LASSO and best subset regression which were performed to identify the best prognostic 5 genes. The gene-based risk score was developed based on the Cox coefficient of the individual gene. Time-dependent receiver operating characteristic (ROC) and Kaplan-Meier (KM) survival analysis were used to assess its prognostic power. GSE29609 dataset from GEO (Gene Expression Omnibus) database was used to validate the signature. Univariate and multivariate Cox regression were performed to screen independent prognostic parameters to construct a nomogram. The predictive power of the nomogram was revealed by time-dependent ROC curves and the calibration plot and verified in the validation set. Finally, Functional enrichment analysis of DEGs and 5 novel genes were performed to suggest the potential biological pathways.

RESULTS

PADI1, ATP6V0D2, DPP6, C9orf135 and PLG were screened to be significantly related to the prognosis of ccRCC patients. The risk score effectively stratified the patients into high-risk group with poor overall survival (OS) based on survival analysis. AJCC-stage, age, recurrence and risk score were regarded as independent prognostic parameters by Cox regression analysis and were used to construct a nomogram. Time-dependent ROC curves showed the nomogram performed best in 1-, 3- and 5-year survival predictions compared with AJCC-stage and risk score in validation sets. The calibration plot showed good agreement of the nomogram between predicted and observed outcomes. Functional enrichment analysis suggested several enriched biological pathways related to cancer.

CONCLUSIONS

In our study, we constructed a gene-based model integrating clinical prognostic parameters to predict prognosis of ccRCC well, which might provide a reliable prognosis assessment tool for clinician and aid treatment decision-making in the clinic.

Clinical significance of urinary plasminogen and fibrinogen gamma chain as novel potential diagnostic markers for non-small-cell lung cancer

BACKGROUND

Urinary proteins could be useful as markers for the detection of non-small-cell lung cancer (NSCLC). We investigated the levels of two different proteins in urine samples from NSCLC patients and assessed their diagnostic value.

METHODS

Urinary plasminogen (PLG) and fibrinogen gamma chain (FGG) levels in 112 NSCLC patients and 197 controls were detected using enzyme linked immunosorbent assay (ELISA). The expression of FGG and PLG in 20 NSCLC tissues and paired adjacent non-tumour tissues were detected through immunohistochemistry. The diagnostic value of FGG and PLG for NSCLC was evaluated through a receiver operating characteristic curve (ROC).

RESULTS

PLG and FGG were significantly elevated in NSCLC tissues vs paired adjacent non-tumour tissues (p = 0.000) and in urinary samples from NSCLC patients vs healthy controls (p = 0.000). The expression level of PLG in urinary samples was related only to the histological type (p = 0.001). Further, ROC curve analysis revealed that PLG, FGG, and their combination could distinguish NSCLC and its subtypes from healthy controls with an AUC ranging from 0.827 to 0. 947. By comparing urine samples with matching plasma CEA from NSCLC stage I-IV patients (n = 81) and healthy controls (n = 31), the combination of CEA with PLG or FGG showed that the AUC was 0.889 and 0.806, respectively, which is superior to a single biomarker alone.

CONCLUSIONS

These two urinary proteins could serve as potential markers for the diagnosis of NSCLC.

Effect of Diosmin Administration in Patients with Chronic Venous Disorders on Selected Factors Affecting Angiogenesis

Diosmin is a natural compound with a wide range of biological activity, e.g., it improves lymphatic drainage, supports microcirculation, and increases venous tone, and venous elasticity, hence, it is applied in the pharmacotherapy of chronic venous disorders (CVD). The aim of this study was to assess the correlation between diosmin administration (2 × 600 mg daily) in patients suffering from CVD and the levels of selected factors influencing angiogenesis, which are involved in CVD pathophysiology. Thirty-five CVD patients were examined. Levels of plasma tumor necrosis factor alpha (TNF alpha), vascular endothelial growth factor (VEGF-A and VEGF-C); angiostatin, interleukin 6 (IL-6), fibroblast growth factor 2 (FGF2); and plasminogen (PLG) were measured with an Elisa assay before and after three months of diosmin administration. The clinical symptoms of CVD were monitored using ultrasound images, echo Doppler assay, visual analogue scale (VAS), and measurement of the leg circumference. The average content of TNF alpha, VEGF-C, VEGF-A IL-6, and FGF2 decreased after the therapy with diosmin in a significant manner; with p < 0.001, p < 0.05, p < 0.05, p < 0.01, and p < 0.01, respectively, and a significant (p < 0.05) increase in the plasma angiostatin level after the three-month treatment was found. A significant (p < 0.05) decrease in edema and the average leg circumference of the patients was observed after the therapy. Diosmin influences the angiogenic and inflammatory mechanisms involved in the pathophysiology of edema presented in patients with a different class of CVD.

