von Hippel-Lindau syndrome: target for anti-vascular endothelial growth factor (VEGF) receptor therapy

Ophthalmological Aspects of von-Hippel-Lindau Syndrome

Background: von Hippel-Lindau (VHL) syndrome is a multisystem neoplastic disorder involving eyes, central nervous system, kidneys, spine, and other tissues. A retinal capillary hemangioma (RCH) is the earliest manifestation of the VHL disease in most cases.Areas covered:This paper aims to provide an up-to-date review of the current literature about von Hippel-Lindau syndrome. Molecular background, systemic and ocular features of the diseases as well as the utility of newer imaging modalities in diagnosis and monitoring of ocular VHL disease have been described. Besides, we have discussed newer treatment modalities and therapeutic targets.Conclusion: Modern imaging technologies like optical coherence tomography and optical coherence tomography angiography are tools of the trade, in making an appropriate diagnosis and monitoring disease activity and response to treatment. Peripheral RCH may be treated using laser photocoagulation in tumors up to 3000 µm. Vascular endothelial growth factor suppression can help in reducing tumor activity and stabilize the tumor size; however, it does not regress the RCH.

Hypoxia, angiogenesis, and metabolism in the hereditary kidney cancers

The field of hereditary kidney cancer has begun to mature following the identification of several germline syndromes that define genetic and molecular features of this cancer. Molecular defects within these hereditary syndromes demonstrate consistent deficits in angiogenesis and metabolic signaling, largely driven by altered hypoxia signaling. The classical mutation, loss of function of the von Hippel-Lindau (VHL) tumor suppressor, provides a human pathogenesis model for critical aspects of pseudohypoxia. These features are mimicked in a less common hereditary renal tumor syndrome, known as hereditary leiomyomatosis and renal cell carcinoma. Here, we review renal tumor angiogenesis and metabolism from a HIF-centric perspective, considering alterations in the hypoxic landscape, and molecular deviations resulting from high levels of HIF family members. Mutations underlying HIF deregulation drive multifactorial aberrations in angiogenic signals and metabolism. The mechanisms by which these defects drive tumor growth are still emerging. However, the distinctive patterns of angiogenesis and glycolysis-/glutamine-dependent bioenergetics provide insight into the cellular environment of these cancers. The result is a scenario permissive for aggressive tumorigenesis especially within the proximal renal tubule. These features of tumorigenesis have been highly actionable in kidney cancer treatments, and will likely continue as central tenets of kidney cancer therapeutics.

Androgen receptor (AR) suppresses miRNA-145 to promote renal cell carcinoma (RCC) progression independent of VHL status

Mutational inactivation of the VHL tumor suppressor plays key roles in the development of renal cell carcinoma (RCC), and mutated VHL-mediated VEGF induction has become the main target for the current RCC therapy. Here we identified a signal pathway of VEGF induction by androgen receptor (AR)/miRNA-145 as a new target to suppress RCC progression. Mechanism dissection revealed that AR might function through binding to the androgen receptor element (ARE) located on the promoter region of miRNA-145 to suppress p53's ability to induce expression of miRNA-145 that normally suppresses expression of HIF2α/VEGF/MMP9/CCND1. Suppressing AR with AR-shRNA or introducing exogenous miRNA-145 mimic can attenuate RCC progression independent of VHL status. MiR-145 mimic in preclinical RCC orthotopic xenograft mouse model revealed its efficacy in suppression of RCC progression. These results together identified signals by AR-suppressed miRNA-145 as a key player in the RCC progression via regulating HIF2α/VEGF/MMP9/CCND1 expression levels. Blockade of the newly identified signal by AR inhibition or miRNA-145 mimics has promising therapeutic benefit to suppress RCC progression.

Neoadjuvant sorafenib treatment of clear cell renal cell carcinoma and release of circulating tumor fragments

BACKGROUND

Clear cell renal cell carcinoma (ccRCC) is characterized by high constitutive vascular endothelial growth factor A (VEGF-A) production that induces a specific vascular phenotype. We previously reported that this phenotype may allow shedding of multicellular tumor fragments into the circulation, possibly contributing to the development of metastasis. Disruption of this phenotype through inhibition of VEGF signaling may therefore result in reduced shedding of tumor fragments and improved prognosis. To test this hypothesis, we investigated the effect of neoadjuvant sorafenib treatment on tumor cluster shedding.

PATIENTS AND METHODS

Patients with renal cancer (n = 10, of which 8 have ccRCC) received sorafenib for 4 weeks before tumor nephrectomy. The resection specimens were perfused, and the perfundate was examined for the presence of tumor clusters. Effects of the treatment on the tumor morphology and overall survival were investigated (follow-up of 2 years) and compared with a carefully matched control group.

RESULTS

Neoadjuvant sorafenib treatment induced extensive ischemic tumor necrosis and, as expected, destroyed the characteristic ccRCC vascular phenotype. In contrast to the expectation, vital groups of tumor cells with high proliferation indices were detected in postsurgical renal venous outflow in 75% of the cases. Overall survival of patients receiving neoadjuvant treatment was reduced compared to a control group, matched with regard to prognostic parameters.

CONCLUSIONS

These results suggest that neoadjuvant sorafenib therapy for ccRCC does not prevent shedding of tumor fragments. Although this is a nonrandomized study with a small patient group, our results suggest that neoadjuvant treatment may worsen survival through as yet undefined mechanisms.

Hypoxia-inducible factor-1 (HIF-1): a potential target for intervention in ocular neovascular diseases

Constant oxygen supply is essential for proper tissue development, homeostasis and function of all eukaryotic organisms. Cellular response to reduced oxygen levels is mediated by the transcriptional regulator hypoxia-inducible factor-1 (HIF-1). It is a heterodimeric complex protein consisting of an oxygen dependent subunit (HIF-1α) and a constitutively expressed nuclear subunit (HIF-1β). In normoxic conditions, de novo synthesized cytoplasmic HIF-1α is degraded by 26S proteasome. Under hypoxic conditions, HIF-1α is stabilized, binds with HIF-1β and activates transcription of various target genes. These genes play a key role in regulating angiogenesis, cell survival, proliferation, chemotherapy, radiation resistance, invasion, metastasis, genetic instability, immortalization, immune evasion, metabolism and stem cell maintenance. This review highlights the importance of hypoxia signaling in development and progression of various vision threatening pathologies such as diabetic retinopathy, retinopathy of prematurity, age-related macular degeneration and glaucoma. Further, various inhibitors of HIF-1 pathway that may have a viable potential in the treatment of oxygen-dependent ocular diseases are also discussed.

