Germline mutations in the vhl gene in patients presenting with phaeochromocytomas

The genetic differences between types 1 and 2 in von Hippel-Lindau syndrome: comprehensive meta-analysis

BACKGROUND

Patients with von Hippel-Lindau (VHL) disease are at risk of developing tumors in the eye, brain, kidney, adrenal gland, and other organs based on their gene mutations. The VHL tumor suppressor gene contains pathogenic variants responsible for these events. This meta-analysis aims to investigate the genetic differences among the various types of VHL syndrome and their correlation with the location of mutations (exons and domains) in the VHL gene.

METHOD

Papers eligible for publication until September 2023 were identified using the electronic databases of PubMed, Google Scholar, Scopus, and EMBASE. The Random Effect model was utilized to evaluate the genetic differences between type 1 and type 2 VHL syndromes.

RESULTS

The prevalence of missense mutations (MSs) was found to be 58.9% in type 1, while it was 88.1% in type 2. Interestingly, the probability of observing MSs in type 1 was 0.42 times lower compared to type 2. The mutation hotspots of the VHL gene were R167Q/W, Y98H, R238W, and S65L, respectively. Although type 2 had a high presentation of Y98H and R238W, it did not have a higher S65L than type 1. The analysis demonstrated a statistically significant higher prevalence of truncated mutations (PTMs) in type 1. Among type 1, large/complete deletions (L/C DELs) were found in 16.9% of cases, whereas in type 2 only 3.7%. This difference was statistically significant with a p-value < 0.001. Overall, the probability of identifying mutations in domain 2 compared to domain 1 was found to be 2.13 times higher in type 1 (p-value < 0.001). Furthermore, the probability of detecting exon 1 in comparison with observing exon 2 in type 1 was 2.11 times higher than type 2 and revealed a statistically significant result (p-value < 0.001). The detection of exon 2 was 2.18 times higher in type 1 (p-value < 0.001). In addition, the likelihood of discovering exon 2 compared with others was significantly lower in type 1 compared with type 2 VHL (OR = 0.63, p-value = 0.015).

CONCLUSIONS

We have revealed a comprehensive genetic difference between types 1 and 2 of VHL syndrome. The significant differences in MS, PTMs, L/C DELs, and the location of the mutations between type 1 and type 2 VHL patients in the Asian, European, and American populations emphasize the genetic heterogeneity of the syndrome. These findings may pave the way for the diagnosis, treatment, and further investigation of the mechanisms behind this complex genetic disorder.

A meta-analysis of different von Hippel Lindau mutations: are they related to retinal capillary hemangioblastoma?

Retinal capillary hemangioblastomas (RCH) is a benign tumor that represents the initial manifestation in roughly half of Von Hippel Lindau (VHL) patients. They may also occur sporadically without systemic involvement. A first meta-analysis study was investigated to estimate the prevalence of Retinal capillary hemangioblastoma (RCH) in Von Hippel Lindau (VHL) syndrome, and its relation to type and location of mutations in VHL gene. The electronic databases of PubMed, Scopus, Embase, and Google Scholar were utilized to find eligible papers published up to May 2020. Lastly, after the different prevalence of RCH in Europe compared to other continents was noted, we decided to consider European and non-European patients separately. The Random effect model was used to evaluate the relation between developing RCH and types of mutations. The overall prevalence of RCH among VHL patients is about 47%. The prevalence of RCH was significantly higher in Europe in comparison with non-Europeans (p value < 0.001). Overall, the differences between the prevalence of RCH among different mutation types were not statistically significant. However, in Europe, the prevalence of RCH was significantly higher in patients with truncation mutation (p value = 0.007). In Europe, the RCH in VHL patients who had a mutation in exon 2 was significantly lower in comparison with exon 1 (p value = 0.001); but in non-Europeans, the prevalence of RCH in VHL patients that involved exon 2 was significantly higher in comparison with VHL patients with a mutation in exon1 (p value = 0.012). The highest risk of developing RCH was reported among Europeans. Overall, this study showed that the prevalence of RCH in VHL syndrome is not related to type or location of mutations and difference of RCH prevalence is probably depends on other genetic or environmental factor that should be considered in subsequent studies.

Novel and recurrent germline mutations in the VHL gene in 5 Arab patients with Von Hippel-Lindau disease

Inherited germline mutations in the VHL gene cause predisposition to Von Hippel-Lindau (VHL) disease. Patients exhibit benign and cancerous lesions in multiple tissues, including hemangioblastomas, clear cell renal cell carcinoma, cysts in kidneys and pancreas, and pheochromocytomas. Although pathogenic germline mutations in the VHL gene have been widely described in different populations, only a single mutation was previously reported in a family from mixed Arab-Persian ethnicity. Here, we present five Arab patients with two new and two recurrent germline mutations in the VHL gene. These mutations include three in-frame deletions and a missense mutation. Infrequent in-frame deletions in previously described patients from other populations, as well as the presence of new mutations, suggests a distinct spectrum of VHL gene mutations in Arab patients. While pulmonary manifestation has been described rarely in VHL disease, we have identified two patients with a recurrent p.Phe76del in-frame deletion exhibiting multiple nodules in lungs. We also describe a first-ever in-frame deletion in the VHL gene in a patient with VHL type 2C disease, exhibiting bilateral pheochromocytoma. Overall, the study provides an insight into the genotype-phenotype relationship of VHL disease in Arab patients and provides a comparison with previously described patients from other ethnicities.

A Guide to Pheochromocytomas and Paragangliomas

Pheochromocytomas and extra-adrenal paragangliomas are rare neuroendocrine neoplasms with characteristic histologic and immunohistochemical features. These tumors can arise in several anatomic locations, necessitating that their diagnostic recognition extends beyond the realm of endocrine disorders. A practical and reproducible risk stratification system for these tumors is still in development. In this rapidly evolving era of molecular medicine, it is essential for pathologists to equip themselves with a framework for understanding the classification of paragangliomas and pheochromocytomas and be informed of how they might advise their colleagues with regard to prognostication and appropriate follow-up.

Gene panel sequencing improves the diagnostic work-up of patients with idiopathic erythrocytosis and identifies new mutations

Erythrocytosis is a rare disorder characterized by increased red cell mass and elevated hemoglobin concentration and hematocrit. Several genetic variants have been identified as causes for erythrocytosis in genes belonging to different pathways including oxygen sensing, erythropoiesis and oxygen transport. However, despite clinical investigation and screening for these mutations, the cause of disease cannot be found in a considerable number of patients, who are classified as having idiopathic erythrocytosis. In this study, we developed a targeted next-generation sequencing panel encompassing the exonic regions of 21 genes from relevant pathways (~79 Kb) and sequenced 125 patients with idiopathic erythrocytosis. The panel effectively screened 97% of coding regions of these genes, with an average coverage of 450×. It identified 51 different rare variants, all leading to alterations of protein sequence, with 57 out of 125 cases (45.6%) having at least one of these variants. Ten of these were known erythrocytosis-causing variants, which had been missed following existing diagnostic algorithms. Twenty-two were novel variants in erythrocytosis-associated genes (EGLN1, EPAS1, VHL, BPGM, JAK2, SH2B3) and in novel genes included in the panel (e.g. EPO, EGLN2, HIF3A, OS9), some with a high likelihood of functionality, for which future segregation, functional and replication studies will be useful to provide further evidence for causality. The rest were classified as polymorphisms. Overall, these results demonstrate the benefits of using a gene panel rather than existing methods in which focused genetic screening is performed depending on biochemical measurements: the gene panel improves diagnostic accuracy and provides the opportunity for discovery of novel variants.

