Elevated ocular levels of vascular endothelial growth factor in patients with von Hippel-Lindau disease

Hyper-reflective retinal foci as possible in vivo imaging biomarker of microglia activation in von Hippel-Lindau disease

Purpose

von Hippel-Lindau (VHL) disease is caused by a mutation of the VHL gene and characterized by the development of retinal hemangioblastomas (RH). Current pathophysiologic mechanisms of RH development and progression are still insufficient to predict RH behavior. VHL gene is involved in the cellular response to hypoxia and in many intracellular signaling pathways expressed both in angiogenesis and inflammation. Optical coherence tomography (OCT) allows to identify hyper-reflective retinal foci (HRF) known as aggregates of activated microglial cells as possible in vivo biomarker of local inflammation. The aim of the present study was to investigate the presence of HRF in patients with genetically confirmed VHL disease.

Methods

In this cross-sectional study, patients with VHL underwent complete ophthalmological examination and OCT with HRA + OCT Spectralis. HRF were manually identified and calculated in inner (IR), outer (OR) and full retina. Age-matched healthy subjects were enrolled as controls.

Results

113 eyes of 63 VHL patients and 56 eyes of 28 healthy subjects were evaluated. HRF number was significantly higher in VHL than in controls in IR (28.06 ± 7.50 vs 25.25 ± 6.64, p = 0.042). No difference was observed in OR and in full retina (OR: 7.73 ± 2.59 vs 7.95 ± 2.51, p = 0.599; full retina: 35.79 ± 8.77 vs 33.20 ± 7.47, p = 0.093).

Conclusion

The increase of HRF, which mirror retinal microglial activation, characterizes VHL eyes. The role of activated microglia in the retina of VHL eyes needs to be better investigated, mainly considering local VHL disease manifestations.

Combined therapy guided by multimodal imaging of fifteen retinal capillary hemangioblastomas in a monocular Von Hippel- Lindau syndrome case report

Background

To report the multimodal imaging and treatment of fifteen retinal capillary hemangioblastomas (RCHs) associated with Von Hippel-Lindau syndrome in a monocular patient during a long-term following-up, which supply high-resolution exquisite SS-OCTA images (VG200; SVision Imaging, Ltd., Luoyang, China) and management experience about multiple RCHs.

Case presentation

A 34-year-old monocular male patient complained decreased visual acuity (20/100) without pain and redness in the left eye five years ago. Von Hippel-Lindau syndrome were diagnosed with genetic testing. He, his son and daughter all carried a heterozygosity missense variant c.499C > T (p. Arg167Trp) in the Hg19 gene, a VHL gene located in Chr3:10,191,506. Fifteen RCHs were identified by the application of multimodal imaging, which including fundus photo, fundus autofluorescence (FAF), B-scan ultrasonography (US), fluorescein fundus angiography (FFA), indocyanine green angiography (ICGA) and swept-source optical coherence tomography angiography (SS-OCTA). Transscleral cryotherapy and laser photocoagulation were performed to destroy the largest RCH with the size of 4 PD in diameter. Laser photocoagulation was conducted to seal the middle or tiny RCHs (< 1.5 PD) and their nourishing vessels. The retinal edema and exudative macular detachment were successfully relieved by intraocular injection of bevacizumab for 5 times. The RCHs in the left eye responded well to these treatments and best corrected visual acuity was 20/25 for three years. Three-month recall visits were recommended for him.

Conclusion

For multiple retinal capillary hemangioblastomas in monocular patients, precise combined therapy guided by multimodal imaging has a profound impact on the management of new and recurrent RCHs.

Clinical Results of Various Treatments for Retinal Capillary Hemangioma

PURPOSE

We report the clinical outcomes of retinal capillary hemangioma (RCH) after the application of various treatments.

METHODS

We performed a retrospective chart analysis of eight eyes treated for RCH between August 2009 and January 2018. During the follow-up period, the status and progression of the RCHs were checked by fundus photography, fluorescein angiography, and optical coherence tomography, and additional treatments were applied when necessary.

