Expression of the proteolytic factors, tPA and uPA, PAI-1 and VEGF during malignant glioma progression

Vascular endothelial growth factor and risk of malignant brain tumor: A genetic correlation and two-sample Mendelian randomization study

Objective

The relationship between vascular endothelial growth factor (VEGF) and the risk of malignant brain tumors has always been a concern in the medical field. However, the causal inferences from published observational studies on this issue may be affected by confounders, coinheritability and reverse causality. We aimed to investigate the causal relationship between VEGF and different types of malignant brain tumors.

Methods

Using publicly available summary data from genome-wide association studies (GWAS) of VEGF (n=16,112) and different types of malignant brain tumors (n=174,097-174,646), we adopted a standard two-sample bidirectional Mendelian randomization (MR) to estimate potential causal associations of circulating VEGF levels and the risk of malignant brain tumors. Inverse variance weighted (IVW) was used as the primary analysis method to estimate causality. MR-Egger regression, weighted median (WM), penalty weighted median (PWM), MR robust adjusted profile score (MR.RAPS) and causal analysis using summary effect estimates (CAUSE) methods were used in sensitivity analyses to verify the robustness of the findings. Meanwhile, we applied the MR pleiotropy residual sum and outlier (MR-PRESSO) test and PhenoScanner tool to identify and remove potential horizontal pleiotropic single nucleotide polymorphisms (SNPs). Additionally, linkage disequilibrium score regression (LDSC) analysis was conducted to assess the coinheritability of exposure and outcome.

Results

A total of 6 (VEGF), 12 (malignant brain tumor), 13 (brain glioblastoma) and 12 (malignant neoplasm of meninges) SNPs were identified as valid instrumental variables. No evidence supported a causal relationship between circulating VEGF levels and the risk of malignant brain tumors (forwards: odds ratio (OR) = 1.277, 95% confidence interval (CI), 0.812~2.009; reversed: β = 0.005, 95% CI, -0.029~0.038), brain glioblastoma (forwards: OR (95% CI) = 1.278(0.463~3.528); reversed: β = 0.010, 95% CI, -0.002~0.022) and malignant neoplasm of meninges (forwards: OR (95% CI) = 0.831(0.486~1.421); reversed: β = 0.010, 95% CI, -0.030~0.050) using the main IVW method. Outliers and pleiotropy bias were not detected by sensitivity analyses and pleiotropy-robust methods in any estimates. LDSC failed to identify genetic correlations between VEGF and different types of malignant brain tumors.

Conclusions

Our findings reported no coinheritability and failed to provide evidence for causal associations between VEGF and the risk of different types of malignant brain tumors. However, certain subtypes of VEGF for which genetic predictors have not been identified may play a role and need to be further investigated.

Plasminogen Activator Inhibitor Type-1 as a Regulator of Fibrosis

Fibrosis is known as a frequent and irreversible pathological condition which is associated with organ failure. Tissue fibrosis is a central process in a variety of chronic progressive diseases such as diabetes, hypertension, and persistent inflammation. This state could contribute to chronic injury and the initiation of tissue repair. Fibrotic disorders represent abnormal wound healing with defective matrix turnover and clearance that lead to excessive accumulation of extracellular matrix components. A variety of identified growth factors, cytokines, and persistently activated myofibroblasts have critical roles in the pathogenesis of fibrosis. Irrespective of etiology, the transforming growth factor-β pathway is the major driver of fibrotic response. Plasminogen activator inhibitor-1 (PAI-1) is a crucial downstream target of this pathway. Transforming growth factor-β positively regulates PAI-1 gene expression via two main pathways including Smad-mediated canonical and non-canonical pathways. Overexpression of PAI-1 reduces extracellular matrix degradation via perturbing the plasminogen activation system. Indeed, elevated PAI-1 levels inhibit proteolytic activity of tissue plasminogen activator and urokinase plasminogen activator which could contribute to a variety of inflammatory elements in the injury site and to excessive matrix deposition. This review summarizes the current knowledge of critical pathways that regulate PAI-1 gene expression and suggests effective approaches for the treatment of fibrotic disease. J. Cell. Biochem. 119: 17-27, 2018. © 2017 Wiley Periodicals, Inc.

Anatomical specificity of vascular endothelial growth factor expression in glioblastomas: a voxel-based mapping analysis

INTRODUCTION

The expression of vascular endothelial growth factor (VEGF) is a common genetic alteration in malignant gliomas and contributes to the angiogenesis of tumors. This study aimed to investigate the anatomical specificity of VEGF expression levels in glioblastomas using voxel-based neuroimaging analysis.