A practice guideline from the American College of Medical Genetics and Genomics and the National Society of Genetic Counselors: referral indications for cancer predisposition assessment

DISCLAIMER

The practice guidelines of the American College of Medical Genetics and Genomics (ACMG) and the National Society of Genetic Counselors (NSGC) are developed by members of the ACMG and NSGC to assist medical geneticists, genetic counselors, and other health-care providers in making decisions about appropriate management of genetic concerns, including access to and/or delivery of services. Each practice guideline focuses on a clinical or practice-based issue and is the result of a review and analysis of current professional literature believed to be reliable. As such, information and recommendations within the ACMG and NSGC joint practice guidelines reflect the current scientific and clinical knowledge at the time of publication, are current only as of their publication date, and are subject to change without notice as advances emerge. In addition, variations in practice, which take into account the needs of the individual patient and the resources and limitations unique to the institution or type of practice, may warrant approaches, treatments, and/or procedures that differ from the recommendations outlined in this guideline. Therefore, these recommendations should not be construed as dictating an exclusive course of management, nor does the use of such recommendations guarantee a particular outcome. Genetic counseling practice guidelines are never intended to displace a health-care provider's best medical judgment based on the clinical circumstances of a particular patient or patient population. Practice guidelines are published by the ACMG or the NSGC for educational and informational purposes only, and neither the ACMG nor the NSGC "approve" or "endorse" any specific methods, practices, or sources of information.Cancer genetic consultation is an important aspect of the care of individuals at increased risk of a hereditary cancer syndrome. Yet several patient, clinician, and system-level barriers hinder identification of individuals appropriate for cancer genetics referral. Thus, the purpose of this practice guideline is to present a single set of comprehensive personal and family history criteria to facilitate identification and maximize appropriate referral of at-risk individuals for cancer genetic consultation. To develop this guideline, a literature search for hereditary cancer susceptibility syndromes was conducted using PubMed. In addition, GeneReviews and the National Comprehensive Cancer Network guidelines were reviewed when applicable. When conflicting guidelines were identified, the evidence was ranked as follows: position papers from national and professional organizations ranked highest, followed by consortium guidelines, and then peer-reviewed publications from single institutions. The criteria for cancer genetic consultation referral are provided in two formats: (i) tables that list the tumor type along with the criteria that, if met, would warrant a referral for a cancer genetic consultation and (ii) an alphabetical list of the syndromes, including a brief summary of each and the rationale for the referral criteria that were selected. Consider referral for a cancer genetic consultation if your patient or any of their first-degree relatives meet any of these referral criteria.

Two single nucleotide polymorphisms in the von Hippel-Lindau tumor suppressor gene in Taiwanese with renal cell carcinoma

Background

Renal cell carcinoma, a common malignant tumor arising from the kidney, occurs in 3.62 and 1.95 cases per one hundred thousand people among men and women, respectively, in Taiwan each year. Approximately 80% of cases are classified as clear-cell renal cell carcinoma. Inactivation of the von Hippel-Lindau tumor suppressor gene has been implicated in the tumorigenic pathway of renal cell carcinoma. Two single nucleotide polymorphisms, rs779805 and rs1642742, located in the promoter and 3′ untranslated regions of the von Hippel-Lindau gene are informative and implicated in the occurrence of renal cell carcinoma worldwide. The aim of this study is to clarify whether these polymorphisms are associated with renal cell carcinoma in Taiwanese. Genomic DNA was isolated from normal and tumor tissues of 19 renal cell carcinoma patients. The samples were screened for allelic polymorphisms by restriction fragment length polymorphism with BsaJ I and Acc I digestion. Reconfirmation was carried out by direct sequencing.

Results

Consistent with Knudson’s two-hit theory, AA to AG somatic mutations were observed in rs779805. In addition, loss of heterozygosity in both rs779805 and rs1642742 was demonstrated in 10 out of 15 RCC patients aged 50 or over. The G allele or AG heterozygote frequencies at these two loci were much higher in patient germline DNA when compared with the control group. After adjusting for age, the frequency of the G allele in both loci was much higher for late onset renal cell carcinoma in the Taiwanese population.

Conclusions

Our current results confirmed that the existence of G allele in both rs779805 and rs1642742 in the von Hippel-Lindau tumor suppressor gene is of importance in renal cell carcinoma tumorigenesis. However, more comprehensive and detailed research is needed to address the clinical relevance. Larger sample size is required to determine the exact power of correlation between these two genetic polymorphisms and renal cell carcinoma.

Electronic supplementary material

The online version of this article (doi:10.1186/1756-0500-7-638) contains supplementary material, which is available to authorized users.

Genotype-phenotype correlations, and retinal function and structure in von Hippel-Lindau disease

PURPOSE

To investigate genotype-phenotype correlation and to analyze functional and structural changes in the retina of patients with von Hippel-Lindau (VHL) disease.

METHODS

Thirteen patients from four families (A, B, C and D) with known VHL disease and known mutations in the VHL gene were examined. All patients underwent clinical examination and optical coherence tomography (OCT). Full-field electroretinography (full-field ERG) was performed in twelve patients.

RESULTS

Family A, with deletion of exon 3 in the VHL gene, and family B, with the missense mutation p.R79P, exhibited type 1 VHL characterized by the absence of pheochromocytoma and a high incidence of central nervous system hemangioblastomas. One member of family B exhibited Goldenhar syndrome. A novel missense mutation (p.L198P) was identified in the VHL gene in the patient from family C. This p.L198P mutation caused a phenotype with early onset of a neuroendocrine tumor of the pancreas, bilateral pheochromocytomas, and optic nerve hemangioblastoma. Full-field ERG showed significantly prolonged implicit times of the b-wave and maximal combined a-wave in VHL patients, compared to controls. Examination of the retinal structure in all patients with VHL, using OCT, showed a significant decrease in retinal thickness in VHL patients without ocular hemangioblastomas, compared to controls.

CONCLUSIONS

Our findings support previously established genotype-phenotype correlations. However, we here describe an unusual phenotype with a novel missense mutation, p.L198P, and report the finding that VHL disease can be associated with Goldenhar syndrome. Electrophysiological and structural findings suggest that VHL disease is a progressive, neurodegenerative disease of the retina.

Sequence variations in the von Hippel-Lindau tumor suppressor gene in patients with intracranial aneurysms

BACKGROUND

The rupture of intracranial aneurysms leads to subarachnoid hemorrhage, which is often associated with poor outcome. Preventive treatment of unruptured intracranial aneurysms is possible and recommended. However, the lack of candidate genes precludes identifying patients at risk by genetic analyses. We observed intracranial aneurysms in 2 patients with von Hippel-Lindau (VHL) disease and the known disease-causing mutation c.292T > C (p.Tyr98His) in the VHL tumor suppressor gene. This study investigates whether the VHL gene is a possible candidate gene for aneurysm formation.

METHODS

Patients with intracranial aneurysms admitted to our department between 2006 and 2009 were enrolled. The peripheral leukocyte DNA of 200 patients was investigated for sequence variations in the VHL gene using denaturing high performance liquid chromatography. Peripheral leukocyte DNA of 100 randomly sampled probands was investigated as a control group. The allelic frequencies of sequence variations between both groups were compared using the Fisher exact test.

RESULTS

Fourteen of 200 patients with intracranial aneurysms had sequence variations at 6 different loci in the VHL gene. In contrast, no sequence variations were identified in 100 probands in the control group (P = 0.0062). However, none of the single-sequence variations had a statistically significant difference in the allelic frequencies compared to the control group.

CONCLUSIONS

There is accumulating evidence for a genetic basis of aneurysm development. Our investigations lead to the conclusion that the VHL gene is potentially involved in the formation of intracranial aneurysms in a subset of patients. Additional candidate genes need to be identified in order to develop sensitive genetic screening for at-risk patients.

