Subtotal adrenalectomy for phaeochromocytoma in multiple endocrine neoplasia type 2A

OBJECTIVE

To describe our surgical technique for, and results of, subtotal adrenalectomy for phaeochromocytoma in multiple endocrine neoplasia (MEN) type 2.

DESIGN

Retrospective study.

SETTING

Teaching hospital, The Netherlands.

SUBJECTS

6 patients (four women and 2 men, mean age 35 years, range 31-46) with MEN type 2 who presented between 1993 and 1996.

INTERVENTIONS

Cortical sparing adrenalectomy (n =4) together with contralateral total adrenalectomy in bilateral disease (n = 2).

MAIN OUTCOME MEASURES

Morbidity, mortality, adrenal function postoperatively, and recurrence.

RESULTS

Cortical sparing adrenalectomy leaving adequate adrenal reserve was possible in all cases. There was no operative morbidity or mortality. Mean follow-up was 40 months (range 1347). One patient developed a recurrent phaeochromocytoma 24 months after subtotal adrenalectomy.

CONCLUSIONS

Subtotal adrenalectomy with preservation of adequate adrenal cortical reserve was feasible in all cases. Long term follow-up is necessary to establish its definitive place in the treatment of familial phaeochromocytoma.

Extensive islet amyloid formation is induced by development of Type II diabetes mellitus and contributes to its progression: pathogenesis of diabetes in a mouse model

AIMS/HYPOTHESIS

Type II (non-insulin-dependent) diabetes mellitus is a multifactorial disease in which pancreatic islet amyloid is a characteristic histopathological finding. Islet amyloid fibrils consist of the beta-cell protein "islet amyloid polypeptide" (IAPP)/"amylin". Unlike human IAPP (hIAPP), mouse IAPP cannot form amyloid. In previously generated transgenic mice, high expression of hIAPP as such did not induce islet amyloid formation. To further explore the potential diabetogenic role of amyloidogenic IAPP, we introduced a diabetogenic trait ("ob" mutation) in hIAPP transgenic mice.

METHODS

Plasma concentrations of IAPP, insulin and glucose were determined at 3.5 (t1), 6 (t2), and 16-19 months of age (t3). At t3, the mice were killed and the pancreas was analysed (immuno)histochemically.

RESULTS

In non-transgenic ob/ob mice, insulin resistance caused a compensatory increase in insulin production, normalizing the initial hyperglycaemia. In transgenic ob/ob mice, concurrent increase in hIAPP production resulted in extensive islet amyloid formation (more often and more extensive than in transgenic non-ob/ob mice), insulin insufficiency and persistent hyperglycaemia: At t3, plasma insulin levels in transgenic ob/ob mice with amyloid were fourfold lower than in non-transgenic ob/ob mice (p < 0.05), and plasma glucose concentrations in transgenic ob/ ob mice were almost twofold higher (p < 0.05). In addition, the degree of islet amyloid formation in ob/ob mice was positively correlated to the glucose:insulin ratio (r(s) = 0.53, p < 0.05).

CONCLUSION/INTERPRETATION

Islet amyloid is a secondary diabetogenic factor which can be both a consequence of insulin resistance and a cause of insulin insufficiency. [Diabetol

[Prophylactic total thyroidectomy in childhood for multiple endocrine neoplasia type 2A: preliminary results]

OBJECTIVE

Evaluation of prophylactic total thyroidectomy in childhood in case of MEN2A gene carriership.

DESIGN

Retrospective.

METHOD

Prophylactic thyroidectomy was performed in 14 MEN2A gene carriers (7 boys, 7 girls; median age 9.1 year (range: 4.8-14.7)), in June 1993-July 1997 at the department Pediatric Surgery of the Wilhelmina Children's Hospital in Utrecht, the Netherlands. Median time between genetic investigation and operation was 5.5 months (range: 2-35). Lymph node dissection was not performed. The parathyroids were identified and left untouched as far as possible, autotransplantation was performed twice because of doubt about viability. Outpatient follow-up took place every 3-6 months.

RESULTS

One patient (13.4 year) showed macroscopic, the other 13 microscopic multifocal medullary thyroid carcinoma, 11 bilateral and 3 unilateral. In 1 child (6.2 year) neuroinvasive growth existed already. Surgical sections were free of tumour. After the operation temporary hoarseness occurred once, temporary hypocalcaemia three times and permanent hypoparathyroidism twice; after autotransplantation no hypocalcaemia occurred. Median follow-up was 3.2 year (range: 1 month-4.0 year). Mild psychological problems were observed in 4 patients, psychiatric problems in 1.

