von Hippel-Lindau disease

Discovering a novel genetic variant in 11 family members who had isolated pheochromocytoma linked to von Hippel-Lindau (VHL) syndrome, aligning with the type 2c phenotype

INTRODUCTION

Von Hippel-Lindau disease (e.g. VHL) is an autosomal dominant multi-organ cancer syndrome caused by a mutation in the VHL tumour suppressor gene. In this study, we introduce a novel genetic variant found in 11 family members diagnosed initially with isolated Pheochromocytoma. Subsequent findings revealed its association with VHL syndrome and corresponds to the Type 2 C phenotype.

METHODS

The VHL gene was amplified through the utilisation of the polymerase chain reaction (PCR). PCR fragments were sequenced using bidirectional Sanger sequencing, using BigDye™ Terminator v3.1 Cycle Sequencing Kit, running on the 3500 genetic analyser. Results were assembled and analysed Using Software SeqA and chromas pro.

RESULTS

A heterozygous in-frame duplication of three nucleotides, specifically ATG, c.377_379dup; p.Asp126dup in exon 2, was identified in all the patients tested within the pedigree.

CONCLUSION

In this study, we disclose the identification of a novel genetic variant in a Jordanian family, affecting eleven family members with pheochromocytoma associated with VHL disease. This finding underscores the importance of screening family members and contemplating genetic testing for individuals newly diagnosed with pheochromocytoma and could enhance our comprehension of the potential adverse consequences associated with VHL germline mutations.

Oncogenic Cell Tagging and Single-Cell Transcriptomics Reveal Cell Type-Specific and Time-Resolved Responses to Vhl Inactivation in the Kidney

Defining the initial events in oncogenesis and the cellular responses they entrain, even in advance of morphologic abnormality, is a fundamental challenge in understanding cancer initiation. As a paradigm to address this, we longitudinally studied the changes induced by loss of the tumor suppressor gene von Hippel Lindau (VHL), which ultimately drives clear cell renal cell carcinoma. Vhl inactivation was directly coupled to expression of a tdTomato reporter within a single allele, allowing accurate visualization of affected cells in their native context and retrieval from the kidney for single-cell RNA sequencing. This strategy uncovered cell type-specific responses to Vhl inactivation, defined a proximal tubular cell class with oncogenic potential, and revealed longer term adaptive changes in the renal epithelium and the interstitium. Oncogenic cell tagging also revealed markedly heterogeneous cellular effects including time-limited proliferation and elimination of specific cell types. Overall, this study reports an experimental strategy for understanding oncogenic processes in which cells bearing genetic alterations can be generated in their native context, marked, and analyzed over time. The observed effects of loss of Vhl in kidney cells provide insights into VHL tumor suppressor action and development of renal cell carcinoma.

SIGNIFICANCE

Single-cell analysis of heterogeneous and dynamic responses to Vhl inactivation in the kidney suggests that early events shape the cell type specificity of oncogenesis, providing a focus for mechanistic understanding and therapeutic targeting.

Endolymphatic sac tumor: An urgent case presenting acute intracranial hypertension successfully treated with suboccipital decompressive craniectomy - 8 years of follow-up

Background

Endolymphatic sac tumor (ELST) is a rare lesion. It may be sporadically or associated with Von Hippel-Lindau syndrome. Progressive audiovestibular symptoms characterize the typical clinical presentation. Here, we report a unique case of ELST with acute intracranial hypertension (IH) due to tumor compression, successfully treated with an urgent suboccipital decompressive craniectomy (SDC).

Case Description

A 33-year-old woman previously underwent a biopsy and ventriculoperitoneal shunt. The histopathological finding revealed an ELST. One year later, she developed headache, vomiting, and somnolence due to brainstem compression. An urgent SDC was performed. One month later, preoperative endovascular embolization and partial tumor resection were carried out. After 6 months adjuvant radiotherapy (RT) therapy was administered. She has been under follow-up for 8 years since the last surgical procedure, and the tumor remains stable.

Conclusion

ELST generally has a progressive clinical course. This is a unique case with acute IH due to tumor compression. The tumor's high vascularity and the unavailability of endovascular embolization precluded its resection. SDC was an alternative approach. The final treatment included tumor embolization, surgical resection, and RT. No progression was observed for 8 years after the last procedure, and long-term follow-up is warranted.

Deficiency in PHD2-mediated hydroxylation of HIF2α underlies Pacak-Zhuang syndrome

Pacak-Zhuang syndrome is caused by mutations in the EPAS1 gene, which encodes for one of the three hypoxia-inducible factor alpha (HIFα) paralogs HIF2α and is associated with defined but varied phenotypic presentations including neuroendocrine tumors and polycythemia. However, the mechanisms underlying the complex genotype-phenotype correlations remain incompletely understood. Here, we devised a quantitative method for determining the dissociation constant (Kd) of the HIF2α peptides containing disease-associated mutations and the catalytic domain of prolyl-hydroxylase (PHD2) using microscale thermophoresis (MST) and showed that neuroendocrine-associated Class 1 HIF2α mutants have distinctly higher Kd than the exclusively polycythemia-associated Class 2 HIF2α mutants. Based on the co-crystal structure of PHD2/HIF2α peptide complex at 1.8 Å resolution, we showed that the Class 1 mutated residues are localized to the critical interface between HIF2α and PHD2, adjacent to the PHD2 active catalytic site, while Class 2 mutated residues are localized to the more flexible region of HIF2α that makes less contact with PHD2. Concordantly, Class 1 mutations were found to significantly increase HIF2α-mediated transcriptional activation in cellulo compared to Class 2 counterparts. These results reveal a structural mechanism in which the strength of the interaction between HIF2α and PHD2 is at the root of the general genotype-phenotype correlations observed in Pacak-Zhuang syndrome.

[The development of innovative therapeutic drugs targeting hypoxia responses]

The 2019 Nobel Prize in Physiology or Medicine was awarded to Dr. William G. Kaelin Jr, Dr. Peter J. Ratcliffe, and Dr. Gregg L. Semenza for their elucidation of new physiological mechanisms "How cells sense and adapt to oxygen availability". Moreover, two different drugs, HIF-PH inhibitors and HIF-2 inhibitors were also developed based on the discovery. Interestingly, those three doctors have different backgrounds as a medical oncologist, a nephrologist, and a pediatrician, respectively. They have started the research based on their own unique perspectives and eventually merged as "the elucidation of the response mechanism of living organisms to hypoxic environments". In this review, we will explain how the translational research that has begun to solve unmet clinical needs successfully contributed to the development of innovative therapeutic drugs.

von-Hippel Lindau and Hypoxia-Inducible Factor at the Center of Renal Cell Carcinoma Biology

The most common form of kidney cancer is clear cell renal cell carcinoma (ccRCC). Biallelic VHL tumor suppressor gene inactivation is the usual initiating event in both hereditary (VHL Disease) and sporadic ccRCCs. The VHL protein, pVHL, earmarks the alpha subunits of the HIF transcription factor for destruction in an oxygen-dependent manner. Deregulation of HIF2 drives ccRCC pathogenesis. Drugs inhibiting the HIF2-responsive growth factor VEGF are now mainstays of ccRCC treatment. A first-in-class allosteric HIF2 inhibitor was recently approved for treating VHL Disease-associated neoplasms and appears active against sporadic ccRCC in early clinical trials.

