Induction of vascular endothelial growth factor by nitric oxide in human glioblastoma and hepatocellular carcinoma cells

Effects of Topic Delivery of an Inhibitor of Serine Racemase on Laser-Induced Choroidal Vasculopathy

Purpose

Intravitreal injection of anti-VEGF antibodies remains the primary therapy for exudative age-related macular degeneration (exAMD), although its efficacy is limited. Previous research has demonstrated that both a loss-of-function mutation of srr and the intravenous injection of a serine racemase inhibitor, L-aspartic acid β-hydroxamate (L-ABH), significantly inhibit laser-induced choroidal neovascularization (CNV) in mice. Given that L-ABH is a small molecule, this study investigated the effects of L-ABH administered via eye drops on CNV, aiming to develop a noninvasive treatment strategy for exAMD.

Methods

CNV models in mice and rhesus macaques were established through laser photocoagulation. Seven monkeys were randomly assigned to receive either saline solution or L-ABH eye drops. Intraperitoneal or intravenous injection of fluorescein characterized CNV in both mice and monkeys. Fluorescein fundus angiography was used to assess leakage, whereas optical coherence tomography measured retinal thickness in the monkeys.

Results

L-ABH eye drops significantly reduced fluorescein leakage in laser-injured mice (P < 0.001 compared to saline). In laser-injured rhesus macaques, the average percent changes in leakage areas treated with L-ABH were 2.5% ± 25.8% (P = 0.004) and 1.5% ± 75.7% (P = 0.023 compared to saline solution) on day 14 and day 28, respectively. However, L-ABH eye drops did not significantly affect the number of grade IV laser spots or retinal thickness, whereas bevacizumab did.

Conclusions

This study demonstrates the potential efficacy of an SRR inhibitor in two animal models of laser-induced CNV.

Translational Relevance

This represents the first investigation into the effects of topical delivery of an SRR inhibitor on CNV.

Nitroproteomics is instrumental for stratification and targeted treatments of astrocytoma patients: expert recommendations for advanced 3PM approach with improved individual outcomes

Protein tyrosine nitration is a selectively and reversible important post-translational modification, which is closely related to oxidative stress. Astrocytoma is the most common neuroepithelial tumor with heterogeneity and complexity. In the past, the diagnosis of astrocytoma was based on the histological and clinical features, and the treatment methods were nothing more than surgery-assisted radiotherapy and chemotherapy. Obviously, traditional methods short falls an effective treatment for astrocytoma. In late 2021, the World Health Organization (WHO) adopted molecular biomarkers in the comprehensive diagnosis of astrocytoma, such as IDH-mutant and DNA methylation, which enabled the risk stratification, classification, and clinical prognosis prediction of astrocytoma to be more correct. Protein tyrosine nitration is closely related to the pathogenesis of astrocytoma. We hypothesize that nitroproteome is significantly different in astrocytoma relative to controls, which leads to establishment of nitroprotein biomarkers for patient stratification, diagnostics, and prediction of disease stages and severity grade, targeted prevention in secondary care, treatment algorithms tailored to individualized patient profile in the framework of predictive, preventive, and personalized medicine (PPPM; 3P medicine). Nitroproteomics based on gel electrophoresis and tandem mass spectrometry is an effective tool to identify the nitroproteins and effective biomarkers in human astrocytomas, clarifying the biological roles of oxidative/nitrative stress in the pathophysiology of astrocytomas, functional characteristics of nitroproteins in astrocytomas, nitration-mediated signal pathway network, and early diagnosis and treatment of astrocytomas. The results finds that these nitroproteins are enriched in mitotic cell components, which are related to transcription regulation, signal transduction, controlling subcellular organelle events, cell perception, maintaining cell homeostasis, and immune activity. Eleven statistically significant signal pathways are identified in astrocytoma, including remodeling of epithelial adherens junctions, germ cell-sertoli cell junction signaling, 14-3-3-mediated signaling, phagosome maturation, gap junction signaling, axonal guidance signaling, assembly of RNA polymerase III complex, and TREM1 signaling. Furthermore, protein tyrosine nitration is closely associated with the therapeutic effects of protein drugs, and molecular mechanism and drug targets of cancer. It provides valuable data for studying the protein nitration biomarkers, molecular mechanisms, and therapeutic targets of astrocytoma towards PPPM (3P medicine) practice.

Supplementary Information

The online version contains supplementary material available at 10.1007/s13167-023-00348-y.

The Triple Crown: NO, CO, and H2S in cancer cell biology

Nitric oxide (NO), carbon monoxide (CO), and hydrogen sulfide (H2S) are three endogenously produced gases with important functions in the vasculature, immune defense, and inflammation. It is increasingly apparent that, far from working in isolation, these three exert many effects by modulating each other's activity. Each gas is produced by three enzymes, which have some tissue specificities and can also be non-enzymatically produced by redox reactions of various substrates. Both NO and CO share similar properties, such as activating soluble guanylate cyclase (sGC) to increase cyclic guanosine monophosphate (cGMP) levels. At the same time, H2S both inhibits phosphodiesterase 5A (PDE5A), an enzyme that metabolizes sGC and exerts redox regulation on sGC. The role of NO, CO, and H2S in the setting of cancer has been quite perplexing, as there is evidence for both tumor-promoting and pro-inflammatory effects and anti-tumor and anti-inflammatory activities. Each gasotransmitter has been found to have dual effects on different aspects of cancer biology, including cancer cell proliferation and apoptosis, invasion and metastasis, angiogenesis, and immunomodulation. These seemingly contradictory actions may relate to each gas having a dual effect dependent on its local flux. In this review, we discuss the major roles of NO, CO, and H2S in the context of cancer, with an effort to highlight the dual nature of each gas in different events occurring during cancer progression.

Roles of nitric oxide and polyamines in brain tumor growth

Nitric oxide (NO) and polyamines: putrescine, spermidine and spermine, are key arginine metabolites in mammalian tissues that play critical roles i.a. in regulation of vascular tone (NO), and cell cycle regulation (polyamines). In the brain, both classes of molecules additionally have neuromodulatory and neuroprotective potential, and NO also a neurotoxic potential. Here we review evidence that brain tumors use the NO- and polyamine-synthesizing machineries to the benefit of their differentiation and growth from healthy glia and neurons. With a few exceptions, brain tumors show increased activities of one or all of the three arginine (Arg) to NO-converting nitric oxide synthase (NOS) isoforms (iNOS, eNOS, nNOS), but also elevated activities of polyamines-generating and modifying enzymes: arginase I/II, ornithine decarboxylase and spermidine/spermine N¹-acetyltransferase. The degree of stimulation of NO- and polyamine synthesis often correlates with brain tumor malignancy. Excess NO, but also spermine, spermidine and their N¹-acetylated forms, are tumor- and context-dependently involved in angiogenesis, tumor initiation and growth, and resistance to chemo- or radiotherapy. Hypothetically, increased demand for NO and/or polyamines is likely to contribute to Arg auxotrophy of malignant brain tumors, albeit the causal nexus awaits experimental verification.

Treatment of pregnancies complicated by intrauterine growth restriction with nitric oxide donors increases placental expression of Epidermal Growth Factor-Like Domain 7 and improves fetal growth: A pilot study

Intrauterine growth restriction (IUGR) is a pathological condition of pregnancy with high perinatal mortality and morbidity, characterized by inadequate fetal growth associated to altered maternal hemodynamics with impaired uteroplacental blood flow and placental insufficiency. To date, iatrogenic premature delivery remains the elective therapeutic strategy. However, in recent years the possibility of a therapeutic approach with vasodilators and myorelaxants, such as nitric oxide (NO) donors, has gained interest. NO controls many endothelial cell functions, including angiogenesis and vascular permeability, by regulating the expression of angiogenic factors, such as Vascular Endothelial Growth Factor. In the present study, we investigated if treatment of pregnancies complicated by IUGR with NO donors affects the expression of Epidermal Growth Factor-Like Domain 7 (EGFL7), a secreted endothelial factor, previously demonstrated to be expressed by both endothelial and trophoblast cells and involved in proper placental development. NO donor treatment induced placental levels of EGFL7 and, in association with oral fluids, significantly improved fetal growth. Ex vivo experiments confirmed that NO donors increased expression and secretion of EGFL7 by villous explants. To specifically investigate the potential response of trophoblast cells to NO, we treated HTR8-sVneo cells with NO donors and observed induction of EGFL7 expression. Altogether, our findings indicate that NO induces endothelial and trophoblast expression of EGFL7 in the placenta and improves fetal growth, suggesting a correlation between placental levels of EGFL7 and pregnancy outcome.

Role of oxidative stress and vascular endothelial growth factor expression in pterygium pathogenesis and prevention of pterygium recurrence after surgical excision

PURPOSE

To assess the roles of oxidative stress and vascular endothelial growth factor (VEGF) in pterygium pathogenesis and prevention of pterygium recurrence after surgical excision.

