Angiostatin's molecular mechanism: aspects of specificity and regulation elucidated

Contemporaneous Perioperative Inflammatory and Angiogenic Cytokine Profiles of Surgical Breast, Colorectal, and Prostate Cancer Patients: Clinical Implications

Surgery-induced tumor growth acceleration and synchronous metastatic growth promotion have been observed for decades. Surgery-induced wound healing, orchestrated through growth factors, chemokines, and cytokines, can negatively impact patients harboring residual or metastatic disease. We provide detailed clinical evidence of this process in surgical breast, prostate, and colorectal cancer patients. Plasma samples were analyzed from 68 cancer patients who had not received treatment before surgery or adjuvant therapy until at least four weeks post-surgery. The levels of plasma cytokines, chemokines, and growth factors were simultaneously quantified and profiled using multiplexed immunoassays for eight time points sampled per patient. The immunologic processes are induced immediately after surgery in patients, characterized by a drastic short-term shift in the expression levels of pro-inflammatory and angiogenic molecules and cytokines. A rapid and significant spike in circulating plasma levels of hepatocyte growth factor (HGF), interleukin-6 (IL-6), placental growth factor (PLGF), and matrix metalloproteinase-9 (MMP-9) after surgery was noted. The rise in these molecules was concomitant with a significant drop in transforming growth factor-β1 (TGF-β1), platelet-derived growth factor (PDGF-AB/BB), insulin-like growth factor-1 (IGF-1), and monocyte chemoattractant protein-2 (MCP-2). If not earlier, each plasma analyte was normalized to baseline levels within 1-2 weeks after surgery, suggesting that surgical intervention alone was responsible for these effects. The effects of surgical tumor removal on disrupting the pro-inflammatory and angiogenic plasma profiles of cancer patients provide evidence for potentiating malignant progression. Our findings indicate a narrow therapeutic window of opportunity after surgery to prevent disease recurrence.

ANGT_HUMAN[448–462], an Anorexigenic Peptide Identified using Plasma Peptidomics

The discovery of bioactive peptides is an important research target that enables the elucidation of the pathophysiology of human diseases and provides seeds for drug discovery. Using a large number of native peptides previously identified using plasma peptidomics technology, we sequentially synthesized selected sequences and subjected them to functional screening using human cultured cells. A 15-amino-acid residue proangiotensinogen-derived peptide, designated ANGT_HUMAN[448–462], elicited cellular responses and bound to cultured human cells. Synthetic fluorescent-labeled and biotinylated ANGT_HUMAN[448–462] peptides were rendered to bind to cell- and tissue-derived proteins and peptide-cell protein complexes were retrieved and analyzed using liquid chromatography-tandem mass spectrometry, revealing the β-subunit of ATP synthase as its cell-surface binding protein. Because ATP synthase mediates the effects of anorexigenic peptides, the ability of ANGT_HUMAN[448–462] to modulate eating behavior in mice was investigated. Both intraperitoneal and intracerebroventricular injections of low doses of ANGT_HUMAN[448–462] suppressed spontaneous food and water intake throughout the dark phase of the diurnal cycle without affecting locomotor activity. Immunoreactive ANGT_HUMAN[448–462], distributed throughout human tissues and in human-derived cells, is mostly co-localized with angiotensin II and is occasionally present separately from angiotensin II. In this study, an anorexigenic peptide, ANGT_HUMAN[448–462], was identified by exploring cell surface target proteins of the human native peptides identified using plasma peptidomics.

Endometriosis-Associated Angiogenesis and Anti-angiogenic Therapy for Endometriosis

Endometriosis is a known estrogen-dependent inflammatory disease affecting reproductive-aged women. Common symptoms include pelvic pain, dysmenorrhea, dyspareunia, heavy menstrual bleeding, and infertility. The exact etiology of endometriosis is largely unknown, and, thus, the diagnosis and treatment of endometriosis are challenging. A complex interplay of many molecular mechanisms is thought to aid in the progression of endometriosis, most notably angiogenesis. This mini-review examines our current knowledge of the molecular etiology of endometriosis-associated angiogenesis and discusses anti-angiogenic therapy, in the blockade of endometriosis-associated angiogenesis, as potential non-hormonal therapy for the treatment of endometriosis.

Drug-metabolizing enzymes: role in drug resistance in cancer

Although continuous researches are going on for the discovery of new chemotherapeutic agents, resistance to these anticancer agents has made it really difficult to reach the fruitful results. There are many causes for this resistance that are being studied by the researchers across the world, but still, success is far because there are several factors that are going along unattended or have been studied less. Drug-metabolizing enzymes (DMEs) are one of these factors, on which less study has been conducted. DMEs include Phase I and Phase II enzymes. Cytochrome P450s (CYPs) are major Phase I enzymes while glutathione-S-transferases (GSTs), UDP-glucuronosyltransferases (UGTs), dihydropyrimidine dehydrogenases are the major enzymes belonging to the Phase II enzymes. These enzymes play an important role in detoxification of the xenobiotics as well as the metabolism of drugs, depending upon the tissue in which they are expressed. When present in tumorous tissues, they cause resistance by metabolizing the drugs and rendering them inactive. In this review, the role of these various enzymes in anticancer drug metabolism and the possibilities for overcoming the resistance have been discussed.

High Lipoprotein(a) Level Is Independently Associated with Adverse Clinicopathological Features in Patients with Prostate Cancer

Background

The effect of lipoprotein(a) (Lp(a)) on prostate cancer (PCa) is unclear. The aim of this study was to investigate the association between serum Lp(a) levels and clinicopathological features in patients with PCa.

Methods

A total of 376 consecutive pathologically diagnosed PCa patients were enrolled and were classified as a low-intermediate-risk group or a high-risk group. The association of Lp(a) and the other lipid parameters including total cholesterol (TC), low-density lipoprotein cholesterol (LDL-C), high-density lipoprotein cholesterol (HDL-C), triglycerides (TG), TC/HDL-C, LDL-C/HDL-C, and remnant cholesterol (RC) with clinicopathological parameters was tested by univariate and multivariate logistic regression analyses.

Results

The high-risk PCa patients tended to have higher Lp(a) levels (p = 0.022) while there was no significant difference regarding the other lipid parameters (p > 0.05) compared to low-intermediate-risk counterparts. Patients with PSA ≥ 100 ng/ml had significantly higher Lp(a) levels than subjects with PSA < 100 ng/ml (p = 0.002). Univariate logistic regression analyses revealed that high Lp(a) levels were correlated with high-risk PCa (Q4 vs. Q1, HR = 2.687, 95% CI: 1.113-6.491, p = 0.028), while the other lipid parameters were not correlated with high-risk PCa. In the stepwise multivariate regression analysis, the association between Lp(a) levels and high-risk PCa remained significant (Q4 vs. Q1, HR = 2.890, 95% CI: 1.148-7.274, p = 0.024) after adjusting for confounding factors including age, body mass index, hypertension, diabetes, coronary artery disease, and lipid-lowering drugs.