Proteostasis modulators prolong missense VHL protein activity and halt tumor progression

Although missense mutations of the von Hippel-Lindau disease (VHL) gene are the most common germline mutation underlying this heritable cancer syndrome, the mechanism of tumorigenesis is unknown. We found a quantitative reduction of missense mutant VHL protein (pVHL) in tumors associated with physiologic mRNA expression. Although mutant pVHL is unstable and degraded contemporarily with translation, it retains its E3 ligase function, including hypoxia-inducible factor degradation. The premature pVHL degradation is due to misfolding and imbalance of chaperonin binding. Histone deacetylase inhibitors (HDACIs) can modulate this pathway by inhibiting the HDAC-Hsp90 chaperone axis, stabilizing pVHL, and restoring activity comparable to wild-type protein, both in vitro and in animal models. Furthermore, HDACI-mediated stabilization of missense pVHL significantly attenuates the growth of 786-O rodent tumor model. These findings provide direct biological insight into VHL-associated tumors and elucidate a treatment paradigm for VHL.

Ubiquitin/SUMO modification regulates VHL protein stability and nucleocytoplasmic localization

Functional inactivation of the von Hippel-Lindau (VHL) tumor suppressor protein is linked to the development of several forms of cancer as well as oncogenic progression like sporadic renal clear-cell carcinomas (RCC). Despite the critical role played by VHL in destruction of hypoxia-inducible factor α (HIFα) via ubiquitin-mediated proteolysis, very little is known about the post-translational modification which regulates VHL activity. Our previous study showed that the SUMO E3 ligase PIASy interacts with VHL and induces VHL SUMOylation on lysine residue 171 (Cai et al, PLoS ONE, 2010, 5(3):e9720). Here we further report that VHL also undergoes ubiquitylation on both lysine residues 171 and 196, which is blocked by PIASy. Moreover, using a VHL-SUMO1 or ubiquitin fusion protein, we found that ubiquitylated VHL is localized predominantly in the cytoplasm, while SUMOylated VHL results in increased VHL protein stability and nuclear redistribution. Interestingly, substitution of lysine 171 and 196 to arginine of VHL abrogates its inhibitory function on the transcriptional activity of HIFα, and tube formation in vitro. This demonstrates that post-translational modifications like ubiquitylation and SUMOylation contributes to VHL protein stability and nucleocytoplasmic shuttling, and that the overall function of VHL in tumor suppression may require a precise and dynamically regulated process which involves protein modification.

Parasympathetic paragangliomas are part of the Von Hippel-Lindau syndrome

CONTEXT

Von Hippel-Lindau (VHL) disease, caused by germline mutations in the VHL gene, is a hereditary tumor syndrome manifested by hemangioblastomas, clear cell renal cell carcinomas, and pheochromocytomas. In addition, a multitude of other rare tumors, including parasympathetic paragangliomas, can occur and even be the sole manifestation of VHL disease. The VHL gene is a bona fide tumor suppressor gene with biallelic inactivation contributing to tumor formation. However, in parasympathetic paragangliomas occurring in VHL disease, biallelic inactivation of the VHL gene has not been demonstrated to date.

DESIGN

The head and neck paragangliomas of two VHL patients were analyzed for mutations by direct sequencing of the VHL gene. In addition loss of heterozygosity analysis was performed for three microsatellite loci near the VHL gene. To rule out other underlying genetic causes of the parasympathetic paragangliomas, mutation analysis of the SDHB, SDHC, and SDHD genes was also performed.

RESULTS

Apart from germline VHL mutations, no additional mutations were found in the paraganglioma-related tumor suppressor genes SDHB, SDHC, and SDHD. Analysis of paraganglioma tissue revealed loss of the VHL wild-type allele in both tumors, indicating that in these tumors biallelic VHL gene inactivation occurred.

CONCLUSIONS

These findings indicate that parasympathetic paragangliomas in VHL disease, although rare, are part of the syndrome and related to VHL gene inactivation. Clinicians should be aware of the potential occurrence of parasympathetic paragangliomas in VHL disease.

Germline VHL gene mutations in Hungarian families with von Hippel-Lindau disease and patients with apparently sporadic unilateral pheochromocytomas

OBJECTIVE

Von Hippel-Lindau (VHL) disease is a hereditary tumor syndrome caused by mutations or deletions of the VHL tumor-suppressor gene. Germline VHL gene alterations may be also present in patients with apparently sporadic pheochromocytoma (ASP), although a wide variation in mutation frequencies has been reported in different patient cohorts.

DESIGN

Herein, we report the analysis of the VHL gene in Hungarian families with VHL disease and in those with ASP.

METHODS

Seven families (35 members) with VHL disease and 37 unrelated patients with unilateral ASP were analyzed. Patients were clinically evaluated and the VHL gene was analyzed using direct sequencing, multiplex ligation-dependent probe amplification, and real-time PCR with SYBR Green chemistry.

RESULTS

Disease-causing genetic abnormalities were identified in each of the seven VHL families and in 3 out of the 37 patients with ASP (one nonsense and six missense mutations, two large gene deletions and one novel 2 bp deletion). Large gene deletions and other genetic alterations resulting in truncated VHL protein were found only in families with VHL type 1, whereas missense mutations were associated mainly, although not exclusively, with VHL type 2B and type 2C.

CONCLUSIONS

The spectrum of VHL gene abnormalities in the Hungarian population is similar to that observed in Western, Japanese, or Chinese VHL kindreds. The presence of VHL gene mutations in 3 out of the 37 patients with ASP suggests that genetic testing is useful not only in patients with VHL disease but also in those with ASP.

Ser80Ile mutation and a concurrent Pro25Leu variant of the VHL gene in an extended Hungarian von Hippel-Lindau family

Von Hippel-Lindau disease (VHL) is a rare autosomal dominant disease characterized by development of cystic and tumorous lesions at multiple sites, including the brain, spinal cord, kidneys, adrenals, pancreas, epididymis and eyes. The clinical phenotype results from molecular abnormalities of the VHL tumor suppressor gene, mapped to human chromosome 3p25-26. The VHL gene encodes two functionally active VHL proteins due to the presence of two translational initiation sites separated by 53 codons. The majority of disease-causing mutations have been detected downstream of the second translational initiation site, but there are conflicting data as to whether few mutations located in the first 53 codons, such as the Pro25Leu could have a pathogenic role. In this paper we report a large Hungarian VHL type 2 family consisting of 32 members in whom a disease-causing AGT80AAT (Ser80Ile) c.239G>A, p.Ser80Ile mutation, but not the concurrent CCT25CTT (Pro25Leu) c.74C>T, p.Pro25Leu variant co-segregated with the disease. To our knowledge, the Ser80Ile mutation has not been previously described in VHL type 2 patients with high risk of pheochromocytoma and renal cell cancer. Therefore, this finding represents a novel genotype-phenotype association and VHL kindreds with Ser80Ile mutation will require careful surveillance for pheochromocytoma. We concluded that the Pro25Leu variant is a rare, neutral variant, but the presence such a rare gene variant may make genetic counseling difficult.