An investigational study of a dual-layer, chorion-free amnion patch as a protective barrier following lumbar laminectomy in a sheep model

The inherent properties of the human amniotic membrane (HAM) suggest its potential for use as a physical barrier during surgery to protect neural elements and vessels from the surrounding environment. The objective of this study was to evaluate the effect of a dual-layer, chorion-free amnion patch (DLAM; ViaShield®, Globus Medical Inc., Audubon, PA, USA) processed from HAM as a protective barrier following lumbar laminectomy in a sheep model. A multiplex immunoassay was performed to quantify the inherent cytokines present in the amnion after processing. Twelve skeletally mature female crossbred Suffolk sheep were randomly divided into two equal post-operative periods (4 and 10 weeks). Each sheep underwent a laminectomy at L3 and L5, and one of the surgical sites randomly received the DLAM treatment. At each postsurgical time point, the extent of epidural fibrosis and neurohistopathological responses at the laminectomy sites was assessed based on epidural fibrosis-dura tenacity scores and decalcified histology, respectively. Immunoassay results showed that inflammatory mediators and immunomodulatory cytokines were present in the amnion after processing, but no proangiogenic cytokines were detected. At 10 weeks, tissue tenacity was significantly less in the DLAM treatment group when compared with the operative control (1.2 ± 0.4 vs. 2.8 ± 0.4, p < 0.05), demonstrating the ability of DLAM to act as a barrier and cover the dura. Gross observations showed fewer fibroblasts in the DLAM group in comparison with the control at both post-operative time points. Fibroblast infiltration analysis indicated that at both 4 and 10 weeks, there were significantly more infiltrated fibroblasts in the operative control sites than in the DLAM-treated sites, expressed as a percentage of the total number of fibroblasts present (4 weeks: 72.3 ± 10.2% vs. 10.8 ± 10.1%, p < .05; 10 weeks: 84.9 ± 15.8% vs. 43.1 ± 11.6%, p < .05). Additionally, fibroblasts travelled further into the dura in the operative control group compared with the DLAM-treated group at both time points. In conclusion, this study found that DLAM reduced fibroblast infiltration and tissue tenacity following lumbar laminectomy in a sheep animal model. These findings support the potential use of DLAM in clinical practice as a protective barrier for neural elements and anterior vessels.

Ping-Pong-Tumor and Host in Pancreatic Cancer Progression

Metastasis is the main cause of high pancreatic cancer (PaCa) mortality and trials dampening PaCa mortality rates are not satisfying. Tumor progression is driven by the crosstalk between tumor cells, predominantly cancer-initiating cells (CIC), and surrounding cells and tissues as well as distant organs, where tumor-derived extracellular vesicles (TEX) are of major importance. A strong stroma reaction, recruitment of immunosuppressive leukocytes, perineural invasion, and early spread toward the peritoneal cavity, liver, and lung are shared with several epithelial cell-derived cancer, but are most prominent in PaCa. Here, we report on the state of knowledge on the PaCIC markers Tspan8, alpha6beta4, CD44v6, CXCR4, LRP5/6, LRG5, claudin7, EpCAM, and CD133, which all, but at different steps, are engaged in the metastatic cascade, frequently via PaCIC-TEX. This includes the contribution of PaCIC markers to TEX biogenesis, targeting, and uptake. We then discuss PaCa-selective features, where feedback loops between stromal elements and tumor cells, including distorted transcription, signal transduction, and metabolic shifts, establish vicious circles. For the latter particularly pancreatic stellate cells (PSC) are responsible, furnishing PaCa to cope with poor angiogenesis-promoted hypoxia by metabolic shifts and direct nutrient transfer via vesicles. Furthermore, nerves including Schwann cells deliver a large range of tumor cell attracting factors and Schwann cells additionally support PaCa cell survival by signaling receptor binding. PSC, tumor-associated macrophages, and components of the dysplastic stroma contribute to perineural invasion with signaling pathway activation including the cholinergic system. Last, PaCa aggressiveness is strongly assisted by the immune system. Although rich in immune cells, only immunosuppressive cells and factors are recovered in proximity to tumor cells and hamper effector immune cells entering the tumor stroma. Besides a paucity of immunostimulatory factors and receptors, immunosuppressive cytokines, myeloid-derived suppressor cells, regulatory T-cells, and M2 macrophages as well as PSC actively inhibit effector cell activation. This accounts for NK cells of the non-adaptive and cytotoxic T-cells of the adaptive immune system. We anticipate further deciphering the molecular background of these recently unraveled intermingled phenomena may turn most lethal PaCa into a curatively treatable disease.