CONCLUSION

Prophylactic total thyroidectomy during the first decade is recommended. Additional lymph node dissection and total parathyroidectomy are unnecessary than. In order to prevent postoperative hypoparathyroidism, autotransplantation of at least one parathyroid is advisable.

Islet amyloid polypeptide/amylin messenger RNA and protein expression in human insulinomas in relation to amyloid formation

OBJECTIVE

Islet amyloid polypeptide (IAPP), also named amylin, is the predominant protein component of amyloid deposits in human islet beta cell tumours of the pancreas (insulinomas). IAPP is co-produced with insulin by islet beta cells. We investigated IAPP expression in relation to insulin expression and to amyloid formation in eleven insulinomas.

DESIGN AND METHODS

RNA and protein extracts were prepared from the same pieces of tumour tissue, and from specimens of two normal human pancreata. IAPP and insulin mRNA and peptide content were quantified using Northern blot analysis and radioimmunoassay (RIA) respectively. Molecular forms of IAPP immunoreactivity were analysed by reversed-phase high-performance liquid chromatography (HPLC). The presence of islet hormones and of amyloid was assessed by (immuno)histochemical staining of paraffin sections. Plasma levels of IAPP and insulin prior to tumour resection were determined by RIA.

RESULTS

IAPP and insulin mRNA and peptide content varied widely between the tumour specimens, and there was considerable intratumour heterogeneity of peptide content. HPLC analysis indicated correct proteolytic processing of the IAPP precursor protein. Amyloid deposits were detected only in the three tumours with the highest IAPP content. In contrast to insulin, plasma levels of IAPP were not elevated in the insulinoma patients.

CONCLUSIONS

The spectrum of hormone production by insulinomas cannot be inferred from only a few tissue sections due to intratumour heterogeneity. Expression of the IAPP and insulin genes is not coupled in insulinomas, which produce properly processed mature IAPP. In addition to IAPP overproduction, additional factors such as intracellular accumulation of IAPP are involved in amyloidogenesis in insulinomas.

Management of renal cell carcinoma in von Hippel-Lindau disease

BACKGROUND

An evaluation of nephron-sparing surgery (NSS) or radical nephrectomy (RN) for treating renal cell carcinoma (RCC) in patients with von Hippel-Lindau disease (VHL) was carried out.

METHODS

Between 1976 and 1997, 10 patients with RCC from four VHL families, of whom seven were from one family, were studied by clinical and histopathological examination. Before 1991, three patients were treated using RN, and thereafter five patients were treated using NSS. Two patients were not operated on.

RESULTS

RCCs in our patients showed a slow growth rate (on average 0.3 cm year-1), and asymptomatic patients presented with tumours of low-grade malignancy. In all patients, tumours were surrounded by a fibrous pseudocapsule. In 5 out of 17 tumours, pseudocapsular invasion was observed, and three of these five tumours broke through the pseudocapsule. To date, these patients have not shown a less favourable outcome than those without pseudocapsular involvement by tumour growth. Multicentricity of RCC was relatively low (4.6 lesions per kidney). In two of the three RN patients, only a single satellite lesion, in the direct vicinity of a RCC, was found in one kidney. Six tumours (1.8-5.5 cm) were enucleated by NSS. During a mean follow-up of 30 months, renal function in these patients was well preserved.

CONCLUSIONS

In our patients, RCCs grew slowly, were of low grade, had a dense fibrous pseudocapsule and were thus good candidates for NSS.

Transgenic overexpression of human islet amyloid polypeptide inhibits insulin secretion and glucose elimination after gastric glucose gavage in mice

Islet amyloid polypeptide (IAPP) is synthesized in islet beta cells and has been implicated in diabetes pathogenesis because it can inhibit insulin secretion and action and form fibrils leading to islet amyloidosis. Its physiological function has, however, not been established. We therefore examined insulin secretion and glucose elimination after i.v. or gastric gavage of glucose in transgenic mice overexpressing human IAPP (hIAPP) resulting in considerably increased circulating IAPP concentrations. The insulin response to and the glucose elimination after i.v. glucose (1 g/kg) were not different in transgenic mice compared with wild type animals, neither in males nor in females. In contrast, the insulin response to gastric glucose (150 mg/mouse) was reduced and the glucose elimination was inhibited in both male and female transgenic mice. The area under the 30 min insulin curve (AUCinsulin) was 21 +/- 2 nmol/l in 30 min in transgenic males (n = 24) vs 43 +/- 3 nmol/l in 30 min in wild type males (n = 26; p < 0.001) and the respective areas under the glucose curve (AUCglucose) were 1.90 +/- 0.12 and 1.62 +/- 0.09 mol/l in 120 min (p < 0.05). Similarly, in females, the AUCinsulin was 17 +/- 2 nmol/l in 30 min in transgenic mice vs 25 +/- 3 nmol/l in 30 min in wild type mice (p < 0.05) and the respective AUCglucose was 1.62 +/- 0.7 and 1.12 +/- 0.07 mol/l in 120 min (p < 0.001). Hence, endogenous hIAPP inhibits insulin secretion and glucose elimination after gastric glucose gavage in both male and female mice, indicating that overexpression of hIAPP could be a diabetogenic factor, via effects on the intestinal tract or the gut-islet axis or both.