HIF2α, Hepcidin and their crosstalk as tumour-promoting signalling

Not all aspects of the disruption of iron homeostasis in cancer have been fully elucidated. Iron accumulation in cancer cells is frequent for many solid tumours, and this is often accompanied by the contemporary rise of two key iron regulators, HIF2α and Hepcidin. This scenario is different from what happens under physiological conditions, where Hepcidin parallels systemic iron concentrations while HIF2α levels are inversely associated to Hepcidin. The present review highlights the increasing body of evidence for the pro-tumoral effect of HIF2α and Hepcidin, discusses the possible imbalance in HIF2α, Hepcidin and iron homeostasis during cancer, and explores therapeutic options relying on these pathways as anticancer strategies.

A complementary comment on primary hepatic angiosarcoma: A case report

BACKGROUND

This article examines primary hepatic angiosarcoma (PHA) and fat-poor angiomyolipoma (AML), two uncommon vascular cancers. Clinical decisions in these situations are frequently aided by pathology reports and imaging techniques. Uncommon malignant tumors of the vascular endothelium include PHA. Another diagnosis that should not be overlooked when employing contrast-enhanced MR and contrast-enhanced computed tomography (CT) imaging techniques is fat-poor AML, one of the uncommon vascular tumors of the liver. In both conditions, biopsy is the primary means of diagnosis.

CASE SUMMARY

In our article, besides the diagnosis of PHA, fat-poor AML, one of the other rare vascular tumors of the liver, is mentioned. In the case, a 50-year-old female patient with VHL Syndrome was admitted to our hospital with nonspecific lesions such as right upper quadrant pain, weight loss, and nausea. Abdominal ultrasonography (US) revealed a hypoechoic heterogeneous lesion with occasional faint contours. In computed tomography, it was observed as a hyperdense nodular lesion in segment 4. Magnetic resonance imaging (MRI) revealed that the lesion did not contain fat. In connection with the known history of VHL Syndrome, we first evaluated the possibility of AML. Thereupon, a histopathological sample was taken and the diagnosis was made as fat-poor AML with 5% fat content.

CONCLUSION

In conclusion, PHA in our case report and fat-poor AML in our clinic are two uncommon liver vascular malignancies with comparable incidences. Important imaging techniques like contrast-enhanced US (CEUS), CECT, and CEMRI give us substantial advantages in both cases. However, a biopsy is used to provide the final diagnosis.

Systematic Review of Endolymphatic Sac Tumor Treatment and Outcomes

OBJECTIVE

Endolymphatic sac tumors are rare neoplasms originating in the endolymphatic sac. Current literature is limited to case reports and small case series. The objective of this study was to systematically review the literature to better describe clinical presentation, treatment options, and outcomes in endolymphatic sac tumors.

DATA SOURCE

PubMed, Embase, and Cochrane Library.

REVIEW METHODS

A systematic review was performed following Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines describing human endolymphatic sac tumors. Risk of bias was assessed using a validated critical appraisal checklist for case series. Studies without inclusion of individual patient characteristics, corresponding treatments, and outcomes were excluded. Heterogeneity of data precluded meta-analysis.

RESULTS

A total of 82 studies met inclusion criteria, and 253 discrete tumors were analyzed. A total of 23.4% of patients had von Hippel-Lindau disease. Von Hippel-Lindau-associated tumors affected females to males in a 2.4:1 ratio. Patients with von Hippel-Lindau disease displayed earlier average age at diagnosis compared to the sporadic cohort. Surgery was the primary treatment modality and was performed in 88.9% of cases. Adjuvant radiation therapy was employed in 18.7% of cases; 16.2% cases recurred, and 10.6% had progression of residual disease after treatment. Mean time to recurrence or progression was 53.1 ± 52.4 months with a range of 3 to 240 months.

CONCLUSION

Endolymphatic sac tumors require a high degree of suspicion for early diagnosis. Complete resection is the standard of care. No strong evidence supports routine use of adjuvant radiation therapy. Given the high rate of recurrence and wide-ranging time to recurrence, long-term follow-up is necessary.

Perioperative Surgical Risks in Patients With Hemangioblastomas: A Retrospective Nationwide Review in Japan

BACKGROUND

The perioperative risk of sporadic hemangioblastomas (HBs) and von Hippel-Lindau disease (VHL)-associated hemangioblastomas (VHL-associated HBs) remains unclear due to the rare prevalence of HB. Therefore, this study aimed to clarify risk factors for better surgical management of patients with HBs.

METHODS

A retrospective analysis of surgically treated HB patients registered in the Diagnosis Procedure Combination database of Japan, between 2010 and 2015, was performed. Age, sex, sporadic HBs or VHL-associated HBs, medical history, tumor location, hospital case load, postoperative complications, and Barthel index (BI) deterioration were assessed. We also evaluated the outcomes and factors of perioperative BI deterioration.

RESULTS

In total, 676 patients with 609 intracranial lesions, 64 spinal lesions, and 3 with both types were eligible. Among them, 618 and 58 patients had sporadic HBs and VHL-associated HBs, respectively. The rates of perioperative BI deterioration were 12.5% and 12.2% for sporadic HBs and VHL-associated HBs, respectively. Perioperative mortality was 1.8% and 0% for sporadic HBs and VHL-associated HBs, respectively. Male sex, old age, high hospital case load, and medical history of diabetes mellitus were significantly associated with perioperative BI deterioration in all cases and sporadic HBs. Only medical history of diabetes mellitus was a significant risk factor for perioperative BI deterioration in VHL-associated HBs.

CONCLUSIONS

No differences in perioperative BI deterioration rates between sporadic HBs and VHL-associated HBs were found. However, different risk factors for perioperative BI deterioration were identified. Consideration of these risk factors is recommended in all patients undergoing surgery for HB.

Investigation of germline VHL variants in Iranian patients with retinal capillary hemangioblastoma and genotype-phenotype analysis

BACKGROUND

Retinal capillary hemangioblastoma (RCH), while sporadic in some cases, is the most common and earliest manifestation of von Hippel-Lindau disease (VHL). This is the first report on different types of VHL variants and genotype-phenotype correlations in Iranian families with RCH.

MATERIALS AND METHODS

In this prospective observational case series study, 17 families with RCH were included. PCR was performed to amplify 3 exons of VHL gene. Afterward, Sanger sequencing was performed on all PCR products. For the detection of VHL copy number variations, MLPA was used.