METHODS

Clinical information, MR scans, and immunohistochemistry stains of 209 patients with glioblastomas were reviewed. All tumor lesions were segmented manually and subsequently registered to standard brain space. Voxel-based regression analysis was performed to correlate the brain regions of tumor involvement with the level of VEGF expression. Brain regions identified as significantly associated with high or low VEGF expression were preserved following permutation correction.

RESULTS

High VEGF expression was detected in 123 (58.9 %) of the 209 patients. Voxel-based statistical analysis demonstrated that high VEGF expression was more likely in tumors located in the left frontal lobe and the right caudate and low VEGF expression was more likely in tumors that occurred in the posterior region of the right lateral ventricle.

CONCLUSION

Voxel-based neuroimaging analysis revealed the anatomic specificity of VEGF expression in glioblastoma, which may further our understanding of genetic heterogeneity during tumor origination. This finding provides primary theoretical support for potential future application of customized antiangiogenic therapy.

Immunohistochemical Detection of Urokinase Plasminogen Activator and Urokinase Plasminogen Activator Receptor in Canine Vascular Endothelial Tumours

Immunohistochemistry was used to assess the expression of urokinase plasminogen activator (uPA) and uPA receptor (uPAR) in 57 canine primary haemangiosarcomas (HSAs), 26 canine cutaneous haemangiomas (HAs) and in control sections of canine cutaneous granulation tissue. The correlation between uPA/uPAR expression and the Ki67 labelling index (LI) was estimated in the HSA and HA tissues. uPA was expressed by 73.2% and 75.0% of splenic HSAs and non-splenic HSAs, respectively. All HSA tissues tested expressed uPAR. Expression of both molecules was significantly higher in HSAs than in cutaneous HAs (3.8% for uPA and 30.7% for uPAR). The average Ki67 LI of the uPA(+)/uPAR(+) HSAs was significantly higher than that of uPA(-)/uPAR(+) HSAs and HA tissues (mean ± SDs 32.8 ± 15.3, 15.2 ± 7.2 and 2.1 ± 0.7, respectively; P <0.05). These results suggest that uPA and uPAR play a significant role in the malignant proliferation of canine HSA, regardless of the primary origin of the tumour.

ProBDNF and its receptors are upregulated in glioma and inhibit the growth of glioma cells in vitro

BACKGROUND

High-grade glioma is incurable, with a short survival time and poor prognosis. The increased expression of p75 neurotrophin receptor (NTR) is a characteristic of high-grade glioma, but the potential significance of increased p75NTR in this tumor is not fully understood. Since p75NTR is the receptor for the precursor of brain-derived neurotrophic factor (proBDNF), it is suggested that proBDNF may have an impact on glioma.

METHODS

In this study we investigated the expression of proBDNF and its receptors p75NTR and sortilin in 52 cases of human glioma and 13 cases of controls by immunochemistry, quantitative real-time PCR, and Western blot methods. Using C6 glioma cells as a model, we investigated the roles of proBDNF on C6 glioma cell differentiation, growth, apoptosis, and migration in vitro.

RESULTS

We found that the expression levels of proBDNF, p75NTR, and sortilin were significantly increased in high-grade glioma and were positively correlated with the malignancy of the tumor. We also observed that tumors expressed proBDNF, p75NTR, and sortilin in the same cells with different subcellular distributions, suggesting an autocrine or paracrine loop. The ratio of proBDNF to mature BDNF was decreased in high-grade glioma tissues and was negatively correlated with tumor grade. Using C6 glioma cells as a model, we found that proBDNF increased apoptosis and differentiation and decreased cell growth and migration in vitro via p75NTR.

CONCLUSIONS

Our data indicate that proBDNF and its receptors are upregulated in high-grade glioma and might play an inhibitory effect on glioma.

Novel approach to analysis of in vitro tumor angiogenesis with a variable-pressure scanning electron microscope: suppression by matrix metalloproteinase inhibitor SI-27