Conclusions

This is the first study showing the positive association between high Lp(a) and adverse clinicopathological features of PCa. PCa patients with high Lp(a) tends to be more aggressive and should receive more attention in clinical practice.

Structural Biology and Protein Engineering of Thrombolytics

Myocardial infarction and ischemic stroke are the most frequent causes of death or disability worldwide. Due to their ability to dissolve blood clots, the thrombolytics are frequently used for their treatment. Improving the effectiveness of thrombolytics for clinical uses is of great interest. The knowledge of the multiple roles of the endogenous thrombolytics and the fibrinolytic system grows continuously. The effects of thrombolytics on the alteration of the nervous system and the regulation of the cell migration offer promising novel uses for treating neurodegenerative disorders or targeting cancer metastasis. However, secondary activities of thrombolytics may lead to life-threatening side-effects such as intracranial bleeding and neurotoxicity. Here we provide a structural biology perspective on various thrombolytic enzymes and their key properties: (i) effectiveness of clot lysis, (ii) affinity and specificity towards fibrin, (iii) biological half-life, (iv) mechanisms of activation/inhibition, and (v) risks of side effects. This information needs to be carefully considered while establishing protein engineering strategies aiming at the development of novel thrombolytics. Current trends and perspectives are discussed, including the screening for novel enzymes and small molecules, the enhancement of fibrin specificity by protein engineering, the suppression of interactions with native receptors, liposomal encapsulation and targeted release, the application of adjuvants, and the development of improved production systems.

Serum angiostatin and endostatin levels in patients with granulomatosis with polyangiitis and immune complex small vessel vasculitis

Objectives

Inflammation has been revealed to be associated with angiogenesis. Granulomatosis with polyangiitis (GPA) and immune complex small vessel vasculitis (ICSVV) are forms of systemic vasculitides of different pathogenesis. GPA is a necrotizing granulomatosis and ICSVV is associated with inflammation of postcapillary venules induced by deposits of immune complexes. The aim of the study was to determine serum levels of angiostatin and endostatin, natural angiogenesis inhibitors, in patients with GPA and ICSVV as well as healthy individuals.

Material and methods

Two groups of patients with GPA (20 patients) and ICSVV (20 patients) as well as 20 controls were investigated. All patients were investigated before initiation of immunosuppressive therapy or administration of corticosteroids. Angiostatin and endostatin levels were assayed with the ELISA method.

Results

Enhanced serum levels of angiostatin and endostatin were found in patients with GPA but not in those suffering from ICSVV. In patients with GPA increased levels of angiogenesis inhibitors correlated with the disease activity. A correlation between angiostatin and endostatin levels was observed in all groups of investigated individuals.

Conclusions

It is suggested that formation of necrotizing granulation is associated with profound activation of angiogenesis and an increase in serum levels of inhibitors is a phenomenon occurring during blood vessel formation in the granulation tissue. The obtained results confirm involvement of angiogenesis in pathogenesis of at least some forms of vasculitides and suggest the need for continuation of investigations in this field.

Radiolabeled Anti-Adenosine Triphosphate Synthase Monoclonal Antibody as a Theragnostic Agent Targeting Angiogenesis

INTRODUCTION

The potential of a radioiodine-labeled, anti-adenosine triphosphate synthase monoclonal antibody (ATPS mAb) as a theragnostic agent for simultaneous cancer imaging and treatment was evaluated.

METHODS

Adenosine triphosphate synthase monoclonal antibody was labeled with radioiodine, then radiotracer uptake was measured in 6 different cancer cell lines. In vivo biodistribution was evaluated 24 and 48 hours after intravenous injection of ¹²⁵I-ATPS mAb into MKN-45 tumor-bearing mice (n = 3). For radioimmunotherapy, 18.5 MBq ¹³¹I-ATPS mAb (n = 7), isotype immunoglobulin G (IgG) (n = 6), and vehicle (n = 6) were injected into MKN-45 tumor-bearing mice for 4 weeks, and tumor volume and percentage of tumor growth inhibition (TGI) were compared each week.

RESULTS

MKN-45 cells showed the highest in vitro cellular binding after 4 hours (0.00324 ± 0.00013%/μg), which was significantly inhibited by unlabeled ATPS mAb at concentrations of greater than 0.4 μM. The in vitro retention rate of ¹²⁵I-ATPS mAb in MKN-45 cells was 64.1% ± 1.0% at 60 minutes. The highest tumor uptake of ¹²⁵I-ATPS mAb in MKN-45 tumor-bearing mice was achieved 24 hours after injection (6.26% ± 0.47% injected dose [ID]/g), whereas tumor to muscle and tumor to blood ratios peaked at 48 hours. The 24-hour tumor uptake decreased to 3.43% ± 0.85% ID/g by blocking with unlabeled ATPS mAb. After 4 weeks of treatment, mice receiving ¹³¹I-ATPS mAb had significantly smaller tumors (679.4 ± 232.3 mm³) compared with control (1687.6 ± 420.4 mm³, P = .0431) and IgG-treated mice (2870.2 ± 484.1 mm³, P = .0010). The percentage of TGI of ¹³¹I-ATPS mAb was greater than 50% during the entire study period (range: 53.7%-75.9%).

CONCLUSION

The specific binding and antitumor effects of radioiodinated ATPS mAb were confirmed in in vitro and in vivo models of stomach cancer.

A Therapeutic Connection between Dietary Phytochemicals and ATP Synthase

For centuries, phytochemicals have been used to prevent and cure multiple health ailments. Phytochemicals have been reported to have antioxidant, antidiabetic, antitussive, antiparasitic, anticancer, and antimicrobial properties. Generally, the therapeutic use of phy-tochemicals is based on tradition or word of mouth with few evidence-based studies. Moreo-ver, molecular level interactions or molecular targets for the majority of phytochemicals are unknown. In recent years, antibiotic resistance by microbes has become a major healthcare concern. As such, the use of phytochemicals with antimicrobial properties has become perti-nent. Natural compounds from plants, vegetables, herbs, and spices with strong antimicrobial properties present an excellent opportunity for preventing and combating antibiotic resistant microbial infections. ATP synthase is the fundamental means of cellular energy. Inhibition of ATP synthase may deprive cells of required energy leading to cell death, and a variety of die-tary phytochemicals are known to inhibit ATP synthase. Structural modifications of phyto-chemicals have been shown to increase the inhibitory potency and extent of inhibition. Site-directed mutagenic analysis has elucidated the binding site(s) for some phytochemicals on ATP synthase. Amino acid variations in and around the phytochemical binding sites can re-sult in selective binding and inhibition of microbial ATP synthase. In this review, the therapeu-tic connection between dietary phytochemicals and ATP synthase is summarized based on the inhibition of ATP synthase by dietary phytochemicals. Research suggests selective target-ing of ATP synthase is a valuable alternative molecular level approach to combat antibiotic resistant microbial infections.