RESULTS

Our study identified 10 different types of VHL variants. Missense mutations were the most common variants found and affected the structure of α domain of the VHL protein (pVHL). The majority of mutations (72.7%) in the patients with RCH and central nervous system hemangioblastoma (CNS-HB) were located on α domain.

CONCLUSION

α domain of VHL may play a potential role in the pathogenesis of RCH. Our findings suggest that genotype-phenotype characteristics in those variants in α- domain may predispose patients to RCH with CNS-HB.

Von Hippel–Lindau disease: insights into oxygen sensing, protein degradation, and cancer

Germline loss-of-function mutations of the VHL tumor suppressor gene cause von Hippel–Lindau disease, which is associated with an increased risk of hemangioblastomas, clear cell renal cell carcinomas (ccRCCs), and paragangliomas. This Review describes mechanisms involving the VHL gene product in oxygen sensing, protein degradation, and tumor development and current therapeutic strategies targeting these mechanisms. The VHL gene product is the substrate recognition subunit of a ubiquitin ligase that targets the α subunit of the heterodimeric hypoxia-inducible factor (HIF) transcription factor for proteasomal degradation when oxygen is present. This oxygen dependence stems from the requirement that HIFα be prolyl-hydroxylated on one (or both) of two conserved prolyl residues by members of the EglN (also called PHD) prolyl hydroxylase family. Deregulation of HIF, and particularly HIF2, drives the growth of VHL-defective ccRCCs. Drugs that inhibit the HIF-responsive gene product VEGF are now mainstays of ccRCC treatment. An allosteric HIF2 inhibitor was recently approved for the treatment of ccRCCs arising in the setting of VHL disease and has advanced to phase III testing for sporadic ccRCCs based on promising phase I/II data. Orally available EglN inhibitors are being tested for the treatment of anemia and ischemia. Five of these agents have been approved for the treatment of anemia in the setting of chronic kidney disease in various countries around the world.

Large scale genotype- and phenotype-driven machine learning in Von Hippel-Lindau disease

Von Hippel-Lindau (VHL) disease is a hereditary cancer syndrome where individuals are predisposed to tumor development in the brain, adrenal gland, kidney, and other organs. It is caused by pathogenic variants in the VHL tumor suppressor gene. Standardized disease information has been difficult to collect due to the rarity and diversity of VHL patients. Over 4100 unique articles published until October 2019 were screened for germline genotype-phenotype data. Patient data were translated into standardized descriptions using Human Genome Variation Society gene variant nomenclature and Human Phenotype Ontology terms and has been manually curated into an open-access knowledgebase called Clinical Interpretation of Variants in Cancer. In total, 634 unique VHL variants, 2882 patients, and 1991 families from 427 papers were captured. We identified relationship trends between phenotype and genotype data using classic statistical methods and spectral clustering unsupervised learning. Our analyses reveal earlier onset of pheochromocytoma/paraganglioma and retinal angiomas, phenotype co-occurrences and genotype-phenotype correlations including hotspots. It confirms existing VHL associations and can be used to identify new patterns and associations in VHL disease. Our database serves as an aggregate knowledge translation tool to facilitate sharing information about the pathogenicity of VHL variants.

Cardio-onco-metabolism: metabolic remodelling in cardiovascular disease and cancer

Cardiovascular disease and cancer are the two leading causes of morbidity and mortality in the world. The emerging field of cardio-oncology has revealed that these seemingly disparate disease processes are intertwined, owing to the cardiovascular sequelae of anticancer therapies, shared risk factors that predispose individuals to both cardiovascular disease and cancer, as well the possible potentiation of cancer growth by cardiac dysfunction. As a result, interest has increased in understanding the fundamental biological mechanisms that are central to the relationship between cardiovascular disease and cancer. Metabolism, appropriate regulation of energy, energy substrate utilization, and macromolecular synthesis and breakdown are fundamental processes for cellular and organismal survival. In this Review, we explore the emerging data identifying metabolic dysregulation as an important theme in cardio-oncology. We discuss the growing recognition of metabolic reprogramming in cardiovascular disease and cancer and view the novel area of cardio-oncology through the lens of metabolism.

Challenges in Von Hippel-Lindau's disease: PRRT in patients on hemodialysis

Summary

Von Hippel-Lindau's disease (VHL) is a hereditary tumor syndrome characterized by its prototype lesions, hemangioblastomas, and renal cell carcinomas. Treatment for renal cell carcinomas can ultimately result in long-term dialysis. Pancreatic neuroendocrine tumors (pNET) can also occur in the course of the disease. Currently, peptide receptor radionuclide therapy (PRRT) is the standard treatment for progressive neuroendocrine tumors. However, little is known about treatment with PRRT in patients on dialysis, an infrequent presentation in patients with VHL. We present a 72-year-old man with VHL on hemodialysis and a progressive pNET. He received four cycles of PRRT with a reduced dose. Only mild thrombopenia was seen during treatments. The patient died 9 months after the last PRRT because of acute bleeding in a hemangioblastoma. Hemodialysis is not a limiting factor for PRRT treatment and it should be considered as it seems a safe short-term treatment option for this specific group.

Learning points

Von Hippel-Lindau disease (VHL) is a complex disease in which former interventions can limit optimal treatment for following VHL-related tumors later in life. Metastasized pancreatic neuroendocrine tumors occur as part of VHL disease. Peptide receptor radionuclide therapy seems a safe short-term treatment option in patients on hemodialysis.

e Santos G, Araujo Tuma Santos C. Anesthetic Management for Resection of a Cerebellar Hemangioblastoma Leading to Brainstem Compression in a Patient With Von Hippel-Lindau Disease

Von Hippel-Lindau (VHL) disease is a complex genetic syndrome characterized by multisystemic vascular neoplastic disorder. The affected population tends to develop tumors mainly involving the central nervous system, adrenal glands, pancreas, and kidneys. We describe anesthetic management for the resection of a cerebellar mass compressing the brainstem in a recently diagnosed 25-year-old female patient with a history of von Hippel-Lindau (VHL) syndrome. An uneventful occipital craniectomy for cerebellar tumor resection was performed under total intravenous anesthesia, without complications. The patient was discharged home on postoperative day five. This case depicts a situation in which a brainstem compressing lesion needs to be addressed urgently, and the pharmacological neuroprotective technique utilized for this procedure.