Degradation of basement membrane by metalloproteinases (MMP) is a critical step in tumor angiogenesis. To evaluate in vitro angiogenesis, several models have been employed, including bovine cornea, fenestrated rat brain, Matrigel, and others. These models did not provide quantitative analysis of capillary formation. The current study aimed for a novel approach to in vitro assay of angiogenesis with a "wet scanning electron microscope (SEM)" to investigate suppression of tumor angiogenesis by the MMP inhibitor, SI-27. The effects of noncytotoxic concentrations of SI-27 (1-100 microM) were determined on nonmitogenic vascular endothelial growth factor (VEGF) (10 ng/ml)-mediated cell motility and in vitro angiogenesis of human umbilical vein endothelial cells (HUVECs). Activities of MMP and tissue inhibitor of metalloproteinase (TIMP) were determined by enzyme-linked immunosorbent assay (ELISA). Subsequently, the inhibitory effect of SI-27 was examined on in vitro angiogenesis stimulated by supernatants of human glioma cell lines (U87MG, U251MG, or U373MG). In vitro angiogenesis was quantitatively analyzed with a variable-pressure SEM. Cell motility and in vitro angiogenesis by HUVECs were significantly increased by VEGF along with elevated MMP-1 and -2 activity, whereas SI-27 significantly suppressed VEGF-mediated in vitro angiogenesis and inactivated both MMP-1 and MMP-2, but not inhibited cell motility. The angiogenesis promoted by glioma supernatants showed a significant reduction in the presence of SI-27. SI-27, a novel MMP inhibitor, inhibited tumor angiogenesis in vitro. It can be anticipated to prevent tumor growth through its angiosuppressive effect. Quantitative analysis with a variable-pressure SEM is a novel approach to in vitro angiogenesis assay.

Clinical utility of level-of-evidence-1 disease forecast cancer biomarkers uPA and its inhibitor PAI-1

The prognostic and/or predictive value of the cancer biomarkers, urokinase-type plasminogen activator (uPA) and its inhibitor (plasminogen activator inhibitor [PAI]-1), determined by ELISA in tumor-tissue extracts, was demonstrated for several cancer types in numerous clinically relevant retrospective or prospective studies, including a multicenter breast cancer therapy trial (Chemo-N0). Consequently, for the first time ever for any cancer biomarker for breast cancer, uPA and PAI-1 have reached the highest level of evidence, level-of-evidence-1. At present, two other breast cancer therapy trials, NNBC-3 and Plan B, also incorporating uPA and PAI-1 as treatment-assignment tools are in effect. Furthermore, small synthetic molecules targeting uPA are currently in Phase II clinical trials in patients afflicted with advanced cancer of the ovary, breast or pancreas.

Induction of the fibrinolytic system by cartilage extract mediates its antiangiogenic effect in mouse glioma

Both the antiangiogenic and antitumoral activity of shark cartilage extracts (SCE) have been demonstrated in animal models and clinical trials. Studies reported that SCE induces the expression of tissue plasminogen activator gene (PLAT) in endothelial cells and increases the activity of the protein (t-PA) in vitro. The aim of this study was to demonstrate the crucial role of t-PA induction in the antiangiogenic and antitumor activity of SCE in experimental glioma. This study showed antiangiogenic and antitumoral effects of SCE in three mice glioma models (C6, HGD and GL26). Histological examination suggested perivascular proteolysis and edema as well as important intratumoral necrosis, which artefactually increased the tumor volume at high doses. Thus, the antiangiogenic effect of SCE correlated with the presence of t-PA and angiostatin in degenerating vessels. Functional in vivo experiments were conducted to modulate the plasminogen pathway. No antiangiogenic effect was observed on tumors overexpressing the plasminogen activator inhibitor-1 (PAI-1). Moreover, therapeutical effects were neutralized in mice that were cotreated with ε-aminocaproic acid (EACA, 120 mg/kg p.o.), an inhibitor that blocks the high-affinity lysine binding sites of both plasminogen and plasmin. In contrast, cotreatment with N-acetylcysteine (NAC, 7,5mg/kg i.p.), a sulfhydril donor that reduces plasmin into angiostatin or other antiangiogenic fragments, increased the benefit of SCE on mice survival. In subcutaneous models, NAC prevented the increase in tumor volume caused by high doses of cartilage extract. In conclusion, this study indicates that induction of t-PA by shark cartilage extract plays an essential role in its antiangiogenic activity, but that control of excessive proteolysis by a plasmin reductor could prevent edema and uncover the full benefit of shark cartilage extract in the treatment of intracranial tumors.

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.