METHODS

Surgically removed pterygium tissue from 35 pterygium patients and normal conjunctival samples from 15 patients matched for age and sex (used as controls) constituted the study samples. The conjunctival samples were preserved at - 80 °C until analysis. Catalase (CAT), superoxide dismutase (SOD), glutathione peroxidase (GSH) and total antioxidant (TAO) enzymatic activity and the levels of nitric oxide (NO), malondialdehyde (MDA) and VEGF were studied in both groups. To evaluate the recurrence rate after surgical excision, the pterygium patients were further subdivided into three groups according to the adjuvant therapy used to prevent recurrence. Group 1 consisted of 10 patients who were treated with 0.2 mg mitomycin-c (MMC) for 2 min. Group 2 consisted of 12 patients treated with subconjunctival bevacizumab injection after surgical removal of the pterygium. Group 3 consisted of 13 patients who underwent combined treatment with 0.2 mg of MMC for 2 min and subconjunctival bevacizumab injection. The follow-up of patients in the three groups ranged from 7 to 15 months.

RESULTS

The activities of CAT, SOD, GSH and TAO were significantly lower in pterygium samples than in normal conjunctival samples (p < 0.0001 each). The levels of MDA (p = 0.046), NO (p < 0.0001) and VEGF (p < 0.0001) were significantly higher in pterygium patients than in controls. The lowest recurrence rate after surgical excision was that of the third group.

CONCLUSIONS

Oxidative stress and VEGF could play a role in the pathogenesis of pterygium as indicated by decreased antioxidant enzymatic activity and increased levels of VEGF in the pterygium tissue and the role of MMC and anti-VEGF therapy in decreasing the recurrence rate after surgical excision.

Anti-Angiogenic Effects of Phytochemicals on miRNA Regulating Breast Cancer Progression

Several phytochemicals have been identified for their role in modifying miRNA regulating tumor progression. miRNAs modulate the expression of several oncogenes and tumor suppressor genes including the genes that regulate tumor angiogenesis. Hypoxia inducible factor-1 alpha (HIF-1α) signaling is a central axis that activates oncogenic signaling and acts as a metabolic switch in endothelial cell (EC) driven tumor angiogenesis. Tumor angiogenesis driven by metabolic reprogramming of EC is crucial for tumor progression and metastasis in many different cancers, including breast cancers, and has been linked to aberrant miRNA expression profiles. In the current article, we identify different miRNAs that regulate tumor angiogenesis in the context of oncogenic signaling and metabolic reprogramming in ECs and review how selected phytochemicals could modulate miRNA levels to induce an anti-angiogenic action in breast cancer. Studies involving genistein, epigallocatechin gallate (EGCG) and resveratrol demonstrate the regulation of miRNA-21, miRNA-221/222 and miRNA-27, which are prognostic markers in triple negative breast cancers (TNBCs). Modulating the metabolic pathway is a novel strategy for controlling tumor angiogenesis and tumor growth. Cardamonin, curcumin and resveratrol exhibit their anti-angiogenic property by targeting the miRNAs that regulate EC metabolism. Here we suggest that using phytochemicals to target miRNAs, which in turn suppresses tumor angiogenesis, should have the potential to inhibit tumor growth, progression, invasion and metastasis and may be developed into an effective therapeutic strategy for the treatment of many different cancers where tumor angiogenesis plays a significant role in tumor growth and progression.

Simvastatin prevents articular chondrocyte dedifferentiation induced by nitric oxide by inhibiting the expression of matrix metalloproteinases 1 and 13

IMPACT STATEMENT

Dedifferentiation of chondrocytes is the main character of cartilage degradation. Therefore the understanding of chondrocytes dedifferentiation is essential for arthritis therapy. However, the molecular mechanism of cartilage destroy is mostly unknown. In this work we show that simvastatin (SVT) inhibits dedifferentiation by nitric oxide by blocking the expression of matrix metalloproteinases 1 and 13. These effects of SVT on dedifferentiation suggest that SVT may be used as a drug for the cure of arthritis.

Targeting VEGF pathway to normalize the vasculature: an emerging insight in cancer therapy

Vascular normalization is a new concept of targeting angiogenesis to restore vessel structure and function and to increase blood perfusion and delivery of drugs. It has been confirmed that vascular normalization can decrease relapse and benefit other cancer therapy, including chemotherapy, radiotherapy, and immune cell therapy. The key point of this therapy is to inhibit pro-angiogenic factors and make it be balanced with anti-angiogenic factors, resulting in a mature and normal vessel characteristic. Vascular endothelial growth factor (VEGF) is a key player in the process of tumor angiogenesis, and inhibiting VEGF is a primary approach to tumor vessel normalization. Herein, we review newly uncovered mechanisms governing angiogenesis and vascular normalization of cancer and place emphasis on targeting VEGF pathway to normalize the vasculature. Also, important methods to depress VEGF pathway and make tumor vascular are discussed.

Preliminary study of microRNA-126 as a novel therapeutic target for primary hypertension

The present study aimed to explore microRNA-126 (miR-126) as a novel therapeutic target for primary hypertension. The lentiviral vector containing human immunodeficiency virus 1 (HIV-1), the miR-126 gene knockdown viral vector (lenti-miR-126-KD), and control lentiviral vector (lenti-scramble-miR) were constructed. Spontaneously hypertensive rats were randomly divided into 4 groups, which received a high dose of lenti-miR-126-KD (1×10⁸, n=5), low dose of lenti-miR-126-KD (1×10⁷, n=6), scramble-miR (5×10⁷, n=6), and PBS (n=6). Lentiviral vectors were injected into the tail vein. Data on the systolic blood pressure, diastolic pressure, mean arterial pressure, and heart rate were collected weekly. After 8 weeks of virus administration, the distribution of lentiviral vectors in different tissues was observed by fluorescence microscopy. Picric acid Sirius red and H&E staining were used to observe the target organ damage, and the ELISA kit was used to determine the serum nitric oxide (NO) content. The lentiviral vector was found to be constructed successfully. Eight weeks after the lentiviral vector injection, green fluorescent protein was observed in different tissues in each group. The blood pressure and heart rate were not significantly altered after lentiviral vector injection (P>0.05). No significant differences in the heart-to-body weight ratio among the four groups were observed (P=0.23). Picric acid Sirius red and H&E staining revealed that there was no significant difference in morphology among the four groups. No significant difference in the serum NO level among the four groups was noted (P=0.23). The miR-126 gene knockdown lentiviral vector was constructed successfully. No significant antihypertensive effect was observed by the knockdown of miR-126 for the treatment of primary hypertension. The target organs were not protected significantly after the treatment. The increased level of miR-126 expression in hypertensive patients may be due to a compensatory mechanism.

Serine racemase deficiency attenuates choroidal neovascularization and reduces nitric oxide and VEGF levels by retinal pigment epithelial cells

Choroidal neovascularization (CNV) is a leading cause of blindness in age-related macular degeneration. Production of vascular endothelial growth factor (VEGF) and macrophage recruitment by retinal pigment epithelial cells (RPE) significantly contributes to the process of CNV in an experimental CNV model. Serine racemase (SR) is expressed in retinal neurons and glial cells, and its product, d-serine, is an endogenous co-agonist of N-methyl-d-aspartate receptor. Activation of the receptor results in production of nitric oxide (^. NO), a molecule that promotes retinal and choroidal neovascularization. These observations suggest possible roles of SR in CNV. With laser-injured CNV mice, we found that inactivation of SR-coding gene (Srr_null ) significantly reduced CNV volume, neovascular density, and invading macrophages. We exploited the underlying mechanism in vivo and ex vivo. RPE from wild-type (WT) mice expressed SR. To explore the possible downstream target of SR inactivation, we showed that choroid/RPE homogenates extracted from laser-injured Srr_null mice contained less inducible nitric oxide synthase and decreased phospho-VEGFR2 compared to amounts in WT mice. In vitro, inflammation-primed WT RPEs expressed more inducible NOS, produced more^. NO and VEGF than did inflammation-primed Srr_null RPEs. When co-cultured with inflammation-primed Srr_null RPE, significantly fewer RF/6A-a cell line of choroidal endothelial cell, migrated to the opposite side of the insert membrane than did cells co-cultured with pre-treated WT RPE. Altogether, SR deficiency reduces RPE response to laser-induced inflammatory stimuli, resulting in decreased production of a cascade of pro-angiogenic cytokines, including^. NO and VEGF, and reduced macrophage recruitment, which contribute synergistically to attenuated angiogenesis.