Vascular endothelial growth factor (VEGF) expression in locally advanced prostate cancer: secondary analysis of radiation therapy oncology group (RTOG) 8610

Background

Angiogenesis is a key element in solid-tumor growth, invasion, and metastasis. VEGF is among the most potent angiogenic factor thus far detected. The aim of the present study is to explore the potential of VEGF (also known as VEGF-A) as a prognostic and predictive biomarker among men with locally advanced prostate cancer.

Methods

The analysis was performed using patients enrolled on RTOG 8610, a phase III randomized control trial of radiation therapy alone (Arm 1) versus short-term neoadjuvant and concurrent androgen deprivation and radiation therapy (Arm 2) in men with locally advanced prostate carcinoma. Tissue samples were obtained from the RTOG tissue repository. Hematoxylin and eosin slides were reviewed, and paraffin blocks were immunohistochemically stained for VEGF expression and graded by Intensity score (0–3). Cox or Fine and Gray’s proportional hazards models were used.

Results

Sufficient pathologic material was available from 103 (23%) of the 456 analyzable patients enrolled in the RTOG 8610 study. There were no statistically significant differences in the pre-treatment characteristics between the patient groups with and without VEGF intensity data. Median follow-up for all surviving patients with VEGF intensity data is 12.2 years. Univariate and multivariate analyses demonstrated no statistically significant correlation between the intensity of VEGF expression and overall survival, distant metastasis, local progression, disease-free survival, or biochemical failure. VEGF expression was also not statistically significantly associated with any of the endpoints when analyzed by treatment arm.

Conclusions

This study revealed no statistically significant prognostic or predictive value of VEGF expression for locally advanced prostate cancer. This analysis is among one of the largest sample bases with long-term follow-up in a well-characterized patient population. There is an urgent need to establish multidisciplinary initiatives for coordinating further research in the area of human prostate cancer biomarkers.

Unexpectedly durable palliation of metastatic olfactory neuroblastoma using anti-angiogenic therapy with Bevacizumab

Olfactory neuroblastomas (ONBs) are rare malignant tumors that arise from olfactory epithelium and typically present with symptoms attributable to locally invasive disease. Kadish radiographic staging and Hyams' histopathologic grading are prognostic. Overall survival rates, averaging 60–70% at 5 years, remain limited by high rates of delayed loco-regional and distant progression. At initial presentation, the available evidence supports the use of multimodality therapy, historically surgery and radiation, to improve disease-free and overall survival. At recurrence/progression, the available evidence supports the use of therapy to improve disease control and symptoms (palliation), but patient heterogeneity dictates individualization of modalities. Although the ideal use of chemotherapy as a modality remains undefined, the available evidence supports it use, historically platinum-based, for palliation. However, recent insights into the molecular-genetic aberrations of ONBs, coupled with the emergence chemotherapeutic agents capable of targeting such aberrations, suggest an expanded role. The authors report a case of a 60 years-old man, heavily pre-treated for metastatic ONB, presenting with profound central-nerve-system and head-and-neck symptoms. He experienced unexpectedly durable palliation with Bevacizumab anti-angiogenic therapy. Additionally, he experienced localized palliation with an Ommaya reservoir. The authors review the literature regarding historical and emerging therapies for ONB to emphasize the needs for individualization and translational-clinical studies.

Antiangiogenic therapy for advanced renal cell carcinoma: management of treatment-related toxicities

Treatment of metastatic renal cell carcinoma (mRCC) has evolved rapidly over the last two decades as major pathways involved in pathogenesis have been elucidated. These include the vascular endothelial growth factor (VEGF) axis and mammalian target of rapamycin (mTOR). Therapies targeting the VEGF pathway include bevacizumab, sorafenib, sunitinib, pazopanib, and axitinib, whereas temsirolimus and everolimus inhibit the mTOR pathway. All of these novel therapies—VEGF and mTOR inhibitors—are associated with a variety of unique toxicities, some of which may necessitate expert medical management, treatment interruption, or dose reduction. Common adverse events with newer drugs include hypertension, skin reactions, gastrointestinal disturbances, thyroid dysfunction, and fatigue. Skilled management of these toxicities is vital to ensure optimal therapeutic dosing and maximize patient outcomes, including improved survival and quality of life. This review describes and compares the toxicity profiles of novel molecularly targeted agents used in the treatment of mRCC and presents guidance on how best to prevent and manage treatment-related toxicities. Particular attention is given to axitinib, the newest agent to enter the armamentarium. Axitinib is a second-generation receptor tyrosine kinase inhibitor with potent VEGF receptor inhibition that provides durable responses and superior progression-free survival in advanced RCC compared with sorafenib.

Vascular abnormalities in human newborns with pulmonary hypertension

Pulmonary vascular disease embodies all congenital or acquired pathologies that affect the pulmonary vasculature. One of them is pulmonary hypertension of the newborn (PHN), which is clinically characterized by a persistent high pulmonary vascular resistance postnatally and an abnormal vascular response. Morphologically, the vascular walls of the small pulmonary arteries become thickened, leading to increased resistance of these vessels and thus a worsening of gas exchange. PHN occurs as a primary disease or in association with abnormal lung development, for example as in congenital diaphragmatic hernia, and is a critical determinant of morbidity and mortality. Here we review the current knowledge about vascular abnormalities in PHN and discuss the vascular abnormalities in different conditions associated with pulmonary hypertension in human newborns in relation to recent findings from molecular biology.