Tissue-Type Plasminogen Activator Is Upregulated in Metastatic Breast Cancer Cells Exposed to Insulin-Like Growth Factor—I

The insulin-like growth factor (IGF) system plays an important role in breast tumorigenesis. Breast cancer cells express the type I IGF receptor (IGF-IR) and respond to IGFs in the environment. Tissue-type plasminogen activator (tPA) has been shown to be associated with neoplastic transformation and the invasive phenotype for highly aggressive tumors; however, its role in breast cancer remains unclear. We asked whether there is a relationship between the IGF system and tPA in estrogen receptor-negative breast cancer cells that could contribute to invasion. When MDA-MB-435s breast cancer cells were exposed to IGF-I, tPA messenger RNA (mRNA) was upregulated in a time-dependent fashion. Tissue-type plasminogen activator protein accumulation was also increased in a similar manner. The invasiveness of MDA-MB-435s cells was enhanced in the presence of IGF-I. When the MDA-MB-435s cells were stably transfected with an antisense IGF-IR expression construct, the transfectants expressed high levels of IGF-IR antisense, dramatically reduced levels of endogenous IGF-IR, and a decrease in relative staining intensity for IGF-IR protein. A marked suppression in tPA mRNA expression occurred in MDA-MB-435s cells accompanying inhibition of IGF-IR. When cells carrying the antisense IGF-IR expression construct were exposed to IGF-I, tPA protein accumulation was significantly lower than that of control transfected cells. To our knowledge, this study is the first to show a relationship between the IGF system and tPA. Strategies that target the IGF/tPA pathway could provide alternative treatments for patients with certain types of metastatic breast cancer.

Diffusion tensor analysis of peritumoral edema using lambda chart analysis indicative of the heterogeneity of the microstructure within edema

Object. Histopathological studies indicate that cerebral edema associated with tumors (peritumoral edema) does not represent a single pathophysiological or clinical entity. In this study the authors investigated peritumoral edema by performing lambda chart analysis (LCA), a noninvasive technique that can be used to make visible and analyze apparent water diffusivity in tissues in vivo, and assessed the utility of LCA in differentiating high-grade gliomas from nonglial tumors.

Methods. The water diffusivity characteristics of peritumoral edema associated with four tumor groups—12 high-grade gliomas, five low-grade gliomas, 11 metastatic tumors, and 15 meningiomas—were assessed in 43 patients by performing magnetic resonance imaging with the aid of a 3-tesla magnetic resonance imaging system. In all tumor groups, peritumoral edema exhibited greater trace values and reduced anisotropy compared with normal white matter. Edema associated with high-grade gliomas had significantly higher trace values than edema associated with the other three tumor groups, although the anisotropic angles of those groups were comparable.

Conclusions. Lambda chart analysis identified two distinct types of peritumoral edema: edema associated with high-grade gliomas and edema associated with low-grade gliomas or nonglial tumors. The apparent water diffusivity was significantly greater in high-grade gliomas, whereas the anisotropy in these lesions was comparable to that of edema in other tumors. These findings indicated that water movement in areas of edema, predominantly in the extracellular spaces, was less restricted in high-grade gliomas, a phenomenon that likely reflected the destruction of the extracellular matrix ultrastructure by malignant cell infiltration and consequently greater water diffusion. Although preliminary, this study indicates that LCA could be used as a clinical tool for differentiating high-grade gliomas and for evaluating the extent of cellular infiltration.

Extracellular proteases: biological and behavioral roles in the mammalian central nervous system

Extracellular proteases and their inhibitors have been implicated in both physiological and pathological states in the central nervous system (CNS). Given the presence of several classes of proteases, it is believed that each enzyme may undertake distinct biological roles. Some are indispensible for neuronal migration, neurite outgrowth and pathfinding, and synaptic plasticity. Others are required for neuronal death and tumor growth and invasion. Furthermore, studies from transgenic animals lacking or overexpressing one or more of the proteases have suggested that functional compensations and redundance among different members do exist. Normally, protease activity is tightly regulated by specific inhibitors to prevent disastrous proteolysis. Various insults can disrupt the fine control of proteolysis and caise pathological changes. Novel strategies have been attempted to maintain or restore protease-inhibitors homeostasis, thus minimizing damages to the CNS. They may provide us with effective therapeutic tools for fighting certain neurological disorders.

Contrasting roles of plasminogen deficiency in different rheumatoid arthritis models

OBJECTIVE

To investigate the contrasting roles of plasminogen deficiency between models of collagen-induced arthritis (CIA) and antigen-induced arthritis (AIA).

METHODS

We developed a new animal model of arthritis, which we have called local injection-induced arthritis (LIA). In this model, we replaced methylated bovine serum albumin, which is normally used as an immunogen and is injected intraarticularly into the knee joint, with type II collagen (CII) to induce AIA. The severity of CIA, LIA, and AIA in wild-type and plasminogen-deficient mice was evaluated by clinical scoring or histologic grading. Necrosis was determined by histology and immunohistochemistry.