High glucose-induced p53 phosphorylation contributes to impairment of endothelial antioxidant system

High levels of glucose (HG) induce reactive oxygen species-mediated oxidative stress in endothelial cells (ECs), which leads to endothelial dysfunction and tissue damage. However, the molecular mechanisms involved in HG-induced endothelial oxidative stress and damage remain elusive. Here we show that cellular ATP level-modulated p53 Thr55 phosphorylation plays a critical role in the process. Upon HG exposure, the elevated ATP levels induced the kinase activity of TAF1 (TBP-associated factor 1), which leads to p53 Thr55 phosphorylation. The phosphorylation dissociates p53 from the glutathione peroxidase 1 (GPX1) promoter and results in reduction of GPX1 expression. Inhibition of TAF1-mediated p53 Thr55 phosphorylation abolished those events, supporting the role of TAF1 in sensing cellular ATP elevation and in regulating GPX1 expression under the HG condition. Importantly, treating cells with HG increased intracellular H₂O₂ and cell apoptosis, as well as suppressed nitric oxide (NO) bioavailability and tube network formation. These effects were also remarkably reversed by inhibition of TAF1 and p53 Thr55 phosphorylation. We conclude that HG leads to endothelial dysfunction via TAF1-mediated p53 Thr55 phosphorylation and subsequent GPX1 inactivation. Our study thus revealed a novel mechanism by which HG induces endothelial oxidative stress and damage and possibly provided an avenue for targeted therapy for diabetes-associated cardiovascular diseases.

NOS Expression and NO Function in Glioma and Implications for Patient Therapies

SIGNIFICANCE

Gliomas are central nervous system tumors that primarily occur in the brain and arise from glial cells. Gliomas include the most common malignant brain tumor in adults known as grade IV astrocytoma, or glioblastoma (GBM). GBM is a deadly disease for which the most significant advances in treatment offer an improvement in survival of only ∼2 months.

CRITICAL ISSUES

To develop novel treatments and improve patient outcomes, we and others have sought to determine the role of molecular signals in gliomas. Recent Advances: One signaling molecule that mediates important biologies in glioma is the free radical nitric oxide (NO). In glioma cells and the tumor microenvironment, NO is produced by three isoforms of nitric oxide synthase (NOS), NOS1, NOS2, and NOS3. NO and NOS affect glioma growth, invasion, angiogenesis, immunosuppression, differentiation state, and therapeutic resistance.

FUTURE DIRECTIONS

These multifaceted effects of NO and NOS on gliomas both in vitro and in vivo suggest the potential of modulating the pathway for antiglioma patient therapies. Antioxid. Redox Signal. 26, 986-999.

L-arginine and arginine ethyl ester enhance proliferation of endothelial cells and preadipocytes - how an arginine ethyl ester-releasing biomaterial could support endothelial cell growth in tissue engineering

Adipose tissue engineering is a promising solution for the reconstruction of soft tissue defects. An insufficient neovascularisation within the scaffolds that leads to necrosis and tissue loss is still a major shortcoming of current tissue engineering attempts. Biomaterials, which release angiogenic factors such as L-arginine, could overcome this challenge by supporting the neovascularisation of the constructs. L-arginine is insoluble in organic solvents and thus cannot be incorporated into commonly used polymers in contrast to its ethyl ester. Here, we compared the effects of arginine and its ethyl ester on endothelial cells and preadipocytes, and generated an arginine ethyl ester-releasing, angiogenic polymer. We cultivated adipose tissue-derived endothelial cells and preadipocytes in arginine-free medium supplemented with L-arginine or L-arginine ethyl ester and assayed the proliferation rate and the degree of adipogenic differentiation, respectively. Additionally, we prepared arginine ethyl ester-releasing poly(D,L-lactide) foils, and investigated their impact on endothelial cell proliferation. We could demonstrate that arginine ethyl ester like arginine significantly increased the proliferation of endothelial cells and preadipocytes without inhibiting an induced adipogenic conversion of the preadipocytes. Further, we could show that the arginine ethyl ester-releasing polymer significantly increased endothelial cell growth. The present data are helpful guidance for generating angiogenic biomaterials that promote endothelial cell growth, and thereby could support neovascularisation within tissue engineering approaches.

Howat W, Szlosarek PW, Pedley RB, Frezza C, Ashcroft M, Maxwell PH. Hypoxia-induced nitric oxide production and tumour perfusion is inhibited by pegylated arginine deiminase (ADI-PEG20)

The hypoxic tumour microenvironment represents an aggressive, therapy-resistant compartment. As arginine is required for specific hypoxia-induced processes, we hypothesised that arginine-deprivation therapy may be useful in targeting hypoxic cancer cells. We explored the effects of the arginine-degrading agent ADI-PEG20 on hypoxia-inducible factor (HIF) activation, the hypoxia-induced nitric oxide (NO) pathway and proliferation using HCT116 and UMUC3 cells and xenografts. The latter lack argininosuccinate synthetase (ASS1) making them auxotrophic for arginine. In HCT116 cells, ADI-PEG20 inhibited hypoxic-activation of HIF-1α and HIF-2α, leading to decreased inducible-nitric oxide synthase (iNOS), NO-production, and VEGF. Interestingly, combining hypoxia and ADI-PEG20 synergistically inhibited ASS1. ADI-PEG20 inhibited mTORC1 and activated the unfolded protein response providing a mechanism for inhibition of HIF and ASS1. ADI-PEG20 inhibited tumour growth, impaired hypoxia-associated NO-production, and decreased vascular perfusion. Expression of HIF-1α/HIF-2α/iNOS and VEGF were reduced, despite an increased hypoxic tumour fraction. Similar effects were observed in UMUC3 xenografts. In summary, ADI-PEG20 inhibits HIF-activated processes in two tumour models with widely different arginine biology. Thus, ADI-PEG20 may be useful in the clinic to target therapy-resistant hypoxic cells in ASS1-proficient tumours and ASS1-deficient tumours.

Involvement of nitric oxide in iodine deficiency-induced microvascular remodeling in the thyroid gland: role of nitric oxide synthase 3 and ryanodine receptors

Iodine deficiency (ID) induces microvascular changes in the thyroid gland via a TSH-independent reactive oxygen species-hypoxia inducible factor (HIF)-1α-vascular endothelial growth factor (VEGF) pathway. The involvement of nitric oxide (NO) in this pathway and the role of calcium (Ca(2+)) and of ryanodine receptors (RYRs) in NO synthase 3 (NOS3) activation were investigated in a murine model of goitrogenesis and in 3 in vitro models of ID, including primary cultures of human thyrocytes. ID activated NOS3 and the production of NO in thyrocytes in vitro and increased the thyroid blood flow in vivo. Using bevacizumab (a blocking antibody against VEGF-A) in mice, it appeared that NOS3 is activated upstream of VEGF-A. L-nitroarginine methyl ester (a NOS inhibitor) blocked the ID-induced increase in thyroid blood flow in vivo and NO production in vitro, as well as ID-induced VEGF-A mRNA and HIF-1α expression in vitro, whereas S-nitroso-acetyl-penicillamine (a NO donor) did the opposite. Ca(2+) is involved in this pathway as intracellular Ca(2+) flux increased after ID, and thapsigargin activated NOS3 and increased VEGF-A mRNA expression. Two of the 3 known mammalian RYR isoforms (RYR1 and RYR2) were shown to be expressed in thyrocytes. RYR inhibition using ryanodine at 10μM decreased ID-induced NOS3 activation, HIF-1α, and VEGF-A expression, whereas RYR activation with ryanodine at 1nM increased NOS3 activation and VEGF-A mRNA expression. In conclusion, during the early phase of TSH-independent ID-induced microvascular activation, ID sequentially activates RYRs and NOS3, thereby supporting ID-induced activation of the NO/HIF-1α/VEGF-A pathway in thyrocytes.

Endothelial hypoxic metabolism in carcinogenesis and dissemination: HIF-A isoforms are a NO metastatic phenomenon

Tumor biology is a broad and encompassing field of research, particularly given recent demonstrations of the multicellular nature of solid tumors, which have led to studies of molecular and metabolic intercellular interactions that regulate cancer progression. Hypoxia is a broad stimulus that results in activation of hypoxia inducible factors (HIFs). Downstream HIF targets include angiogenic factors (e.g. vascular endothelial growth factor, VEGF) and highly reactive molecules (e.g. nitric oxide, NO) that act as cell-specific switches with unique spatial and temporal effects on cancer progression. The effect of cell-specific responses to hypoxia on tumour progression and spread, as well as potential therapeutic strategies to target metastatic disease, are currently under active investigation. Vascular endothelial remodelling events at tumour and metastatic sites are responsive to hypoxia, HIF activation, and NO signalling. Here, we describe the interactions between endothelial HIF and NO during tumor growth and spread, and outline the effects of endothelial HIF/NO signalling on cancer progression. In doing so, we attempt to identify areas of metastasis research that require attention, in order to ultimately facilitate the development of novel treatments that reduce or prevent tumour dissemination.