A Pathogenic Relationship of Bronchopulmonary Dysplasia and Retinopathy of Prematurity? A Review of Angiogenic Mediators in Both Diseases

Bronchopulmonary dysplasia (BPD) and retinopathy of prematurity (ROP) are common and significant morbidities of prematurely born infants. These diseases have in common altered and pathologic vascular formation in the face of incomplete organ development. Therefore, it is reasonable to question whether factors affecting angiogenesis could have a joint pathogenic role for both diseases. Inhibition or induced expression of a single angiogenic factor is unlikely to be 100% causative or protective of either of BPD or ROP. It is more likely that interactions of multiple factors leading to disordered angiogenesis are present, increasing the likelihood of common pathways in both diseases. This review explores this possibility by assessing the evidence showing involvement of specific angiogenic factors in the vascular development and maldevelopment in each disease. Theoretical interactions of specific factors mutually contributing to BPD and ROP are proposed and, where possible, a timeline of the proposed relationships between BPD and ROP is developed. It is hoped that future research will be inspired by the theories put forth in this review to enhance the understanding of the pathogenesis in both diseases.

Plasmin(ogen) serves as a favorable biomarker for prediction of survival in advanced high-grade serous ovarian cancer

In serous ovarian cancer, the clinical relevance of tumor cell-expressed plasmin(ogen) (PLG) has not yet been evaluated. Due to its proteolytic activity, plasmin supports tumorigenesis, however, angiostatin(-like) fragments, derived from PLG, can also function as potent anti-tumorigenic factors. In the present study, we assessed PLG protein expression in 103 cases of advanced high-grade serous ovarian cancer (FIGO III/IV) by immunohistochemistry (IHC). In 70/103 cases, positive staining of tumor cells was observed. In univariate Cox regression analysis, PLG staining was positively associated with prolonged overall survival (OS) [hazard ratio (HR)=0.59, p=0.026] of the patients. In multivariable analysis, PLG, together with residual tumor mass, remained a statistically significant independent prognostic marker (HR=0.49, p=0.009). In another small patient cohort (n=29), we assessed mRNA expression levels of PLG by quantitative PCR. Here, elevated PLG mRNA levels were also significantly associated with prolonged OS of patients (Kaplan-Meier analysis; p=0.001). This finding was validated by in silico analysis of a microarray data set (n=398) from The Cancer Genome Atlas (Kaplan-Meier analysis; p=0.031). In summary, these data indicate that elevated PLG expression represents a favorable prognostic biomarker in advanced (FIGO III/IV) high-grade serous ovarian cancer.

Future options of anti-angiogenic cancer therapy

In human patients, drugs that block tumor vessel growth are widely used to treat a variety of cancer types. Many rigorous phase 3 clinical trials have demonstrated significant survival benefits; however, the addition of an anti-angiogenic component to conventional therapeutic modalities has generally produced modest survival benefits for cancer patients. Currently, it is unclear why these clinically available drugs targeting the same angiogenic pathways produce dissimilar effects in preclinical models and human patients. In this article, we discuss possible mechanisms of various anti-angiogenic drugs and the future development of optimized treatment regimens.

[Role of angiostatins in diabetic complications]

Angiogenesis is a process through which new blood vessels form from pre-existing vessels. Angiogenesis is regulated by a number of factors of peptide nature. Disbalance of angiogenic system appears to be the major causative factor contributing vascular abnormalities in diabetes mellitus, resulting in various complications. Angiostatins, which are kringle-containing fragments of plasminogen/plasmin, are known to be powerful physiological inhibitors of neovascularization. In the present review, current literature data on peculiarities of production of angiostatins and their functioning at diabetes mellitus are summarized and analyzed for the first time. Also, role of angiostatins in the pathogenesis of typical diabetic complications, including retinopathies, nephropathies and cardiovascular diseases, is discussed. Data presented in this review may be useful for elaboration of novel effective approaches for diagnostics and therapy of vascular abnormalities in diabetes mellitus.