RESULTS

Three of the five patients had bilateral RCH, and two had unilateral RCH. Six eyes received laser photocoagulation; two eyes received cryotherapy, and one eye received intravitreal Avastin injection. Three eyes each had intravitreal triamcinolone injection, subtenon triamcinolone injection, and intravitreal dexamethasone injection to control inflammation. Also, two patients took oral prednisolone, and one patient used prednisolone eye drops to control inflammation. Two eyes underwent vitrectomy and scleral buckling due to deterioration of the epiretinal membrane and vitreal traction, respectively. As a result of those treatments, the tumors were stable in five of the eight eyes. However, one eye is now in a pre-phthisis state, and one patient who refused treatment showed progression of the tumor, epiretinal membrane, and traction.

CONCLUSIONS

Because RCHs vary in size, the degree of inflammation, and symptoms, this disorder should be actively treated on a case-by-case basis. Fluorescein angiography should be used periodically to determine recurrence of the tumor or inflammation, and the appropriate treatment should be repeated as necessary. Moreover, regular systemic screening tests for von Hippel-Lindau disease should be performed in RCH patients to ensure that they have no abnormalities other than in the eye.

Laser photocoagulation, intravitreal anti-VEGF, and vitreous surgery for the treatment of juxtapapillary retinal capillary hemangioma

Juxtapapillary retinal capillary hemangiomas (JRCHs) are benign vascular tumors located on or adjacent to the optic nerve head. A 19-year-old girl presented with epiretinal membrane (ERM) associated with an elevated and round vascular tumoral mass located in the juxtapapillary region of her left eye. She was subsequently diagnosed with isolated JRCH. A combined approach with laser photocoagulation and intravitreal bevacizumab injection was used to facilitate shrinkage of the tumor preoperatively and pars plana vitrectomy was used to remove the tumor and ERM. A small remnant of tumoral mass remained intact and did not show any growth for 7 years.

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.

Systemic Sunitinib Malate Treatment for Advanced Juxtapapillary Retinal Hemangioblastomas Associated with von Hippel-Lindau Disease

PURPOSE

To describe the clinical course of advanced juxtapapillary retinal capillary hemangioblastomas (RCH) associated with von Hippel-Lindau (VHL) disease treated with systemic sunitinib malate, an agent that inhibits both anti-vascular endothelial growth factor and anti-platelet-derived growth factor signaling.

DESIGN

Observational case review.

PARTICIPANTS

Three patients with advanced VHL-related juxtapapillary RCH treated with systemic sunitinib malate.

METHODS

Patient 1 was followed routinely every 4 months while on systemic sunitinib prescribed by her oncologist for metastatic pancreatic neuroendocrine and kidney tumors. Patients 2 and 3 were part of a prospective clinical trial evaluating the use of systemic sunitinib for ocular VHL lesions during a period of 9 months. Visual acuity, size of RCH, and degree of exudation were recorded at each visit. Optical coherence tomography (OCT) and fluorescein angiography were also obtained at some visits.

MAIN OUTCOME MEASURES

Visual acuity, size of RCH, and degree of exudation.

RESULTS

Three patients with advanced VHL-associated juxtapapillary RCH were treated with systemic sunitinib malate. While none of the patients lost vision during therapy, treatment with sunitinib malate did not improve visual acuity or reduce the size of RCH. Improvements in RCH-associated retinal edema were observed in two patients. All patients experienced multiple adverse effects, including thyroid toxicity, thrombocytopenia, nausea, fatigue, jaundice, and muscle aches. Two of the three patients had to discontinue treatment prematurely and the third required dose reduction.

CONCLUSIONS

Systemic sunitinib malate may be useful in slowing progression of ocular disease from VHL-associated RCH. However, significant systemic adverse effects limited its use in this small series, and systemic sunitinib malate may not be safe for treatment of RCH when used at the doses described in this report. Further studies are required to determine if this medication used at lower doses with different treatment strategies, other medications in the same class or drugs directed at multiple targets in the tumor, may be safer and more effective for the treatment of advanced VHL-associated RCH.