Protein degradation fragments as diagnostic and prognostic biomarkers of connective tissue diseases: understanding the extracellular matrix message and implication for current and future serological biomarkers

The aim of this review is to discuss the potential usefulness of novel biochemical markers of connective tissues: neo-epitopes of extracellular matrix proteins generated by post-translational modifications by tissue proteinases. As each modification results from a specific local physiological or pathobiological process, the identification of specific proteinase-mediated cleavage products of tissue-specific proteins may produce a unique disease-specific biochemical marker. The authors present a novel interpretation of the process of tissue degradation described by neo-epitope fragments of the interstitial and basement membrane matrix in fibrotic disease, and the diagnostic and prognostic potential of such markers. Moreover, the authors highlight the importance of matrix protein fragments not only as markers of tissue remodeling, but also as players in tissue remodeling, due to their signaling properties.

Lipoprotein(a) and vitamin C impair development of breast cancer tumors in Lp(a)+; Gulo-/- mice

Cancer progression is characterized by loss of extracellular matrix (ECM) integrity, which is a precondition for tumor growth and metastasis. In order to elucidate the precise mechanisms of ECM degradation in cancer we used a genetically modified mouse mimicking two distinct human metabolic features associated with carcinogenesis, the lack of endogenous vitamin C synthesis and the production of human Lp(a). Female Lp(a)+; Gulo(−/−) and control wild-type Balb/c mice without these two metabolic features were orthotopically inoculated with 4T1 breast cancer cells (5×10⁵). The transgenic and control mice were divided into 4 different dietary groups in respect to dietary vitamin C intake: i) low ascorbate intake for 6 weeks; ii) high ascorbate intake for 6 weeks; iii) low ascorbate intake for 3 weeks followed by high ascorbate for 3 weeks; iv) high ascorbate intake for 3 weeks followed by low ascorbate for 3 weeks. After 6 weeks, all wild-type mice developed tumors. In contrast, Lp(a)+; Gulo(−/−) mice developed one third less primary tumors (low ascorbate diet) or no primary tumors at all (high ascorbate diet). Significantly, tumors from Lp(a)+; Gulo(−/−) mice immunostained positively for Lp(a) and their size was inversely proportional to Lp(a) serum levels. The results implicate that Lp(a) may play a role in controlling tumor growth and expansion. The most likely mechanism is the competitive inhibition of plasmin-induced ECM degradation due to the homology of Lp(a) components to plasminogen. The confirmation of this pathomechanism could lead to a universal therapeutic target for the prevention and treatment of cancer.

Effect of the transdermal low-level laser therapy on endothelial function

The effect of low-level laser therapy (LLLT) on the cardiovascular system is not fully established. Since the endothelium is an important endocrine element, establishing the mechanisms of LLLT action is an important issue.The aim of the study was to evaluate the effect of transdermal LLLT on endothelial function.In this study, healthy volunteers (n = 40, age = 20–40 years) were enrolled. N = 30 (14 female, 16 male, mean age 30 ± 5 years) constituted the laser-irradiated group (LG). The remaining 10 subjects (6 women, 4 men, mean age 28 ± 5 years) constituted the control group (CG). Participants were subjected to LLLT once a day for three consecutive days. Blood for biochemical assessments was drawn before the first irradiation and 24 h after the last session. In the LG, transdermal illumination of radial artery was conducted (a semiconductor laser λ = 808 nm, irradiation 50 mW, energy density 1.6 W/cm² and a dose 20 J/day, a total dose of 60 J). Biochemical parameters (reflecting angiogenesis: vascular endothelial growth factor (VEGF), fibroblast growth factor (FGF), angiostatin; antioxidative status: glutathione (GSH) and the nitric oxide metabolic pathway: symmetric dimethylarginine (SDMA), asymmetric dimethylarginine (ADMA) and l-arginine) were assessed. In the LG, a significant increase in GSH levels and considerable decrease in angiostatin concentration following the LLLT were observed. No significant differences in levels of the VEGF, FGF, SDMA, ADMA were observed.LLLT modifies vascular endothelial function by increasing its antioxidant and angiogenic potential. We found no significant differences in levels of the nitric oxide pathway metabolites within 24 h following the LLLT irradiation.

PLASMINOGEN AND ANGIOSTATIN LEVELS IN FEMALE BENIGN BREAST LESIONS

It is known that benign breast tissue exhibit relatively low angiogenic capacity. Activation of angiogenesis in mammary pre-malignant lesions could be associated with disease progression and high risk of transformation into the breast cancer. However, insight into the underlying molecular mechanisms involved in angiogenesis regulation in non-cancerous breast pathologies is still poorly defined. The purpose of the present study was to determine levels of plasminogen and its proteolytic fragments (angiostatins) in mammary dysplasia (mastopathy and breast cyst) and benign neoplasms (fibroadenomas). Plasminogen and angiostatins were analyzed using immunoblotting and quantified by densitometric scanning. The significant increase in plasminogen levels was found in fibrocystic, cysts, and non-proliferatious fibroadenoma masses (4.7-, 3.7-, and 3.5-fold, respectively) compared to healthy breast tissues (control). In the same benign lesions, 6.7-, 4-, and 3.7-fold increase in plasminogen 50 kDa fragment (angiostatin) levels as compared with control were also observed. Activation of matrix metalloproteinase-9, which was detected using gelatine zymography, could be responsible for plasminogen cleavage and abundance of angiostatin infibrocystic and cyst masses. In contrast, dramatic decrease of both plasminogen and angiostatin levels (3.8- and 5.3-folds, respectively) was shown in tissues of proliferatious form of fibroadenoma in comparison with that of the dormant type of this neoplasm. Based on the obtained results, we concluded that angiostatin, a potent vessel growth inhibitor and anti-inflammatory molecule, can play a crucial role in pathophysiology of non-cancerous breast diseases. Further studies are needed to evaluate potential diagnostic and clinical implications of these proteins for prediction and therapy of benign breast pathologies.

A Hypothesis Concerning the Biphasic Dose-response of Tumors to Angiostatin and Endostatin

This manuscript proposes a hypothesis to explain the U-shaped dose-response observed for angiostatin and other high-molecular-weight drugs in various anti-cancer bio-assays. The dose-response curves for angiostatin and endostatin (measured as suppression of tumor growth) go through an optimum (i.e., minimum tumor growth) and then becomes less effective at higher doses. The literature suggests that at lower doses the primary action of these high-molecular-weight drugs is to counteract the angiogenic effects of vascular endothelial growth factor (VEGF). To do this, the drugs must pass out of the blood vessel and enter the extra-cellular matrix (ECM) where VEGF induces the growth and fusion of tip cells. Ironically, VEGF actually facilitates access of the drugs to the ECM by making the vascular endothelium leaky. At higher doses, the high-molecular-weight drugs seem to reverse VEGF-induced permeability of the endothelium. Thus, at high dose rates, it is hypothesized that the drugs are not able to enter the ECM and block the angiogenic effects of VEGF there. As a result, high doses of the drugs do not suppress vascularization of the tumor or tumor growth. Moreover, if the permeability of the vessels is suppressed, the VEGF released by the stroma is concentrated in the ECM where it amplifies the angiogenic activity around the tumor.