Metastasis: recent discoveries and novel perioperative treatment strategies with particular interest in the hemostatic compound desmopressin

Metastatic disease is responsible for most of cancer lethality. A main obstacle for therapy of advanced cancers is that the outcome of metastasis depends on a complex interplay between malignant and host cells. The perioperative period represents an underutilized window of opportunity for cancer treatment where tumor-host interactions can be modulated, reducing the risk of local recurrences and distant metastases. Blood-saving agents are attractive compounds to be administered during tumor surgery. Desmopressin (DDAVP) is a safe and convenient hemostatic peptide with proved antimetastastic properties in experimental models and veterinary clinical trials. The compound seems to induce a dual angiostatic and antimetastatic effect, breaking the cooperative function of cancer cells and endothelial cells during residual tumor progression. DDAVP is therefore an interesting lead compound to develop novel synthetic peptide analogs with enhanced antitumor properties.

Mechanisms of vessel regression: toward an understanding of the resolution of angiogenesis

Physiological angiogenesis refers to a naturally occurring process of blood vessel growth and regression, and it occurs as an integral component of tissue repair and regeneration. During wound healing, sprouting and branching results in an extensive yet immature and leaky neovascular network that ultimately resolves by systematic pruning of extraneous vessels to yield a stable, well-perfused vascular network ideally suited to maintain tissue homeostasis. While the molecular mechanisms of blood vessel growth have been explored in numerous cell and animal models in remarkable detail, the endogenous factors that prevent further angiogenesis and control vessel regression have not received much attention and are largely unknown. In this review, we introduce the relevant literature from various disciplines to fill the gaps in the current limited understanding of the major molecular and biomechanical inducers of vascular regression. The processes are described in the context of endothelial cell biology during wound healing: hypoxia-driven activation and sprouting followed by apoptosis or maturation of cells comprising the vasculature. We discuss and integrate the likely roles of a variety of endogenous factors, including oxygen availability, vessel perfusion and shear stress, intracellular negative feedback mechanisms (Spry2, vasohibin), soluble cytokines (CXCL10), matrix-binding proteins (TSP, PEDF), protein cleavage products (angiostatin, vasostatin), matrix-derived anti-angiogenic peptides (endostatin, arresten, canstatin, tumstatin), and the biomechanical properties of remodeling the extra-cellular matrix itself. These factors aid in the spatio-temporal control of blood vessel pruning by inducing specific anti-angiogenic signaling pathways in activated endothelial cells, pathways which compete with pro-angiogenic and maturation signals in the resolving wound. Gaining more insight into these mechanisms is bound to shed light on unresolved questions regarding scar formation, tissue regeneration, and increase our understanding of the many diseases with angiogenic phenotypes, especially cancer.

Attributes of antiangiogenic factor plasminogen kringle 5 in glomerulonephritis

CONTEXT

Plasminogen kringle domain (K) 5 is known to inhibit endothelial cell growth, but limited data are available investigating the relationship between K5 and glomerulonephritis (GN).

OBJECTIVE

To understand the relationships among K5, GN, and glomerular endothelial cells in GN mice models and human subjects.

DESIGN

Two mice models of GN and 2 categories of human GN biopsy samples were collected to gain insight into the disease mechanism from the laboratory to bedside. In the mechanistic animal study, membranous nephropathy (MN) and focal segmental glomerulosclerosis mice models were used. Kringle domain 5 in the diseased kidney was located by immunofluorescence and quantified by Western blotting. In the kinetic animal study, different MN time points were stained with K5, immunoglobulin G, and C3 by immunofluorescence. CD31 and proliferating cell nuclear antigen were evaluated by immunohistochemical double staining for alterations in the glomerular endothelial cells. Biopsy samples from patients diagnosed with antibody (Ab)-mediated and non-Ab-mediated GN were collected for K5 analysis.

RESULTS

The expression level of K5 was found to be significant in MN, but not in focal segmental glomerulosclerosis, and was markedly elevated in the diseased glomeruli along the capillary walls. Kringle domain 5 levels increased steadily with the evolution of MN, appearing after the deposition of Abs. In altered glomerular endothelial cells, CD31 decreased with the evolution of MN. In human subjects, K5 occurred only in patients with Ab GN.

CONCLUSIONS

Kringle domain 5 might be involved in the progression of Ab-mediated GN and associated with the alteration of MN glomerular endothelial cell growth.