Influence of vascular endothelial growth factor inhibition on simple renal cysts in patients receiving bevacizumab-based chemotherapy

Purpose

Although angiogenesis has been implicated in the promotion of renal cyst growth in autosomal dominant polycystic kidney disease, no studies have investigated the role of angiogenesis in the growth of simple renal cysts. The aim of current study was to investigate the effect of chemotherapy with the antivascular endothelial growth factor antibody bevacizumab on renal cyst development and growth in cancer patients.

Materials and Methods

We retrospectively reviewed the medical records of 136 patients with a variety of cancers that were treated with bevacizumab-based chemotherapy for metastatic disease. The presence of and changes in renal cysts were evaluated by retrospective analysis of computed tomography scans performed for assessment of tumor response to bevacizumab-based therapy.

Results

The median age of the patients was 64 years. Renal cysts were identified in 66 patients, in whom 33 (50%) had a single cyst and the rest had 2 or more cysts. The average dose of bevacizumab was 2.68 mg/kg per week. Median duration of treatment was 33 weeks. Average cyst size was 1.9±2.4 cm at the beginning of the study and the majority of the cysts (54 patients, 84%) did not change in size or shape during bevacizumab treatment. No patients were identified with new cysts. Cyst size changed in 10 patients (16%): an increase of 15% to 40% from the baseline size in 5 patients and a decrease in size of 10% to 70% in another 5 patients. The duration of bevacizumab therapy was significantly longer in the subgroup of patients with diminished or increased cyst size than in the patients with stable cyst size: 62 weeks versus 29 weeks, respectively (p=0.0002).

Conclusions

Our data demonstrated that simple renal cysts were stable in size and number in the vast majority of cancer patients treated with bevacizumab.

Intravitreal bevacizumab for retinal capillary hemangioblastoma: A case series and literature review

OBJECTIVE

To evaluate the long-term outcomes of intravitreal bevacizumab for peripheral and juxtapapillary retinal capillary hemangioblastoma (RCH).

DESIGN

We conducted a retrospective noncomparative interventional case series.

PARTICIPANTS

There were 4 patients (5 eyes) presenting with RCH.

METHODS

Five eyes with RCH presented with exudative changes and visual loss. Three eyes of 2 patients with peripheral RCH were treated with cryotherapy and 2 intravitreal injections of bevacizumab (0.5 mg). Two eyes with juxtapapillary RCH were treated with 3 intravitreal injections of bevacizumab. The main outcome measures were changes in best-corrected visual acuity (BCVA), lesion size, exudation, and retinal thickness.

RESULTS

In peripheral RCH, improvement of BCVA from counting fingers to 20/400 was obtained in 1 eye. One patient with bilateral RCH maintained a vision of 20/20 in 1 eye with complete anatomic regression of the 3 small peripheral RCH lesions. The fellow eye with fibrotic bands from the RCH to the optic nerve head developed a tractional retinal detachment after the first injection and was treated with pars plana vitrectomy. In patients with juxtapapillary RCH, bevacizumab injections resulted in an improvement of BCVA from 20/80 to 20/20 in 1 eye, whereas the second eye did not show an improvement of BCVA despite a regression of the tumour.

CONCLUSIONS

Intravitreal anti-vascular endothelial growth factor agents, alone or in combination with other treatment modalities, may improve visual acuity. Further trials evaluating the dose, the number of injections, and the route of administration will be important in advancing antiangiogenic therapies for RCH.

Pathology characteristics of ocular von Hippel-Lindau disease with neovascularization of the iris and cornea: a case report

Introduction

Retinal hemangioblastoma is one of the most common tumors in von Hippel-Lindau disease. In addition to the classical pathological characteristics of von Hippel-Lindau disease, we report, for what we believe to be the first time, a severe and rare ocular complication characterized by neovascularization in the cornea and iris.

Case presentation

A 41-year-old white man with a long history of retinal hemangioblastoma presented with neovascularization of his iris and cornea as well as corneal perforation. His right eye was blind and painful, leading to a decision of enucleation. On microscopy, the enucleated eye showed neovascularization of the cornea and iris. The cornea was perforated with an expulsive hemorrhage and extruding intraocular contents, including the retina. A large retinal hemangioblastoma was located at the posterior pole adjacent to the optic nerve head. The tumor was mainly composed of large cells with foamy cytoplasm. Bone formation was also present.