Prevalence, morphology and biology of renal cell carcinoma in von Hippel-Lindau disease compared to sporadic renal cell carcinoma

PURPOSE

Renal cell carcinoma occurs as a sporadic tumor but may be part of the autosomal dominant von Hippel-Lindau disease, characterized by retinal and central nervous system hemangioblastoma, pheochromocytoma, pancreatic cysts and renal cell carcinoma. We determine the prevalence of von Hippel-Lindau disease in a series of unselected renal cell carcinoma cases by molecular genetic analysis, and compare sporadic to von Hippel-Lindau renal cell carcinoma with respect to morphology and biology.

MATERIALS AND METHODS

We established registers comprising 63 subjects with von Hippel-Lindau renal cell carcinoma, belonging to 30 distinct families (register A), and 460 unselected patients operated on for renal cell carcinoma in an 11-year period (register B). Molecular genetic analysis of the von Hippel-Lindau gene was performed for living patients of register A, representing 80% of von Hippel-Lindau families, and register B, 62% living patients, to identify von Hippel-Lindau germline mutations. In addition, register B was evaluated by a questionnaire (95% response) for familial occurrence of von Hippel-Lindau disease.

RESULTS

The prevalence of von Hippel-Lindau renal cell carcinoma was 1.6% in 189 consenting unselected renal cell carcinoma patients. Risk factors for occult germline von Hippel-Lindau gene mutations in register B included familial renal cell carcinoma in 3 of 3 patients (100%), multifocal or bilateral renal cell carcinoma in 1 of 10 (10%) and age younger than 50 years at diagnosis in 1 of 33 (3%). Compared to sporadic von Hippel-Lindau renal cell carcinoma was characterized by an occurrence 25 years earlier, association with renal cysts, multifocal and bilateral tumors, cystic organization and low grade histology, and a better 10-year survival (p < 0.001 each). In von Hippel-Lindau disease metastases occurred only in tumors larger than 7 cm.

CONCLUSIONS

von Hippel-Lindau differs from sporadic renal cell carcinoma in morphology and biology. Our data provide arguments for planning surgery for von Hippel-Lindau renal cell carcinoma and should stimulate future investigations.

The eye in von Hippel-Lindau disease. Long-term follow-up of screening and treatment: recommendations

Von Hippel-Lindau disease (VHL) is an autosomal dominant tumour syndrome caused by germline mutations of the VHL tumour suppressor gene located on chromosome 3p25-26. In VHL tumours may occur in 14 different target organs, including the eye. Retinal angiomas are considered the first manifestation of VHL disease in 43% of cases, and the cumulative probability of developing a retinal angioma in one or both eyes rises during each decade of life, reaching 80% for patients over 80 years old. Since 1976 patients with VHL at the University Hospital of Utrecht and their at-risk relatives have been screened periodically by a multidisciplinary team. Long-term follow-up ophthalmological data were analysed with special attention to natural course and results of treatment. In addition, we looked for a genotype-phenotype correlation. Retinal angiomas were found in all families. In one large family with a missense mutation (V170D) of the VHL gene, in which the complete spectrum of visceral- and central nervous system (CNS) features of VHL is present, macular, parapapillary, optic disc and ora serrata angiomas were also found. In general, however, a clear-cut genotype-phenotype correlation could not be found. Only early detection and treatment of peripheral retinal angiomas can be expected to decrease the percentage of patients with decreased visual acuity. Therefore, early detection and treatment of these tumours is of paramount importance. Ophthalmological screening of patients and persons at risk should start as early as possible. In patients with apparently sporadic retinal angiomas it is advisable to perform germline DNA analysis, since the risk of developing VHL is high, especially if the angiomas are bilateral, or unilateral and multifocal, if the patient is young, or if there is a family history suggestive of VHL.