Circulating tumour tissue fragments in patients with pulmonary metastasis of clear cell renal cell carcinoma

Tumour metastasis is the result of a complex sequence of events, including migration of tumour cells through stroma, proteolytic degradation of stromal and vessel wall elements, intravasation, transport through the circulation, extravasation and outgrowth at compatible sites in the body (the 'seed and soil' hypothesis). However, the high incidence of metastasis from various tumour types in liver and lung may be explained by a stochastic process as well, based on the anatomical relationship of the primary tumour with the circulation and mechanical entrapment of metastatic tumour cells in capillary beds. We previously reported that constitutive VEGF-A expression in tumour xenografts facilitates this type of metastatic seeding by promoting shedding of multicellular tumour tissue fragments, surrounded by vessel wall elements, into the circulation. After transport through the vena cava, such fragments may be trapped in pulmonary arteries, allowing them to expand to symptomatic lesions. Here we tested whether this process has clinical relevance for clear cell renal cell carcinoma (ccRCC), a prototype tumour in the sense of high constitutive VEGF-A expression. To this end we collected and analysed outflow samples from the renal vein, directly after tumour nephrectomy, in 42 patients diagnosed with ccRCC. Tumour fragments in venous outflow were observed in 33% of ccRCC patients and correlated with the synchronous presence or metachronous development of pulmonary metastases (p < 0.001, Fisher's exact test). In patients with tumours that, in retrospect, were not of the VEGF-A-expressing clear cell type, tumour fragments were never observed in the renal outflow. These data suggest that, in ccRCC, a VEGF-A-induced phenotype promotes a release of tumour cell clusters into the circulation that may contribute to pulmonary metastasis.

Monotherapy with thalidomide for treatment of spinal cord hemangioblastomas in a patient with von Hippel-Lindau disease

Von Hippel-Lindau (VHL) disease is a cancer-prone syndrome characterized by abnormalities in vascular proliferation and the development of both the visceral and CNS tumors. Complications from hemangioblastoma are among the principal causes of death from this syndrome. Antiangiogenic therapy has been used with different modalities in patients suffering from such complications. Here, we describe an adolescent with VHL complicated by progressive, multifocal spinal hemangioblastomas. Treatment with single-agent thalidomide over the course of 3 years was associated with an unexpected stabilization of the disease. The antiangiogenic effect of thalidomide may be associated with the control of progressive hemangioblastoma.

COX-2, VEGF and tumour angiogenesis

Epidemiological evidence suggests a protective effective of regular NSAID use against developing cancer. Cyclooxygenase-2, a target of NSAIDs, is upregulated in many cancers and has been associated with increased VEGF production and angiogenesis. Angiogenesis is the formation of new vessels from existing vasculature and as an essential process for tumour development represents an important therapeutic target. Following an extensive review of the literature this article details the current knowledge on the role of COX-2 in tumorigenesis focusing on its relationship to angiogenesis and VEGF production by tumour cells. While COX-2 is clearly detrimental to prognosis and NSAIDs have a beneficial effect, the possibility of COX-2 independent effects being partly or wholly responsible for this benefit cannot be excluded.

Retinal Capillary Hemangiomas and von Hippel-Lindau Disease

von Hippel-Lindau disease is a multisystem familial cancer syndrome that commonly manifests in the eye as retinal capillary hemangiomas. As the earliest manifestation of the disease, these benign hamartomas can lead to secondary visual loss. Their typical clinical characteristics can lead to accurate diagnosis and appropriate treatment with either laser photocoagulation or cryotherapy enhancing one's probability of preserving vision before becoming symptomatic. Accurate diagnosis can also lead to surveillance of the various other organ systems involved in the disease such as the CNS, kidneys, adrenal glands and pancreas. This will also enable the clinician to provide genetic counseling for patients regarding the lifelong manifestations of this disease.

Intravitreal anti-vascular endothelial growth factor therapy with pegaptanib for advanced von Hippel-Lindau disease of the retina

OBJECTIVE

This pilot study was designed to provide preliminary data concerning the safety and efficacy of pegylated anti-vascular endothelial growth factor (VEGF) therapy, pegaptanib, for patients with juxtapapillary or large peripheral angiomas secondary to von Hippel-Lindau (VHL) disease.

METHODS

This study was an open label, nonrandomized, prospective, pilot study of intravitreal injections of pegaptanib (3 mg/100 microL), given every 6 weeks for minimum of 6 injections. Five patients with severe ocular VHL lesions were enrolled in the study. The primary outcome of this study was a change of > or =15 letters (3 lines) in best-corrected visual acuity by 1 year. Secondary outcomes included changes in macular thickness, as determined by optical coherence tomography, and changes in fluorescein leakage.

RESULTS

Two of five patients completed the course of treatment and 1 year of follow-up. These two patients had progressive decrease in retinal hard exudate and reduction in central retinal thickness measured by optical coherence tomography. One of these two patients had improvement in visual acuity of 3 lines. No significant change in fluorescein leakage or tumor size was detected in either patient. Lesions in the other three patients continued to progress despite treatment, and these patients did not complete the entire treatment course. One patient developed a tractional retinal detachment. Additional serious adverse events included transient postinjection hypotony in two eyes.

CONCLUSIONS

Intravitreal injections of anti-VEGF therapy (pegaptanib) may decrease retinal thickening minimally and reduce retinal hard exudates in some patients with advanced VHL angiomas. This finding may be related to a reduction in vasopermeability, because there was no apparent effect of treatment on the size of the primary retinal angiomas in this small pilot study.

Loss of vascular endothelial growth factor expression reduces vascularization, but not growth, of tumors lacking the Von Hippel-Lindau tumor suppressor gene

Individuals bearing germ line mutations in the Von Hippel-Lindau (VHL) tumor suppressor gene are predisposed to the development of highly angiogenic tumors. This is correlated with an increased expression of the angiogenic factor vascular endothelial growth factor (VEGF) in these tumors, which is in part caused by elevated expression of the HIF-1 hypoxia inducible transcription factors. We created malignant astrocytes with genetic deletions of the VHL gene and implanted them in subcutaneous and intracranial sites; these sites are respectively vessel poor and vessel-rich tissues. When grown in a vessel poor site, VEGF expression in VHL null cells was important for both vascularization and tumor growth. However, when the same cells are grown in the vessel-rich intracranial environment, loss of VEGF expression reduces vascularization, but does not affect tumor growth. This indicates that antiangiogenic therapies for tumors that express high levels of angiogenic factors such as VEGF may vary in their efficacy, with potentially lowered effectiveness in sites, such as the brain, that are inherently vessel rich.