[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.

The angiogenic asset of soft tissue sarcomas: a new tool to discover new therapeutic targets

STS (soft tissue sarcomas) are rare malignant tumours deriving from cells of mesenchymal origin and represent only 1% of all malignant neoplasms. It has been extensively demonstrated that angiogenesis has an important role in cancer malignancy. Particularly, a lot of studies demonstrate the importance of angiogenesis in the development of carcinomas, whereas little is known about the role of angiogenesis in sarcomas and especially in STS. This review aims at summarizing the new discoveries about the nature and the importance of angiogenesis in STS and the new possible therapeutic strategies involved. Only a few studies concerning STS focus on tumour neovascularization and proangiogenic factors and look for a correlation with the patients prognosis/survival. These studies demonstrate that intratumoural MVD (microvessels density) may not accurately represent the angiogenic capacity of STS. Nevertheless, this does not exclude the possibility that angiogenesis could be important in STS. The importance of neoangiogenesis in soft tissue tumours is confirmed by the arising number of publications comparing angiogenesis mediators with clinical features of patients with STS. The efficacy of anti-angiogenic therapies in other types of cancer is well documented. The understanding of the involvement of the angiogenic process in STS, together with the necessity to improve the therapy for this often mortal condition, prompted the exploration of anti-tumour compounds targeting this pathway. In conclusion, this review emphasizes the importance to better understand the mechanisms of angiogenesis in STS in order to subsequently design-specific target therapies for this group of poorly responding tumours.

Gelatinase B/MMP-9 in Tumour Pathogenesis and Progression

Since its original identification as a leukocyte gelatinase/type V collagenase and tumour type IV collagenase, gelatinase B/matrix metalloproteinase (MMP)-9 is now recognised as playing a central role in many aspects of tumour progression. In this review, we relate current concepts concerning the many ways in which gelatinase B/MMP-9 influences tumour biology. Following a brief outline of the gelatinase B/MMP-9 gene and protein, we analyse the role(s) of gelatinase B/MMP-9 in different phases of the tumorigenic process, and compare the importance of gelatinase B/MMP-9 source in the carcinogenic process. What becomes apparent is the importance of inflammatory cell-derived gelatinase B/MMP-9 in tumour promotion, early progression and triggering of the "angiogenic switch", the integral relationship between inflammatory, stromal and tumour components with respect to gelatinase B/MMP-9 production and activation, and the fundamental role for gelatinase B/MMP-9 in the formation and maintenance of tumour stem cell and metastatic niches. It is also apparent that gelatinase B/MMP-9 plays important tumour suppressing functions, producing endogenous angiogenesis inhibitors, promoting inflammatory anti-tumour activity, and inducing apoptosis. The fundamental roles of gelatinase B/MMP-9 in cancer biology underpins the need for specific therapeutic inhibitors of gelatinase B/MMP-9 function, the use of which must take into account and substitute for tumour-suppressing gelatinase B/MMP-9 activity and also limit inhibition of physiological gelatinase B/MMP-9 function.

Angiostatin inhibits activation and migration of neutrophils

There is a critical need to identify molecules that modulate the biology of neutrophils because activated neutrophils, though necessary for host defense, cause exuberant tissue damage through production of reactive oxygen species and increased lifespan. Angiostatin, an endogenous anti-angiogenic cleavage product of plasminogen, binds to integrin αvβ3, ATP synthase and angiomotin and its expression is increased in inflammatory conditions. We test the hypothesis that angiostatin inhibits neutrophil activation, induces apoptosis and blocks recruitment in vivo and in vitro. The data show immuno-reactivity for plasminogen/angiostatin in resting neutrophils. Angiostatin conjugated to FITC revealed that angiostatin was endocytozed by activated mouse and human neutrophils in a lipid raft-dependent fashion. Co-immunoprecipitation of human neutrophil lysates, confocal microscopy of isolated mouse and human neutrophils and functional blocking experiments showed that angiostatin complexes with flotillin-1 along with integrin αvβ3 and ATP synthase. Angiostatin inhibited fMLP-induced neutrophil polarization, as well as caused inhibition of hsp-27 phosphorylation and stabilization of microtubules. Angiostatin treatment, before or after LPS-induced neutrophil activation, inhibited phosphorylation of p38 and p44/42 MAPKs, abolished reactive oxygen species production and released the neutrophils from suppressed apoptosis, as indicated by expression of activated caspase-3 and morphological evidence of apoptosis. Finally, intravital microscopy and myeloperoxidase assay showed inhibition of neutrophil recruitment in post-capillary venules of TNFα-treated cremaster muscle in mouse. These in vitro and in vivo data demonstrate angiostatin as a broad deactivator and silencer of neutrophils and an inhibitor of their migration. These data potentially open new avenues for the development of anti-inflammatory drugs.

Angiostatin inhibits acute lung injury in a mouse model

Acute lung injury is marked by profound influx of activated neutrophils, which have delayed apoptosis, along with fluid accumulation that impairs lung function and causes high mortality. Inflammatory and antimicrobial molecules, such as reactive oxygen species from activated neutrophils with prolonged lifespan, cause tissue damage and contribute to lung dysfunction. Angiostatin, an endogenous antiangiogenic molecule, is expressed in the lavage fluid of patients with acute respiratory distress syndrome and modifies neutrophil infiltration in a mouse model of peritonitis. Our aim was to investigate the therapeutic role of angiostatin in acute lung injury. We analyzed bronchoalveolar lavage and lung tissues from C57BL/6 mouse model of Escherichia coli LPS-induced acute lung injury to assess the effects of angiostatin treatment. Subcutaneous angiostatin administered at 5 h after LPS treatment reduces histological signs of inflammation, protein accumulation, lung Gr1+ neutrophils, myeloperoxidase activity, and expression of phosphorylated p38 MAPK in lung tissues and peripheral blood neutrophils, while increasing the number of apoptotic cells in the lungs without affecting the levels of macrophage inflammatory protein-1 α, IL-1β, keratinocyte chemoattractant, and monocyte chemoattractant protein-1 in lavage and lung homogenates at 9 and 24 h after LPS treatment. In contrast, angiostatin administered intravenously 5 h after LPS treatment did not reduce histological sign of inflammation, BAL cell recruitment, and protein concentration at 9 h of LPS treatment. We conclude that angiostatin administered subcutaneously after LPS challenge inhibits acute lung inflammation up to 24 h after LPS treatment.

Surgery, wound healing, and metastasis: recent insights and clinical implications

BACKGROUND

Surgery-induced acceleration of tumour growth has been observed since several centuries.

METHODS

We reviewed recent insights from in vitro data, animal experimentation, and clinical studies on how surgery-induced wound healing or resection of a primary cancer influences the tumour-host ecosystem in patients harbouring minimal residual or metastatic disease.