Conclusion

Our pathology findings were consistent with previously described features of retinal hemangioblastoma. The present case is unusual because of the co-existing neovascularization in the iris and cornea, which may have led to corneal perforation and vision loss.

Intravitreal anti-VEGF injection for the treatment of progressive juxtapapillary retinal capillary hemangioma: a case report and mini review of the literature

We report a case of a patient known to have a von Hippel–Lindau disease with documented progressive juxtapapillary retinal capillary hemangioma (JRCH) with well-preserved visual acuity (VA) and visual field (VF). The patient received a single injection of intravitreal ranibizumab (IVR). Six months after IVR injection, the JRCH showed reduced vascularization, fibrosis, and mild shrinkage, and VA and VF remained unchanged. IVR therapy might therefore be considered as an alternative treatment for progressive JRCH, especially in patients with well-preserved VA and VF.

Low aerobic mitochondrial energy metabolism in poorly- or undifferentiated neuroblastoma

BACKGROUND

Succinate dehydrogenase (SDH) has been associated with carcinogenesis in pheochromocytoma and paraganglioma. In the present study we investigated components of the oxidative phosphorylation system in human neuroblastoma tissue samples.

METHODS

Spectrophotometric measurements, immunohistochemical analysis and Western blot analysis were used to characterize the aerobic mitochondrial energy metabolism in neuroblastomas (NB).

RESULTS

Compared to mitochondrial citrate synthase, SDH activity was severely reduced in NB (n = 14) versus kidney tissue. However no pathogenic mutations could be identified in any of the four subunits of SDH. Furthermore, no genetic alterations could be identified in the two novel SDH assembly factors SDHAF1 and SDH5. Alterations in genes encoding nfs-1, frataxin and isd-11 that could lead to a diminished SDH activity have not been detected in NB.

CONCLUSION

Because downregulation of other complexes of the oxidative phosphorylation system was also observed, a more generalized reduction of mitochondrial respiration seems to be present in neuroblastoma in contrast to the single enzyme defect found in hereditary pheochromocytomas.

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.

Interplay between VHL/HIF1α and Wnt/β-catenin pathways during colorectal tumorigenesis

Activation of the Wnt signaling pathway initiates the transformation of colorectal epithelial cells, although the transition to metastatic cancer requires angiogenesis. We have investigated the expression of the von Hippel-Lindau (VHL) tumor suppressor in the intestines from humans and mice. Here, we show that VHL expression is regulated by TCF4 and is restricted to the proliferative compartment at the bottom of intestinal crypts. Accordingly, VHL is completely absent from the proliferative intestinal pockets of Tcf4(-/-) perinatal mice. We observed complementary staining of the hypoxia-inducible factor (HIF) 1alpha to VHL in normal intestinal epithelium as well as in all stages of colorectal cancer (CRC). To the best of our knowledge, this is the first report demonstrating the presence of nuclear HIF1alpha in normoxic healthy adult tissue. Although we observed upregulated levels of VHL in very early CRC lesions from sporadic and familial adenomatous polyposis patients - presumably due to activated Wnt signaling - a clear reduction of VHL expression is observed in later stages of CRC progression, coinciding with stabilization of HIF1alpha. As loss of VHL in later stages of CRC progression results in stabilization of HIF, these data provide evidence that selection for VHL downregulation provides a proangiogenic impulse for CRC progression.

Cyclooxygenase-2 Is a Target of KRASD12, Which Facilitates the Outgrowth of Murine C26 Colorectal Liver Metastases

Purpose: Mutational activation of the KRAS oncogene and overexpression of cyclooxygenase-2 (COX-2) contribute to colorectal carcinoma (CRC) development, but the relationship between these two events is unclear. This study was designed to clarify that relationship and to assess the contribution of KRAS-dependent COX-2 to the seeding of CRC cells in the liver and to their outgrowth as liver metastases in an experimental mouse model.