Allosteric effects in the marginally stable von Hippel-Lindau tumor suppressor protein and allostery-based rescue mutant design

Many multifunctional tumor suppressor proteins have low stability, a property linked to cancer development. The von Hippel-Lindau tumor suppressor protein (pVHL) is one of these proteins. pVHL forms part of the E3 ubiquitin ligase complex that regulates the degradation of the hypoxia-inducible factor (HIF). Under native conditions, free pVHL is a molten globule, but it is stabilized in the E3 complex. By using molecular dynamics simulations, we observed that the interface between the two pVHL domains is the least stable region in unbound pVHL. We designed five stable mutants: one with a mutation at the interdomain interface and the others in the alpha- or beta-domains. Experimentally, type 2B pVHL disease mutant Y98N at the HIF binding site was shown to destabilize pVHL and decrease its binding affinity to HIF. Our simulations showed that the decrease in pVHL stability and binding affinity are allosterically regulated. The mutations designed to stabilize unbound wild-type pVHL, which are away from the elongin C and HIF binding sites, successfully stabilized the Y98N pVHL-elongin C complex and lowered the binding free energy of pVHL with HIF. Our results indicated both the enthalpic and dynamic allosteric components between the elongin C and HIF binding sites in pVHL, in the alpha- and beta-domains, respectively, mediated by the interdomain interface and linker. Drugs mimicking the allosteric effects of these mutants may rescue pVHL function in von Hippel-Lindau disease.

A patient with bilateral pheochromocytoma as part of a Von Hippel-Lindau (VHL) syndrome type 2C

Background

Von Hippel-Lindau (VHL) disease is an autosomal dominant inherited disease. It is relatively recent that type 2C was identified as a separate group solely presenting with pheochromocytomas. As an illustration, an interesting case is presented of a pregnant woman with refractory hypertension. It proved to be the first manifestation of bilateral pheochromocytomas. The family history may indicate the diagnosis, but only identification of a germ line mutation in the DNA of a patient will confirm carriership.

Case presentation

A 27 year pregnant patient with intra uterine growth retardation presented with hypertension and pre-eclampsia. Magnetic resonance imaging revealed bilateral adrenal pheochromocytoma. She underwent laparoscopic adrenelectomy and a missense mutation (Gly93Ser) in exon 1 of the VHL gene on chromosome 3 (p25 – p26) was shown in the patient, her father and her daughter confirming the diagnosis of VHL.

Conclusion

In almost all VHL families molecular genetic analysis of DNA will demonstrate an inherited mutation. Because of the involvement in several organs, periodic clinical evaluation should take place in a well coordinated, multidisciplinary setting. VHL disease can be classified into several subtypes. VHL type 2C patients present with pheochromocytomas without evidence of haemangioblastomas in the central nervous system and/or retina and a low risk of renal cell carcinoma. Therefore, in such families, periodic clinical screening can be focussed on pheochromocytomas.

Genetic analyses of apparently sporadic pheochromocytomas: the Rotterdam experience

Pheochromocytomas (PCCs) are neuroendocrine tumors of chromaffin tissue that produce catecholamines. They are usually located in the adrenal medulla, although in about 10% the tumors arise from extra-adrenal chromaffin tissue. The majority of PCCs arise sporadically, but PCCs occur also in the context of hereditary cancer syndromes. Familial PCC is inherited as an autosomal dominant trait alone or as a component of the multiple endocrine neoplasia Type 2 (MEN2) syndrome (RET gene), Von Hippel-Lindau (VHL) disease (VHL gene), neurofibromatosis Type 1 (NF1 gene), or familial pheochromocytoma-paraganglioma (PCC-PGL) syndrome (SDHD/B and C genes). It has been reported that 24% of apparently sporadic PCCs patients harbor germline mutations in these PCC-causing genes. We investigated the contribution of the inherited PCC-causing genes in a partly retrospectively and partly prospectively obtained series of 213 apparently sporadic PCCs. Mutation analysis was performed for RET (56 cases), VHL (136 cases), and SDHD (126 cases) and SDHB (47 cases). No germline RET mutations, six (4.4%) germline VHL mutations, two (1.5%) germline SDHD mutations, and one germline (1.6%) SDHB mutation were found. In total we found germline mutations in about 7.5% of the investigated apparently sporadic PCCs. Although 7.5% germline mutations in a series of apparently sporadic PCCs are far less than the more than 20% reported in the literature, the figure is significant enough to consider germline mutation testing for each patient with PCC.

Genetic mutation screening in an italian cohort of nonsyndromic pheochromocytoma/paraganglioma patients

To assess the prevalence of genetic mutations in nonsyndromic pheochromocytoma/paraganglioma (PHEO/PGL) patients we have performed a systematic search for mutations in the succinate dehydrogenase (SDH) B, C, and D subunits, von Hippel-Lindau (VHL), and RET genes by direct bidirectional sequencing. Patients were selected from the medical records of hypertension centers. After exclusion of syndromic patients, 45 patients with familial (F+, n=3) and sporadic (F-, n=42) cases of isolated PHEO/PGL were considered. They included 35 patients with PHEO, 7 with PGL, and 3 with head/neck PGL (hnPGL). Three patients with PHEO (2F-, 1F+) presented VHL mutations (P86A, G93C, and R167W), six with PGL (4F-, 2F+) were positive for SDH or VHL mutations (SDHB R230G in two patients, SDHB S8F, R46Q, R90Q, and VHL P81L in one subject each), and one with hnPGL carried the SDHD 348-351delGACT mutation. We have also detected missense (SDHB S163P, SDHD H50R and G12S), synonymous (SDHB A6A, SDHD S68S), and intronic mutations that have been considered nonpathological polymorphic variants. No mutation was found in SDHC or RET genes. Our data indicate that germline mutations of VHL and SDH subunits are not infrequent in familial as well as in sporadic cases of nonsyndromic PHEO/PGL (overall, 12 of 45 probands, 22%). Accordingly, screening for such mutations seems to be justified. However, a more precise characterization of the functional relevance of any observed sequence variant and of other genetic and environmental determinants of neoplastic transformation is essential in order to plan appropriate protocols for family screening and follow-up.

VHL P25L is not a pathogenic von Hippel-Lindau mutation: a family study

BACKGROUND

von Hippel-Lindau (VHL) disease is a hereditary tumor syndrome in which affected individuals may develop CNS and retinal hemangioblastomas, pheochromocytomas, renal cell carcinoma, and cysts of various organs. The VHL gene has been localized to chromosome 3p25-26 and >500 germline mutations have been identified. A rare variant of the VHL gene results in the substitution of lysine for proline at position 25 (P25L) in the larger of the two VHL proteins. This VHL variant has previously been described in a limited number of cases and has been strongly suggested to be non-pathogenic, but this has not been proven.

METHODS

A family with a medical history suggestive of VHL disease was investigated using DNA sequence analysis to determine the presence of the P25L variant of the VHL protein.

RESULTS

Sequence analysis identified the VHL P25L variant in 7 of 14 family members, one of whom had a single retinal hemangioma, which is in itself insufficient to diagnose VHL disease. The variant was not identified in a family member with clear cell renal carcinoma, which is a hallmark feature of VHL disease.

CONCLUSIONS

On the basis of these results, it is concluded that P25L is a benign variant of the VHL protein and individuals carrying this variant should not be required to undergo screening for VHL manifestations.

Ubiquitin pathway in VHL cancer syndrome

The physiologic response to changes in cellular oxygen tension is ultimately governed by a heterodimeric transcription factor called hypoxia-inducible factor (HIF), which, in adaptation to compromised oxygen availability, transactivates a myriad of genes, including those responsible for de novo vascularization, production of oxygen-carrying red blood cells, and anaerobic metabolism. Accumulation of HIF is observed in most types of solid tumors and is frequently associated with poor prognosis and disease progression, underscoring the importance and relevance of HIF in cancer. The protein stability and, thereby, the activity of HIF are principally regulated by the von Hippel-Lindau (VHL) tumor suppressor-containing E3 ubiquitin ligase complex (ECV) that targets the catalytic subunit HIFalpha for oxygen-dependent ubiquitin-mediated destruction. Individuals who inherit germline VHL mutation develop VHL disease, which is characterized by the development of hypervascular tumors in multiple yet specific organs. This review will examine recent progress in our understanding of the molecular mechanisms governing the function of ECV and the significance of consequential regulation of HIF in oncogenesis.