Clinical management of the multiple endocrine neoplasia syndromes: results of a computerized opinion poll at the Sixth International Workshop on Multiple Endocrine Neoplasia and von Hippel-Lindau disease

OBJECTIVES AND DESIGN

In order to provide all participants of the Sixth International Workshop on Multiple Endocrine Neoplasia and von Hippel-Lindau Disease with the opportunity to express their opinion on medical, ethical and social issues on clinical management of these hereditary cancer syndromes, a meeting employing an interactive voting system was organized.

RESULTS

In many aspects, the majority of the participants shared the same opinion. The following percentages of participants felt that, if a specific germline mutation is present in a definitely affected family member, DNA diagnosis should be performed in the offspring of this patient before the age of 10: 78% for MEN-1, 93% for MEN-2, and 71% for VHL. About 71% felt the clinical specialist should provide information about the consequences of DNA analysis and be responsible for disclosing the DNA test results and performing genetic counselling. If possible, selective surgery is preferred to maintain organ function. To make a complete diagnosis in a patient with an apparently sporadic tumour, 89% believed that mutation analysis of germline DNA is mandatory in order to investigate the possibility of inherited disease. In several areas, controversial opinions exist, depending on diversity in discipline, specific research area, experience in the field, and cultural and religious backgrounds. In particular, in vitro fertilization combined with pre-implantation genetic diagnosis is an area which attracts considerable emotion.

CONCLUSIONS

In order to avoid confusion in the families, explicit and common guidelines are needed for the identification, treatment and follow-up of individuals who have predisposing MEN or VHL mutations. Close collaboration between endocrinologists, oncologists, surgeons, pathologists, psychologists and geneticists is required in order to establish and verify such guidelines.

A putative human zinc-finger gene (ZFPL1) on 11q13, highly conserved in the mouse and expressed in exocrine pancreas. The European Consortium on MEN 1

In the process of identification of the multiple endocrine neoplasia type 1 gene, which was recently published, we isolated a novel gene in the 11q13 region. This gene (named ZFPL1, for zinc-finger protein-like 1) is expressed strongly in the exocrine pancreas as a 1.4-kb polyadenylated RNA encoding a putative protein of 310 amino acids. A mouse EST contig predicts an equally sized murine protein with 91% amino acid sequence identity to the human protein. No significant homology with known proteins could be found through database screening. However, zinc-finger-like domains and leucine-zipper-like motifs in the predicted ZFPL1 protein were identified, suggesting the presence of DNA-binding and dimerization domains possibly involved in transcription regulation. This notion is supported by the presence of a putative bipartite nuclear localization signal. This paper presents the full-length cDNA sequence for this gene, its genomic structure and chromosomal orientation, and expression studies by Northern blot hybridization and RNA in situ hybridization.

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

BACKGROUND

Von Hippel Lindau disease (VHL) is a rare autosomal dominant inherited disorder characterized by highly vascularized tumors in various organs. The abundant presence of endothelial cells in VHL tumors strongly suggest a role of the VHL tumor suppressor gene in the regulation of angiogenesis. Recently, in vitro studies have shown that the VHL tumor suppressor gene regulates the expression of vascular endothelial growth factor (VEGF). We investigated whether VHL patiens have increased levels of VEGF in their body fluids.

PATIENTS AND METHODS

The concentration of VEGF was measured in fluid of the anterior chamber of the eye, serum, urine, and fluid from renal cysts of VHL patients and unaffected individuals by ELISA. In addition, levels of basic fibroblast growth factor (bFGF), interleukin-8 (IL-8) and endothelin-1 (ET-1) were measured in urine and serum of VHL patients and control subjects.

RESULTS

In 80% of the VHL patients VEGF was detectable in aqueous fluid of the anterior chamber of their eyes. A strong positive correlation (r = 0.90) was found between the age of VHL patients and ocular VEGF concentrations. At comparable age, VEGF levels in ocular fluid of VHL patients were significantly higher (P < 0.001) than in unaffected subjects. No correlation was found between VEGF concentration and the presence of retinal angiomas. A 10 and 16 fold increase of VEGF concentration was seen in fluid from two independent VHL-related cysts as compared with VEGF serum levels of the same patient. The mean concentration of VEGF in serum of VHL patients (n = 15) (319 +/- 84 pg/ml) was higher than in matched controls (238 +/- 68 pg/ml; P = NS). The mean concentration of VEGF in urine of VHL patients (128 +/- 36 pg/ml) was lower than in matched controls (183 +/- 25 pg/ml; P = NS). Concentrations of VEGF did not correlate with the presence of VHL-related tumors. No differences were observed between concentrations of bFGF, IL-8 and ET-1 in serum and urine of VHL patients and matched controls.