Experimental Design: The effect of RNA interference–mediated KRAS knockdown on COX-2 expression and activity was tested in murine C26 CRC cells. The contribution of KRAS-dependent COX-2 to early metastatic tumor cell seeding (by intravital microscopy) and outgrowth of metastases in the liver (by bioluminescence imaging) was studied by using parecoxib, a novel and highly selective liver-activated COX-2 inhibitor. Intratumoral cell proliferation, apoptosis, and tumor-associated angiogenesis were assessed by immunohistochemistry on liver tissue sections.

Results: Stable knockdown of mutant KRASD12 in murine C26 CRC cells by RNA interference lead to a dramatic reduction of COX-2 synthesis and prostaglandin E2 production. Inhibition of host or tumor cell COX-2 activity had no effect on early metastatic cell seeding in the liver but greatly reduced intrahepatic tumor cell proliferation and the rate of liver metastasis outgrowth. COX-2 inhibition had no effect on early tumor vascularization or on tumor cell apoptosis.

Conclusions: The high levels of COX-2 enzyme and prostaglandin production in C26 CRC cells are primarily caused by the presence of endogenous mutant KRASD12. Furthermore, COX-2 inhibition affects the tumoral rather than the vascular compartment during the early stages of C26 liver metastasis outgrowth.

Neuro-ophthalmology of von Hippel-Lindau

von Hippel-Lindau (VHL) disease is a multisystem inherited cancer syndrome with characteristic tumors and a known genetic basis. Patients with VHL develop, among other tumors, retinal capillary hemangiomas, central nervous system hemangioblastomas, renal clear cell carcinomas, and pheochromocytomas. Nearly all patients can be shown to have a mutation in the VHL gene, which is located on chromosome 3p25. Genetic abnormalities result in abnormal levels of pVHL, which in turn lead to the different tumors. Four distinct phenotypes of VHL disease have been identified based on the relative frequency of and propensity for the development of different VHL tumors. Aggressive screening of patients with VHL disease can prevent morbidity and mortality from these tumors. Although these tumors typically have been treated with observation or surgery, trials of newer medical therapies that target some of the cellular dysregulation caused by mutation in pVHL are ongoing. Even though these trials have not been wholly successful, they present an exciting direction for future research. This article presents a summary of new developments in VHL disease with a focus on ophthalmic and neuro-ophthalmic practice.

Interleukin-6 and Tumor Necrosis Factor-α in Patients with Obstructive Sleep Apnea-Hypopnea Syndrome

BACKGROUND

In previous studies, significantly elevated levels of vascular endothelial growth factor (VEGF) have been reported in patients with severe obstructive sleep apnea-hypopnea syndrome (OSAHS). On the other hand, plasma tumor necrosis factor-alpha (TNF-alpha) and interleukin-6 (IL-6) have been significantly higher in mild sleep apneics than in normal controls. However, this study included a small number of patients and milder cases of OSAHS.

OBJECTIVES AND METHODS

To assess the involvement of IL-6 and TNF-alpha in VEGF increases in patients with severe OSAHS, serum levels of IL-6 and TNF-alpha were determined in patients with severe OSAHS (n=110) and compared to those of controls (n=45) using an enzyme-linked immunosorbent assay.

RESULTS

No significant increase in IL-6 or TNF-alpha was detected in the present study cohort. However, the body mass index was significantly correlated with the severity of the apnea-hypopnea index.

CONCLUSIONS

These data suggest that the elevation in VEGF is not directly related to IL-6 or TNF-alpha levels. However, the question of whether VEGF is the cause or the result of OSAHS remains to be determined. Further studies are needed to clarify the role of IL-6 and TNF-alpha in the pathogenesis of OSAHS, in which obesity should be entered as an independent factor.