Antisense HIF-1alpha prevents acquired tumor resistance to angiostatin gene therapy

Angiostatin is a naturally occurring inhibitor of angiogenesis that is being developed as a drug to fight cancer. In this study we reveal that EL-4 tumors established in mice rapidly develop resistance to angiostatin gene therapy by upregulating hypoxia-inducible pathways. Angiostatin initially delayed tumor growth for 6 days by reducing blood vessel density. However, tumors quickly responded by upregulating the production of hypoxia-inducible factor-1alpha (HIF-1alpha) and its effector vascular endothelial growth factor (VEGF) in response to increasing tumor hypoxia, leading to restored angiogenesis and rapid tumor growth. Theoretically, blockade of HIF-1 should prevent resistance to anti-angiogenic therapy by preventing a tumor from responding to induced hypoxia. Antisense HIF-1alpha inhibited the expression of HIF-1alpha and of the HIF-1 effectors VEGF, glucose transporter-1 and lactate dehydrogenase. As a monotherapy, it was effective in eradicating small 0.1 cm diameter tumors, but only delayed the growth of large 0.4 cm diameter tumors. In contrast, timed injection of a combination of angiostatin and antisense HIF-1alpha plasmids completely eradicated large EL-4 tumors within 2 weeks, and prevented upregulation of hypoxia-inducible pathways induced by angiostatin. The data indicate that blocking hypoxia-inducible pathways by antisense HIF-1alpha can circumvent hypoxia-induced drug resistance and thereby augment the efficacy of anti-angiogenic therapies.

Angiostatins decrease in the kidney of newborn piglets after hypoxia-reoxygenation

Little is known about the expression of kidney angiostatin in the hypoxia and reoxygenation of neonates. In this study, we compared the effect of 21% and 100% reoxygenation on kidney levels of angiostatin and its related factors in newborn piglets subjected to hypoxia-reoxygenation. Newborn piglets were subjected to 2h hypoxia followed by 1h of reoxygenation with either 21% or 100% oxygen and observed for 4days. There were 3 isoforms (38, 43 and 50kDa) of angiostatins identified in the kidney tissue of newborn piglets with the 38kDa being the major isoform (~60%). The 38kDa, but not 43 and 50kDa, angiostatin isoform correlated significantly with the levels of total angiostatin and plasminogen (r=0.95 and r=0.58, respectively). On day 4 of recovery in 100% hypoxic-reoxygenated group, there were decreases in kidney tissue levels of plasminogen, total angiostatin, angiostatin (38 and 43kDa, but not 50kDa), whereas no significant changes were found in the 21% hypoxic-reoxygenated group when compared to the sham-operated piglets with no hypoxia-reoxygenation. Both 21% and 100% hypoxic-reoxygenated groups did not show significant changes in kidney tissue levels of 50kDa angiostatin, MMP-2, MMP-9 and HIF-1alpha. In comparison to 21% oxygen, neonatal resuscitation with 100% oxygen decreased the kidney tissue levels of plasminogen and angiostatin that may play a role in neonatal kidney injury and altered renal development in adulthood.

Residues essential for plasminogen binding by the cation-independent mannose 6-phosphate receptor

The 300 kDa cation-independent mannose 6-phosphate receptor (CI-MPR) is a multifunctional protein that binds diverse intracellular and extracellular ligands with high affinity. The CI-MPR is a receptor for plasminogen, and this interaction can be inhibited by lysine analogues. To characterize the molecular basis for this interaction, surface plasmon resonance (SPR) analyses were performed using truncated forms of the CI-MPR and plasminogen. The results show that the N-terminal region of the CI-MPR containing domains 1 and 2, but not domain 1 alone, of the receptor's 15-domain extracytoplasmic region binds plasminogen (K(d) = 5 +/- 1 nM) with an affinity similar to that of the full-length receptor (K(d) = 20 +/- 6 nM). In addition to its C-terminal serine protease domain, plasminogen contains lysine binding sites (LBS), which are located within each of its five kringle domains, except kringle 3. We show that kringles 1-4, but not kringles 1-3, bind the CI-MPR, indicating an essential role for the LBS in kringle 4 of plasminogen. To identify the lysine residue(s) of the CI-MPR that serve(s) as an essential determinant for recognition by the LBS of plasminogen, site-directed mutagenesis studies were carried out using a construct encoding the N-terminal three domains of the CI-MPR (Dom1-3His) which contains both a mannose 6-phosphate (Man-6-P) and plasminogen binding site. The results demonstrate two lysine residues (Lys53 located in domain 1 and Lys125 located in the loop connecting domains 1 and 2) of the CI-MPR are key determinants for plasminogen binding but are not required for Man-6-P binding.