Von Hippel-Lindau (VHL) small-molecule inhibitor binding increases stability and intracellular levels of VHL protein

Von Hippel-Lindau (VHL) disease is characterized by frequent mutation of VHL protein, a tumor suppressor that functions as the substrate recognition subunit of a Cullin2 RING E3 ligase complex (CRL2VHL). CRL2VHL plays important roles in oxygen sensing by targeting hypoxia-inducible factor-alpha (HIF-α) subunits for ubiquitination and degradation. VHL is also commonly hijacked by bifunctional molecules such as proteolysis-targeting chimeras to induce degradation of target molecules. We previously reported the design and characterization of VHL inhibitors VH032 and VH298 that block the VHL:HIF-α interaction, activate the HIF transcription factor, and induce a hypoxic response, which can be beneficial to treat anemia and mitochondrial diseases. How these compounds affect the global cellular proteome remains unknown. Here, we use unbiased quantitative MS to identify the proteomic changes elicited by the VHL inhibitor compared with hypoxia or the broad-spectrum prolyl-hydroxylase domain enzyme inhibitor IOX2. Our results demonstrate that VHL inhibitors selectively activate the HIF response similar to the changes induced in hypoxia and IOX2 treatment. Interestingly, VHL inhibitors were found to specifically upregulate VHL itself. Our analysis revealed that this occurs via protein stabilization of VHL isoforms and not via changes in transcript levels. Increased VHL levels upon VH298 treatment resulted in turn in reduced levels of HIF-1α protein. This work demonstrates the specificity of VHL inhibitors and reveals different antagonistic effects upon their acute versus prolonged treatment in cells. These findings suggest that therapeutic use of VHL inhibitors may not produce overt side effects from HIF stabilization as previously thought.

A Tale of Two Organ Systems: Imaging Review of Diseases Affecting the Thoracic and Neurological Systems. Part 2

In an era of rapidly expanding knowledge and sub-specialization, it is becoming increasingly common to focus on one organ system. However, the human body is intimately linked, and disease processes affecting one region of the body not uncommonly affect the other organ systems as well. Understanding diseases from a macroscopic perspective, rather than a narrow vantage point, enables efficient and accurate diagnosis. This tenet holds true for diseases affecting both the thoracic and neurologic systems; in isolation, the radiologic appearance of disease in one organ system may be nonspecific, but viewing the pathophysiologic process in both organ systems may markedly narrow the differential considerations, and potentially lead to a definitive diagnosis. In this article, we discuss a variety of disease entities known to affect both the thoracic and neurological systems, either manifesting simultaneously or at different periods of time. Some of these conditions may show neither thoracic nor neurological manifestations. These diseases have been systematically classified into infectious, immune-mediated/ inflammatory, vascular, syndromic/ hereditary and neoplastic disorders. The underlying pathophysiological mechanisms linking both regions and radiologic appearances in both organ systems are discussed. When appropriate, brief clinical and diagnostic information is provided. Ultimately, accurate diagnosis will lead to expedited triage and prompt institution of potentially life-saving treatment for these groups of complex disorders.

Genetic approaches to understand cellular responses to oxygen availability

Oxygen-sensing mechanisms have evolved to allow organisms to respond and adapt to oxygen availability. In metazoans, oxygen-sensing is predominantly mediated by the hypoxia inducible factors (HIFs). These transcription factors are stabilised when oxygen is limiting, activating genes involved in angiogenesis, cell growth, pH regulation and metabolism to reset cell function and adapt to the cellular environment. However, the recognition that other cellular pathways and enzymes can also respond to changes in oxygen abundance provides further complexity. Dissecting this interplay of oxygen-sensing mechanisms has been a key research goal. Here, we review how genetic approaches have contributed to our knowledge of oxygen-sensing pathways which to date have been predominantly focused on the HIF pathway. We discuss how genetic studies have advanced the field and outline the implications and limitations of such approaches for the development of therapies targeting oxygen-sensing mechanisms in human disease.

Intersecting Mechanisms of Hypoxia and Prostaglandin E2-Mediated Inflammation in the Comparative Biology of Oral Squamous Cell Carcinoma

The importance of inflammation in the pathogenesis of cancer was first proposed by Rudolph Virchow over 150 years ago, and our understanding of its significance has grown over decades of biomedical research. The arachidonic acid pathway of inflammation, including cyclooxygenase (COX) enzymes, PGE2 synthase enzymes, prostaglandin E2 (PGE2) and PGE2 receptors has been extensively studied and has been associated with different diseases and different types of cancers, including oral squamous cell carcinoma (OSCC). In addition to inflammation in the tumour microenvironment, low oxygen levels (hypoxia) within tumours have also been shown to contribute to tumour progression. Understandably, most of our OSCC knowledge comes from study of this aggressive cancer in human patients and in experimental rodent models. However, domestic animals develop OSCC spontaneously and this is an important, and difficult to treat, form of cancer in veterinary medicine. The primary goal of this review article is to explore the available evidence regarding interaction between hypoxia and the arachidonic acid pathway of inflammation during malignant behaviour of OSCC. Overlapping mechanisms in hypoxia and inflammation can contribute to tumour growth, angiogenesis, and, importantly, resistance to therapy. The benefits and controversies of anti-inflammatory and anti-angiogenic therapies for human and animal OSCC patients will be discussed, including conventional pharmaceutical agents as well as natural products.

Comprehensive characterization of Alu-mediated breakpoints in germline VHL gene deletions and rearrangements in patients from 71 VHL families

Von Hippel-Lindau (VHL) is a hereditary multisystem disorder caused by germline alterations in the VHL gene. VHL patients are at risk for benign as well as malignant lesions in multiple organs including kidney, adrenal, pancreas, the central nervous system, retina, endolymphatic sac of the ear, epididymis, and broad ligament. An estimated 30%-35% of all families with VHL inherit a germline deletion of one, two, or all three exons. In this study, we have extensively characterized germline deletions identified in patients from 71 VHL families managed at the National Cancer Institute, including 59 partial (PD) and 12 complete VHL deletions (CD). Deletions that ranged in size from 1.09 to 355 kb. Fifty-eight deletions (55 PD and 3 CD) have been mapped to the exact breakpoints. Ninety-five percent (55 of 58) of mapped deletions involve Alu repeats at both breakpoints. Several novel classes of deletions were identified in this cohort, including two cases that have complex rearrangements involving both deletion and inversion, two cases with inserted extra Alu-like sequences, six cases that involve breakpoints in Alu repeats situated in opposite orientations, and a "hotspot" PD of Exon 3 observed in 12 families that involves the same pair of Alu repeats.