Congenital disorder of oxygen sensing: association of the homozygous Chuvash polycythemia VHL mutation with thrombosis and vascular abnormalities but not tumors

Adaptation to hypoxia is critical for survival and regulates multiple processes, including erythropoiesis and vasculogenesis. Chuvash polycythemia is a hypoxia-sensing disorder characterized by homozygous mutation (598C>T) of von Hippel-Lindau gene (VHL), a negative regulator of hypoxia sensing. Although endemic to the Chuvash population of Russia, this mutation occurs worldwide and originates from a single ancient event. That VHL 598C>T homozygosity causes elevated normoxic levels of the transcription factor hypoxia inducible factor-1alpha (HIF-1alpha), serum erythropoietin and hemoglobin is known, but the disease phenotype has not been documented in a controlled manner. In this matched cohort study, VHL 598C>T homozygosity was associated with vertebral hemangiomas, varicose veins, lower blood pressures, and elevated serum vascular endothelial growth factor (VEGF) concentrations (P <.0005), as well as premature mortality related to cerebral vascular events and peripheral thrombosis. Spinocerebellar hemangioblastomas, renal carcinomas, and pheochromocytomas typical of classical VHL syndrome were not found, suggesting that overexpression of HIF-1alpha and VEGF is not sufficient for tumorigenesis. Although hemoglobin-adjusted serum erythropoietin concentrations were approximately 10-fold higher in VHL 598C>T homozygotes than in controls, erythropoietin response to hypoxia was identical. Thus, Chuvash polycythemia is a distinct VHL syndrome manifested by thrombosis, vascular abnormalities, and intact hypoxic regulation despite increased basal expression of hypoxia-regulated genes.

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.

Regulation of tyrosine hydroxylase promoter activity by the von Hippel-Lindau tumor suppressor protein and hypoxia-inducible transcription factors

Tyrosine hydroxylase (TH), the rate-limiting enzyme in catecholamine biosynthesis, is induced by hypoxia in oxygen-sensitive cells of the carotid body and pheochromocytoma-derived PC12 cells. TH is also regulated by the von Hippel-Lindau tumor suppressor protein (pVHL). Here, we report that induction of TH gene expression involves activation of the hypoxia-inducible transcription factors (HIFs) that interact with a specific hypoxia-responsive element (HRE) in the proximal region of the TH promoter. We also show that some of the effects of pVHL on activity of the TH promoter are mediated through HIFs. Low levels of pVHL are associated with decreased HIFalpha ubiquitination, increased accumulation of HIFalpha proteins, increased binding of HIFs to the HRE within the TH promoter, and increased activity of a TH promoter-reporter construct. In contrast, high levels of pVHL repress HIF accumulation and inhibit its activity in hypoxic cells. These results indicate that HIFs may play an important role in regulation of TH gene expression in oxygen-sensitive cells and also in the development of hypercatecholaminemia in pheochromocytoma tumors.

Vascular endothelial growth factor in the cerebrospinal fluid of infants who died of sudden infant death syndrome: evidence for antecedent hypoxia

OBJECTIVES

Recurrent hypoxemia has been proposed as an important pathophysiological mechanism underlying sudden infant death syndrome (SIDS). However, conflicting results emerged when xanthines were used as markers for hypoxia. The vascular endothelial growth factor (VEGF) gene is highly sensitive to changes in tissue partial oxygen tension, and changes in genomic and protein expression occur even after changes in oxygenation within the physiologic range.

METHODS

For determining whether hypoxia precedes SIDS, VEGF levels were measured using an enzyme-linked immunosorbent assay in the cerebrospinal fluid (CSF) of 51 SIDS infants and in 33 additional control infants who died of an identifiable cause. In addition, 6 rats that had a chronically implanted catheter in the lateral ventricle were exposed to a short hypoxic challenge, and VEGF concentrations were measured in CSF at various time points for 24 hours. Another set of 6 rats were killed with a pentobarbital overdose, and VEGF CSF levels were obtained at different time points after death.

RESULTS

Mean VEGF concentrations in CSF were 308.2 +/- 299.1 pg/dL in the SIDS group and 85.1 +/- 82.9 pg/dL in those who died of known causes. Mean postmortem delay averaged 22 hours for both groups. In rat experiments, hypoxic exposures induced time-dependent increases in VEGF, peaking at 12 hours and returning to baseline at 24 hours. Postmortem duration in the animals was associated with gradual increases in VEGF that reached significance only at 36 hours.