NF-kappaB activation in endothelial cells is critical for the activity of angiostatic agents

In tumor cells, the transcription factor NF-kappaB has been described to be antiapoptotic and proproliferative and involved in the production of angiogenic factors such as vascular endothelial growth factor. From these data, a protumorigenic role of NF-kappaB has emerged. Here, we examined in endothelial cells whether NF-kappaB signaling pathway is involved in mediating the angiostatic properties of angiogenesis inhibitors. The current report describes that biochemically unrelated agents with direct angiostatic effect induced NF-kappaB activation in endothelial cells. Our data showed that endostatin, anginex, angiostatin, and the 16-kDa N-terminal fragment of human prolactin induced NF-kappaB activation in endothelial cells in both cultured human endothelial cells and in vivo in a mouse tumor model. It was also found that NF-kappaB activity was required for the angiostatic activity, because inhibition of NF-kappaB in endothelial cells impaired the ability of angiostatic agents to block sprouting of endothelial cells and to overcome endothelial cell anergy. Therefore, activation of NF-kappaB in endothelial cells can result in an unexpected antitumor outcome. Based on these data, the current approach of systemic treatment with NF-kappaB inhibitors may therefore be revisited because NF-kappaB activation specifically targeted to endothelial cells might represent an efficient strategy for the treatment of cancer.

Microenvironmental regulation of metastasis

Metastasis is a multistage process that requires cancer cells to escape from the primary tumour, survive in the circulation, seed at distant sites and grow. Each of these processes involves rate-limiting steps that are influenced by non-malignant cells of the tumour microenvironment. Many of these cells are derived from the bone marrow, particularly the myeloid lineage, and are recruited by cancer cells to enhance their survival, growth, invasion and dissemination. This Review describes experimental data demonstrating the role of the microenvironment in metastasis, identifies areas for future research and suggests possible new therapeutic avenues.

Tissue-type plasminogen activator has antiangiogenic properties without effect on tumor growth in a rat C6 glioma model

Tissue-type plasminogen activator (tPA) plays a major role in the fibrinolytic system. According to several reports, tPA may also have antiangiogenic properties, especially in combination with a free sulfhydryl donor (FSD). In the rat C6 glioma model, in vitro and in vivo tPA synthesis by glioma cells is enhanced by differentiation therapy. To address the antiangiogenic potential of tPA in this model, tPA was overexpressed in glioma tumors by ex vivo transduction of C6 cells with a lentiviral vector encoding tPA. The transduced cells were subcutaneously implanted into nude mice. Gene transfer allowed for efficient synthesis of tPA by the C6 tumors. Although the treatment of tPA+ tumor-bearing animals with the FSD captopril generated angiostatin in situ and reduced endothelial vascularization of the tumors, it had no effect on tumor growth. Alternative mechanisms could account for this lack of effect and consequently have important implications for vascular the treatment of glioblastoma.

Transgenic mouse models of angiogenesis and lymphangiogenesis

The development of transgenic technologies in mice has allowed the study of the consequences of genetic alterations on angiogenesis and lymphangiogenesis. This review summarizes the murine models currently available for studies involving the manipulation of angiogenesis and lymphangiogenesis. Abnormal embryonic vascular development, resulting from defects in the formation of a primitive vascular plexus, has been observed in mice lacking vascular endothelial growth factor, vascular endothelial growth factor receptor-1 and -2, transforming growth factor-beta, fibronectin, or vascular endothelial cadherin. Defects in the expansion and remodeling of the embryonic vasculature occur in mice deficient in Tie-1, Tie-2, or angiopoietin-1, and in mice overexpressing neuropilin or angiopoietin-2. Impaired recruitment and investment of mural cells have been observed in mice with disruption of the genes encoding platelet-derived growth factor-B, platelet-derived growth factor-B receptor, and tissue factor. Gene-targeting experiments in mice have identified the EphB/ephrinB system as a critical and rate-limiting determinant of arteriovenous differentiation during embryonic vascular development. Vascular endothelial growth factor-C is necessary for the initial sprouting and migration of lymphatic endothelial cells from embryonic veins, and mice lacking vascular endothelial growth factor-C die prenatally, whereas vascular endothelial growth factor-D is dispensable for embryonic lymphatic development.