A comparative study of NONOate based NO donors: spermine NONOate is the best suited NO donor for angiogenesis

Nitric oxide (NO) is a known modulator of angiogenesis. The NONOate subfamily of NO donors has long been used in experimental and clinical studies to promote angiogenesis. However, no studies have been conducted yet to compare the angiogenesis potential of these NO donors in respect to their pattern of NO release. We hypothesize that having different pattern of NO release, each of the NO donors in NONOate subfamily can promote key stages of angiogenesis in differential manner. To verify our hypothesis, NO donors with half life ranging from seconds to several hours and having very different pattern of NO release were selected to evaluate their efficacy in modulating angiogenesis. Endothelial tube formation using EAhy926 cells was maximally increased by Spermine NONOate (SP) treatment. SP treatment maximally induced both ex vivo and in vivo angiogenesis using egg yolk and cotton plug angiogenesis models respectively. Experiment using chick embryo partial ischemia model revealed SP as the best suited NO donor to recover ischemia driven hampered angiogenesis. The present study elaborated that differential release pattern of NO by different NO donors can modulate angiogenesis differentially and also suggested that SP have a unique pattern of NO release that best fits for angiogenesis.

Calreticulin transacetylase mediated upregulation of thioredoxin by 7,8-diacetoxy-4-methylcoumarin enhances the antioxidant potential and the expression of vascular endothelial growth factor in peripheral blood mononuclear cells

Extensive research carried out in our group on polyphenolic acetates (PAs) substantiated the potential role of PAs in causing diverse biological and pharmacological actions. Our earlier investigations firmly established the calreticulin transacetylase (CRTAase) catalyzed activation of nitric oxide synthase (NOS) by PAs. In this report, we have studied the effect of 7,8-diacetoxy-4-methylcoumarin (DAMC, a model PA) and other acetoxy coumarins on the thioredoxin and VEGF expression in human peripheral blood mononuclear cells (PBMCs), with a view to substantiate our earlier observation that DAMC was a superb inducer of angiogenesis. Real time RT-PCR analysis revealed the enhanced expression of thioredoxin reductase (TRXR) and diminished expression of thioredoxin interacting protein (TRXIP) leading to the increased expression and activity of thioredoxin (TRX) in PBMCs due to the the action of DAMC. The fact that TRX activity of PBMCs was enhanced by various acetoxy coumarins in tune with their affinity to CRTAase as substrate, suggested the possible activation of TRX due to acetylation. The overexpression of thioredoxin was found to correlate with that of VEGF as proved by real time RT-PCR and VEGF -ELISA results, apart from the DAMC-caused enhanced production of NO acting as an inducer of VEGF. Moreover, the intracellular ROS levels were also found to be reduced drastically, by DAMC thus reducing the oxidative stress in cells. These observations strongly evidenced the crucial role of TRX in DAMC-induced tissue angiogenesis with the involvement of VEGF.

Nitric oxide induces vascular endothelial growth factor expression in the rat placenta in vivo and in vitro

We investigated the role of nitric oxide (NO) in vascular endothelial growth factor (VEGF) expression in the rat placenta. A nitric oxide synthase (NOS) inhibitor, N(G)-nitro-L-arginine-methyl ester (L-NAME), was constantly infused into pregnant rats 6-24 h before sacrifice on gestational day (GD) 15.5. NO production declined to about 15% of the control level as monitored by NO trapping and electron paramagnetic resonance spectroscopy. VEGF mRNA expression was temporally decreased by L-NAME, but recovered to normal levels after 24 h of treatment, whereas hypoxia inducible factor (HIF)-1α and induced NOS (iNOS) expression increased. VEGF expression decreased significantly in placental explants after 6 h of co-treatment with L-NAME and lipopolysaccharide, an iNOS inducer. Our data indicate that NO induce VEGF expression in vivo and in vitro in the rat placenta, suggesting that peaked NO production was maintained by a reciprocal relationship between NO and VEGF via HIF-1α.

Adipose tissue-derived stem cell treatment prevents renal disease progression

Adipose tissue-derived stem cells (ASCs) are an attractive source of stem cells with regenerative properties that are similar to those of bone marrow stem cells. Here, we analyze the role of ASCs in reducing the progression of kidney fibrosis. Progressive renal fibrosis was achieved by unilateral clamping of the renal pedicle in mice for 1 h; after that, the kidney was reperfused immediately. Four hours after the surgery, 2 × 10(5) ASCs were intraperitoneally administered, and mice were followed for 24 h posttreatment and then at some other time interval for the next 6 weeks. Also, animals were treated with 2 × 10(5) ASCs at 6 weeks after reperfusion and sacrificed 4 weeks later to study their effect when interstitial fibrosis is already present. At 24 h after reperfusion, ASC-treated animals showed reduced renal dysfunction and enhanced regenerative tubular processes. Renal mRNA expression of IL-6 and TNF was decreased in ASC-treated animals, whereas IL-4, IL-10, and HO-1 expression increased despite a lack of ASCs in the kidneys as determined by SRY analysis. As expected, untreated kidneys shrank at 6 weeks, whereas the kidneys of ASC-treated animals remained normal in size, showed less collagen deposition, and decreased staining for FSP-1, type I collagen, and Hypoxyprobe. The renal protection seen in ASC-treated animals was followed by reduced serum levels of TNF-α, KC, RANTES, and IL-1α. Surprisingly, treatment with ASCs at 6 weeks, when animals already showed installed fibrosis, demonstrated amelioration of functional parameters, with less tissue fibrosis observed and reduced mRNA expression of type I collagen and vimentin. ASC therapy can improve functional parameters and reduce progression of renal fibrosis at early and later times after injury, mostly due to early modulation of the inflammatory response and to less hypoxia, thereby reducing the epithelial-mesenchymal transition.

C/EBP homologous protein-10 (CHOP-10) limits postnatal neovascularization through control of endothelial nitric oxide synthase gene expression

BACKGROUND

C/EBP homologous protein-10 (CHOP-10) is a novel developmentally regulated nuclear protein that emerges as a critical transcriptional integrator among pathways regulating differentiation, proliferation, and survival. In the present study, we analyzed the role of CHOP-10 in postnatal neovascularization.

METHODS AND RESULTS

Ischemia was induced by right femoral artery ligation in wild-type and CHOP-10(-/-) mice. In capillary structure of skeletal muscle, CHOP-10 mRNA and protein levels were upregulated by ischemia and diabetes mellitus. Angiographic score, capillary density, and foot perfusion were increased in CHOP-10(-/-) mice compared with wild-type mice. This effect was associated with a reduction in apoptosis and an upregulation of endothelial nitric oxide synthase (eNOS) levels in ischemic legs of CHOP-10(-/-) mice compared with wild-type mice. In agreement with these results, eNOS mRNA and protein levels were significantly upregulated in CHOP-10 short interfering RNA-transfected human endothelial cells, whereas overexpression of CHOP-10 inhibited basal transcriptional activation of the eNOS promoter. Using a chromatin immunoprecipitation assay, we also showed that CHOP-10 was bound to the eNOS promoter. Interestingly, enhanced postischemic neovascularization in CHOP-10(-/-) mice was fully blunted in CHOP-10/eNOS double-knockout animals. Finally, we showed that induction of diabetes mellitus is associated with a marked upregulation of CHOP-10 that substantially inhibited postischemic neovascularization.

CONCLUSIONS

This study identifies CHOP-10 as an important transcription factor modulating vessel formation and maturation.

The dual role of TLR3 in metastatic cell line

Toll-like receptors (TLRs) are members of transmembrane proteins that recognize conserved molecular motifs of viral and bacterial origin and initiate innate immune response. As the role of TLRs in tumors cells is still not clear, our aim was to investigate the role of TLR3 in primary tumor and metastatic cells (SW480, SW620, FaDu and Detroit 562). We have reported here on the dual role of TLR3 in pharynx metastatic cell line (Detroit 562); on one hand TLR3 activation drove cells to apoptosis while on the other its stimulation contributed to tumor progression by altering the expression of tumor promoting genes (PLAUR, RORB) and enhancing the cell migration potential. In addition, we have shown TLR3 signaling pathway is functional in another metastatic cancer cell line (SW620) suggesting TLR3 might be important in the process of tumor metastasis. Since TLR3 agonists have been used in tumor therapy with the aim to activate immune system, scientific contribution of this work is drawing attention to the importance of further work on this topic, especially pro-tumor effect of TLR3, in order to avoid possible side-effects.