E3 Ligase Ligands for PROTACs: How They Were Found and How to Discover New Ones

Bifunctional degrader molecules, also called proteolysis-targeting chimeras (PROTACs), are a new modality of chemical tools and potential therapeutics to understand and treat human disease. A required PROTAC component is a ligand binding to an E3 ubiquitin ligase, which is then joined to another ligand binding to a protein to be degraded via the ubiquitin-proteasome system. The advent of nonpeptidic small-molecule E3 ligase ligands, notably for von Hippel-Lindau (VHL) and cereblon (CRBN), revolutionized the field and ushered in the design of drug-like PROTACs with potent and selective degradation activity. A first wave of PROTAC drugs are now undergoing clinical development in cancer, and the field is seeking to extend the repertoire of chemistries that allow hijacking new E3 ligases to improve the scope of targeted protein degradation.Here, we briefly review how traditional E3 ligase ligands were discovered, and then outline approaches and ligands that have been recently used to discover new E3 ligases for PROTACs. We will then take an outlook at current and future strategies undertaken that invoke either target-based screening or phenotypic-based approaches, including the use of DNA-encoded libraries (DELs), display technologies and cyclic peptides, smaller molecular glue degraders, and covalent warhead ligands. These approaches are ripe for expanding the chemical space of PROTACs and usher in the advent of other emerging bifunctional modalities of proximity-based pharmacology.

Reeling in the Zebrafish Cancer Models

Zebrafish are rapidly becoming a leading model organism for cancer research. The genetic pathways driving cancer are highly conserved between zebrafish and humans, and the ability to easily manipulate the zebrafish genome to rapidly generate transgenic animals makes zebrafish an excellent model organism. Transgenic zebrafish containing complex, patient-relevant genotypes have been used to model many cancer types. Here we present a comprehensive review of transgenic zebrafish cancer models as a resource to the field and highlight important areas of cancer biology that have yet to be studied in the fish. The ability to image cancer cells and niche biology in an endogenous tumor makes zebrafish an indispensable model organism in which we can further understand the mechanisms that drive tumorigenesis and screen for potential new cancer therapies.

TCEAL2 as a Tumor Suppressor in Renal Cell Carcinoma is Associated with the Good Prognosis of Patients

Background

Renal cell carcinoma (RCC) is one of the most common tumors in urinary tract tumors. However, the mechanism that supports renal cell carcinoma is unclear. The function of transcription elongation factor A (SII)-like 2 (TCEAL2) and its association with human cancer have not been reported.

Materials and Methods

To explore the role of TCEAL2 in carcinogenesis of clear cell renal cell carcinoma (ccRCC), we performed bioinformatics analysis to determine the expression levels of TCEAL2 in ccRCC specimens and normal kidney tissue and then verified findings with our samples by qPCR, Western blot and immunohistochemistry staining. Furthermore, the lentiviral vectors were used to increase the expression of TCEAL2 in ccRCC cell lines. The immunofluorescence assay was taken to observe the subcellular location of TCEAL2 in ccRCC cells, and CCK-8 and flow cytometry were introduced for assessing cell proliferation and cell cycle of ccRCC cells, respectively.

Results

Compared with adjacent normal kidney tissue and human proximal tubular epithelial cells, the expression of TCEAL2 in ccRCC tissues and cell lines was down-regulated. Patients who had low expression of TCEAL2 had a statistically significant late tumor stage. Restore of TCEAL2 in ccRCC cells inhibited cell proliferation and induced cell cycle arrest in S phase of ccRCC cells.

Conclusion

To our knowledge, this is the first report of TCEAL2 expression changes in ccRCC. We found that the decrease of TCEAL2 expression may be related to the occurrence of ccRCC. Further research is needed to clarify the molecular mechanism of TCEAL2 in progress of ccRCC.

Targeting the HIF2-VEGF axis in renal cell carcinoma

Insights into the role of the tumor suppressor pVHL in oxygen sensing motivated the testing of drugs that target the transcription factor HIF or HIF-responsive growth factors, such as VEGF, for the treatment of cancers caused by VHL inactivation, such as clear-cell renal cell carcinoma (ccRCC). Multiple VEGF inhibitors are now approved for the treatment of ccRCC, and a HIF2α inhibitor has advanced to phase 3 development for this disease. These inhibitors are now also increasingly combined with immune-checkpoint blockers. In this Perspective, we describe the understanding of the mechanisms of oxygen sensing and hypoxia signaling that resulted in the development of HIF2α-targeted therapies for patients with VHL-associated tumors. We also present future directions for extending the use of these therapies to other cancers.

VON HIPPEL-LINDAU DISEASE: Update on Pathogenesis and Systemic Aspects

PURPOSE

To provide an update summarizing the biologic pathways governing von Hippel-Lindau (VHL) disease pathogenesis and to provide an overview of systemic manifestations as well as screening recommendations.

METHODS

A PubMed search of the English language literature was reviewed using the following search terms: von Hippel-Lindau, von Hippel-Lindau disease, and VHL. Of 6,696 publications, the most current and pertinent information related to the pathogenesis and systemic aspects of VHL disease were included in this review.

RESULTS

von Hippel-Lindau disease is one of the most frequently occurring multisystem familial cancer syndromes. The disease results from germline mutation in the VHL tumor suppressor gene on the short arm of chromosome 3. Mutation in the VHL gene affects multiple cellular processes including transcriptional regulation, extracellular matrix formation, apoptosis, and, in particular, the cellular adaptive response to hypoxia. As a result, there is widespread development of vascular tumors affecting the retina, brain, and spine, as well as a spectrum of benign and malignant tumors and/or cysts in visceral organs.

CONCLUSION

The ophthalmologist plays a key role in VHL disease diagnosis, as retinal hemangioblastoma is frequently the first disease manifestation. Screening guidelines for individuals with known VHL disease, and those at risk of VHL disease, help to ensure early detection of potentially vision-threatening and life-threatening disease.

The Daam2-VHL-Nedd4 axis governs developmental and regenerative oligodendrocyte differentiation

Here, Ding et al. sought to understand whether and how the ubiquitin–proteasomal system (UPS) contributes to oligodendrocyte dysfunction and repair after white matter injury (WMI). They demonstrate that the E3 ligase VHL interacts with Daam2 and their mutual antagonism regulates oligodendrocyte differentiation during development.

Dysregulation of the ubiquitin–proteasomal system (UPS) enables pathogenic accumulation of disease-driving proteins in neurons across a host of neurological disorders. However, whether and how the UPS contributes to oligodendrocyte dysfunction and repair after white matter injury (WMI) remains undefined. Here we show that the E3 ligase VHL interacts with Daam2 and their mutual antagonism regulates oligodendrocyte differentiation during development. Using proteomic analysis of the Daam2–VHL complex coupled with conditional genetic knockout mouse models, we further discovered that the E3 ubiquitin ligase Nedd4 is required for developmental myelination through stabilization of VHL via K63-linked ubiquitination. Furthermore, studies in mouse demyelination models and white matter lesions from patients with multiple sclerosis corroborate the function of this pathway during remyelination after WMI. Overall, these studies provide evidence that a signaling axis involving key UPS components contributes to oligodendrocyte development and repair and reveal a new role for Nedd4 in glial biology.