RESULTS

Most of the growth factors, chemokines, and cytokines orchestrating surgical wound healing promote tumour growth, invasion, or angiogenesis. In addition, resection of a primary tumour may accelerate synchronous metastatic growth. In the clinical setting, indirect evidence supports the relevance of the above findings. Randomized clinical trials are underway comparing resection versus observation in metastatic breast and colon cancer with asymptomatic primary tumours.

CONCLUSIONS

In depth knowledge of how surgical intervention alters the tumour-host-metastasis communicating ecosystems could have important implications for clinical decision making in patients with synchronous metastatic disease and for the design and timing of multimodality treatment strategies.

Impaired coronary collateral growth in the metabolic syndrome is in part mediated by matrix metalloproteinase 12-dependent production of endostatin and angiostatin

OBJECTIVE

We have previously shown that transient coronary artery occlusion stimulated coronary collateral growth (CCG) in healthy (Sprague Dawley) but not in metabolic syndrome (JCR:LA-cp [JCR] ) rats. Here, we sought to determine whether matrix metalloproteinases (MMPs) negatively regulate CCG in the metabolic syndrome via release of endostatin and angiostatin.

APPROACH AND RESULTS

Rats underwent transient, repetitive left anterior descending occlusion and resultant myocardial ischemia (RI) for 0 to 10 days. CCG was measured in the collateral-dependent and normal zones using microspheres, MMP activation by Western blot, and endostatin and angiostatin by ELISA on days 0, 3, 6, 9, or 10 of RI. Endostatin and angiostatin were increased in JCR but not in Sprague Dawley rats on days 6 and 9 of RI. Increased endostatin and angiostatin correlated with increased MMP12 (≈ 4-fold) activation in JCR but not in Sprague Dawley rats on days 6 and 9 of RI. Inhibition of MMP12 in JCR rats nearly completely blocked endostatin (≈ 85%) and angiostatin (≈ 90%) generation and significantly improved CCG (collateral-dependent zone flow was ≈ 66% of normal zone flow versus ≈ 12% for JCR RI).

CONCLUSIONS

Compromised CCG in the metabolic syndrome is, in large part, because of increased MMP12 activation and consequent increased generation of endostatin and angiostatin, which inhibits late-stage collateral remodeling.

A monoclonal antibody against F1-F0 ATP synthase beta subunit

As a transmembrane enzyme, ATP synthase plays an important role in energy metabolism of organ tissues, as well as in tumors. In this study we generated a monoclonal antibody, 6G11, to the catalytic subunit of F1-F0 ATP synthase (ATP5B). The SDS-PAGE result demonstrated that the hybridoma clone had a molecular weight of 50 and 27 kDa components that could be the heavy and light chains of the monoclonal antibody, respectively. Chromosome analysis of the hybridoma clone proved that they had 98 to 102 chromosomal numbers that were the sum of the SP2/0 and spleen cells. Western blot assay revealed that the hybridoma clone reacted specifically with the ATP synthase beta subunit, but not with other proteins. In addition, the subclass of the hybridoma clone was identified as IgG1 by capture ELISA. Furthermore, it demonstrated that the antibody retained stability after half a year. These results indicated that the hybridoma clone 6G11 was a monoclonal antibody with significant stability and special reactivity to ATP5B antigen.

Angiostatin inhibits endothelial MMP-2 and MMP-14 expression: a hypoxia specific mechanism of action

Angiostatin is an angiogenesis inhibitor in part generated by and released from platelets. Since platelets upon thrombus formation can give rise to areas of hypoxia, we investigated the effects of angiostatin on endothelial cell migration and apoptosis during hypoxia. Human microvascular endothelial cells (HMVEC-L) were exposed to angiostatin under normoxic or hypoxic conditions. Apoptosis was measured by flow-cytometry. HMVEC-L migration was studied using a modified Boyden Chamber assay, in which migration is MMP-dependent. MMP-2, MMP-14, and VEGF levels were measured using immunoblot, Q-PCR and ELISA. During hypoxia HMVEC-L were protected from angiostatin-induced apoptosis due to increased hypoxia-induced VEGF expression. However, MMP-dependent migration of HMVEC-L was inhibited by angiostatin under hypoxic but not normoxic conditions. Angiostatin decreased MMP-2 at the gene and protein levels only in HMVEC-L exposed to hypoxia. A similar result was obtained for MMP-14. Higher angiostatin concentrations, as would be seen during thrombosis, induced HMVEC-L apoptosis, which was not rescued by VEGF. Under hypoxic conditions angiostatin's primary anti-angiogenic mechanism is likely inhibition of endothelial cell MMP-dependent endothelial cell migration. Only at higher concentrations does angiostatin induce endothelial cell death. This study identifies a novel angiostatin anti-angiogenesis mechanism that is only triggered under pathological-like conditions.

Exercise training and peripheral arterial disease

Peripheral arterial disease (PAD) is a common vascular disease that reduces blood flow capacity to the legs of patients. PAD leads to exercise intolerance that can progress in severity to greatly limit mobility, and in advanced cases leads to frank ischemia with pain at rest. It is estimated that 12 to 15 million people in the United States are diagnosed with PAD, with a much larger population that is undiagnosed. The presence of PAD predicts a 50% to 1500% increase in morbidity and mortality, depending on severity. Treatment of patients with PAD is limited to modification of cardiovascular disease risk factors, pharmacological intervention, surgery, and exercise therapy. Extended exercise programs that involve walking approximately five times per week, at a significant intensity that requires frequent rest periods, are most significant. Preclinical studies and virtually all clinical trials demonstrate the benefits of exercise therapy, including improved walking tolerance, modified inflammatory/hemostatic markers, enhanced vasoresponsiveness, adaptations within the limb (angiogenesis, arteriogenesis, and mitochondrial synthesis) that enhance oxygen delivery and metabolic responses, potentially delayed progression of the disease, enhanced quality of life indices, and extended longevity. A synthesis is provided as to how these adaptations can develop in the context of our current state of knowledge and events known to be orchestrated by exercise. The benefits are so compelling that exercise prescription should be an essential option presented to patients with PAD in the absence of contraindications. Obviously, selecting for a lifestyle pattern that includes enhanced physical activity prior to the advance of PAD limitations is the most desirable and beneficial.

Extracellular matrix and fibroblast communication following myocardial infarction

The extracellular matrix (ECM) provides structural support by serving as a scaffold for cells, and as such the ECM maintains normal tissue homeostasis and mediates the repair response following injury. In response to myocardial infarction (MI), ECM expression is generally upregulated in the left ventricle (LV), which regulates LV remodeling by modulating scar formation. The ECM directly affects scar formation by regulating growth factor release and cell adhesion and indirectly affects scar formation by regulating the inflammatory, angiogenic, and fibroblast responses. This review summarizes the current literature on ECM expression patterns and fibroblast mechanisms in the myocardium, focusing on the ECM response to MI. In addition, we discuss future research areas that are needed to better understand the molecular mechanisms of ECM action, both in general and as a means to optimize infarct healing.