Redox regulation of the hypoxia-inducible factor

Reactive oxygen species (ROS) have long been considered only as cyto- and genotoxic. However, there is now compelling evidence that ROS also act as second messengers in response to various stimuli, such as growth factors, hormones and cytokines. The hypoxia-inducible transcription factor (HIF) is a master regulator of oxygen-sensitive gene expression. More recently, HIF has also been shown to respond to non-hypoxic stimuli. Interestingly, recent reports indicate that ROS regulate HIF stability and transcriptional activity in well-oxygenated cells, as well as under hypoxic conditions. Consequently, ROS appear to be key players in regulating HIF-dependent pathways under both normal and pathological circumstances. This review summarizes the current understanding of the role of ROS in the regulation of the mammalian HIF system.

Development of the tumor vascular bed in response to hypoxia-induced VEGF-A differs from that in tumors with constitutive VEGF-A expression

Tumors arise initially as avascular masses in which central hypoxia induces expression of vascular endothelial growth factor-A (VEGF-A) and subsequently tumor vascularization. However, VEGF-A can also be constitutively expressed as a result of genetic events. VEGF-A is alternatively spliced to yield at least 6 different isoforms. Of these, VEGF-A(121) is freely diffusible whereas basically charged domains in the larger isoforms confer affinity for cell surface or extracellular matrix components. We previously reported that in a mouse brain metastasis model of human melanoma, VEGF-A(121) induced a qualitatively different tumor vascular phenotype than VEGF-A(165) and VEGF-A(189): in contrast to the latter ones, and VEGF-A(121) did not induce a neovascular bed but rather led to leakage and dilatation of preexistent brain vessels. Here, we correlate vascular phenotypes with spatial VEGF-A expression profiles in clinical brain tumors (low grade gliomas; n = 6, melanoma metastases; n = 4, adenocarcinoma metastases; n = 4, glioblastoma multiforme; n = 3, sarcoma metastasis; n = 1, renal cell carcinoma metastasis; n = 1). We show that tumors that constitutively express VEGF-A present with different vascular beds than tumors in which VEGF-A is expressed as a response to central hypoxia. This phenotypic difference is consistent with a model where in tumors with constitutive VEGF-A expression, all isoforms exert their effects on vasculature, resulting in a classical angiogenic phenotype. In tumors where only central parts express hypoxia-induced VEGF-A, the larger angiogenic isoforms are retained by extracellular matrix, leaving only freely diffusible VEGF-A(121) to exert its dilatation effects on distant vessels.

Angiogenic inhibitors: a new therapeutic strategy in oncology

Angiogenesis is a multistep, complex and tightly regulated process that is necessary for tumor growth and metastasis. Based on data of preclinical models, several antiangiogenic compounds has been shown to modify activated tumor endothelium, which suggests that these compounds can improve cytotoxic drug delivery. Such agents have entered clinical trials as single agents or in combination with cytotoxic drugs, and have shown promising antitumor activity. The pharmacodynamic and pharmacokinetic characteristics of antiangiogenic drugs are reviewed here. Most of the early clinical testing of these agents was conducted in patients with advanced disease resistant to standard therapies. Phase III trials compared the efficacy of standard chemotherapy alone with standard chemotherapy in combination with an experimental angiogenesis inhibitor. Although some of these studies were negative or controversial, recent studies validated in large clinical trials with an anti-vascular endothelial growth factor antibody demonstrated significant clinical benefit and renewed enthusiasm for this therapeutic strategy. This review describes the clinical studies of antiangiogenic agents and highlights the challenges related to choosing appropriate strategies for the selection of patients, study design and choice of appropriate endpoints for the studies' development.

Tumours can adapt to anti-angiogenic therapy depending on the stromal context: lessons from endothelial cell biology

It has long been recognized that interference with the blood supply of a tumour is an effective way to halt tumour progression, and even induce tumour regression. This can be accomplished by anti-angiogenic treatment which prevents the formation of a tumour neovasculature, or anti-vascular treatment, which aims at destruction of existent tumour vessels. The latter has received relatively little attention because there is a lack of specific tumour-endothelial markers. Instead, the current detailed knowledge on the factors and mechanisms, involved in angiogenesis, has enabled the development of a variety of angiogenesis inhibitors, especially those that target cellular signalling by vascular endothelial growth factor-A (VEGF-A), the most potent angiogenic factor known. These inhibitors have received lots of attention because they effectively inhibit tumour growth in pre-clinical models. However, in clinical trials these same inhibitors showed very poor anti-tumour activity. In this review we discuss this discrepancy, and we show that the tumour microenvironment is crucial to the sensitivity of tumours to anti-angiogenic therapy.

Detection of carbonic anhydrase 9-expressing tumor cells in the lymph nodes of vulvar carcinoma patients by RT-PCR

Regional lymph node status is an important prognostic factor for vulvar cancer. The goal of our study was to elaborate a reliable test for detecting micrometastases, undetectable by traditional methods, in the lymph nodes of vulvar squamous carcinoma patients. For this purpose, carbonic anhydrase-9 (CA9) was investigated as a cancer-related marker by RT-PCR. Firstly, primary carcinoma specimens were examined for CA9 expression by immunohistochemistry with M75 monoclonal antibody. All 19 tissues exhibited a variable degree of staining, which was mostly confined to the plasma membranes of tumor cells. Correspondingly, all primary tumor specimens and the control A-431 vulvar cancer cell line gave a positive signal in the nested RT-PCR assay designed to detect CA9-expressing cells with a high sensitivity. Analysis of 77 lymph node specimens from 20 patients revealed a full correlation between RT-PCR results and standard hematoxylin-eosin staining in 75% of samples, whereas 25% of specimens were negative by the standard method and positive for CA9 mRNA, accounting for 28% of all histologically negative lymph nodes. There were no false-negatives with RT-PCR. A positive inguinal lymph node with a negative sentinel node was observed in the same groin only once in 38 specimens. Our findings clearly indicate potential value of CA9 as a molecular marker for the assessment of regional lymph node status in vulvar cancer patients and support a possible utility of our RT-PCR assay in the detection of micrometastases.