PTEN gene loss, but not mutation, in benign and malignant phaeochromocytomas

Mutations of the 'phosphatase and tensin homologue deleted on chromosome 10' (PTEN/MMAC1) gene have been associated with a variety of human cancers, including prostate cancer, glioblastoma, and melanoma. The gene is thought to be one of the most frequently mutated tumour suppressor genes and inactivation of PTEN is associated with disease progression and angiogenesis. High vascularization and resistance to chemo- and radio-therapy are two well-established features of phaeochromocytomas (PCCs). Furthermore, benign and malignant PCCs are found in several PTEN knockout mouse models. This study therefore evaluated whether inactivation of PTEN may be involved in the tumourigenesis of PCC in man and whether PTEN abnormalities may help to define the malignant potential of these tumours. Tumour and germline DNA was analysed from 31 patients with apparently sporadic PCC, including 14 clinically benign and 17 malignant tumours, for loss of the PTEN gene locus, mutations in the PTEN gene, and for PTEN protein expression by immunohistochemistry. Loss of heterozygosity (LOH) analysis showed loss of PTEN in four malignant tumours (40%) and in one benign tumour (14%). However, no mutations of PTEN were observed. Immunohistochemistry showed no correlation with clinical behaviour and/or LOH status. The results indicate that inactivation of the PTEN/MMAC1 gene may play a minor role in the development of malignant phaeochromocytomas.

Review: Should patients with apparently sporadic pheochromocytomas or paragangliomas be screened for hereditary syndromes?

CONTEXT

The recent identification of germline mutations of the mitochondrial complex II genes in variants of paraganglioma/pheochromocytoma syndrome has enlarged the number of known causative genes for hereditary pheochromocytoma. A question confronting clinicians is whether they should screen patients with apparently sporadic pheochromocytomas for unsuspected germline mutations of some or all of the seven genes known to cause hereditary paraganglioma or pheochromocytoma (NF1, VHL, RET, MEN1, SDHD, SDHC, and SDHB). A positive answer was suggested by a report that placed the estimate of hereditary disease in apparently sporadic pheochromocytoma as high as 24%.

EVIDENCE ACQUISITION

We applied clinically useful criteria to a review of the literature, defining cases of apparently sporadic pheochromocytoma as those without a suspicious personal or family history, with a focal, unilateral pheochromocytoma, and presenting at age less than 50 yr.

EVIDENCE SYNTHESIS

We reduced the overall estimate of unsuspected hereditary pheochromocytoma patients with apparently sporadic pheochromocytoma to approximately 17%. Mutations in only three genes (VHL, SDHB, and SDHD) accounted for almost this entire minority, and unsuspected RET mutation was rare. Costs, coverage by insurance, the potential effect on insurability, and deficient information for populations outside of referral centers should be considered before recommending genetic testing in patients with apparently sporadic presentations of pheochromocytomas.

CONCLUSION

We recommend genetic testing for patients with an apparently sporadic pheochromocytoma under the age of 20 yr with family history or features suggestive of hereditary pheochromocytoma or for patients with sympathetic paragangliomas. For individuals who do not meet these criteria, genetic testing is optional.

Von hippel-lindau disease

A germline mutation in the Von-Hippel Lindau (VHL) gene predisposes carriers to development of abundantly vascularised tumours in the retina, cerebellum, spine, kidney, adrenal gland and pancreas. Most VHL patients die from the consequences of cerebellar haemangioblastoma or renal cell carcinoma. The VHL gene is a tumour suppressor gene and is involved in angiogenesis by regulation of the activity of hypoxia-inducible factor 1-alpha (HIF1-alpha). Clinical diagnosis of VHL can be confirmed by molecular genetic analysis of the VHL gene, which is informative in virtually all VHL families. A patient with (suspicion for) VHL is an indication for genetic counselling and periodical examination.

Pheochromocytoma and functional paraganglioma syndrome: no longer the 10% tumor

Pheochromocytomas and abdominal paragangliomas are catecholamine-producing tumors of the sympathetic nervous system, while head and neck paragangliomas are non-secreting tumors of parasympathetic origin. Recent developments in clinical and molecular research on these tumor forms have significantly clarified their genetic backgrounds and challenged the view of "pheochromocytoma as the 10% rule tumor." Firstly, a larger proportion of these tumors are today discovered in normotensive patients during imaging carried out for other reasons than suspicion of pheochromocytoma. Secondly, although the differential diagnosis between malignant and benign tumors remains a challenge, the risk of malignancy well exceeds the classical 10% in patients with extra-adrenal disease, and/or carriers of germ-line SDHB mutations. Finally, up to a third of patients carry a germ-line mutation in a gene predisposing to pheochromocytoma and/or paraganglioma. Identification of a constitutional mutation in RET, VHL, SDHD, or SDHB has implications for clinical screening and follow-up for both the patient and for relatives at risk who can be identified by screening for the same mutation. Genetic testing in apparently sporadic cases is therefore regarded as beneficial, especially in patients diagnosed before 50 years of age, and in patients with bilateral, multifocal, malignant and/or extra-adrenal disease.

Role of VHL gene mutation in human cancer

Germline inactivation of the von Hippel-Lindau (VHL) tumor suppressor gene causes the von Hippel-Lindau hereditary cancer syndrome, and somatic mutations of this gene have been linked to the development of sporadic hemangioblastomas and clear-cell renal carcinomas. The VHL tumor suppressor protein (pVHL), through its oxygen-dependent polyubiquitylation of hypoxia-inducible factor (HIF), plays a central role in the mammalian oxygen-sensing pathway. This interaction between pVHL and HIF is governed by post-translational prolyl hydroxylation of HIF in the presence of oxygen by a conserved family of Egl-nine (EGLN) enzymes. In the absence of pVHL, HIF becomes stabilized and is free to induce the expression of its target genes, many of which are important in regulating angiogenesis, cell growth, or cell survival. Moreover, preliminary data indicate that HIF plays a critical role in pVHL-defective tumor formation, raising the possibility that drugs directed against HIF or its downstream targets (such as vascular endothelial growth factor) might one day play a role in the treatment of hemangioblastoma and renal cell carcinoma. On the other hand, clear genotype-phenotype correlations are emerging in VHL disease and can be rationalized if pVHL has functions separate from its control of HIF.

Inactivation of VHL by tumorigenic mutations that disrupt dynamic coupling of the pVHL.hypoxia-inducible transcription factor-1alpha complex

The von Hippel-Lindau (VHL) gene product, pVHL, targets the alpha subunit of the hypoxia-inducible transcription factor (HIF-alpha) for ubiquitin-dependent degradation. This tumor suppressor function is mediated by the alpha- and beta-domains responsible for assembling the pVHL E3 ubiquitin ligase complex and for recognizing the prolyl-hydroxylated HIF-alpha, respectively. The molecular basis for a large number of tumor-derived mutations can be attributed to alterations that directly compromise the ability of pVHL to assemble the E3 or to contact the substrate. Here we describe a new mechanism of oncogenic inactivation by VHL missense mutations that lie in the L1 and L7 linker regions distal to the HIF-alpha-binding pocket. Employing molecular dynamics simulations, we show that the tumorigenic L1 loop mutation of Ser(65) to Leu, deficient in promoting the degradation of HIF-alpha, disrupts the coordination of internal motions of the pVHL.HIF-1alpha complex. Furthermore, we demonstrate that in addition to S65L, five other tumor-derived VHL mutations located within the L1 loop are each defective in mediating proteolysis of HIF-2alpha. Moreover, dynamic organization of pVHL.HIF-1alpha recognition is focally centered on Gln(145) within the L7 loop, and its tumorigenic mutant Q145H abolishes almost all of the correlated dynamic motions. Intriguingly, Q145H, whereas defective in targeting cellular HIF-alpha for degradation, had an attenuated hydroxylation dependence in binding to HIF-1alpha in vitro. Taken together, our results suggest that specific association between pVHL and the hydroxylated HIF-alpha requires both the L1 and L7 loops to coordinate dynamic coupling among distant pVHL regions, whose mutational disruption inactivates VHL and is hence responsible for tumorigenesis.