RESULTS

After CII immunization alone, wild-type mice developed arthritis in most of the paws as well as in the knee joints, whereas plasminogen-deficient mice were totally resistant to the disease. Local knee injections of CII or saline slightly enhanced the severity of the knee arthritis in wild-type mice during a 60-day experimental period. Unexpectedly, the plasminogen-deficient mice also developed arthritis in joints that were injected with CII or saline. However, the arthritis was milder than that in their wild-type littermates. Sustained tissue necrosis was found only in the plasminogen-deficient mice after the local injection.

CONCLUSION

Our data show that both the antigen and the joint trauma caused by the local injection are critical to explaining the contrasting roles of plasminogen deficiency in CIA and AIA. This further indicates that CIA and AIA have distinct pathogenic mechanisms. The data also suggest that plasmin may be required for the induction of these arthritis models that are critically dependent on complement activation.

SB-431542, a small molecule transforming growth factor-β-receptor antagonist, inhibits human glioma cell line proliferation and motility

Transforming growth factor-β (TGF-β) is a multifunctional cytokine that promotes malignant glioma invasion, angiogenesis, and immunosuppression. Antisense oligonucleotide suppression of TGF-β2 ligand expression has shown promise in preclinical and clinical studies but at least two ligands mediate the effects of TGF-β in gliomas. Therefore, we examined the effects of SB-431542, a novel, small molecule inhibitor of the type I TGF-β receptor, on a panel of human malignant glioma cell lines. SB-431542 blocked the phosphorylation and nuclear translocation of the SMADs, intracellular mediators of TGF-β signaling, with decreased TGF-β–mediated transcription. Furthermore, SB-431542 inhibited the expression of two critical effectors of TGF-β-vascular endothelial growth factor and plasminogen activator inhibitor-1. SB-431542 treatment of glioma cultures inhibited proliferation, TGF-β–mediated morphologic changes, and cellular motility. Together, our results suggest that small molecule inhibitors of TGF-β receptors may offer a novel therapy for malignant gliomas by reducing cell proliferation, angiogenesis, and motility.

Drug-induced apoptosis by a matrix metalloproteinase inhibitor, SI-27 on human malignant glioma cell lines; in vitro study

Matrix metalloproteinase (MMP) plays important roles in cell invasion and tumor angiogenesis. SI-27, an anti-MMP agent, has already been shown to possess both in vitro anti-invasive and anti-angiogenic properties against malignant gliomas in non-cytotoxic dose concentrations. However, to the best of our knowledge, the molecular mechanism mediating the cytotoxic action by this agent and the molecular mechanism in the cytotoxic action against malignant glioma cell have not yet been clarified. Therefore, we assessed the effect in the cytotoxic dose concentrations to investigate whether this cytotoxic action is related to apoptosis in this study. The effect on human glioma cell lines (U87MG, U251MG, and U373MG) was examined by transmission electron microscope, agarose gel electrophoresis with the DNA fragmentation, flow cytometry with FITC-conjugated Annexin V, and detection of caspase activity. Drug-induced apoptosis was observed in the cytotoxic dose. The result indicated that the cytotoxity of SI-27 might be related to the drug-induced apoptosis mediated by caspase.

The mannose receptor in the brain

The mannose receptor is a transmembrane glycoprotein mainly expressed by macrophages, that specifically binds to mannosylated molecules and mediates their endocytosis. Known ligands of the receptor are lysosomases and various pathogens. Ligand specificity and cellular distribution provide the mannose receptor with a very important role in homeostasis and in the immune response. Expression of the mannose receptor has recently been demonstrated in the brain. Astrocytes and microglia, two types of glial cells that can be turned into immune-competent cells, are the main site of expression in vivo and in vitro. The mannose receptor mediates in vitro pinocytosis by astrocytes and microglia and phagocytosis by microglia. Expression and endocytic activities of the mannose receptor in these cells are regulated by various cytokines. Based on our current knowledge on mannose receptor activities in brain cells, on its regional and temporal expression in that organ, and on its putative ligands therein, the possible involvement of the mannose receptor in brain homeostasis, neuronal functions, and brain defense is discussed.

Genetic and Plasma Markers of Venous Thromboembolism in Patients with High Grade Glioma

PURPOSE

Deep venous thrombosis/pulmonary embolism (DVT/PE) is a frequent complication in the course of cancer, particularly in brain tumors. We investigated genetic and plasma factors possibly associated with risk of DVT/PE in patients with high-grade glioma.