Von Hippel-Lindau Syndrome: Multi-Organ Involvement Highlighting Its Diverse Clinical Spectrum in Two Adult Cases

There is an assortment of disorders that have multisystem involvement. Von Hippel-Lindau (VHL) syndrome, a rare autosomal dominant disease, falls in that category. VHL syndrome is associated with the formation of benign and malignant tumors in the central nervous system (CNS), adrenal gland, kidney, and eyes. In this report, we present two unusual cases of VHL syndrome presenting with multisystem engagement. The first case is of a 27-year-old male exhibiting multiple manifestations, which included hemangioblastoma of the spine, pheochromocytoma, pancreatic cyst, and retinal hemangioblastoma. The second case pertains to a 25-year-old male with various presentations ranging from retinal hemangioblastoma and pancreatitis to spinal and cerebellar hemangioblastoma. These cases emphasize the value of radiologic imaging and genetic assessment early in life when the presentation of the disease is in its preliminary stage. When an individual presents with a condition characterized by unexplained multifarious organ involvement of CNS, adrenal glands, and kidneys in the span of a few years, a differential diagnosis of VHL syndrome should be considered.

Von Hippel-Lindau Disease: Current Challenges and Future Prospects

Understanding of molecular mechanisms of tumor growth has an increasing impact on the development of diagnostics and targeted therapy of human neoplasia. In this review, we summarize the current knowledge on molecular mechanisms and their clinical implications in von Hippel-Lindau (VHL) disease. This autosomal dominant tumor syndrome usually manifests in young adulthood and predisposes affected patients to the development of benign and malignant tumors of different organ systems mainly including the nervous system and internal organs. A consequent screening and timely preventive treatment of lesions are crucial for patients affected by VHL disease. Surgical indications and treatment have been evaluated and optimized over many years. In the last decade, pharmacological therapies have been evolving, but are largely still at an experimental stage. Effective pharmacological therapy as well as detection of biomarkers is based on the understanding of the molecular basis of disease. The molecular basis of von Hippel-Lindau disease is the loss of function of the VHL protein and subsequent accumulation of hypoxia-inducible factor with downstream effects on cellular metabolism and differentiation. Organs affected by VHL disease may develop frank tumors. More characteristically, however, they reveal multiple separate microscopic foci of neoplastic cell proliferation. The exact mechanisms of tumorigenesis in VHL disease are, however, still not entirely understood and knowledge on biomarkers and targeted therapy is scarce.

pVHL-mediated regulation of the anti-angiogenic protein thrombospondin-1 decreases migration of Clear Cell Renal Carcinoma Cell Lines

Thrombospondin-1 (TSP-1) is a multifunctional matrix protein with antitumor activities due in part to its ability to inhibit angiogenesis, which in turn contributes to determine the fate of many tumours. Previous studies have shown that TSP-1 expression supports normal kidney angiostasis, and decreased TSP-1 levels contribute to the angiogenic phenotype of renal cell carcinomas (RCC). The loss of the von Hippel-Lindau tumour suppressor gene (VHL) in these tumours favours stabilization of the Hypoxia Inducible Factors (HIF), which in turn contribute to adapt tumour cells to hostile environments promoting tumour progression. However, HIF-independent regulation of certain genes might also be involved. We have previously shown that TSP-1 is regulated in hypoxia in clear cell RCC (ccRCC) in a HIF-independent manner; however, the effect of VHL protein (pVHL) on TSP-1 expression has not been evaluated. Our results proved that pVHL loss or mutation in its alpha or beta domain significantly decreased TSP-1 levels in ccRCC in a HIF-independent manner. Furthermore, this regulation proved to be important for ccRCC cells behaviour showing that decreased TSP-1 levels rendered ccRCC cells more migratory. This data substantiates a unique regulation pattern for TSP-1 in a pVHL-dependent manner, which may be relevant in the aggressiveness of ccRCC.

An Oxygen Sensation: Progress in Macromolecule Hydroxylation Triggered by the Elucidation of Cellular Oxygen Sensing

The 2019 Nobel Prize in Physiology or Medicine honours three scientists that devoted their careers to pursuing an audacious basic science question: by what mechanisms do animals sense oxygen, and how can cells adapt to a lack of oxygen? The identification of the human hypoxia inducible factor pathway has enabled new approaches for the therapy of related diseases including cancer, cardiovascular disease, anaemia, and stroke. The intricate molecular details of oxygen sensing broadened interest in the family of iron- and 2-oxoglutarate-dependent oxygenases known from elaborate natural product chemistry, and catalysed major progress in macromolecule hydroxylation. The laureates' work enables numerous avenues for molecular scientists, from C-H activation chemistry to PROTAC technology, medicinal chemistry, and epigenetics.

Retinal capillary hemangioblastoma and hemiretinal vein occlusion in a patient with primary congenital glaucoma: A case report

The presence of retinal capillary hemangioblastoma and cerebellar hemangioblastoma in the context of Von Hippel-Lindau syndrome (VHL) is not characteristically associated with other ophthalmologic conditions. Here, we report the case of a 22-yearold female with a history of bilateral primary congenital glaucoma who presented with a right juxtapapillary retinal capillary hemangioblastoma and an old hemiretinal vein occlusion in which the retinal capillary hemangioblastoma was likely the contributing factor. Her systemic work up was positive for VHL syndrome and revealed the presence of a fatal large brainstem hemangioblastoma. To our knowledge, the association of VHL and congenital glaucoma and/or retinal venous occlusion has not been reported.

Epigenetic modifiers: activities in renal cell carcinoma

Renal cell carcinomas (RCCs) are a diverse set of malignancies that have recently been shown to harbour mutations in a number of chromatin modifier genes - including PBRM1, SETD2, BAP1, KDM5C, KDM6A, and MLL2 - through high-throughput sequencing efforts. Current research focuses on understanding the biological activities that chromatin modifiers employ to suppress tumorigenesis and on developing clinical approaches that take advantage of this knowledge. Unsurprisingly, several common themes unify the functions of these epigenetic modifiers, particularly regulation of histone post-translational modifications and nucleosome organization. Furthermore, chromatin modifiers also govern processes crucial for DNA repair and maintenance of genomic integrity as well as the regulation of splicing and other key processes. Many chromatin modifiers have additional non-canonical roles in cytoskeletal regulation, which further contribute to genomic stability, expanding the repertoire of functions that might be essential in tumorigenesis. Our understanding of how mutations in chromatin modifiers contribute to tumorigenesis in RCC is improving but remains an area of intense investigation. Importantly, elucidating the activities of chromatin modifiers offers intriguing opportunities for the development of new therapeutic interventions in RCC.