Active site mutant dimethylarginine dimethylaminohydrolase 1 expression confers an intermediate tumour phenotype in C6 gliomas

Dimethylarginine dimethylaminohydrolase (DDAH) metabolizes the endogenous inhibitor of nitric oxide synthesis, asymmetric dimethylarginine (ADMA). Constitutive over-expression of DDAH1, the isoform primarily associated with neuronal nitric oxide synthase (nNOS) results in increased tumour growth and vascularization, and elevated VEGF secretion. To address whether DDAH1-mediated tumour growth is reliant upon the enzymatic activity of DDAH1, cell lines expressing an active site mutant of DDAH1 incapable of metabolizing ADMA were created. Xenografts derived from these cell lines grew significantly faster than those derived from control cells, yet not as fast as those over-expressing wild-type DDAH1. VEGF expression in DDAH1 mutant-expressing tumours did not differ from control tumours but was significantly lower than that of wild-type DDAH1-over-expressing tumours. Fluorescence microscopy for CD31 and pimonidazole adduct formation demonstrated that DDAH1 mutant-expressing tumours had a lower endothelial content and demonstrated less hypoxia, respectively, than wild-type DDAH1-expressing tumours. However, there was no difference in uptake of the perfusion marker Hoechst 33342. Non-invasive multiparametric quantitative MRI, including the measurement of native T(1) and T(2) relaxation times and apparent water diffusion coefficient, was indicative of higher cellularity in DDAH1-expressing xenografts, which was confirmed by histological quantification of necrosis. C6 xenografts expressing active site mutant DDAH1 displayed an intermediate phenotype between tumours over-expressing wild-type DDAH1 and control tumours. These data suggest that enhanced VEGF expression downstream of DDAH1 was dependent upon ADMA metabolism, but that the DDAH1-mediated increase in tumour growth was only partially dependent upon its enzymatic activity, and therefore must involve an as-yet unidentified mechanism. DDAH1 is an important mediator of tumour progression, but appears to have addition roles independent of its metabolism of ADMA, which need to be considered in therapeutic strategies targeted against the NO/DDAH pathway in cancer.

Gene expression of neuropilin-1 and its receptors, VEGF/Semaphorin 3a, in normal and cancer cells

Extracellular domains of the transmembrane glycoprotein, neuropilin-1 (Np1), specifically bind an array of factors and co-receptors including class-3 semaphorins (Sema3a), vascular endothelial growth factor (VEGF), hepatocyte growth factor, platelet-derived growth factor BB, transforming growth factor-β 1 (TGF-β1), and fibroblast growth factor2 (FGF2). Np1 may have a role in immune response, tumor cell growth, and angiogenesis, but its relative expression in comparison to its co-primary receptors, VEGF and Sema3a, is not known. In this study we determined the mRNA expression of Np1 and its co-receptors, VEGF and Sema3a, and the ratio of VEGF/Sema3a in different human and rodent cell lines. Expression of Np1, VEGF and Sema3a is very low in cells derived from normal tissues, but these proteins are highly expressed in tumor-derived cells. Furthermore, the ratio of VEGF/Sema3a is highly variable in different tumor cells. The elevated mRNA expression of Np1 and its putative receptors in tumor cells suggests a role for these proteins in tumor cell migration and angiogenesis. As different tumor cells exhibit varying VEGF/Sema3a ratios, it appears that cancer cells show differential response to angiogenic factors. These results bring to light the individual variation among the cancer-related genes, Np1, VEGF, and Sema3a, and provide an important impetus for the possible personalized therapeutic approaches for cancer patients.

The role of tumour-derived iNOS in tumour progression and angiogenesis

Background:

Progressive tumour growth is dependent on the development of a functional tumour vasculature and highly regulated by growth factors and cytokines. Nitric oxide (NO) is a free radical, produced both by tumour and host cells, and functions as a signalling molecule downstream of several angiogenic factors. Both pro- and antitumourigenic properties have been attributed to NO.

Methods:

The expression of the inducible isoform of NO synthase (iNOS) was knocked down in the C6 glioma cell line using constitutive expression of antisense RNA, and the effect of tumour-derived NO on tumour progression and angiogenesis was investigated.

Results:

Tumours in which iNOS expression was decreased displayed significantly reduced growth rates compared with tumours derived from parental C6 cells. Quantitative non-invasive magnetic resonance imaging and fluorescence microscopy of tumour uptake of Hoechst 33342, and haematoxylin and eosin staining, revealed significantly impaired vascular development and function in antisense iNOS tumours compared with control in vivo, primarily associated with the more necrotic tumour core. Decreased iNOS expression had no effect on tumour VEGF expression.

Conclusion:

Nitric oxide derived from tumour iNOS is an important modulator of tumour progression and angiogenesis in C6 gliomas and further supports the therapeutic strategy of inhibiting iNOS for the treatment of cancer.

Sphingosine kinase 1 is critically involved in nitric oxide-mediated human endothelial cell migration and tube formation

BACKGROUND AND PURPOSE

Sphingosine kinases (SKs) convert sphingosine to sphingosine 1-phosphate (S1P), which is a bioactive lipid that regulates a variety of cellular processes including proliferation, differentiation and migration.

EXPERIMENTAL APPROACH

We used the human endothelial cell line EA.hy926 to investigate the effect of nitric oxide (NO) donors on SK-1 expression, and on cell migration and tube formation.

KEY RESULTS

We showed that exposure of EA.hy926 cells to Deta-NO (125-1000 microM) resulted in a time- and concentration-dependent up-regulation of SK-1 mRNA and protein expression, and activity with a first significant effect at 250 microM of Deta-NO. The increased SK-1 mRNA expression resulted from an enhanced SK-1 promoter activity. A similar effect was also seen with various other NO donors. In mechanistic terms, the NO-triggered effect occurred independently of cGMP, but involved the classical mitogen-activated protein kinase cascade because the MEK inhibitor U0126 abolished the NO-induced SK-1 expression. The effect of NO was also markedly reduced by the thiol-reducing agent N-acetylcysteine, suggesting a redox-dependent mechanism. Functionally, Deta-NO triggered an increase in the migration of endothelial cells in an adapted Boyden chamber assay, and also increased endothelial tube formation in a Matrigel assay. These responses were both abolished in cells depleted of SK-1.

CONCLUSIONS AND IMPLICATIONS

These data show that NO donors up-regulate specifically SK-1 expression and activity in human endothelial cells, and SK-1 in turn critically contributes to the migratory capability and tube formation of endothelial cells. Thus, SK-1 may be considered an attractive novel target to interfere with pathological processes involving angiogenesis.

Role of angiogenic factors in acute experimental Strongyloides venezuelensis infection

This study aims to investigate the role of angiogenic factors in the pathogenesis of experimental strongyloidiasis. Two complementary approaches were used: Firstly, CD1 mice were treated with endostatin, an angiogenesis inhibitor, and infected with Strongyloides venezuelensis. Also, the mechanisms involved in this process were studied. Parasitological examination revealed a significant decrease in egg per gram of faeces, number of collected larvae from lung tissue and number of collected adult females in mice treated with endostatin. Direct mechanisms with diminution of angiogenesis factors and an indirect mechanism with increase of eosinophil perhaps produced their effect. Secondly, the effect of the antigens responsible for stimulation of angiogenic factors [vascular endothelial growth factor (VEGF) and fibroblast growth factor 2 (FGF2)] from alveolar macrophages and the mechanisms involved in their production were investigated. Alveolar macrophage cells obtained by bronchoalveolar lavage were incubated at different concentrations of somatic and excretory/secretory antigens of S. venezuelensis. Also, mRNA levels of VEGF and FGF2 in macrophage cells were detected by RT-PCR. L3-PBS larvae antigens induced angiogenic factors. The relationship between angiogenesis factors and nitric oxide has been observed using nitric oxide synthase inhibitors.

Effects of TLR agonists on the hypoxia-regulated transcription factor HIF-1alpha and dendritic cell maturation under normoxic conditions

Dendritic cells (DC) are professional antigen presenting cells that represent an important link between innate and adaptive immunity. Danger signals such as toll-like receptor (TLR) agonists induce maturation of DC leading to a T-cell mediated adaptive immune response. In this study, we show that exogenous as well as endogenous inflammatory stimuli for TLR4 and TLR2 induce the expression of HIF-1alpha in human monocyte-derived DC under normoxic conditions. On the functional level, inhibition of HIF-1alpha using chetomin (CTM), YC-1 and digoxin lead to no consistent effect on MoDC maturation, or cytokine secretion despite having the common effect of blocking HIF-1alpha stabilization or activity through different mechanisms. Stabilization of HIF-1alpha protein by hypoxia or CoCl(2) did not result in maturation of human DC. In addition, we could show that TLR stimulation resulted in an increase of HIF-1alpha controlled VEGF secretion. These results show that stimulation of human MoDC with exogenous as well as endogenous TLR agonists induces the expression of HIF-1alpha in a time-dependent manner. Hypoxia alone does not induce maturation of DC, but is able to augment maturation after TLR ligation. Current evidence suggests that different target genes may be affected by HIF-1alpha under normoxic conditions with physiological roles that differ from those induced by hypoxia.