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The HIF-2alpha/VEGF pathway activation in cutaneous capillary haemangiomas

AIM

To investigate the pathogenesis of capillary haemangiomas, a common form of vascular malformation.

METHODS

Twenty-five cutaneous capillary haemangiomas, excised from patients under 14 years of age, were studied immunohistochemically for endothelial cells, the angiogenic factors thymidine phosphorylase (TP) and vascular endothelial growth factor (VEGF), the proliferation index Ki-67, and the hypoxia inducible factors-1alpha (HIF-1alpha) and -2alpha (HIF-2alpha).

RESULTS

Endothelial-lined channels reacted strongly with CD31 in all cases, clearly definining capillary spaces. Between 5 and 20% of the endothelial cells were Ki-67 positive, indicating an intense proliferative activity; more importantly, they consistently expressed VEGF and HIF-2alpha, and in many cases TP, but failed to react with HIF-1alpha.

CONCLUSION

It is suggested that the activation of the HIF-2alpha pathway and the consequent overexpression of VEGF by the endothelial cells are involved in the pathogenesis of cutaneous capillary haemangiomas.

Combination of antiangiogenic therapy with other anticancer therapies: results, challenges, and open questions

Angiogenesis is necessary for tumor growth. Drug discovery efforts have identified several potential therapeutic targets on endothelial cells and selective inhibitors capable of slowing tumor growth or producing tumor regression by blocking angiogenesis in in vivo tumor models. Certain antiangiogenic therapeutics increase the activity of cytotoxic anticancer treatments in preclinical models. More than 75 antiangiogenic compounds have entered clinical trials. Most of the early clinical testing was conducted in patients with advanced disease resistant to standard therapies. Several phase III trials have been undertaken to compare the efficacy of standard chemotherapy versus the same in combination with an experimental angiogenesis inhibitor. Preliminary results of the clinical studies suggest that single-agent antiangiogenic therapy is poorly active in advanced tumors. Although some of the results of combination trials are controversial, recent positive outcomes with an antivascular endothelial growth factor antibody combined with chemotherapy as front-line therapy of metastatic colorectal cancer have renewed enthusiasm for this therapeutic strategy. This article presents an overview of experimental and clinical studies of combined therapy with antiangiogenic agents and highlights the challenges related to the appropriate strategies for selection of the patients, study design, and choice of proper end points for preclinical and clinical studies using these agents.

HIF-1alpha: a valid therapeutic target for tumor therapy

Hypoxia plays a major role in the induction of angiogenesis during tumor development. One mechanism by which tumor cells respond to a reduced oxygen level is via the activation of hypoxia-inducible factor-1 (HIF-1). HIF-1 is an oxygen-dependent transcriptional activator that plays crucial roles in the angiogenesis of tumors and mammalian development. HIF-1 consists of a constitutively expressed HIF-1beta subunit and the highly regulated HIF-1alpha subunits. The stability and activity of HIF-1alpha are regulated by various post-translational modifications, hydroxylation, acetylation, phosphorylation and sumoyaltion. Therefore, HIF-1alpha interacts with several protein factors including PHD, pVHL, ARD-1, SUMO and p300/CBP. Under normoxia, the HIF-1alpha subunit is rapidly degraded via the von Hippel-Lindau tumor suppressor gene product (pVHL)-mediated ubiquitin/proteasome pathway. The association of pVHL and HIF-1alpha under normoxic conditions is triggered by the hydroxylation of prolines and the acetylation of lysine within a polypeptide segment known as the oxygen-dependent degradation (ODD) domain. On the contrary, under the hypoxia condition, the HIF-1alpha subunit becomes stable and interacts with coactivators such as p300/CBP to modulate its transcriptional activity. Under hypoxic conditions, HIF-1 eventually acts as a master regulator of numerous hypoxia-inducible genes. The target genes of HIF-1 are especially related to angiogenesis, cell proliferation and survival, and to glucose and iron metabolism. Moreover, it was reported that the activation of HIF-1alpha is closely associated with a variety of tumors and oncogenic pathways. Hence, the blocking of HIF-1alpha itself or the blocking of HIF-1alpha interacting proteins inhibits tumor growth. Based on these findings, HIF-1 can be a prime target for anticancer therapies. Therefore, this review summarizes the molecular mechanism of HIF-1alpha stability, the biological functions of HIF-1 and its potential applications for cancer therapies.

Expression of angiogenesis-related factors in lungs of patients with congenital diaphragmatic hernia and pulmonary hypoplasia of other causes

Congenital diaphragmatic hernia (CDH) is a congenital disorder, complicated by pulmonary hypoplasia (PH) and pulmonary hypertension. Hypoplastic lungs have fewer and smaller airspaces than normal, with thicker interalveolar septa; the adventitia and media of pulmonary arteries are thickened, and the total size of the pulmonary vascular bed is decreased compared to normal. Although histological abnormalities in PH have been described, less is known about the underlying molecular mechanisms. Therefore, we have investigated a series of proteins, known to be involved in angiogenesis, including von Hippel-Lindau protein (pVHL), hypoxia-inducible factor-1a (HIF-1a), vascular endothelial growth factor (VEGF), fetal liver kinase 1 (Flk-1), and endothelial and inducible nitric oxide synthase (eNOS, iNOS) by immunohistochemistry on paraffin-embedded lung tissue of CDH patients ( n = 13), patients with lung hypoplasia due to other causes ( n = 20), and normal controls ( n = 33). pVHL was expressed more frequently in the arterial smooth muscle cells of CDH lungs compared with both other groups. Furthermore, HIF-1a was expressed less frequently in the endothelium of arteries, veins, and capillaries of CDH lungs as compared with both other groups. No differences were observed in the expression patterns of VEGF, Flk-1, eNOS, and iNOS between the different groups. Our data suggest a role for pVHL and HIF-1a in normal and abnormal pulmonary angiogenesis. The differential expression of these proteins may provide a molecular basis for the histological differences observed in the lung vessels of patients with CDH.