HIF-2α-pVHL complex reveals broad genotype-phenotype correlations in HIF-2α-driven disease

It is definitively established that mutations in transcription factor HIF-2α are causative of both neuroendocrine tumors (class 1 disease) and polycythemia (class 2 disease). However, the molecular mechanism that underlies this emergent genotype–phenotype relationship has remained unclear. Here, we report the structure of HIF-2α peptide bound to pVHL-elongin B-elongin C (VBC) heterotrimeric complex, which shows topographical demarcation of class 1 and 2 mutations affecting residues predicted, and demonstrated via biophysical analyses, to differentially impact HIF-2α-pVHL interaction interface stability. Concordantly, biochemical experiments showed that class 1 mutations disrupt pVHL affinity to HIF-2α more adversely than class 2 mutations directly or indirectly via impeding PHD2-mediated hydroxylation. These findings suggest that neuroendocrine tumor pathogenesis requires a higher HIF-2α dose than polycythemia, which requires only a mild increase in HIF-2α activity. These biophysical data reveal a structural basis that underlies, and can be used to predict de novo, broad genotype-phenotype correlations in HIF-2α-driven disease.

Hypoxia inducible factor (HIF)-2α transcription factor is mutated in polycythemia and various neuroendocrine tumors. Here the authors present the crystal structure of a HIF-2α peptide bound to the pVHL-elongin B-elongin C (VBC) heterotrimeric complex and propose a classification scheme for HIF-2α mutations that helps to predict disease phenotype outcome.

Differences in genetic and epigenetic alterations between von Hippel-Lindau disease-related and sporadic hemangioblastomas of the central nervous system

Background

Although inactivation of the von Hippel-Lindau gene (VHL), located on chromosome 3p25, is considered to be a major cause of hemangioblastomas (HBs), the incidence of biallelic inactivation of VHL is reportedly low. The aim of this study was to determine the prevalence of VHL alterations in HBs, as well as to identify additional molecular aberrations.

Methods

Genetic and epigenetic alterations were comprehensively and comparatively analyzed in 11 VHL-related and 21 sporadic HBs.

Results

VHL alterations detected by sequencing and multiplex ligation-dependent probe amplification (MLPA) analysis were more frequent in VHL-related HBs than in sporadic HBs (100% vs 62%; P = 0.029). VHL alterations were found only in 4 sporadic HBs by direct sequencing; however, targeted deep sequencing detected 9 additional alterations. Loss of heterozygosity (LOH) on chromosome 3 was found in 64% and 57% of VHL-related and sporadic HBs, respectively, by single nucleotide polymorphism (SNP) array analysis. Among 19 tumors with chromosome 3 LOH, 5 were classified as copy-neutral LOH. VHL promoter hypermethylation was detected only in sporadic HBs (33%), indicating that epigenetic suppression of VHL is a common mechanism in sporadic HBs. The rate of biallelic VHL inactivation among VHL-related and sporadic HBs was 64% and 52%, respectively. LOH on either chromosome 6 or 10 was detected only in sporadic HBs (43%).

Conclusion

Although biallelic inactivation of VHL is a dominant mechanistic cause of the pathogenesis of HB, other unknown mechanisms may also be involved, and such mechanisms may be different between VHL-related and sporadic HB.

Identification of a new VHL exon and complex splicing alterations in familial erythrocytosis or von Hippel-Lindau disease

Chuvash polycythemia is an autosomal recessive form of erythrocytosis associated with a homozygous p.Arg200Trp mutation in the von Hippel-Lindau (VHL) gene. Since this discovery, additional VHL mutations have been identified in patients with congenital erythrocytosis, in a homozygous or compound-heterozygous state. VHL is a major tumor suppressor gene, mutations in which were first described in patients presenting with VHL disease, which is characterized by the development of highly vascularized tumors. Here, we identify a new VHL cryptic exon (termed E1') deep in intron 1 that is naturally expressed in many tissues. More importantly, we identify mutations in E1' in 7 families with erythrocytosis (1 homozygous case and 6 compound-heterozygous cases with a mutation in E1' in addition to a mutation in VHL coding sequences) and in 1 large family with typical VHL disease but without any alteration in the other VHL exons. In this study, we show that the mutations induced a dysregulation of VHL splicing with excessive retention of E1' and were associated with a downregulation of VHL protein expression. In addition, we demonstrate a pathogenic role for synonymous mutations in VHL exon 2 that altered splicing through E2-skipping in 5 families with erythrocytosis or VHL disease. In all the studied cases, the mutations differentially affected splicing, correlating with phenotype severity. This study demonstrates that cryptic exon retention and exon skipping are new VHL alterations and reveals a novel complex splicing regulation of the VHL gene. These findings open new avenues for diagnosis and research regarding the VHL-related hypoxia-signaling pathway.

Two Childhood Pheochromocytoma Cases due to von Hippel-Lindau Disease, One Associated with Pancreatic Neuroendocrine Tumor: A Very Rare Manifestation

von Hippel-Lindau (VHL) disease is an autosomal dominantly inherited disorder, characterized by hemangioblastomas of the retina and central nervous system (CNS); renal cysts; clear cell carcinoma; pheochromocytoma (PCC); endolymphatic sac tumors; cystadenomas of the epididymis in males; broad ligament of uterus in females; pancreatic cysts; cystadenomas; and neuroendocrine tumors. We report two cases of VHL disease that presented with PCC as the first manifestation. Further clinical developments during follow-up, hemangioblastoma of CNS in one case and a pancreatic neuroendocrine tumor (PNET) in the second case led to the diagnosis of VHL disease. Genetic analyses of the two cases revealed p.Arg161Gln (c.482G>A) and p.Leu129Pro (c.386T>G) heterozygous missense mutations in the VHL gene, respectively. In children, PCC may be the only and/or initial manifestation of VHL with delayed manifestations of the syndrome in other organs. PNET is a very rare manifestation of VHL disease. To the best of our knowledge, this is only the second reported case presenting with a combination of a PNET and bilateral PCC as components of childhood VHL disease. Pediatric patients diagnosed with PCC should be investigated for genetic causes and especially for VHL.

VHL Gene Alterations in Italian Patients with Isolated Renal Cell Carcinomas

Clear cell renal cell carcinoma (ccRCC) is the most common malignant neoplasm of the kidney and belongs to the few human tumors known to develop from mutations of the VHL tumor suppressor gene. VHL germline mutations are associated with hereditary ccRCCs in VHL disease. However, somatic VHL gene defects may also occur in sporadic ccRCCs. In this study, we analyzed the frequency and the spectrum of VHL gene alterations in 35 Italian patients with sporadic renal cell carcinoma (RCC). Tumor-specific intragenic VHL pathogenic mutations were detected in 38% (11/29) of the ccRCC patients and 33% (2/6) of the patients with other types of RCC. One novel 18-bp in-tandem duplication and 4 previously unreported nucleotide changes in the VHL gene were described. Microsatellite analysis showed loss of heterozygosity for at least 1 informative marker in 43% (9/21) of the ccRCCs and 50% (3/6) of the non-ccRCCs; 5 of the 13 tumors (38%) harboring VHL gene alterations also had loss of heterozygosity for at least 1 microsatellite marker. Our results confirm that somatic inactivation of the VHL gene may play a pivotal role in the tumorigenesis of sporadic ccRCCs in Italian patients and suggests that mutation analysis of the VHL gene may be helpful for discriminating sporadic, VHL-gene-related ccRCCs from those related to VHL disease.