EXPERIMENTAL DESIGN

In a case-control study, we studied polymorphisms of the genes coding for factor II (G20210A), factor V (G1691A), methylenetetrahydrofolate-reductase (C677T), tissue-type plasminogen activator (tPA; insertion/deletion), plasminogen activator inhibitor-1 (PAI-1; 4G/5G), and vascular endothelial growth factor (VEGF; C936T). We also measured plasma levels of D-dimer, lipoprotein (lp) (a), homocysteine, VEGF, tPA, and PAI-1, comparing healthy control patients with patients with glioma or with patients with neurological nonneoplastic disease (multiple sclerosis).

RESULTS

Genotype frequencies of polymorphisms analyzed were similar in patients with glioma and in healthy matched population. D-dimer, lp (a), homocysteine, VEGF, tPA, and PAI-1 plasma levels were significantly higher in patients with glioma than in healthy controls, whereas patients having neurological nonneoplastic disease had plasma values of these molecules not significantly different from healthy controls. VEGF, tPA, and PAI-1 were also found at high-plasma levels in patients carrying genotypes that, in healthy controls, were associated with "low-producing" phenotypes.

CONCLUSIONS

Genetic risk factors alone did not explain the high incidence of DVT/PE observed in patients with glioma. Higher plasma levels of molecules influencing the coagulation pathways indicate that the tumor itself might confer an increased risk of DVT/PE; thus, D-dimer, homocysteine, lp (a), VEGF, tPA, and PAI-1 look like good candidates to be evaluated as DVT/PE prognostic factors.

Cerebral angiogenesis and expression of VEGF after subarachnoid hemorrhage (SAH) in rats

Subarachnoid hemorrhage (SAH) leads to the development of vasospasm in which endothelin-1 plays a very important role. The effect of its vasoconstricting action is hypoxia of the nervous tissue, which stimulates the release of growth factors. Vascular endothelial growth factor (VEGF) released in excessive amounts from hypoxically altered cerebrovascular endothelial cells is the most potent angiogenic factor and may enhance angiogenesis after SAH. If endothelin-1 is mainly responsible for vasospasm after SAH, it is possible that early administration of endothelin converting enzyme inhibitor or endothelin receptor antagonist may protect neurons against. The aim of the study was to establish whether prolonged vasospasm and endothelial cell hypoxia stimulate VEGF expression and, in consequence, promote angiogenesis in the central nervous system after subarachnoid hemorrhage. Investigations were also performed to determine whether the administration of phosphoramidon, an endothelin-converting enzyme (ECE) inhibitor, and BQ-123, an endothelin receptor ET(A) antagonist, suppresses angiogenesis and VEGF expression. Experiments were carried out in male Wistar rats injected with phosphoramidon or BQ-123 into the cisterna magna following the induction of subarachnoid hemorrhage. The brains were removed 48 h after the hemorrhage for histopathological and immunohistochemical examinations of VEGF expression and angiogenesis in the cerebral hemispheres, brainstem, and cerebellum. Statistical analysis was performed using nonparametric Wilcoxon test (P<0.05). The results obtained have shown for the first time a close correlation between endothelial hypoxia after SAH in cerebral microvessels and enhanced angiogenesis. There is also an increase in VEGF expression in cerebral vessels and neurons within the cerebral hemispheres, brainstem, and cerebellum. The administration of phosphoramidon or BQ-123 has been found to inhibit angiogenesis. Angiogenesis in the chronic phase of SAH-induced vasospasm is the result of prolonged narrowing of vessels due to excessive secretion of endothelin by damaged endothelial cells. Present results obtained indicate that it is possible to reduce or prevent the late effects of SAH, i.e., neuronal hypoxia and cerebral edema, through the inhibition of endothelin-1 induced vasospasm.

Identification of differentially expressed proteins in human glioblastoma cell lines and tumors