CONCLUSIONS

We conclude that VEGF CSF concentrations are significantly higher in infants who die of SIDS. We postulate that hypoxia is a frequent event that precedes the sudden and unexpected death of these infants.

Peripheral retinoschisis and exudative retinal detachment in pars planitis

PURPOSE

To review and describe bullous retinoschisis and exudative retinal detachment in patients with pars planitis.

METHODS

Retrospective, multicenter study of patients with pars planitis who presented with retinoschisis and exudative retinal detachments.

RESULTS

The authors describe 13 eyes of 9 patients with pars planitis who presented with inferior peripheral retinoschisis and/or exudative retinal detachment. Four patients were male; five were female. Patients' ages ranged from 8 years to 35 years (median, 12 years). The follow-up interval ranged from 1 month to 10 years (median, 4 years). These peripheral retinal elevations had a tendency to remain stable, although those with telangiectatic vessels or vasoproliferative tumors occasionally demonstrated an increase in accumulation of exudate. Treatment of such eyes with cryotherapy, or low-dose plaque radiotherapy, resulted in vasoproliferative tumor and telangiectatic vessel regression, absorption of the hard exudate, and resolution of the retinal elevation in four of five eyes. One patient had spontaneous regression of the retinoschisis cavity over a 4-year period.

CONCLUSION

Patients with pars planitis may present with bullous retinoschisis and/or exudative retinal detachment. These findings may be related to a Coats disease-like vascular response (telangiectatic vessels and vasoproliferative tumors) secondary to chronic inflammation. Treatment of the vascular leakage tended to result in resolution of the detachment and/or schisis.

Vascular endothelial growth factor is increased in aqueous humor of glaucomatous eyes

PURPOSE

To assess the concentrations of vascular endothelial growth factor (VEGF) in aqueous humor in eyes with and without glaucoma.

METHODS

Concentrations of VEGF were measured using a sandwich ELISA kit in aqueous humor aspirates taken during anterior segment surgery from 87 patients, of whom 54 had glaucoma (27 primary open-angle glaucoma, 8 angle-closure glaucoma, 16 exfoliative glaucoma) and 33 had cataract only.

RESULTS

Vascular endothelial growth factor was detected in all samples. The concentration in eyes with cataract only without glaucoma was 102.4 +/- 29.7 pg/mL (mean +/- SD), which was significantly lower than that from eyes with glaucoma (146.7 +/- 51.8 pg/mL). There were no significant differences between primary open-angle glaucoma (140.4 +/- 51.0 pg/mL), angle-closure glaucoma (142.8 +/- 40.2 pg/mL), and exfoliative glaucoma (158.6 +/- 58.9 pg/mL). An unusually high VEGF concentration was detected in one eye with neovascular glaucoma (759 pg/mL) and two eyes with uveitic glaucoma (322 pg/mL). No effect of age, gender, or previous history of medical, laser, or surgical treatment of the aqueous humor VEGF concentration could be detected ( > 0.05). Aqueous humor and plasma VEGF concentrations were measured and compared in 46 patients. The aqueous humor VEGF concentration (144.2 +/- 107.9 pg/mL) was significantly higher ( < 0.01) than the plasma concentration (79.2 +/- 46.1 pg/mL). No significant correlation was found between aqueous humor and plasma VEGF concentrations.

CONCLUSION

Aqueous VEGF concentration is increased in eyes with glaucoma.

Detection of connective tissue growth factor in human aqueous humor

PURPOSE

Connective tissue growth factor (CTGF) has been shown to be substantially involved in various processes of fibrosis. We investigated if CTGF is present in aqueous humor (AH).

METHODS

Samples from AH were collected from 10 volunteers during cataract surgery. Specific ELISA analysis was performed with goat IGG against human CTGF.

RESULTS

CTGF was above the detection limit of the assay in 80% of the samples. The concentration of CTGF in the anterior chamber fluid was 1.24 +/- (SD) 0.26 ng/ml.