The role of von Hippel-Lindau tumor suppressor protein and hypoxia in renal clear cell carcinoma

The majority of kidney cancers are caused by the mutation of the von Hippel-Lindau (VHL) tumor suppressor gene. VHL protein (pVHL) is part of an E3 ubiquitin ligase complex called VEC that is composed of elongin B, elongin C, cullin 2, NEDD8, and Rbx1. VEC targets a hypoxia-inducible factor (HIF) transcription factor for ubiquitin-mediated destruction selectively in the presence of oxygen. In the absence of wild-type pVHL, as in VHL patients or in the majority of sporadic clear cell renal cell carcinomas, HIF-responsive genes are inappropriately activated even under normoxia. Recent insights into the molecular mechanisms regulating the function of pVHL, and thereby HIF, in the context of kidney cancer are the focus of this review.

Morphologic changes and altered gene expression in an epithelioid hemangioendothelioma during a ten-year course of disease

Epithelioid hemangioendothelioma (EHE) is a rare low-grade malignant vascular neoplasm with unpredictable prognosis. We report on a patient suffering from a vascular neoplasm with primary manifestation in the skeleton and subsequent development of lesions of EHE in the spleen, liver and lung. Based on the assumption that involvement of visceral organs was due to metastatic spread, changes in clinical behavior, morphology, and proliferation index suggest malignant progression of the tumor. Analyzing the expression of genes known to be involved in the pathogenesis of vascular tumors, we found that the appearance of less differentiated tumor was paralleled by an accumulation of TP53 and murine double minute-2 (MDM-2) protein, decreased caveolin-1 (CAV-1) expression, and increased vascular endothelial growth factor (VEGF) expression. Mutations of the von-Hippel-Lindau-tumor-suppressor-gene (VHL) were excluded as mechanism of VEGF upregulation. Therefore, we propose that the expression of TP53, MDM-2, CAV-1 and VEGF as a marker of biologic behavior be verified in a larger case study of EHE.

Hypoxia inducible factor activates the transforming growth factor-alpha/epidermal growth factor receptor growth stimulatory pathway in VHL(-/-) renal cell carcinoma cells

Bi-allelic-inactivating mutations of the VHL tumor suppressor gene are found in the majority of clear cell renal cell carcinomas (VHL(-/-) RCC). VHL(-/-) RCC cells overproduce hypoxia-inducible genes as a consequence of constitutive, oxygen-independent activation of hypoxia inducible factor (HIF). While HIF activation explains the highly vascularized nature of VHL loss lesions, the relative role of HIF in oncogenesis and loss of growth control remains unknown. Here, we report that HIF plays a central role in promoting unregulated growth of VHL(-/-) RCC cells by activating the transforming growth factor-alpha (TGF-alpha)/epidermal growth factor receptor (EGF-R) pathway. Dominant-negative HIF and enzymatic inhibition of EGF-R were equally efficient at abolishing EGF-R activation and serum-independent growth of VHL(-/-) RCC cells. TGF-alpha is the only known EGF-R ligand that has a VHL-dependent expression profile and its overexpression by VHL(-/-) RCC cells is a direct consequence of HIF activation. In contrast to TGF-alpha, other HIF targets, including vascular endothelial growth factor (VEGF), were unable to stimulate serum-independent growth of VHL(-/-) RCC cells. VHL(-/-) RCC cells expressing reintroduced type 2C mutants of VHL, and which retain the ability to degrade HIF, fail to overproduce TGF-alpha and proliferate in serum-free media. These data link HIF with the overproduction of a bona fide renal cell mitogen leading to activation of a pathway involved in growth of renal cancer cells. Moreover, our results suggest that HIF might be involved in oncogenesis to a much higher extent than previously appreciated.

Pheochromocytoma: the expanding genetic differential diagnosis

Pheochromocytomas and paragangliomas are tumors of the autonomic nervous system; pheochromocytomas are tumors of the adrenal medulla, and paragangliomas are extra-adrenal tumors arising from either the sympathetic nervous system or parasympathetic ganglia. It has previously been estimated that approximately 10%-15% of pheochromocytomas are due to hereditary causes. However, our increased understanding of the three hereditary syndromes (neurofibromatosis 1, multiple endocrine neoplasia type 2, and von Hippel-Lindau syndrome) in which pheochromocytoma is found and the recent discovery that mutations in genes in the succinate dehydrogenase family (SDHB and SDHD) predispose to pheochromocytoma have necessitated a re-evaluation of the genetic basis of pheochromocytoma. These studies indicate that the frequency of germline mutations associated with isolated pheochromocytoma is higher than previously estimated, with both hospital-based series and a large population-based series indicating that the frequency of germline mutations in RET, VHL, SDHB, and SDHD taken together approximates 20%. In all patients with pheochromocytoma, including those with known hereditary syndrome or a positive family history, the frequency of germline mutations in these four genes together approaches 30%. Given the frequency of germline mutations, consideration should be given to genetic counseling for all patients with pheochromocytoma and is particularly important for individuals with a positive family history, multifocal disease, or a diagnosis before age 50. Identification of patients with hereditary pheochromocytoma is important because it can guide medical management in mutation-positive patients and their families. This review provides an overview of the known genetic syndromes that are commonly associated with pheochromocytoma, examines recent data on the association of germline mutations in the succinate dehydrogenase gene family with pheochromocytoma, and suggests guidelines for the genetic evaluation of pheochromocytoma patients.

Von Hippel-Lindau gene alterations in sporadic benign and malignant pheochromocytomas

The Von Hippel-Lindau (VHL) gene product has a wide spectrum of tissue-specific functions, and specific germline mutations are associated with clinical phenotypes in VHL disease. In particular, missense mutations are correlated with the susceptibility to pheochromocytomas. An association between VHL aberrations and prognosis has been suggested in renal clear cell carcinoma but has not been studied in pheochromocytomas. We studied the frequency and spectrum of VHL alterations in apparently sporadic pheochromocytomas in relation to the clinical behavior in 72 patients, including 48 patients with clinically benign and 24 patients with malignant pheochromocytomas. Single-strand conformation polymorphism (SSCP) analysis followed by DNA sequencing, loss of heterozygosity analysis of the VHL locus and immunohistochemistry for VHL protein expression were used to investigate somatic VHL gene alterations. In 2 patients, 1 with a malignant tumor, germline mutations were identified in the stop codon. Tumor-specific intragenic VHL mutations and accompanying loss of heterozygosity were identified in 2 (4.3%) of 47 sporadic benign pheochromocytomas compared to 4 (17.4%) of 23 malignant tumors (p = 0.064). Only one of these mutations has been previously described, in a renal clear cell carcinoma. Expression of the VHL protein was observed in all pheochromocytomas. No distinction in the nature of VHL alterations between benign and malignant pheochromocytomas and no correlation with histopathologic or clinical features was observed. We report novel VHL mutations in sporadic pheochromocytomas, which are slightly correlated with malignancy. VHL mutations may have some impact on the malignant transformation of pheochromocytomas.