Targeting nitric oxide for cancer therapy

A blueprint for the ideal anticancer molecule would include most of the properties of nitric oxide (NO•), but the ability to exploit these characteristics in a therapeutic setting requires a detailed understanding of the biology and biochemistry of the molecule. These properties include the ability of NO• to affect tumour angiogenesis, metastasis, blood flow and immuno surveillance. Furthermore NO• also has the potential to enhance both radio- and chemotherapy. However, all of these strategies are dependent on achieving appropriate levels of NO•, since endogenous levels of NO• appear to have a clear role in tumour progression. This review aims to summarize the role of NO• in cancer with particular emphasis on how the properties of NO• can be exploited for therapy.

Central role of guanylyl cyclase in natriuretic peptide signaling in hypertension and metabolic syndrome

Studied for nearly 30 years for its ability to control many parameters, such as vascular smooth muscle cell relaxation, heart fibrosis, and kidney function, the natriuretic peptide (NP) system is now considered to be a key element in several other major metabolic pathways. After stimulation by NPs, natriuretic peptide receptors (NPR) convert GTP to the second messenger cGMP. In addition to its vasodilatory effects and natriuretic and diuretic functions, cGMP has been positively associated with fat cell function, apoptosis, and NPR expression/activity modulation. The NP system is also closely linked to metabolic syndrome (MetS) progression and obesity control. A new era is now on its way targeting the NP system to not only treat high blood pressure, but to also assist in the fight against the obesity pandemic. Here, we summarize recent data on the role of NPs in hypertension and MetS.

Retinoic acid is a cofactor for translational regulation of vascular endothelial growth factor in human endometrial stromal cells

Vascular endothelial growth factor (VEGF) and endometrial angiogenesis play a critical role in successful embryonic implantation. Despite many studies of the effects of estrogen and progesterone on VEGF expression, its focal regulation at the site of implantation is unknown. Retinoic acid (RA) has been reported to regulate VEGF in a variety of cell types. Because localized RA synthesis occurs within the periimplantation endometrium, we tested the possibility that RA regulates VEGF production in endometrial stromal cells. Using primary and telomerase-immortalized human endometrial stromal cells, we determined that RA alone did not alter constitutive levels of VEGF production, but markedly amplified secretion when the cells were cotreated with activators of VEGF gene transcription (12-O-tetradecanoyl phorbol-13-acetate, TPA; TGF-beta; and IL-1beta). Whereas TPA or TGF-beta alone stimulated VEGF promoter activity and up-regulated mRNA levels, significant protein secretion was detected only after RA was added to the culture systems. Analysis of retinoids in secretory phase endometrial biopsies indicated that endogenous RA accumulated at concentrations sufficient to induce VEGF secretion. Polyribosome profile analysis showed that the addition of RA to transcriptional activators of VEGF shifted the translational suppressed VEGF mRNA transcripts into larger polyribosome complexes engaged in active translation. Although the precise mechanism(s) of the RA effect remains to be defined, it appears to be mediated by reactive oxygen species; the antioxidant N-acetylcysteine inhibited RA+TPA-stimulated secretion of VEGF by more than 80%. Together, our results demonstrate that in human endometrial stromal cells, RA can combine with transcriptional activators of VEGF to augment VEGF secretion through a translational mechanism of action mediated by reactive oxygen species. These findings suggest a link between the spatiotemporal changes of retinoid synthesis in the periimplantation stroma and the capacity to quickly up-regulate focal VEGF secretion needed to induce early angiogenic events of pregnancy.

NF-kappaB promotes iNOS and VEGF expression in salivary gland adenoid cystic carcinoma cells and enhances endothelial cell motility in vitro

Tumour cell-derived angiogenic-related factors and endothelial cell mobility are essential for neovascularization and haematogenous metastasis of adenoid cystic carcinoma (ACC) of the human salivary glands. Our previous study demonstrated that vascular endothelial growth factor (VEGF), inducible nitric oxide synthase (iNOS), and nuclear factor kappaB (NF-kappaB) staining correlated with ACC microvessel density. However, there still remains a lack of direct evidence to clarify the function of liposaccharide-induced NF-kappaB activity in ACC angiogenesis.

OBJECTIVES

This study aimed to demonstrate the function of liposaccharide-induced NF-kappaB signalling pathway (which would be relevant to angiogenesis) of ACC cell lines.

MATERIALS AND METHODS

A PCMV-IkappaBalphaM vector transfection assay was performed to inhibit NF-kappaB activity. Constitutive and liposaccharide-induced NF-kappaB activity, along with VEGF and iNOS expression, was detected by electrophoretic mobility shift assays, reverse transcription-polymerase chain reaction and Western blot assay. Tumour cell-derived NO(2) (-) was evaluated by a nitrite determination assay, and endothelial cell mobility was investigated by endothelial cell proliferation, migration and tube formation assays.

RESULTS

We demonstrated that regulation of VEGF and iNOS expression utilized the NF-kappaB signalling pathway in ACC cell lines. In the constitutive and liposaccharide-induced condition, NF-kappaB activity was blocked by phosphorylation-defective IkappaBalpha. Accordingly, mRNA and protein expression of VEGF and iNOS were significantly decreased, with a great drop in endogenous NO(2) (-). Furthermore, supernatant from ACC-2/IkBaM and ACC-M/IkBaM cells resulted in much lower endothelial cell mobility than that from ACC-2 and ACC-M cells.

CONCLUSIONS

Our results suggest that NF-kappaB promotes iNOS and VEGF expression in salivary gland ACC cells and enhances endothelial cell motility in vitro.

Induced nitric oxide synthase as a major player in the oncogenic transformation of inflamed tissue

Nitric oxide (NO) is a free radical that is involved in the inflammatory process and carcinogenesis. There are four nitric oxide synthase enzymes involved in NO production: induced nitric oxide synthase (iNOS), endothelial NO synthase (eNOS), neural NO synthase (nNOS), and mitochondrial NOS. iNOS is an inducible and key enzyme in the inflamed tissue. Recent literatures indicate that NO as well as iNOS and eNOS can modulate cancer-related events including nitro-oxidative stress, apoptosis, cell cycle, angio-genesis, invasion, and metastasis. This chapter focuses on linking NO/iNOS/eNOS to inflammation and carcinogenesis from experimental evidence to potential targets on cancer prevention and treatment.

Plasma levels of vascular endothelial growth factor after treatment for cerebral arteriovenous malformations

BACKGROUND AND PURPOSE

The role of abnormal angiogenesis in the formation and progression of cerebral arteriovenous malformations (AVMs) is unclear. Previous studies have demonstrated increased local expression of vascular endothelial growth factor (VEGF) in AVM tissue and increased circulating levels of VEGF in AVM patients. We sought to further investigate the role of VEGF in AVM pathophysiology by examining changes in plasma VEGF levels in patients undergoing treatment for AVMs.

METHODS

Three serial blood samples were obtained from 13 AVM patients undergoing treatment: (1) before any treatment, (2) 24 hours postresection, and (3) 30 days postresection. Plasma VEGF concentrations were measured via commercially available enzyme-linked immunosorbent assay (ELISA). For controls, blood samples were obtained from 29 lumbar laminectomy patients.

RESULTS

The mean plasma VEGF level in AVM patients at baseline was 36.08+/-13.02 pg/mL, significantly lower than that of the control group (80.52+/-14.02 pg/mL, P=0.028). Twenty-four hours postresection, plasma VEGF levels dropped to 20.09+/-4.54 pg/mL, then increased to 66.81+/-26.45 pg/mL 30 days later (P=0.048). The mean plasma VEGF concentration 30 days after resection was no longer significantly different from the control group (P=0.33).

CONCLUSIONS

Plasma VEGF levels in 13 AVM patients were unexpectedly lower than controls, dropped early after AVM resection, then significantly increased 30 days later. These results support the key role of abnormal angiogenesis in AVM pathophysiology and suggest that a disruption in systemic VEGF expression may contribute to the natural history of these lesions.