Complete radiological and metabolic response of metastatic renal cell carcinoma to SU5416 (semaxanib) in a patient with probable von Hippel-Lindau syndrome

We report a case of a patient with probable von Hippel-Lindau (VHL) syndrome and metastatic renal cell cancer (RCC) who had a complete radiological and metabolic response to SU5416 (semaxanib). The patient was enrolled on a clinical study examining the efficacy of SU5416 in patients with metastatic cancer. Treatment with SU5416 was given at a dose of 145 mg/m2 intravenously twice-weekly for 11 doses. The patient achieved an early metabolic response on an F-18 fluorodeoxyglucose (FDG) Positron Emission Tomographic (PET) scan within 2 weeks of therapy. Subsequent computerized tomography (CT) and PET scans (9 and 12 months after treatment, respectively) confirmed ongoing complete radiological and metabolic response. He remains tumor-free 18 months after treatment. This is the first documented report of metastatic RCC in the setting of presumed VHL syndrome responding to treatment with SU5416. While vascular endothelial growth factor (VEGF) inhibitors have been shown to produce a modest response in sporadic metastatic RCC, further studies utilizing VEGF inhibitors in patients with VHL syndrome and RCC warrants exploration.

Angiogenesis in endocrine tumors

Angiogenesis is the process of new blood vessel development from preexisting vasculature. Although vascular endothelium is usually quiescent in the adult, active angiogenesis has been shown to be an important process for new vessel formation, tumor growth, progression, and spread. The angiogenic phenotype depends on the balance of proangiogenic growth factors such as vascular endothelial growth factor (VEGF) and inhibitors, as well as interactions with the extracellular matrix, allowing for endothelial migration. Endocrine glands are typically vascular organs, and their blood supply is essential for normal function and tight control of hormone feedback loops. In addition to metabolic factors such as hypoxia, the process of angiogenesis is also regulated by hormonal changes such as increased estrogen, IGF-I, and TSH levels. By measuring microvascular density, differences in angiogenesis have been related to differences in tumor behavior, and similar techniques have been applied to both benign and malignant endocrine tumors with the aim of identification of tumors that subsequently behave in an aggressive fashion. In contrast to other tumor types, pituitary tumors are less vascular than normal pituitary tissue, although the mechanism for this observation is not known. A relationship between angiogenesis and tumor size, tumor invasiveness, and aggressiveness has been shown in some pituitary tumor types, but not in others. There are few reports on the role of microvascular density or angiogenic factors in adrenal tumors. The mechanism of the vascular tumors, which include adrenomedullary tumors, found in patients with Von Hippel Lindau disease has been well characterized, and clinical trials of antiangiogenic therapy are currently being performed in patients with Von Hippel Lindau disease. Thyroid tumors are more vascular than normal thyroid tissue, and there is a clear correlation between increased VEGF expression and more aggressive thyroid tumor behavior and metastasis. Although parathyroid tissue induces angiogenesis when autotransplanted and PTH regulates both VEGF and MMP expression, there are few studies of angiogenesis and angiogenic factors in parathyroid tumors. An understanding of the balance of angiogenesis in these vascular tumors and mechanisms of vascular control may assist in therapeutic decisions and allow appropriately targeted treatment.

Treatment of von Hippel-Lindau retinal hemangioblastoma by the vascular endothelial growth factor receptor inhibitor SU5416 is more effective for associated macular edema than for hemangioblastomas

PURPOSE

To test the efficacy of the novel vascular endothelial growth factor (VEGF) receptor inhibitor SU5416, in a case of refractory von Hippel-Lindau (VHL) retinal hemangioblastoma (RHB).

DESIGN

Interventional case report.

METHODS

Patient included in a multicenter phase II trial. A 30-year-old woman presenting with VHL disease and multiple RHB on her only eye, refractory to conventional treatments, had decreased visual acuity due to cystoid macular edema (CME). SU5416 was administered intravenously for 7 months. Best-corrected visual acuity (BCVA) and macular thickness were measured by optical coherence tomography.

RESULTS

Under treatment, the size of the RHB did not change, but CME improved significantly. Best-corrected visual acuity rose from 20/40 to 20/25. However, CME recurred after the end of the treatment.

CONCLUSION

The VEGF receptor inhibitor SU5416 failed to reduce the size of RHB but was very effective for the associated CME.

Retinal angioma associated with von Hippel-Lindau disease

Von Hippel-Lindau disease is a multi-system disorder that can produce hamartomas (benign tumour-like nodules) of the eyes, skin and nervous system. Retinal capillary angioma is a common ocular association of this congenital phakomatosis that may result in blinding sequelae, if not managed appropriately. We present a case of retinal angioma associated with von Hippel-Lindau disease and discuss the ocular and systemic signs, diagnosis and management. The optometrist is of particular importance in screening for this disorder, as it is often first detected in a routine eye examination.

Imidazole ring-opened DNA purines and their biological significance

Fragmentation of purine imidazole ring and production of formamidopyrimidines in deoxynucleosides (Fapy lesions) occurs upon DNA oxidation as well as upon spontaneous or alkali-triggered rearrangement of certain alkylated bases. Many chemotherapeutic agents such as cyclophosphamide or thiotepa produce such lesions in DNA. Unsubstituted FapyA and FapyG, formed upon DNA oxidation cause moderate inhibition of DNA synthesis, which is DNA polymerase and sequence dependent. Fapy-7MeG, a methylated counterpart of FapyG-, a efficiently inhibits DNA replication in vitro and in E.coli, however its mutagenic potency is low. This is probably due to preferential incorporation of cytosine opposite Fapy-7MeG and preferential extension of Fapy-7MeG:C pair. In contrast, FapyA and Fapy-7MeA possess miscoding potential. Both lesions in SOS induced E.coli preferentially mispair with cytosine giving rise to A-->G transitions. Fapy lesions substituted with longer chain alkyl groups also show simult aneous lethal and mutagenic properties. Fapy lesions are actively eliminated from DNA by repair glycosylases specific for oxidized purines and pyrimidines both in bacteria and eukaryotic cells. Bacterial enzymes include E.coli formamidopyrimidine-DNA-glycosylase (Fpg protein), endonuclease III (Nth protein) and endonuclease VIII (Nei protein).