The molecular pathogenesis of hereditary and sporadic adrenocortical and adrenomedullary tumors

Modern imaging modalities lead to frequent detection of adrenal masses, most of them incidental findings. Although the majority of adrenocortical and adrenomedullary tumors are benign, there are no reliable clinical and laboratory markers to distinguish most of them from malignant neoplasms. The molecular mechanisms underlying the pathogenesis of these tumors have recently begun to be unraveled. A fruitful avenue for the elucidation of tumorigenesis has been the study of adrenal tumors that are manifestations of hereditary or postzygotic genetic syndromes, because one knows the "first hit", i.e. the primary gene defect. In contrast, in sporadic adrenal tumors the first hit, possibly a somatic mutation of a tumor-related gene, is unknown, and therefore the sequence of genetic alterations is difficult to establish. In this article we review in addition to our own work the literature on molecular aspects of adrenocortical and adrenomedullary tumorigenesis.

New insights into the genetics of familial chromaffin cell tumors

We review genetic aspects and recent advances in our understanding of the molecular pathogenesis of familial chromaffin cell tumors (pheochromocytoma, paraganglioma). About 10 percent of pheochromocytomas are familial and occur as part of multiple endocrine neoplasia type 2 (MEN 2), von Hippel-Lindau (VHL) disease, and neurofibromatosis type 1 (NF 1). A subset of paragangliomas, tumors that can also produce and secrete catecholamines, are also familial and occur in patients with germline mutations in genes that encode subunits of the mitochondrial complex II. The precise molecular mechanisms underlying the pathogenesis of chromaffin cell tumors remain widely unknown, although recent studies in hereditary tumors help elucidate their development. In MEN 2, overrepresentation of mutant RET in selected adrenomedullary cells may be an important mechanism in initiating the formation of a pheochromocytoma. In VHL disease, pheochromocytoma development appears to occur according to Knudson's two-hit model, a VHL germline mutation and wildtype allelic deletion. Tumorigenesis of NF1-associated pheochromocytomas remains unknown, as does tumor formation (i.e., carotid body tumor) in patients with germline mutations in SDHB, SDHC, and SDHD, genes that encode subunits of the mitochondrial complex II, the smallest complex in the respiratory chain. Many genetic alterations have been found in sporadic chromaffin cell tumors. However, at present such genetic changes are difficult to place into context with regard to tumor formation and progression.

Hereditary paraganglioma targets diverse paraganglia

Paragangliomas are highly vascularised and often heritable tumours derived from paraganglia, a diffuse neuroendocrine system dispersed from skull base to the pelvic floor. The carotid body, a small oxygen sensing organ located at the bifurcation of the carotid artery in the head and neck and the adrenal medulla in the abdomen, are the most common tumour sites. It now appears that mutations in SDHB, SDHC, and SDHD, which encode subunits of mitochondrial complex II (succinate dehydrogenase; succinate-ubiquinone oxidoreductase), are responsible for the majority of familial paragangliomas and also for a significant fraction of non-familial tumours. Germline mutations in complex II genes are associated with the development of paragangliomas in diverse anatomical locations, including phaeochromocytomas, a finding that has important implications for the clinical management of patients and genetic counselling of families. Consequently, patients with a paraganglioma tumour, including phaeochromocytoma, and a complex II germline mutation should be diagnosed with hereditary paraganglioma, regardless of family history, anatomical location, or multiplicity of tumours. This short review attempts to bring together relevant genetic data on paragangliomas with a particular emphasis on head and neck paragangliomas and phaeochromocytomas.

Recurrent polytopic chromaffin paragangliomas in a 9-year-old boy resulting from a novel germline mutation in the von Hippel-Lindau gene

Pheochromocytomas are frequently associated with inherited cancer syndromes such as von Hippel-Lindau disease (VHL). Retinal angioma and hemangioblastomas of the central nervous system are hallmarks of VHL, but its clinical variety is remarkably broad. Pheochromocytomas as the sole or first manifestation of VHL are rare but have been observed. In this case report, the authors describe an unusual case of initial collapse, seizures, and hypertensive crisis in a child who later was found to have multiple extraadrenal pheochromocytomas. Molecular diagnostics revealed a novel point mutation in the VHL gene (VHL nt. 406 T-->G). Only 7 months after the first lesions had been removed, a new paraganglioma developed in the contralateral periadrenal region. When encountering pheochromocytomas in children, the clinician should be aware that an associated tumor syndrome might be present, and appropriate molecular screening should be initiated. Molecular genetics aid in the clinical decision-making and clinical management of individual patients with pheochromocytoma.

Molecular genetic analysis of the von Hippel-Lindau and human peroxisome proliferator-activated receptor gamma tumor-suppressor genes in adenocarcinomas of the gastroesophageal junction

We investigated whether 2 candidate tumor-suppressor genes, VHL at 3p25-26 and PPAR gamma at 3p24.2-25, are involved in GEJ adenocarcinogenesis. In 43 GEJ tumor samples from 40 patients, the entire coding sequence of the VHL gene and the 5' and part of the 3' UTR as well as exons 3 and 5 of the PPAR gamma gene were screened by PCR-SSCP analysis. LOH at 3p25-26 was analyzed with 2 polymorphic microsatellite markers and with the VHL exon 1 and intron 2 polymorphisms. The relationship between LOH and clinicopathologic parameters was assessed. Expression of VHL was investigated by immunohistochemistry with a VHL-specific antibody. PCR-SSCP analysis of VHL revealed 2 different aberrant patterns in 19 patients. Upon DNA sequencing, 1 pattern appeared to be a previously described exon 1 polymorphism. The other single aberrant pattern was an intron 2 polymorphism, not yet described. PCR-SSCP analysis of PPAR gamma showed no aberrant migration patterns. LOH analysis revealed 3p25-26 loss in 24/36 (67%) informative cases, but this was not significantly correlated with clinicopathologic parameters. By immunohistochemistry, all tumors showed expression of VHL protein. Despite the very frequent LOH of 3p in GEJ adenocarcinomas, mutations in VHL and PPAR gamma were not detected. Mutations outside the screened sequences, a gene dosage effect or involvement of another tumor-suppressor gene on 3p as the target of LOH should be considered.

The von Hippel-Lindau tumor suppressor gene

Germline mutations of the von Hippel-Lindau tumor suppressor gene (VHL) in humans causes a hereditary cancer syndrome characterized by the development of retinal and central nervous system hemangioblastomas. Other tumors associated with von Hippel-Lindau disease include clear cell renal carcinomas and pheochromocytomas. Tumor development in this setting is due to functional loss of the remaining wild-type VHL allele. Biallelic VHL inactivation is also common in nonhereditary hemangioblastomas and clear cell renal carcinomas, in keeping with Knudson's 2-Hit Model of carcinogenesis. The VHL gene product, pVHL, is a component of an E3 ubiquitin ligase that targets the alpha subunits of the HIF (hypoxia-inducible factor) transcription factor for destruction in the presence of oxygen. Consequently, tumor cells lacking pVHL overproduce the products of HIF target genes such as vascular endothelial growth factor and transforming growth factor alpha. pVHL has been implicated in a variety of processes that are central to carcinogenesis including cell-cycle control, differentiation, extracellular matrix formation and turnover, and angiogenesis.