Low lipoprotein(a) concentration is associated with cancer and all-cause deaths: a population-based cohort study (the JMS cohort study)

BACKGROUND

Experimental studies support the anti-neoplastic effect of apo(a), but several clinical studies have reported contradictory results. The purpose of this study was to determine whether a low lipoprotein(a) [Lp(a)] concentration is related to mortality from major causes of death, especially cancer.

METHODS

The subjects were 10,413 participants (4,005 men and 6,408 women) from a multi-center population-based cohort study in Japan (The Jichi Medical School cohort study). The average age at registration was 55.0 years, and the median observation period was 4,559 days. As the estimated hazard ratio was high for both the low and very high Lp(a) levels, we defined two Lp(a) groups: a low Lp(a) group [Lp(a)<80 mg/L] and an intermediate-to-high Lp(a) group [Lp(a) ≥ 80]. Participants who died from malignant neoplasms (n = 316), cardiovascular disease (202), or other causes (312) during the observation period were examined.

RESULTS

Cumulative incidence plots showed higher cumulative death rates for the low Lp(a) group than for the intermediate-to-high Lp(a) group for all-cause, cancer, and miscellaneous-cause deaths (p<0.001, p = 0.03, and p = 0.03, respectively). Cox proportional hazards analyses with the sex and age of the participants, body mass index, and smoking and drinking histories as covariates showed that a low Lp(a) level was a significant risk for all-cause, cancer, and miscellaneous-cause deaths (p<0.001, p = 0.003, and p = 0.01, respectively). The hazard ratio (95% CI) [1.48, 1.15-1.92] of a low Lp(a) level for cancer deaths was almost the same as that for a male sex (1.46, 1.00-2.13).

CONCLUSIONS

This is the first report to describe the association between a low Lp(a) level and all-cause or cancer death, supporting the anti-neoplastic effect of Lp(a). Further epidemiological studies are needed to confirm the present results.

The β-Chain of Cell Surface F 0 F 1 ATPase Modulates ApoA-I and HDL Transcytosis Through Aortic Endothelial Cells

Objective—

Both HDLs and their major protein constituent apolipoprotein A-I (apoA-I) are transported through aortic endothelial cells. The knock-down of the ATP-binding cassette transporters A1 (ABCA1), G1 (ABCG1), and of the scavenger receptor-BI (SR-BI) diminishes but does not completely block the transport of apoA-I or HDL, so that other receptors appear to be involved. The ectopic β-chain of F 0 F 1 ATPase has been previously characterized as an apoA-I receptor, triggering HDL internalization in hepatocytes.

Methods and Results—

The ectopic presence of the β-chain of F 0 F 1 ATPase on the surface of endothelial cells was confirmed by cell surface biotinylation. RNA-interference and the F 0 F 1 ATPase inhibitory peptide IF 1 reduced cell binding of apoA-I but not HDL, as well as association and transendothelial transport of both apoA-I and HDL. Furthermore, apoA-I stimulated F 0 F 1 ATPase catalyzed ATP hydrolysis. The generated ADP as well as apoA-I stimulated the binding, cell association, and internalization of HDL. Both in the presence and absence of ADP inhibition of the purinergic receptor P2Y 12 but not P2Y 1 decreased the cell association of apoA-I and HDL. Coinhibition of β-ATPase and ABCA1 had no additive effects on the cell association and transport of apoA-I. Reduced cell association of HDL by β-ATPase inhibition was not further decreased by additional knock-down of ABCG1 or SR-BI.

Conclusion—

Binding of apoA-I to ectopic F 0 F 1 ATPase triggers the generation of ADP, which via activation of the purinergic receptor P2Y 12 stimulates the uptake and transport of HDL and initially lipid-free apoA-I by endothelial cells.

Proteolytic networks in cancer

Proteases are important for multiple processes during malignant progression, including tumor angiogenesis, invasion and metastasis. Recent evidence reveals that tumor-promoting proteases function as part of an extensive multidirectional network of proteolytic interactions, in contrast to the unidirectional caspase cascade. These networks involve different constituents of the tumor microenvironment and key proteases, such as cathepsin B, urokinase-type plasminogen activator and several matrix metalloproteinases, occupy central nodes for amplifying proteolytic signals passing through the network. The proteolytic network interacts with other important signaling pathways in tumor biology, involving chemokines, cytokines, and kinases. Viewing these proteolytic interactions as a system of activating and inhibiting reactions provides insight into tumor biology and reveals relevant pharmaceutical targets. This review examines recent advances in understanding proteases in cancer and summarizes how the network of activity is co-opted to promote tumor progression.

ADAMTS-2 functions as anti-angiogenic and anti-tumoral molecule independently of its catalytic activity

ADAMTS-2 is a metalloproteinase that plays a key role in the processing of fibrillar procollagen precursors into mature collagen molecules by excising the amino-propeptide. We demonstrate that recombinant ADAMTS-2 is also able to reduce proliferation of endothelial cells, and to induce their retraction and detachment from the substrate resulting in apoptosis. Dephosphorylation of Erk1/2 and MLC largely precedes the ADAMTS-2 induced morphological alterations. In 3-D culture models, ADAMTS-2 strongly reduced branching of capillary-like structures formed by endothelial cells and their long-term maintenance and inhibited vessels formation in embryoid bodies (EB). Growth and vascularization of tumors formed in nude mice by HEK 293-EBNA cells expressing ADAMTS-2 were drastically reduced. A similar anti-tumoral activity was observed when using cells expressing recombinant deleted forms of ADAMTS-2, including catalytically inactive enzyme. Nucleolin, a nuclear protein also found to be associated with the cell membrane, was identified as a potential receptor mediating the antiangiogenic properties of ADAMTS-2.

Two Endogenous Antiangiogenic Inhibitors, Endostatin and Angiostatin, Demonstrate Biphasic Curves in their Antitumor Profiles

Angiogenesis refers to growth of blood vessels from pre-existing ones. In 1971, Folkman proposed that by choking off the blood supply to tumors, they are starved, leading to their demise. A few years ago, the monoclonal antibody Avastin became the first antiangiogenic biological approved by FDA, for treatment of cancer patients. Two other antiangiogenic endogenous protein fragments were isolated in Folkman's laboratory more than a decade ago. Here, we present a short review of data demonstrating that angiostatin and endostatin display a biphasic antitumor dose-response. This behavior is common among a large number of antiangiogenic agents and the reduced effectiveness of antiangiogenic agents at high dose rates may be due to suppression of growth of new vessels carrying the agent into the critical region around the tumor.

Anti-angiogenic effect of high-dose resveratrol in a swine model of metabolic syndrome

BACKGROUND

Resveratrol has been reported to induce angiogenesis in ischemic tissue. We hypothesized that high-dose resveratrol would improve native angiogenesis in a swine model of metabolic syndrome and chronic myocardial ischemia.