An in-frame deletion of 801 bp in exons 2-7 (type III mutation) of the epidermal growth factor receptor (EGFR) is detected at high incidence in primary glioblastoma tumors. A proteomic approach was used to generate differential protein expression maps of fetal human astrocytes (FHA), human glioblastoma cell lines U87MG and U87MG expressing type III EGFR deletion (U87MGdeltaEGFR) that confers high malignancy to tumor cells. Two-dimensional gel electrophoresis followed by in-gel digestion of separated spots and protein identification by LC-MS-MS and matrix-assisted laser desorption ionization time-of-flight mass spectrometry (MALDI-TOF MS) identified 23 proteins expressed at higher levels or exclusively in FHA and 29 proteins expressed at higher levels or exclusively in U87MG cells. Three proteins, ubiquitin, cystatin B, and tissue transglutaminase (TTG), were upregulated in U87MGdeltaEGFR relative to U87MG. Four proteins highly expressed by U87MG cells, Hsp27, major vault protein, TTG, and cystatin B, were analyzed by Western blot, ELISA, or RT-PCR in cell extracts and in tissue samples of glioblastoma multiforme (GBM; grade IV), low-grade astrocytomas (grades I and II), and nonmalignant brain lesions. All four proteins were highly expressed in GBM tissues compared to nonmalignant brain. These proteins may be used as diagnostic or functional (e.g., multiple drug resistance, invasiveness) markers for glioblastoma tumors.

Coagulation, fibrinolysis and angiogenesis: new insights from knockout mice

Angiogenesis plays a key role in a broad array of physiologic and pathologic processes. Two major systems--coagulation and fibrinolysis--maintaining hemostasis, have recently been implicated in angiogenesis. Generation of mice deficient in components of coagulation and plasminogen systems has provided an extraordinary opportunity to define the role of each of these systems in vivo and to elucidate molecular mechanisms involved in angiogenesis. It appears that several factors of the coagulation system, such as the tissue factor, the factor V and the thrombin receptor, play an important role in embryonic vessel formation, most probably in the formation of the primitive vascular wall. In addition, the plasminogen system appears to play a significant role in angiogenesis in adulthood, regulating the migration of endothelial and smooth muscle cells, the degradation of the extracellular matrix and activity of the metalloproteinase system. These new revelations open a possibility for future therapeutic strategies to specifically control angiogenesis in different pathological processes where abnormalities of tissue vascularization are pathogenetically prominent.

SI-27, a novel inhibitor of matrix metalloproteinases with antiangiogenic activity: detection with a variable-pressure scanning electron microscope

OBJECTIVE

Degradation of basement membrane is one the of crucial steps in tumor angiogenesis and is performed by matrix metalloproteinases (MMPs). This study was designed to investigate the suppression of tumor angiogenesis by SI-27, an MMP inhibitor.

METHODS

SI-27 was applied at noncytotoxic concentrations (1-100 micromol/L), and its effect on nonmitogenic vascular endothelial growth factor (VEGF)-enhanced cell motility and in vitro angiogenesis by human umbilical vein endothelial cells was determined. The activity of MMP-1, MMP-2, and tissue inhibitor of metalloproteinase 1 was determined by enzyme-linked immunosorbent assay. The effect of SI-27 on in vitro angiogenesis stimulated by supernatants of human glioma cell lines (U87MG, U251MG, and U373MG) also was examined. Angiogenesis was detected with variable vacuum scanning electron microscopy.

RESULTS

Cell motility and in vitro angiogenesis by human umbilical vein endothelial cells were significantly increased by VEGF. The maximal effect on cell motility by VEGF was noted at 5 ng/ml (P < 0.001), and the maximal effect on the capillary network was observed at 10 ng/ml (P < 0.001), along with elevated MMP-1 and MMP-2 activity. Whereas SI-27 significantly suppressed VEGF-mediated in vitro angiogenesis (50 micromol/L; P < 0.001) and inactivated both MMP-1 and MMP-2, the expression of tissue inhibitor of metalloproteinase 1 and VEGF-mediated cell motility were not affected by SI-27. The angiogenesis promoted by glioma supernatants showed a significant reduction in the presence of SI-27 (10 micromol/L; U87MG, P < 0.01; U251MG, P < 0.01; U373MG, P < 0.01).

CONCLUSION

SI-27 inhibited in vitro tumor angiogenesis by suppression of MMP. This agent may be anticipated to prevent tumor growth through an angiosuppressive effect.

The hemostatic system and angiogenesis in malignancy

Coagulopathy and angiogenesis are among the most consistent host responses associated with cancer. These two respective processes, hitherto viewed as distinct, may in fact be functionally inseparable as blood coagulation and fibrinolysis, in their own right, influence tumor angiogenesis and thereby contribute to malignant growth. In addition, tumor angiogenesis appears to be controlled through both standard and non-standard functions of such elements of the hemostatic system as tissue factor, thrombin, fibrin, plasminogen activators, plasminogen, and platelets. "Cryptic" domains can be released from hemostatic proteins through proteolytic cleavage, and act systemically as angiogenesis inhibitors (e.g., angiostatin, antiangiogenic antithrombin III aaATIII). Various components of the hemostatic system either promote or inhibit angiogenesis and likely act by changing the net angiogenic balance. However, their complex influences are far from being fully understood. Targeted pharmacological and/or genetic inhibition of pro-angiogenic activities of the hemostatic system and exploitation of endogenous angiogenesis inhibitors of the angiostatin and aaATIII variety are under study as prospective anti-cancer treatments.