Phenyl-tert-butylnitrone induces tumor regression and decreases angiogenesis in a C6 rat glioma model

The prognosis of patients who are diagnosed with glioblastoma multiforme is very poor, due to the difficulty of an early and accurate diagnosis and the lack of currently efficient therapeutic compounds. The efficacy of phenyl-tert-butylnitrone (PBN) as a potential anti-glioma therapeutic drug was assessed by magnetic resonance (MR) imaging (T(1)/T(2)-weighted imaging) and MR angiography (time-of-flight imaging, in conjunction with a Mathematica-based program) methods by monitoring morphologic properties, growth patterns, and angiogenic behaviors of a moderately aggressive rat C6 glioma model. MR results from untreated rats showed the diffusive invasiveness of C6 gliomas, with some associated angiogenesis. PBN administration as a pretreatment was found to clearly induce a decrease in growth rate and tumor regression as well as preventing angiogenesis. This compound even had a 40% efficiency in reducing well-established tumors. MR findings rivaled those from histology and angiogenesis marker immunostaining evaluations. In this study we demonstrated the efficiency of PBN as a potential anti-glioma drug and found it to inhibit tumor cell proliferation and prevent vascular alterations in early stages of glioma progression. The MR methods that we used also proved to be particularly suitable in following the angiogenic behavior and treatment response of a potential anti-glioma agent in a rat C6 glioma model.

Antioxidant and anti-inflammatory properties of curcumin

Curcumin, a yellow pigment from Curcuma longa, is a major component of turmeric and is commonly used as a spice and food-coloring agent. It is also used as a cosmetic and in some medical preparations. The desirable preventive or putative therapeutic properties of curcumin have also been considered to be associated with its antioxidant and anti-inflammatory properties. Because free-radical-mediated peroxidation of membrane lipids and oxidative damage of DNA and proteins are believed to be associated with a variety of chronic pathological complications such as cancer, atherosclerosis, and neurodegenerative diseases, curcumin is thought to play a vital role against these pathological conditions. The anti-inflammatory effect of curcumin is most likely mediated through its ability to inhibit cyclooxygenase-2 (COX-2), lipoxygenase (LOX), and inducible nitric oxide synthase (iNOS). COX-2, LOX, and iNOS are important enzymes that mediate inflammatory processes. Improper upregulation of COX-2 and/or iNOS has been associated with the pathophysiology of certain types of human cancer as well as inflammatory disorders. Because inflammation is closely linked to tumor promotion, curcumin with its potent anti-inflammatory property is anticipated to exert chemopreventive effects on carcinogenesis. Hence, the past few decades have witnessed intense research devoted to the antioxidant and anti-inflammatory properties of curcumin. In this review, we describe both antioxidant and anti-inflammatory properties of curcumin, the mode of action of curcumin, and its therapeutic usage against different pathological conditions.

Vascular endothelial growth factor and nitric oxide in rat liver regeneration

In this work we investigated the role of nitric oxide (NO) in the angiogenesis mediated by vascular endothelial growth factor (VEGF) during rat liver regeneration after two-thirds partial hepatectomy. Sham operated (Sh) and partially hepatectomized (PH) male Wistar rats were randomized in three experimental groups: control (treated with vehicle); pre-treated with sodium nitroprusside (SNP: 0.25 mg/kg body weight, i.v. at a rate of 1 ml/h) and pre-treated with the preferential iNOS inhibitor, aminoguanidine (AG, 100 mg/kg body weight, i.p.). Animals were killed at 5, 24 and 72 h after surgery. At 5 h post-surgery, NO production was estimated by EPR (Sh-Control: 37.65+/-10.70; PH-Control: 88.13+/-1.60(); Sh-SNP: 90.35+/-3.11(); PH-SNP: 119.5+/-12.10()(#); Sh-AG: 33.27+/-5.23, PH-AG: 36.80+/-3.40(#)) (p<0.05 vs Sh-Control; (#)p<0.05 vs PH-Control). At 24 h after PH, VEGF levels showed no difference between PH-Control and PH-SNP animals. However, after 72 h, VEGF protein levels in PH-SNP animals were found to be increased (above 300%) with respect to PH-Control. On the other hand, aminoguanidine (AG) pre-treatment blocked the rise of inhibition of NO generation and decreased VEGF expression. Our results demonstrated that NO plays a role in modulating VEGF protein expression after hepatectomy in rats.

Nitric oxide, a double edged sword in cancer biology: Searching for therapeutic opportunities

Nitric oxide (NO) is a pleiotropic molecule critical to a number of physiological and pathological processes. The last decade has witnessed major advances in dissecting NO biology and its role in cancer pathogenesis. However, the complexity of the interactions between different levels of NO and several aspects of tumor development/progression has led to apparently conflicting findings. Furthermore, both anti-NO and NO-based anticancer strategies appear effective in several preclinical models. This paradoxical dichotomy is leaving investigators with a double challenge: to determine the net impact of NO on cancer behavior and to define the therapeutic role of NO-centered anticancer strategies. Only a comprehensive and dynamic view of the cascade of molecular and cellular events underlying tumor biology and affected by NO will allow investigators to exploit the potential antitumor properties of drugs interfering with NO metabolism. Available data suggest that NO should be considered neither a universal target nor a magic bullet, but rather a signal transducer to be modulated according to the molecular makeup of each individual cancer and the interplay with conventional antineoplastic agents.

Reactive oxygen species drives myocardial angiogenesis?

Neovascularization, the natural physiological process of formation of new blood vessels, is extremely important for ameliorating the function of the heart that undergoes ischemic stress. This process is potentially important for the treatment of ischemic heart and limb diseases, which includes formation of capillaries (angiogenesis) and collateral arteries. Ischemia or coronary artery occlusion induces vascular endothelial growth factor (VEGF) in the experimental rat myocardial infarction model, and this molecule encourages development of coronary collateral circulation and retention of the blood supply to the ischemic area. Restoration of the blood supply to the ischemic area prevents cardiomyocyte death and cardiac remodeling. Among the various triggers and enhancers of angiogenesis, hypoxic or ischemic preconditioning, as well as pharmacologic agents such as statin and resveratrol, have been identified as important stimuli for the induction of new vessel growth. It has already been demonstrated that the VEGF family and its receptor system is the fundamental regulator in the redox cell signaling of angiogenesis. This review article will focus on the role of reactive oxygen species in the process of myocardial angiogenesis.

The role of nitric oxide in tumour progression

Nitric oxide (NO) and nitric oxide synthases are ubiquitous in malignant tumours and are known to exert both pro- and anti-tumour effects. We summarize our current understanding of the role of NO in tumour progression, especially in relation to angiogenesis and vascular functions. We also discuss potential strategies for cancer treatment that modulate NO production and/or its downstream signalling pathways.

Signalling networks regulating cyclooxygenase-2

Cyclooxygenease-2 (COX-2) is the key enzyme regulating the production of prostaglandins, central mediators of inflammation. The expression of cyclooxygenease-2 is induced by several extra cellular signals including pro-inflammatory and growth-promoting stimuli. All signals converge to the activation of mitogen-activated protein kinases (MAPK) that regulate cyclooxygenease-2 mRNA levels both at the transcriptional and post-transcriptional level. The machinery appears to be highly specialized involving activation of distinct signalling molecules depending on the type of extracellular stimulus. Expression of cyclooxygenease-2 mRNA is regulated by several transcription factors including the cyclic-AMP response element binding protein (CREB), nuclear factor kappa B (NFkB) and the CCAAT-enhancer binding protein (C/EBP). Cyclooxygenease-2 is also affected post-transcriptionaly, at the level of mRNA stability. Finally, cyclooxygenease-2 can be affected directly at its enzymatic activity by nitric oxide and nitric oxide synthase (iNOS). Each step of cyclooxygenease-2 regulation can be used as potential therapeutic target.

Inducible nitric oxide synthase activity correlates with lymphangiogenesis and vascular endothelial growth factor-C expression in head and neck squamous cell carcinoma

Nitric oxide (NO) is a diatomic free radical molecule that has been implicated in tumour angiogenesis and progression of head and neck squamous cell carcinoma (HNSCC). However, the mechanism underlying the effect of NO on tumour spread remains largely unknown. Tumour lymphangiogenesis has recently received considerable attention and there is increasing evidence that it is relevant for metastasis to lymph nodes in HNSCC. Here, we study the correlation between inducible NOS synthase (iNOS) activity and lymphangiogenesis in a series of 60 HNSCCs and the possible involvement of the lymphangiogenic factor vascular endothelial growth factor (VEGF)-C. HNSCC presenting with lymph node metastasis had a significantly higher lymphatic vessel density in both the tumour mass and the peritumour area (p = 0.006 and p = 0.001, respectively). Similarly, tumours with lymph node metastasis showed greater lymphatic vessel area than tumours with no lymph node involvement (p = 0.001 for intratumour lymphatics and p < 0.001 for peritumour lymphatics). iNOS activity measured in specimens from the tumour periphery correlated strongly with both lymphatic vessel density and lymphatic vessel area (p = 0.01, rs = 0.45 and p < 0.001, rs = 0.725, respectively). Conversely, these correlations were not observed in specimens from the tumour core. In addition, VEGF-C mRNA expression was significantly elevated in tumours with high iNOS activity (p = 0.008, rs = 0.563), and VEGF-C expression correlated positively with the presence of lymph node metastases (p = 0.03). In vitro, in the A431 human squamous carcinoma cell line, exogenous and endogenous stimulation of the iNOS pathway led to up-regulation of VEGF-C, which was blocked by the NOS inhibitor L-NNA. Taken together, our results indicate that iNOS activity may promote lymphangiogenesis and spread to lymph nodes in HNSCC, with the possible involvement of VEGF-C.