Analysis of host- and tumor-derived proteinases using a custom dual species microarray reveals a protective role for stromal matrix metalloproteinase-12 in non-small cell lung cancer

We used a customized Affymetrix protease microarray (Hu/Mu ProtIn chip) designed to distinguish human and mouse genes to analyze the expression of proteases and protease inhibitors in lung cancer. Using an orthotopic lung cancer model, we showed that murine matrix metalloproteinase (MMP)-12, MMP-13, and cathepsin K were up-regulated in tumor tissue compared with normal mouse lung. To determine the relevance of stromal proteases detected using this model system, we compared the results to an analysis of human lung adenocarcinoma specimens using the U133 Plus 2.0 Affymetrix microarray. MMP-12, MMP-13, and cathepsin K showed an increase in expression in human tumors compared with normal lung similar to that seen in the orthotopic model. Immunohistochemical analysis confirmed MMP-12 expression in the stroma of human lung tumor samples. To determine the biological relevance of stromal MMP-12, murine Lewis lung carcinoma cells were injected into the tail vein of syngeneic wild-type (WT) and MMP-12-null mice. MMP-12-null and WT mice developed equivalent numbers of lung tumors; however, there was a 2-fold increase in the number of tumors that reached >2 mm in diameter in MMP-12-null mice compared with WT controls. The increase in tumor size correlated with an increase in CD31-positive blood vessels and a decrease in circulating levels of the K1-K4 species of angiostatin. These results show a protective role for stromal MMP-12 in lung tumor growth. The use of the Hu/Mu ProtIn chip allows us to distinguish tumor- and host-derived proteases and guides the further analysis of the significance of these genes in tumor progression.

No evidence for vasculogenesis regulation by angiostatin during mouse embryonic stem cell differentiation

During embryogenesis, the formation of blood vessels proceeds by both vasculogenesis and angiogenesis. Both processes appear to be finely regulated. To date, factors and genes involved in the negative regulation of embryonic vasculogenesis remain largely unknown. Angiostatin is a proteolytic fragment of plasminogen that acts as an inhibitor of angiogenesis. In this study, we analyzed the potential role of angiostatin during early stages of embryonic stem (ES) cell endothelial in vitro differentiation, as a model of vasculogenesis. We found an early expression of the known angiostatin binding sites (angiomotin, alphav integrin and c-met oncogene) during ES cell differentiation. Nevertheless, we did not detect any significant effect of angiostatin on mesoderm induction and on differentiation commitment into cells of the endothelial lineage. In both control and angiostatin-treated conditions, the temporal and extent of formation of the Flk1 positive and Flk-1/CD31 (PECAM-1) positive cell populations were not significantly different. Quantitative RT-PCR experiments of endothelial gene expression (Flk-1, PECAM-1 and tie-2) confirm a lack of interference with early steps of endothelial differentiation in embryoid bodies. No evidence for an angiostatin effect on endothelial cord-like formation could be detected at later differentiation stages. On the other hand, angiostatin inhibits vascular endothelial growth factor-induced endothelial sprouting from embryoid bodies cultured in three dimensional type I collagen gels. Taken together, these findings support a selective inhibitory effect on the sprouting angiogenesis response for angiostatin during embryonic vascular development.

Expression of angiostatin and its related factors in the plasma of newborn pigs with hypoxia and reoxygenation

Little is known about angiostatin and its related factors in the hypoxia-reoxygenation of neonates. In this study we compared the effect of 21% and 100% reoxygenation on temporal changes in the plasma level of these factors in newborn piglets subjected to hypoxia. Newborn piglets were subjected to 2 h hypoxia followed by 1 h of reoxygenation with either 21% or 100% oxygen and observed for 4 days. On day 4 of recovery in 100% hypoxic-reoxygenated group, there were increases in total angiostatin, plasminogen/plasmin and MMP-2 levels, and decreases in VEGF levels (vs. respective baseline levels, all P <0.001), whereas no significant temporal changes were found in the 21% hypoxic-reoxygenated and sham-operated groups. Angiostatin levels correlated positively with the levels of MMP-2 and HIF-1alpha and negatively with VEGF levels in 100% hypoxic-reoxygenated group (all P <0.05). In comparison to 21% oxygen, neonatal resuscitation with 100% oxygen was found to increase the levels anti-angiogenic factors.