A critical evaluation of DNA adducts as biological markers for human exposure to polycyclic aromatic compounds

The causative role of polycyclic aromatic hydrocarbons (PAH) in human carcinogenesis is undisputed. Measurements of PAH-DNA adduct levels in easily accessible white blood cells therefore represent useful early endpoints in exposure intervention or chemoprevention studies. The successful applicability of DNA adducts as early endpoints depends on several criteria: i. adduct levels in easily accessible surrogate tissues should reflect adduct levels in target-tissues, ii. toxicokinetics and the temporal relevance should be properly defined. iii. sources of interand intra-individual variability must be known and controllable, and finally iv. adduct analyses must have advantages as compared to other markers of PAHexposure. In general, higher DNA adduct levels or a higher proportion of subjects with detectable DNA adduct levels were found in exposed individuals as compared with nonexposed subjects, but saturation may occur at high exposures. Furthermore, DNA adduct levels varied according to changes in exposure, for example smoking cessation resulted in lower DNA adduct levels and adduct levels paralleled seasonal variations of air-pollution. Intraindividual variation during continuous exposure was low over a short period of time (weeks), but varied significantly when longer time periods (months) were investigated. Inter-individual variation is currently only partly explained by genetic polymorphisms in genes involved in PAH-metabolism and deserves further investigation. DNA adduct measurements may have three advantages over traditional exposure assessment: i. they can smooth the extreme variability in exposure which is typical for environmental toxicants and may integrate exposure over a longer period of time. Therefore, DNA adduct assessment may reduce the monitoring effort. ii. biological monitoring of DNA adducts accounts for all exposure routes. iii. DNA adducts may account for inter-individual differences in uptake, elimination, distribution, metabolism and repair amongst exposed individuals. In conclusion, there is now a sufficiently large scientific basis to justify the application of DNA adduct measurements as biomarkers in exposure assessment and intervention studies. Their use in risk-assessment, however, requires further investigation.

Hypoxia-induced angiogenesis during carcinogenesis

The formation of new blood vessels, angiogenesis, is an essential process during development and disease. Angiogenesis is well known as a crucial step in tumor growth and progression. Angiogenesis is induced by hypoxic conditions and regulated by the hypoxia-inducible factor 1 (HIF-1). The expression of HIF-1 correlates with hypoxia-induced angiogenesis as a result of the induction of the major HIF-1 target gene, vascular endothelial cell growth factor (VEGF). In this review, a brief overview of the mechanism of angiogenesis is discussed, focusing on the regulatory processes of the HIF-1 transcription factor. HIF-1 consists of a constitutively expressed HIF-1 beta (HIF-1beta) subunit and an oxygen-regulated HIF-1 alpha (HIF-1a) subunit. The stability and activity of HIF-1alpha are regulated by the interaction with various proteins, such as pVHL, p53, and p300/CBP as well as by post-translational modifications, hydroxylation, acetylation, and phosphorylation. It was recently reported that HIF-1alpha binds a co-activator of the AP-1 transcription factor, Jab-1, which inhibits the p53-dependent degradation of HIF-1 and enhances the transcriptional activity of HIF-1 and the subsequent VEGF expression under hypoxic conditions. ARD1 acetylates HIF-1alpha and stimulates pVHL-mediated ubiquitination of HIF-1alpha. With a growing knowledge of the molecular mechanisms in this field, novel strategies to prevent tumor angiogenesis can be developed, and from these, new anticancer therapies may arise.

Therapies directed at vascular endothelial growth factor

The inhibition of angiogenesis through vascular endothelial growth factor (VEGF) receptor targeting is a strategy that is relatively tumour selective. The high selectivity achieved with neutralising antibodies, soluble receptors and ribozymes reduces the risk of adverse reactions not related to VEGF inhibition itself. Small-molecule, orally-active protein kinase inhibitors provide an attractive alternative for chronic therapy, although specifically targeting a small subset of protein kinases from the approximately 550 expressed in mammalian cells is a challenge. Current efforts have resulted in promising clinical data for several synthetic VEGF receptor kinase inhibitors, of which PTK787/ZK222584 and ZD6474 are proceeding into large size clinical trials. It seems likely that blockers of the VEGF signalling pathway will be unsuitable for monotherapy, and that their role will be as an adjunct to additional antiangiogenic agents together with directly-acting antitumour agents or radiation therapy. Caution is needed with combinations of anti-VEGF therapies and cytotoxic agents, as coadministration of cytotoxic agents with either the kinase inhibitor SU5416 or the VEGF antibody avastin appears to be associated with bleeding and thrombotic adverse events.

Vascular endothelial growth factor as a target opportunity in hematological malignancies

Vascular endothelial growth factor (VEGF) is a potent angiogenic peptide with diverse biologic effects. There are seven members of the VEGF family, VEGF-A through VEGF-E, placental growth factor and the newly described, tissue-specific endocrine gland-derived VEGF. VEGF expression is induced by a number of stimuli including hypoxia, activated oncogenes, and inflammatory cytokines while negative regulators include wild type von Hippel-Lindau and p53 tumor suppressor genes. VEGF activity is mediated through interactions with high affinity tyrosine kinase receptors. To date, three have been identified. Interaction with these receptors activates multiple signal pathways leading to the diverse biologic activity of VEGF. Evidence suggests that VEGF is also a survival factor for endothelial cells and perhaps tumor cells. The importance of angiogenic factors such as VEGF, while clearly established in solid tumors, has not been fully elucidated in human hematopoietic neoplasms. Evolving data generally that elevated levels of VEGF confer a poor prognosis to patients with these diseases. The central role of VEGF in angiogenesis coupled with the relatively restricted expression of its receptors, has led to the development of a number of agents to target this system that are currently under clinical investigation.