METHODS

Yorkshire swine were fed a normal diet (Control, n = 7), hypercholesterolemic diet (HCD, n = 7), or hypercholesterolemic diet with supplemental resveratrol (100 mg/kg/day orally, HCD-R; n = 7) beginning 1 month prior to surgery. Chronic ischemia was created by placing an ameroid constrictor on the left circumflex coronary artery. After 7 weeks, swine underwent functional MRI, coronary angiography, and serum and heart tissue harvest for analysis.

RESULTS

HCD-R animals had lower body mass index (P < .001), total cholesterol (P < .001), low-density lipoprotein (LDL; P < .001), blood glucose levels (P < .001), and systolic blood pressure (P = .03) than HCD animals. There was no difference in regional myocardial function at 7 weeks (P = .25). Coronary angiograms revealed no difference in Rentrop collateral scores (P = .68). Staining for platelet endothelial cell adhesion molecule-1 demonstrated higher capillary density in the Control group (versus HCD and HCD-R; P = .02). Immunoblotting demonstrated decreased expression of the pro-angiogenic protein vascular endothelial (VE)-cadherin (P = .002) and an increase in anti-angiogenic proteins angiostatin (P = .001) and thrombospondin (P = .02) in the HCD and HCD-R groups. Matrix metalloprotease 2 (MMP 2; P = .47) and MMP 9 (P = .12) were not different among groups.

CONCLUSION

Supplemental resveratrol positively modified cardiovascular risk factors including body mass index, cholesterol, glucose tolerance, and systolic blood pressure. However, it did not increase native collateral formation in the ischemic myocardium. This may be a result of increased angiostatin and thrombospondin leading to decreased expression of VE-cadherin and other pro-angiogenic factors.

Pigment epithelium-derived factor binds to cell-surface F(1)-ATP synthase

Pigment epithelium-derived factor (PEDF), a potent blocker of angiogenesis in vivo, and of endothelial cell migration and tubule formation, binds with high affinity to an as yet unknown protein on the surfaces of endothelial cells. Given that protein fingerprinting suggested a match of a approximately 60 kDa PEDF-binding protein in bovine retina with Bos taurus F(1)-ATP synthase beta-subunit, and that F(1)F(o)-ATP synthase components have been identified recently as cell-surface receptors, we examined the direct binding of PEDF to F(1). Size-exclusion ultrafiltration assays showed that recombinant human PEDF formed a complex with recombinant yeast F(1). Real-time binding as determined by surface plasmon resonance demonstrated that yeast F(1) interacted specifically and reversibly with human PEDF. Kinetic evaluations revealed high binding affinity for PEDF, in agreement with PEDF affinities for endothelial cell surfaces. PEDF blocked interactions between F(1) and angiostatin, another antiangiogenic factor, suggesting overlapping PEDF-binding and angiostatin-binding sites on F(1). Surfaces of endothelial cells exhibited affinity for PEDF-binding proteins of approximately 60 kDa. Antibodies to F(1)beta-subunit specifically captured PEDF-binding components in endothelial plasma membranes. The extracellular ATP synthesis activity of endothelial cells was examined in the presence of PEDF. PEDF significantly reduced the amount of extracellular ATP produced by endothelial cells, in agreement with direct interactions between cell-surface ATP synthase and PEDF. In addition to demonstrating that PEDF binds to cell-surface F(1), these results show that PEDF is a ligand for endothelial cell-surface F(1)F(o)-ATP synthase. They suggest that PEDF-mediated inhibition of ATP synthase may form part of the biochemical mechanisms by which PEDF exerts its antiangiogenic activity.

Tumor angiogenesis: insights and innovations

Angiogenesis is a vital process resulting in the formation of new blood vessels. It is normally a highly regulated process that occurs during human development, reproduction, and wound repair. However, angiogenesis can also become a fundamental pathogenic process found in cancer and several other diseases. To date, the inhibition of angiogenesis has been researched at both the bench and the bedside. While several studies have found moderate improvements when treating with angiogenesis inhibitors, greater success is being seen when the inhibition of angiogenesis is combined with other traditional forms of available therapy. This review summarizes several important angiogenic factors, examines new research and ongoing clinical trials for such factors, and attempts to explain how this new knowledge may be applied in the fight against cancer and other angiogenic-related diseases.

Functional genomics of endothelial cells treated with anti-angiogenic or angiopreventive drugs

Angiogenesis is a highly regulated physiological process that has been studied in considerable detail given its importance in several chronic pathologies. Many endogenous factors and hormones intervene in the regulation of angiogensis and classical as well as targeted drugs have been developed for its control. Angiogenesis inhibition has come off the bench and entered into clinical application for cancer therapy, particularly for metastatic disease. While the clinical benefit is currently in terms of months, preclinical data suggest that novel drugs and drug combinations could lead to substantial improvement. The many targets of endogenous angiogenesis inhibitors reflect the complexity of the process; in contrast, current clinical therapies mainly target the vascular endothelial growth factor system. Cancer chemopreventive compounds can retard tumor insurgence and delay or prevent metastasis and many of these molecules hinder angiogenesis, a mechanism that we termed angioprevention. Angiopreventive drugs appear to prevalently act through the inhibition of the pro-inflammatory and anti-apoptotic player NFkappaB, thus contrasting inflammation dependent angiogenesis. Relatively little is known concerning the effects of these angiogenesis inhibitors on gene expression of endothelial cells, the main target of many of these molecules. Here we provide an exhaustive list of anti-angiogenic molecules, and summarize their effects, where known, on the transcriptome and functional genomics of endothelial cells. The regulation of specific genes can be crucial to preventive or therapeutic intervention. Further, novel targets might help to circumvent resistance to anti-angiogenic therapy. The studies we review are relevant not only to cancer but also to other chronic degenerative diseases involving endothelial cells, such as cardiovascular disorders, diabetes, rheumatoid arthritis and retinopaties, as well as vessel aging.

Angiogenesis and vascular function in the ovary

Ovarian function is dependent on the establishment and continual remodelling of a complex vascular system. This enables the follicle and/or corpus luteum (CL) to receive the required supply of nutrients, oxygen and hormonal support as well as facilitating the release of steroids. Moreover, the inhibition of angiogenesis results in the attenuation of follicular growth, disruption of ovulation and drastic effects on the development and function of the CL. It appears that the production and action of vascular endothelial growth factor A (VEGFA) is necessary at all these stages of development. However, the expression of fibroblast growth factor 2 (FGF2) in the cow is more dynamic than that of VEGFA with a dramatic upregulation during the follicular–luteal transition. This upregulation is then likely to initiate intense angiogenesis in the presence of high VEGFA levels. Recently, we have developed a novel ovarian physiological angiogenesis culture system in which highly organised and intricate endothelial cell networks are formed. This system will enable us to elucidate the complex inter-play between FGF2 and VEGFA as well as other angiogenic factors in the regulation of luteal angiogenesis. Furthermore, recent evidence indicates that pericytes might play an active role in driving angiogenesis and highlights the importance of pericyte–endothelial interactions in this process. Finally, the targeted promotion of angiogenesis may lead to the development of novel strategies to alleviate luteal inadequacy and infertility.