Lipoprotein[a] and cancer: Anti-neoplastic effect besides its cardiovascular potency

While the death rate from cancer has substantially decreased over the past decade, the search for effective and tolerable therapies is a great challenge as yet. The evidence that malignant cells cannot grow to a clinically detectable tumor mass and spread in the absence of an adequate vascular support, has opened a new area of research towards the selective inhibition or even destruction of tumor vessels. Angiostatin and angiostatin-related proteins are a family of specific angiogenesis inhibitors produced by tumors from a family of naturally occurring proteins, which also includes plasminogen and lipoprotein[a]. The anti-angiogenic activity of these proteins resides in cryptic and highly-repetitive molecular domains hidden within the protein moiety, called kringles. Lipoprotein[a] is an intriguing molecule consisting of a low-density lipoprotein core in addition to the covalently bound apolipoprotein[a]. Apolipoprotein[a] is characterized by an inactive protease domain, a single copy of the plasminogen kringle V and multiple repeats of domains homologous to the plasminogen kringle IV. Reliable studies on animal models indicate that the proteolytic break-down products of apolipoprotein[a] would posses anti-angiogenic and anti-tumoral properties both in vitro and in vivo, a premise to develop novel therapeutic modalities which may efficiently suppress tumor growth and metastasis. This review is focused on the biochemical structure, metabolism and the anti-angiogenic activity of this unique and elusive kringle-containing lipoprotein.

Angiostatin-like activity of a monoclonal antibody to the catalytic subunit of F1F0 ATP synthase

The antiangiogenic protein angiostatin inhibits ATP synthase on the endothelial cell surface, blocking cellular proliferation. To examine the specificity of this interaction, we generated monoclonal antibodies (mAb) directed against ATP synthase. mAb directed against the beta-catalytic subunit of ATP synthase (MAb3D5AB1) inhibits the activity of the F(1) domain of ATP synthase and recognizes the catalytic beta-subunit of ATP synthase. We located the antibody recognition site of MAb3D5AB1 in domains containing the active site of the beta-subunit. MAb3D5AB1 also binds to purified Escherichia coli F(1) with an affinity 25-fold higher than the affinity of angiostatin for this protein. MAb3D5AB1 inhibits the hydrolytic activity of F(1) ATP synthase at lower concentrations than angiostatin. Like angiostatin, MAb3D5AB1 inhibits ATP generation by ATP synthase on the endothelial cell surface in acidic conditions, the typical tumor microenvironment where cell surface ATP synthase exhibits greater activity. MAb3D5AB1 disrupts tube formation and decreases intracellular pH in endothelial cells exposed to low extracellular pH. Neither angiostatin nor MAb3D5AB1 showed an antiangiogenic effect in the corneal neovascularization assay; however, both were effective in the low-pH environment of the chicken chorioallantoic membrane assay. Thus, MAb3D5AB1 shows angiostatin-like properties superior to angiostatin and may be exploited in cancer chemotherapy.

Ocular neovascularization: Implication of endogenous angiogenic inhibitors and potential therapy

Ocular neovascularization (NV) is the primary cause of blindness in a wide range of ocular diseases, such as diabetic retinopathy (DR) and age-related macular degeneration (AMD). The exact mechanism underlying the pathogenesis of ocular NV is not yet well understood, and as a consequence, there is no satisfactory therapy for ocular NV. In the last 10 years, a number of studies provided increasing evidence demonstrating that the imbalance between angiogenic stimulating factors and angiogenic inhibitors is a major contributor to the angiogenesis induced by various insults, such as hypoxia or ischemia, inflammation and tumor. The angiogenic inhibitors alone or in combination with other existing therapies are, therefore, believed to be promising in the treatment of ocular NV in the near future. This article reviews recent progress in studies on the mechanisms and treatment of ocular NV, focusing on the implication and therapeutic potential of endogenous angiogenic inhibitors in ocular NV.

Angiogenesis and antiangiogenic therapy in hematologic malignancies

Angiogenesis, the generation of new blood capillaries from preexisting blood vessels, is tightly regulated in the adult organism. Although many of the initial studies were performed on solid tumors, increasing evidence indicates that angiogenesis also plays an important role in hematologic malignancies. Overexpression of angiogenic factors in particular VEGF and bFGF in most hematologic malignancies may explain the increased angiogenesis found in these malignancies and correlate with poor prognosis as well as decreased overall survival. In this review, we focus on the current literature of angiogenesis and antiangiogenic therapy in hematologic malignancies, and finally describe advances and potential challenges in antiangiogenic treatment in hematologic malignancies.