Atlas on substrate recognition subunits of CRL2 E3 ligases

The Cullin2-type ubiquitin ligases belong to the Cullin-Ring Ligase (CRL) family, which is a crucial determinant of proteasome-based degradation processes in eukaryotes. Because of the finding of von Hippel-Lindau tumor suppressor (VHL), the Cullin2-type ubiquitin ligases gain focusing in the research of many diseases, especially in tumors. These multisubunit enzymes are composed of the Ring finger protein, the Cullin2 scaffold protein, the Elongin B&C linker protein and the variant substrate recognition subunits (SRSs), among which the Cullin2 scaffold protein is the determining factor of the enzyme mechanism. Substrate recognition of Cullin2-type ubiquitin ligases depends on SRSs and results in the degradation of diseases associated substrates by intracellular signaling events. This review focuses on the diversity and the multifunctionality of SRSs in the Cullin2-type ubiquitin ligases, including VHL, LRR-1, FEM1b, PRAME and ZYG11. Recently, as more SRSs are being discovered and more aspects of substrate recognition have been illuminated, insight into the relationship between Cul2-dependent SRSs and substrates provides a new area for cancer research.

A Clinical Roadmap to Investigate the Genetic Basis of Pediatric Pheochromocytoma: Which Genes Should Physicians Think About?

Pheochromocytoma is very rare at a pediatric age, and when it is present, the probability of a causative genetic mutation is high. Due to high costs of genetic surveys and an increasing number of genes associated with pheochromocytoma, a sequential genetic analysis driven by clinical and biochemical phenotypes is advised. The published literature regarding the genetic landscape of pediatric pheochromocytoma is scarce, which may hinder the establishment of genotype-phenotype correlations and the selection of appropriate genetic testing at this population. In the present review, we focus on the clinical phenotypes of pediatric patients with pheochromocytoma in an attempt to contribute to an optimized genetic testing in this clinical context. We describe epidemiological data on the prevalence of pheochromocytoma susceptibility genes, including new genes that are expanding the genetic etiology of this neuroendocrine tumor in pediatric patients. The clinical phenotypes associated with a higher pretest probability for hereditary pheochromocytoma are presented, focusing on differences between pediatric and adult patients. We also describe new syndromes, as well as rates of malignancy and multifocal disease associated with these syndromes and pheochromocytoma susceptibility genes published more recently. Finally, we discuss new tools for genetic screening of patients with pheochromocytoma, with an emphasis on its applicability in a pediatric population.

Loss of vhl in the zebrafish pronephros recapitulates early stages of human clear cell renal cell carcinoma

Patients with von Hippel–Lindau (VHL) disease harbor a germline mutation in the VHL gene leading to the development of several tumor types including clear cell renal cell carcinoma (ccRCC). In addition, the VHL gene is inactivated in over 90% of sporadic ccRCC cases. ‘Clear cell’ tumors contain large, proliferating cells with ‘clear cytoplasm’, and a reduced number of cilia. VHL inactivation leads to the stabilization of hypoxia inducible factors 1a and 2a [HIF1a and HIF2a (HIF2a is also known as EPAS1)] with consequent up-regulation of specific target genes involved in cell proliferation, angiogenesis and erythropoiesis. A zebrafish model with a homozygous inactivation in the VHL gene (vhl^−/−) recapitulates several aspects of the human disease, including development of highly vascular lesions in the brain and the retina and erythrocytosis. Here, we characterize for the first time the epithelial abnormalities present in the kidney of the vhl^−/− zebrafish larvae as a first step in building a model of ccRCC in zebrafish. Our data show that the vhl^−/− zebrafish kidney is characterized by an increased tubule diameter, disorganized cilia, the dramatic formation of cytoplasmic lipid vesicles, glycogen accumulation, aberrant cell proliferation and abnormal apoptosis. This phenotype of the vhl^−/− pronephros is reminiscent of clear cell histology, indicating that the vhl^−/− mutant zebrafish might serve as a model of early stage RCC. Treatment of vhl^−/− zebrafish embryos with a small-molecule HIF2a inhibitor rescued the pronephric abnormalities, underscoring the value of the zebrafish model in drug discovery for treatment of VHL disease and ccRCC.

Summary: Zebrafish with an inactivating mutation in the vhl gene can be used as a model of early stage clear cell renal cell carcinoma, with applications for genetic studies and drug screens.

The HIF and other quandaries in VHL disease

Mutations in VHL underlie von Hippel-Lindau (VHL) disease, a hereditary cancer syndrome with several subtypes depending on the risk of developing certain combination of classic features, such as clear cell renal cell carcinoma (ccRCC), hemangioblastoma and pheochromocytoma. Although numerous potential substrates and functions of pVHL have been described over the past decade, the best-defined role of pVHL has remained as the negative regulator of the heterodimeric hypoxia-inducible factor (HIF) transcription factor via the oxygen-dependent ubiquitin-mediated degradation of HIF-α subunit. Despite the seminal discoveries that led to the molecular elucidation of the mammalian oxygen-sensing VHL-HIF axis, which have provided several rational therapies, the mechanisms underlying the complex genotype-phenotype correlation in VHL disease are unclear. This review will discuss and highlight the studies that have provided interesting insights as well as uncertainties to the underlying mechanisms governing VHL disease.

Single-stage laparoscopic adrenalectomy for pheochromocytoma and enucleation of a pancreatic neuroendocrine tumor in Von Hippel-Lindau disease: A case report

Von Hippel-Lindau (VHL) disease is an inherited syndrome with autosomal-dominant transmission, characterized by central nervous system and retinal hemangioblastomas, visceral cysts and tumors. Optimal surgical treatment, including its timing, remains a controversial topic. The present study reports the case of a 67-year-old female patient with adrenal and pancreatic manifestations of VHL. A laparoscopic cortex-sparing left adrenalectomy for a 4-cm pheochromocytoma and pancreatic enucleation for pancreatic polypeptidoma of the pancreas tail were performed during the same operative procedure. The total operative time was 240 min. There were no operative complications, and the surgery was completed laparoscopically with minimal blood loss. A prolonged hospital stay was necessary to treat a grade C postoperative pancreatic fistula. The histopathological result was an adrenal pheochromocytoma and a well-differentiated neuroendocrine tumor, secreting pancreatic polypeptides. In conclusion, organ-sparing laparoscopic surgery is an important option for treating simultaneous lesions in several abdominal solid viscera, such as VHL disease, and the present case study represents, to the best of the authors' knowledge, the first report of single-stage laparoscopic adrenalectomy and pancreatic tumor enucleation.