Association of hypoxia-inducible factors 1alpha and 2alpha with activated angiogenic pathways and prognosis in patients with endometrial carcinoma

BACKGROUND

Hypoxia-inducible factor 1alpha (HIF-1alpha) and HIF-2alpha are essential regulatory proteins for the adaptation of tumor cells to hypoxia, and they stimulate angiogenesis through activation of the vascular endothelial growth factor (VEGF) gene.

METHODS

HIF-1alpha and HIF-2alpha proteins were studied immunohistochemically in a group of 81 patients with Stage I endometrial adenocarcinoma of the endometrioid cell type. The results were correlated with intratumoral angiogenesis, the expression of the angiogenic factors VEGF and thymidine phosphorylase (TP), and the VEGF/receptor (VEGF/KDR) complex. Relations also were sought with estrogen receptor (ER) and progesterone receptor (PR), with the apoptosis-related proteins bcl-2 and p53, with several histopathologic parameters, and with patient prognosis. In addition, a sample of 25 normal endometria at various phases of the menstrual cycle was studied for the presence of HIF-1alpha and HIF-2alpha.

RESULTS

HIF-1alpha expression was detected in 49% of endometrial carcinomas. The expression was cytoplasmic or mixed nuclear/cytoplasmic. HIF-1alpha expression was associated with up-regulation of the VEGF pathway and with increased standard microvessel density (sMVD) and activated VEGF/KDR microvessel density (aMVD). It also was associated with a poor prognosis in both univariate and multivariate analyses. HIF-2alpha protein showed a pattern of expression similar to the pattern seen in HIF-1alpha, but expression of HIF-2alpha protein occurred in only 17% of endometrial carcinomas, and it was associated with increased TP reactivity. There also was a relation of HIF-1alpha expression with well-differentiated endometrial neoplasms, and there was a marginal association of HIF-1alpha and HIF-2alpha with ER expression. With reference to normally cycling tissues, HIF-1alpha nuclear/cytoplasmic expression was particularly strong in the samples of early proliferative phase endometrium compared with HIF-2alpha protein expression, which showed a constant reaction throughout the menstrual cycle.

CONCLUSIONS

The up-regulation of HIF-1alpha and, to a lesser extent, of HIF-2alpha is a common event in Stage I endometrial adenocarcinomas. In these tumors, HIF-1alpha expression is related to increased angiogenesis, through activation of the VEGF angiogenic pathway, and to an unfavorable prognosis. HIF-2alpha accumulation is associated with increased expression of the angiogenic factor TP.

Paradoxical secondary polycythemia in von Hippel-Lindau patients treated with anti-vascular endothelial growth factor receptor therapy

Von Hippel-Lindau (VHL) disease is a dominantly inherited familial cancer syndrome caused by germline mutations in the VHL tumor-suppressor gene. Central nervous system (CNS) and retinal hemangioblastomas are highly vascular tumors that are hallmarks of the disease. These tumors overexpress vascular endothelial growth factor (VEGF) and represent a potential target for anti-angiogenic drugs. We observed, after 3 to 4 months of treatment, secondary paradoxical polycythemia in 3 VHL patients with CNS or retinal hemangioblastomas treated by the anti-VEGF receptor SU5416. Hematocrit was normal before the beginning of the trial, and no progression of hemangioblastomas was observed. Polycythemia vera and all known causes of secondary polycythemia were also ruled out. Polycythemia has never been reported in current SU5416 trials for advanced malignancies and could express a specific action on red blood cell precursors occurring only in the absence of a functional VHL gene. These findings could also affect the inclusion of VHL patients with pre-existing polycythemia in future anti-VEGF receptor trials.

[Contribution of genetics to knowledge and management of hereditary kidney diseases progressing to renal failure]

Genes of most of the hereditary renal diseases progressing to renal insufficiency are now identified. In the first part of this paper we describe their multi-faceted genetics. Genetic heterogeneity has been demonstrated in many of these diseases, such as Alport's syndrome and nephronophtisis. In some of them an allelic heterogeneity is present as in the X-linked form of Alport's syndrome (more than 300 different mutations have been described along the COL4A5 gene). Besides these classical mendelian diseases, mendelian subentities have been isolated within common diseases such as cortico-resistant nephrosis. Many diseases also demonstrate a variability of their phenotype resulting from allelic and/or genetic heterogeneity, or from modifier genes. In the second part of the paper we discuss the consequences of this explosion of knowledge with respect to epidemiology, genetic diagnosis, prenatal diagnosis and treatment.

Oxygen regulation of gene expression: a study in opposites

Oxygen is crucial to aerobic metabolism, but excesses of oxygen or reactive oxygen species (ROS) can injure cells. This minireview addresses two transcription factors that regulate several cellular responses to oxygen tension. Hypoxia inducible factor-1 (HIF-1) is a heterodimeric protein activated by hypoxia. Levels of HIF-1 are regulated by removal of the HIF-1alpha subunit through ubiquination and proteasomal destruction under normoxic conditions. Hypoxia inhibits the ubiquination of HIF-1alpha, preventing its destruction and allowing it to bind to hypoxia-responsive elements in gene promoter, enhancer, and intronic sequences. HIF-1 induces the expression of the hypoxia responsive genes vascular endothelial growth factor and erythropoietin. Its dysregulation has been implicated in von Hippel-Lindau disease. Nuclear factor kappaB (NFkappaB) is a family of pleotropic, dimeric transcription factors, and has a complex pattern of regulation. Under normoxic conditions, NFkappaB is bound to one of several inhibitory proteins (e.g., IkappaB) that prevent its nuclear translocation. Hyperoxia or elevations of ROS cause the ubiquination and destruction of the inhibitory proteins, freeing NFkappaB and allowing it to bind to target gene promoters. Hyperoxia in cell and animal models and acute lung injury in humans induce the expression of multiple proinflammatory cytokines through NFkappaB-dependent mechanisms. Although HIF-1 and NFkappaB respond to changes in pO(2), the precise nature of the oxygen sensing and transduction pathways is unclear in both cases. Both heme-protein and redox-sensitive mechanisms have been proposed. Improved understanding of oxygen-sensitive gene regulation may suggest targeted therapies for human disease.