Losses of chromosomes 1p and 3q are early genetic events in the development of sporadic pheochromocytomas

Despite several loss of heterozygosity studies, a comprehensive genomic survey of pheochromocytomas is still lacking. To identify DNA copy number changes which might be important in tumor development and progression and which may have diagnostic utility, we evaluated genetic aberrations in 29 sporadic adrenal and extra-adrenal pheochromocytomas (19 clinically benign tumors and 10 malignant lesions). Comparative genomic hybridization was performed using directly fluorochrome-conjugated DNA extracted from frozen (16) and paraffin-embedded (13) tumor tissues. The most frequently observed changes were losses of chromosomes 1p11-p32 (86%), 3q (52%), 6q (34%), 3p, 17p (31% each), 11q (28%), and gains of chromosomes 9q (38%) and 17q (31%). No amplification was identified and no difference between adrenal and extra-adrenal tumors was detected. Progression to malignant tumors was strongly associated with deletions of chromosome 6q (60% versus 21% in clinically benign lesions, P = 0.0368) and 17p (50% versus 21%). Fluorescence in situ hybridization confirmed the comparative genomic hybridization data of chromosomes 1p, 3q, and 6q, and revealed aneuploidy in some tumors. Our results suggest that the development of pheochromocytomas is associated with specific genomic aberrations, such as losses of 1p, 3q, and 6q and gains of 9q and 17q. In particular, tumor suppressor genes on chromosomes 1p and 3q may be involved in early tumorigenesis, and deletions of chromosomes 6q and 17p in progression to malignancy.

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

von Hippel-Lindau (VHL) syndrome is a familial cancer syndrome caused by germline mutations in the VHL tumor suppressor gene. Mutations in the VHL gene result in the constitutive stabilization of transcription factors hypoxia-inducible factors 1alpha and 2alpha, which bind to specific enhancer elements in the vascular endothelial growth factor (VEGF) gene and stimulate angiogenesis. This increase in angiogenesis under normoxic conditions in key target organs such as the brain, kidney, and eye leads to high morbidity and reduced life expectancy. Drugs designed to block the VEGF signaling pathway may prevent the long-term complications of the disease. To test this hypothesis, a clinical study was initiated to evaluate the effect of the VEGF tyrosine kinase receptor inhibitor SU5416 in patients with VHL syndrome. Preliminary data on SU5416 indicate that it is well tolerated when administered chronically in such patients. However, since little is known about the long-term use of such inhibitors, patients will need careful monitoring. Data obtained from monitoring these patients will provide valuable information for adjuvant treatment trials in cancer patients.

Sporadic endocrine tumours and their relationship to the hereditary endocrine neoplasia syndromes

In the last years of the previous century the genes involved in the aetiology of five endocrine tumour syndromes have been identified. The tumour-suppressor gene that is responsible for Von Hippel-Lindau Disease was cloned in 1993; multiple endocrine neoplasia (MEN) types 2A and 2B and familial medullary thyroid carcinoma were found to be caused by activating mutations in the ret proto-oncogene in 1993 and 1994, and most recently the menin-gene, another tumour-suppressor gene, was shown to be associated with MEN-1. As usual, the answer to one question leads to innumerable new questions. And so, now we want to know the extent to which germ-line mutations (de novo, or otherwise previously undetected) in these genes play a role in the occurrence of the various endocrine tumours that are associated with these syndromes in apparently sporadic cases. We also want to know if the nature of the (germ-line) mutation conveys any information about the characteristics (phenotype) of the disease. We want to know the role of somatic mutations in these genes in truly sporadic tumours. And finally we want to know the exact function of the proteins that are encoded by these genes. The paper by Roijers et al. [1] elsewhere in this issue is an example of a small but well-directed step on the way to address some of these questions with respect to the menin-gene. It addresses the problem of patient selection when looking for germ-line mutations in apparently sporadic MEN-1 patients. In this review we want to give a brief summary of the present status with regard to some of the questions mentioned above, in relation to the endocrine tumour syndromes caused by the vhl, ret and menin genes.

Expression of the von Hippel-Lindau Tumor Suppressor Gene in Nonneoplastic and Neoplastic Lesions of the Thyroid

Alterations of the von Hippel-Lindau (VHL) gene, which is supposed to act as a tumor suppressor gene, can cause hereditary tumors associated with the VHL syndrome and are found in different sporadic cancers as well. While VHL protein is distinctly detectable in thyroid follicles, so far its expression in nonneoplastic and neoplastic lesions of the thyroid has not been investigated comprehensively. To illuminate the role of VHL for thyroid tumorigenesis, we investigated 12 follicular adenomas; 22 follicular carcinomas; 11 papillary carcinomas; 6 poorly differentiated carcinomas (PDTCs); 9 undifferentiated carcinomas (UTCs); 8 medullary carcinomas; 13 cases with nonneoplastic as well as normal thyroid tissue of 10 patients with antibodies against VHL, vascular endothelial growth factor (VEGF); and the proliferation marker MIB1 immunohistochemically; and selected cases by Western blot analysis. VHL was clearly expressed in nonneoplastic lesions and differentiated tumors derived from follicular epithelium, diminished in PDTCs and very weakly or not detectable in UTCs (p = 0.001), nonneoplastic, and neoplastic C-cells. Although slightly increased in certain differentiated tumors, VEGF was found to be reduced in UTCs as well. In summary, VHL is expressed differently in nonneoplastic and neoplastic lesions of the thyroid in proportion to the level of differentiation. VHL gene alterations appear to be a late event in tumorigenesis of the thyroid and a reduction in VHL protein expression is associated with a loss of differentiation and increased aggressiveness in thyroid tumors. There is no apparent inverse correlation between VHL and VEGF expression as described for other sporadic carcinomas. Therefore, the role of VHL for angiogenesis and the molecular basis of the inactivation of VHL in thyroid tumors remains to be elucidated.

Advances in the management of adrenal tumors

Adrenal tumors are very common, with the majority being nonhypersecretory and benign and less than 1% being malignant. Most primary adrenal tumors are sporadic, but may be associated with other endocrine and familial disorders, especially pheochromocytoma. All patients with "sporadic" pheochromocytoma should be screened for MEN-2 and Von Hippel-Lindau disease. As in many endocrine tumors, there are no uniform definitive histologic criteria to distinguish malignancy, which is dependent on the clinical behavior of the tumor and is accurately diagnosed in the presence of adjacent organ invasion, recurrence, or distant metastasis. Surgery remains the cornerstone and the treatment of choice for functional and primary malignant adrenal tumors, both for cure and palliation, with low morbidity and mortality.

Two distinct phenotypes caused by two different missense mutations in the same codon of the VHL gene

We have identified a family segregating von Hippel-Lindau (VHL) disease with a previously unreported T547A mutation in exon 1 of the VHL gene that causes a Tyr112 to Asn missense alteration in the protein. The mutation was identified by nucleotide sequencing and confirmed by restriction enzyme digestion. The mutation cosegregated with the disease in all five tested affected individuals from the extended family. The family consists of more than 100 at-risk individuals over seven generations. To date, we have identified 13 affected individuals of whom seven have had renal cell carcinoma and one has had a pheochromocytoma. No other case of a neuroendocrine tumor of the pancreas or adrenal gland (pheochromocytoma) was found or recognized retrospectively. Other manifestations in this family include retinal angioma and hemangioblastoma of the central nervous system. We also found the T547A mutation in three asymptomatic members of the family, ages 12, 19, and 20. Another mutation, T547C, which causes Tyr112 to His, has been seen at the same position and has been associated with VHL type 2A (pheochromocytoma, but no renal cell carcinoma) in two families with a total of 22 affected individuals [Chen F, Slife L, Kishida T, Mulvihill J, Tisherman SE, Zbar B, 1996: J Med Genet 33:716-717]. Thus, different amino acid changes at the same position can cause very distinct clinical phenotypes. It will be interesting to elucidate the functional differences that underlie the different phenotypes.