Effects of human recombinant PEDF protein and PEDF-derived peptide 34-mer on choroidal neovascularization

PURPOSE

Pigment epithelium-derived factor (PEDF) is a serpin with antiangiogenic properties. Previously, the authors showed that PEDF injected into the subconjunctiva reaches the choroid. Here, they examined the effects of PEDF polypeptide fragments on vessel sprouting and on choroidal neovascularization (CNV) after subconjunctival administration.

METHODS

Recombinant human PEDF (rhuPEDF) was cleaved at its serpin-exposed loop by limited chymotrypsin proteolysis. Synthetic PEDF peptides 34-mer (Asp(44)-Asn(77)) and 44-mer (Val(78)-Thr(121)) were used. Ex vivo chick aortic vessel sprouting assays were performed. CNV was induced in rats by laser injury of Bruch's membrane. Daily subconjunctival injections (0.01-10 pmol/d protein) were performed for 5 days starting at day of injury or at the seventh day after injury. New vessel volumes were quantified using optical sections of choroid/RPE flat-mounts labeled with isolectin-Ib4. PEDF distribution was evaluated by immunofluorescence of choroid/RPE/retina cross-sections.

RESULTS

Full-length rhuPEDF, cleaved rhuPEDF, or peptide 34-mer exhibited ex vivo antiangiogenic activity, but peptide 44-mer was inefficient. PEDF immunostaining around CNV lesions diminished after laser injury. Subconjunctival administration of rhuPEDF or 34-mer at 0.1 pmol/d decreased CNV lesion volumes by 52% and 47%, respectively, whereas those of 44-mer were similar to vehicle injections. Doses of 0.1 and 1 pmol/d rhuPEDF decreased fully developed CNV complex volumes by 45% and 50%, respectively, compared with vehicle injections.

CONCLUSIONS

A functional region for the inhibition of vessel sprouting and CNV resides within the 34-mer region of PEDF. Furthermore, subconjunctival administration of optimal range dosages of rhuPEDF or 34-mer can suppress and regress rat CNV lesions, demonstrating that these agents reach the choroid/RPE complex as functionally active molecules.

Biology of angiogenesis and invasion in glioma

Treatment of adult brain tumors, in particular glioblastoma, remains a significant clinical challenge, despite modest advances in surgical technique, radiation, and chemotherapeutics. The formation of abnormal, dysfunctional tumor vasculature and glioma cell invasion along white matter tracts are believed to be major components of the inability to treat these tumors effectively. Recent insight into the fundamental processes governing glioma angiogenesis and invasion provide a renewed hope for development of novel strategies aimed at reducing the morbidity of this uniformly fatal disease. In this review, we discuss background biology of the blood brain barrier and its pertinence to blood vessel formation and tumor invasion. We will then focus our attention on the biology of glioma angiogenesis and invasion, and the key mediators of these processes. Last, we will briefly discuss recent and ongoing clinical trials targeting mediators of angiogenesis or invasion in glioma patients. The findings provide a renewed hope for those endeavoring to improve treatment of patients with glioma by providing a novel set of rational targets for translational drug discovery.

Drug resistance associated with antiangiogenesis therapy

Neovascularization is one of the hallmarks associated with tumor growth. In the recent years, a number of angiogenesis inhibitors have been approved for clinical use in cancer patients. However, the efficacy of antiangiogenic therapy is in most cases short-lasting, with likely drug resistance developing within a few months. It is becoming clear also that there are a subset of malignant tumors that are inherently resistant to angiogenesis inhibition. The knowledge regarding resistance mechanisms towards angiogenesis inhibitors is still evolving and here we propose some theories and in some cases provide experimental evidence.

Angiostatin regulates the expression of antiangiogenic and proapoptotic pathways via targeted inhibition of mitochondrial proteins

Angiostatin, a proteolytic fragment of plasminogen, is a potent endogenous antiangiogenic agent. The molecular mechanisms governing angiostatin's antiangiogenic and antitumor effects are not well understood. Here, we report the identification of mitochondrial compartment as the ultimate target of angiostatin. After internalization of angiostatin into the cell, at least 2 proteins within the mitochondria bind this molecule: malate dehydrogenase, a member of Krebs cycle, and adenosine triphosphate synthase. In vitro and in vivo studies revealed differential regulation of key prosurvival and angiogenesis-related proteins in angiostatin-treated tumors and tumor-endothelium. Angiostatin induced apoptosis via down-regulation of mitochondrial BCL-2. Angiostatin treatment led to down-regulation of c-Myc and elevated levels of another key antiangiogenic protein, thrombospondin-1, reinforcing its antitumor and antiangiogenic effects. Further evidence is provided for reduced recruitment and infiltration of bone marrow-derived macrophages in angiostatin-treated tumors. The observed effects of angiostatin were restricted to the tumor site and were not observed in other major organs of the mice, indicating unique tumor specific bioavailability. Together, our data suggest mitochondria as a novel target for antiangiogenic therapy and provide mechanistic insights to the antiangiogenic and antitumor effects of angiostatin.

The hemopexin domain of MMP-9 inhibits angiogenesis and retards the growth of intracranial glioblastoma xenograft in nude mice

Matrix Metalloproteinase-9 (MMP-9) consists of a prodomain, catalytic domain with 3 fibronectin-like type II modules and C-terminal hemopexin-like (PEX) domain. These domains play distinct roles in terms of proteolytic activity, substrate binding and interaction with inhibitors and receptors. To assess the potential of the MMP-9-PEX domain to interfere with tumor progression, we stably transfected human glioblastoma cells with an expression vector containing a cDNA sequence of the MMP-9-PEX. The selected clones exhibited decreased MMP-9 activity and reduced invasive capacity. We assessed how secretion of MMP-9-PEX by glioblastoma cells affects angiogenic capabilities of human microvascular endothelial cells (HMECs) in vitro. MMP-9-PEX conditioned medium treatment caused a reduction in migration of HMECs and inhibited capillary-like structure formation in association with suppression of vascular endothelial growth factor (VEGF) secretion and VEGF receptor-2 protein level. The suppression of HMECs survival by conditioned medium from MMP-9-PEX stable transfectants was associated with apoptosis induction characterized by an increase in cells with a sub-G0/G1 content, fragmentation of DNA, caspase-3, -8 and -9 activation and poly (ADP-ribose) polymerase (PARP) cleavage. A significant tumor growth inhibition was observed in intracranial implants of MMP-9-PEX stable transfectants in nude mice with attenuation of CD31 and MMP-9 protein expression. These results demonstrate that MMP-9-PEX inhibits angiogenic features of endothelial cells and retards intracranial glioblastoma growth.