Involvement of reactive nitrogen oxides for acquisition of metastatic properties of benign tumors in a model of inflammation-based tumor progression

The cells of a weakly tumorigenic and non-metastatic murine fibrosarcoma (QR-32) are converted into highly malignant tumors (acquiring metastatic potential) once they have grown in vivo after being co-implanted with gelatin sponge which induces inflammation. In the present study, we examined whether nitric oxide (NO) is involved in the inflammation-based tumor progression by administrating a specific inhibitor to inducible nitric oxide synthase, aminoguanidine (AG). First, we co-implanted 1 x 10(5) QR-32 cells with gelatin sponge (10 x 5 x 3 mm piece) into a subcutaneous space in C57BL6 mice. Administration of AG in drinking water (1%) had started 2 days before the tumor implantation and continued until the termination of the experiment. The incidence of tumor formation and the tumor growth did not differ between AG-treated group and -untreated group. On day 28, we excised the arising tumors to establish culture cell lines for evaluation of their acquisition of metastatic phenotype in other normal mice. Metastasis incidence and the number of metastatic colonies were significantly reduced in the tumor cell lines obtained from AG-treated mice compared to those from non-treated mice (p < 0.05). Immunohistochemical analysis demonstrated that inducible nitric oxide synthase and nitrotyrosine in the inflamed lesion were reduced in the AG-administered mice. However, intensity of 8-hydroxy-2-deoxyguanosine was not different between the groups. These results showed that nitric oxide and its reactive nitrogen oxide species cooperatively play a pivotal role in the progression of benign tumor cells in inflamed lesions.

Expressions of nuclear factor kappaB, inducible nitric oxide synthase, and vascular endothelial growth factor in adenoid cystic carcinoma of salivary glands: correlations with the angiogenesis and clinical outcome

OBJECTIVE

To evaluate the expressions of nuclear factor kappaB (NF-kappaB p65), inducible nitric oxide synthase enzyme (iNOS), and vascular endothelial growth factor (VEGF) in relation to angiogenesis (microvessel density, MVD) and clinical outcomes in adenoid cystic carcinoma (ACC) of salivary glands.

METHODS

Immunohistochemical staining was used to quantify the protein expression levels of NF-kappaB p65, iNOS, and VEGF in 80 surgically resected ACCs and 20 normal salivary tissues. In all cases of ACCs, MVD was evaluated by counting CD34-reactive endothelial cells or endothelial cell clusters.

RESULTS

The nuclear localization of NF-kappaB p65 was only detected in ACC cells. Both iNOS and VEGF staining activities in ACCs were more significant than those in normal gland tissues (P < 0.01). MVD had significant correlations with NF-kappaB p65, iNOS, and VEGF expressions (P < 0.01). In three histologic types of ACCs, the NF-kappaB, iNOS, VEGF expressions, and MVD were significantly higher in solid type than in cribriform and tubular types (P < 0.01). The NF-kappaB, iNOS, VEGF expressions, and MVD were significantly correlated with clinical stage, tumor size, vascular invasion, recurrence, and metastasis (P < 0.05). Multivariate analysis showed NF-kappaB, iNOS and VEGF expression, MVD, solid histotype, and perineural invasion had an independent prognostic effect on overall survival.

CONCLUSION

The expressions of NF-kappaB p65, iNOS, and VEGF were related with MVD. Clinical outcomes raised the possibility that the overexpression of these cytokines might contribute to tumor angiogenesis and have prognostic value in ACCs.

Exogenous Nitric Oxide Stimulates Cell Proliferation via Activation of a Mitogen-Activated Protein Kinase Pathway in Ovine Fetoplacental Artery Endothelial Cells1

Sodium nitroprusside (SNP), a nitric oxide (NO) donor and a nitrovasodilator drug used for patients with hypertensive crisis, has been shown to promote angiogenesis. However, direct evidence showing the involvement of NO in the SNP-induced angiogenesis is not available. Accordingly, we assessed whether NO generated from SNP-stimulated ovine fetoplacental artery endothelial (OFPAE) cell proliferation via activation of mitogen-activated protein kinase 3/1 (MAPK3/1, also termed ERK1/2). We observed that SNP dose dependently stimulated (P < 0.05) cell proliferation with a maximal effect at 1 microM and that SNP rapidly (<or=15 min) phosphorylated (P < 0.05) MAPK3/1 but not v-akt murine thymoma viral oncogene homolog 1 (AKT1). Treatment of cells with SNP caused a rapid increase in NO levels in media. These increased NO levels were inhibited (P < 0.05) by 2-phenyl-4,4,5,5 tetramethylimidazoline-1-oxyl 3-oxide (PTIO), a NO scavenger. The SNP-induced cell proliferation and MAPK3/1 phosphorylation were attenuated (P < 0.05) by both PTIO and PD98059, a specific mitogen-activated protein kinase kinase 1 and 2 (MAP2K1/2, also termed MEK1/2) inhibitor. Using a semiquantitative RT-PCR analysis, we also showed that up to 12 h of treatment, SNP and N(G)-monomethyl-L-arginine (L-NMMA, a NOS inhibitor) did not alter mRNA expression of VEGF, FGF2, and their major receptors in OFPAE cells. The SNP's stimulatory effects on OFPAE cell proliferation and MAPK3/1 activation were confirmed in a human placental artery endothelial (HPAE) cell line. These data indicate that exogenous NO generated from SNP is able to stimulate fetoplacental artery endothelial cell proliferation at least partly via activation of the MAP2K1/2/MAPK3/1 cascade. These data also suggest that SNP could potentially be used to modulate placental angiogenesis.

Molecular regulation of tumor angiogenesis: mechanisms and therapeutic implications

Angiogenesis, the process of new capillary formation from a pre-existing vessel plays an essential role in both embryonic and postnatal development, in the remodeling of various organ systems, and in several pathologies, particularly cancer. In the last 20 years of angiogenesis research, a variety of angiogenic regulators, both positive and negative, have been identified. The discovery of several anti-angiogenic factors has led to the development of novel cancer therapies based on targeting a tumor's vascular supply. A number of these new therapies are currently being tested in clinical trials in the U.S.A. and elsewhere. A major advance in the field of anti-angiogenic therapy occurred recently when the FDA approved Avastin (bevacizumab), the first solely anti-angiogenesis therapy approved for treatment of human cancer. While it has long been appreciated that tumor growth and progression are dependent on angiogenesis, it is only recently that progress has been made in elucidating the molecular mechanisms that regulate the earliest stage in the angiogenic program, the angiogenic switch. This checkpoint is characterized by the transition of a dormant, avascular tumor into an active, vascular one. Anti-angiogenic therapies to date have essentially been designed to suppress the neovasculature in established tumors. However, identifying the mechanisms that cause a tumor to acquire an angiogenic phenotype may lead to the discovery of new therapeutic modalities and complementary diagnostics that could be used to block the angiogenic switch, thereby preventing subsequent tumor progression. In this chapter on the role of angiogenesis in cancer, we (1) provide an overview of the process of angiogenesis with special regard to the molecules and physiological conditions that regulate this process, (2) review recent studies describing the use of anti-angiogenic approaches in the treatment of a variety of human cancers, and (3) discuss the recent literature focused on the study of the molecules and molecular mechanisms that may be regulating the initiation of the angiogenic phenotype in tumors, and the clinical impact that this knowledge may have in the future.

Endogenous stimulators and inhibitors of angiogenesis in gastrointestinal cancers: basic science to clinical application

Progression of cancer is dependent on acquisition of vascular networks within the tumor. Tumor angiogenesis is dependent on up-regulation of angiogenesis stimulators to overcome the endogenous anti-angiogenic barrier. Such disruption of angiogenesis balance to favor neovascularization is a key step for progression of tumor growth and metastasis. In this regard, the vascular basement membrane and the extracellular matrix have been found to be rich sources of angiogenesis stimulators and inhibitors that become bioavailable on proteolysis of the matrix by tumor microenvironment-related enzymes. In this review the subgroup of endogenous angiogenesis stimulators and inhibitors is discussed, and their mechanism of action during tumor angiogenesis is evaluated. The role in regulating tumor growth and the possibility of using them as prognostic markers for human gastrointestinal cancers is discussed. Furthermore, we specifically address the role of vascular endothelial growth factor in human gastrointestinal cancers and discuss the development and use of bevacizumab (Avastin; anti-vascular endothelial growth factor antibody [Genentech, CA]) in the treatment of colorectal and other gastrointestinal cancers.