Species specificity of amidine-based urokinase inhibitors

Inhibition of the proteolytic activity of urokinase has been shown to inhibit the progression of tumors in rodent models and is being investigated for use in human disease. Understanding the rodent/human species-specificity of urokinase inhibitors is therefore critical for interpretation of rodent cancer progression models that use these inhibitors. We report here studies with a panel of 11 diverse urokinase inhibitors in both human and mouse enzymatic assays. Inhibitors such as amiloride, B428, and naphthamidine, that occupy only the S1 subsite pocket were found to be nearly equipotent between the human and the murine enzymes. Inhibitors that access additional, more distal, pockets were significantly more potent against the human enzyme but there was no corresponding potency increase against the murine enzyme. X-ray crystallographic structures of these compounds bound to the serine protease domain of human urokinase were solved and examined in order to explain the human/mouse potency differences. The differences in inhibitor potency could be attributed to four amino acid residues that differ between murine and human urokinases: 60, 99, 146, and 192. These residues are Asp, His, Ser, and Gln in human and Gln, Tyr, Glu, and Lys in mouse, respectively. Compounds bearing a cationic group that interacts with residue 60 will preferentially bind to the human enzyme because of favorable electrostatic interactions. The hydrogen bonding to residue 192 and steric considerations with residues 99 and 146 also contribute to the species specificity. The nonparallel human/mouse enzyme inhibition observations were extended to a cell-culture assay of urokinase-activated plasminogen-mediated fibronectin degradation with analogous results. These studies will aid the interpretation of in vivo evaluation of urokinase inhibitors.

Cathepsins B and L are markers for clinically invasive types of meningiomas

OBJECTIVE

Meningiomas are benign neoplasms that derive from coverings of the brain. Approximately 10% of benign tumors progress into atypical, malignant tumors, thus constituting a subset of histopathologically benign tumors that are clinically invasive. The aim of this study was to evaluate cathepsins B and L and their inhibitors as new prognostic factors that could distinguish malignant from benign forms of meningiomas.

METHODS

Using immunohistochemical analysis and specific monoclonal antibodies, we evaluated the levels of cathepsins B and L and the levels of the endogenous cysteine proteinase inhibitors stefin A and cystatin C in 88 meningiomas. Immunohistochemical scores were determined as the sum of the frequency (0-3) and intensity (0-3) of immunolabeling of the tumor cells.

RESULTS

Of the 88 tumors studied, 67 were benign meningiomas and 21 were atypical meningiomas. Among the benign group, nine tumors had certain features of malignancy. These tumors were classified as border benign meningiomas, and the rest were classified as clear benign meningiomas. A high immunohistochemical score (4-6) for cathepsin B was more frequent in atypical tumors than in clear benign tumors (P < 0.001). Compared with clear benign tumors, higher cathepsin B immunohistochemical scores were found in atypical tumors (P < 0.001) and border benign tumors (P < 0.03). No statistical difference in immunohistochemical staining of cathepsin B was found between atypical meningiomas and border benign meningiomas. Higher expression of cathepsin L was found in atypical tumors as compared with clear benign tumors (P < 0.03), but it was not observed in border benign as compared with clear benign meningiomas. No immunostaining for stefin A and cystatin C was detected in any of the tumors.

CONCLUSION

We show that the levels of cathepsin B and cathepsin L antigens are significantly higher in invasive types of benign meningioma. Specifically, cathepsin B may be used as a diagnostic marker to distinguish histomorphologically benign but invasive meningiomas from histomorphologically clear benign tumors.

Genes that regulate metastasis and angiogenesis

Genetic instability and an accumulation of genetic and epigenetic changes during tumor progression lead to an increasingly aggressive and treatment-resistant phenotype, and ultimately metastasis. In recent years it has become well established that angiogenesis, the process by which new vasculature is formed from pre-existing vessels, is an essential component to primary tumor growth and distant metastasis. A greater understanding of the complex multitude of factors involved in tumor angiogenesis and metastasis is fundamental to the development of potential therapeutics to treat malignant disease. As highlighted throughout this review, angiogenesis and metastasis share many common cellular and molecular features. We will briefly discuss the pertinent genes involved in the regulation of angiogenesis and metastasis.