CONCLUSION

CTGF is present in a majority of AH samples, possibly representing a constant component in this fluid. The origin and physiological importance of CTGF is yet unclear. The involvement of CTGF in processes of intraocular fibrosis and wound healing is possible.

Hypoxia-induced regulation of mRNA stability

Because molecular oxygen is essential for generating cellular energy in aerobic organisms, and because survival depends on this fundamental requirement for oxygen, all higher organisms have evolved numerous diversely regulated mechanisms to detect and respond to potentially life-threatening occurrences of decreased oxygen availability (hypoxia). While the oxygen-dependent regulation of gene expression involves both transcriptional- and post-transcriptional mechanisms, investigations have focused mainly on mechanisms working at the transcriptional level. In this review, the focus is on a growing body of work that looks at post-transcriptional mechanisms acting at a level of mRNA stability.

Heparin-mediated selective release of hepatocyte growth factor in humans

AIMS

The aim of this investigation was to compare the effects of standard (S) with low molecular weight (LMW) heparin on circulating levels of heparin-binding growth factors (HBGF), known to have angiogenic properties in humans.

METHODS

In two consecutive trials 18 healthy male volunteers were studied on three separate occasions, following a placebo-controlled crossover design. Subjects were randomised to receive either S-heparin or LMW heparin or placebo. Heparins were administered either by intravenous (i.v.) or subcutaneous (s.c.) injection and saline placebo by i.v. injection. Serum concentrations of hepatocyte growth factor (HGF), vascular endothelial cell growth factor (VEGF) and basic fibroblast growth factor (bFGF) were measured before and up to 24 h after injection.

RESULTS

Administration of i.v. S-or LMW-heparin (50 IU kg(-1) resulted in rapid, highly significant (47 fold for S, 30.9 fold for LMW) increases in HGF serum values, reaching maxima of 10.51+/-1.65 ng ml(-1) (S) and 8.28+/-1.04 ng ml(-1) (LMW), respectively, 10 min after drug application. S.c. injection of S-heparin or LMW heparin resulted in 4.1 and 5.4 fold increases in HGF serum values, respectively. Both agents showed no effects on circulating VEGF or bFGF levels, independent of the route of administration.

CONCLUSIONS

Circulating HGF levels were selectively increased in response to pharmacological doses of two, widely used heparin preparations. This may, in part, explain some of the biological effects of heparin separate from its anticoagulant properties. By this mechanism, the systemic administration of heparin may facilitate collateral vessel formation in various clinical settings of tissue ischaemia.

An important von Hippel-Lindau tumor suppressor domain mediates Sp1-binding and self-association

VHL is the causative gene for both von Hippel-Lindau (VHL) disease and sporadic clear-cell renal cancer. We showed earlier that VHL downregulates vascular endothelial growth factor transcription by directly binding and inhibiting the transcriptional activator Sp1. We have now mapped the VHL Sp1-binding domain to amino acids 96-122. The 96-122 domain is disproportionately affected by substitution mutations, which interfere with the VHL-Sp1 interaction. Deletion of the 96-122 domain prevents VHL effects on Sp1 DNA binding and on VHL target gene expression, indicating the domain contributes importantly to VHL tumor suppressor activity. Nevertheless, prevention of the VHL-Sp1 interaction only partially abrogates VHL's transcriptional repressor activity, supporting the existence of VHL transcriptional effectors in addition to Sp1. VHL also directly interacts with the Sp1 zinc fingers and self-associates via the 96-122 domain, which furthermore suggest the domain may bind other metalloproteins and contribute to VHL dominant-negative effects.

New strategies in anti-vascular cancer therapy

Angiogenesis is a critical step in the progression of tumours from dormancy to a clinical relevant cancer. Inhibition of this process is one of the most promising new anti-cancer strategies. To develop new drugs that interfere with the cascade of events required for the formation of new blood vessels, insight into this process is essential. Here, we discuss the molecular basis of angiogenesis and the concepts of vascular targeting. Furthermore new strategies will be discussed to discover surface markers on endothelial cells that confer sufficient specificity for targeted intervention in the tumour vasculature.