CONCLUSIONS

These findings support a role for the VHL tumor suppressor gene in the in vivo regulation of VEGF.

Psychological risks of genetically testing children for a hereditary cancer syndrome

Parents in families with a hereditary cancer syndrome are often familiar with periodical clinical testing of both themselves and their children. Genetic testing is an additional early diagnostic option that is becoming available for an increasing number of hereditary cancer syndromes. Participants in genetic counseling programs for cancer syndromes are often parents who apply for their children. If a child is identified as a carrier of a specific disease-causing gene mutation, sometimes its parents must decide on when it will be treated can treatment be postponed until expression of the disease or should the child receive presymptomatic surgery? We discuss some of the possible risks of genetically testing children: distress as a result of ambivalent feelings towards testing, preoccupation with disease-related signs, changes in family interactions, the burdening prospect of a future disease and medicalization of the carrier-child.

Mapping of the gene encoding the B56 beta subunit of protein phosphatase 2A (PPP2R5B) to a 0.5-Mb region of chromosome 11q13 and its exclusion as a candidate gene for multiple endocrine neoplasia type 1 (MEN1)

The multiple endocrine neoplasia type 1 (MEN1) locus has been previously localised to 11q13 by combined tumour deletion mapping and recombination studies, and a 0.5-Mb region, flanked by PYGM and D11S449, has been defined. In the course of constructing a conting, we have identified the location of the gene encoding the B56 beta subunit of protein phosphatase 2A (PP2A), which is involved in cell signal transduction pathways and thus represents a candidate gene for MEN1. We have searched for mutations in the PP2A-B56 beta coding region, together with the 5' and 3' untranslated regions in six MEN1 patients. DNA sequence abnormalities were not identified and thus the PP2A-B56 beta gene is excluded as the candidate gene for MEN1. However, our precise localisation of PP2A-B56 beta to this region of 11q13 may help in elucidating the basis for other disease genes mapping to this generich region.

Construction of a 1.2-Mb sequence-ready contig of chromosome 11q13 encompassing the multiple endocrine neoplasia type 1 (MEN1) gene. The European Consortium on MEN1

Multiple endocrine neoplasia type 1 (MEN1) is an autosomal dominant familial cancer syndrome characterized by parathyroid, pancreatic, and anterior pituitary tumors. The MEN1 locus has been previously localized to chromosome 11q13, and a 2-Mb gene-rich region flanked by D11S1883 and D11S449 has been defined. We have pursued studies to facilitate identification of the MEN1 gene by narrowing this critical region to a 900-kb interval between the VRF and D11S1783 loci through melotic mapping. This was achieved by investigating 17 cosmids for microsatellite polymorphisms, which defined two novel polymorphisms at the VRF and A0138 loci, and utilizing these to characterize recombinants in MEN1 families. In addition, we have established a 1200-kb sequence-ready contig consisting of 26 cosmids, eight BACs, and eight PACs that encompass this region. The precise locations for 19 genes and three ESTs within this contig have been determined, and three gene clusters consisting of a centromeric group (VRF, FKBP2, PNG, and PLCB3), a middle group (PYGM, ZFM1, SCG1, SCG2 (which proved to be the MEN1 gene), and PPP2R5B), and a telomeric group (H4B, ANG3, ANG2, ANG1, FON, FAU, NOF, NON, and D11S2196E) were observed. These results represent a valuable transcriptional map of chromosome 11q13 that will help in the search for disease genes in this region.

Pancreatic cancer in rats and hamsters does not induce IAPP-related hyperglycaemia

Many patients with exocrine pancreatic cancer develop diabetes mellitus due to insulin resistance. This may relate to concurrent over-production of islet amyloid polypeptide (IAPP) by the pancreatic beta cells. We investigated the effects of pancreatic cancer on circulating IAPP and glucose homeostasis in azaserine-treated rats (developing acinar pancreatic tumours) and BOP-treated hamsters (developing ductular pancreatic tumours). Glucose, insulin and IAPP levels in plasma were neither affected in azaserine-only treated rats nor in animals with enhanced carcinogenesis after chronic caerulein treatment. Azaserine-treated rats on a high-fat diet had decreased insulin levels and enhanced IAPP/insulin ratios in plasma, without hyperglycaemia. All BOP-treated hamsters showed pancreatic carcinogenesis at 6 months post-treatment. Supranormal plasma glucose levels in animals on a low-fat diet were the only change observed. After a second 6-month period, subnormal plasma glucose levels, at least 4-fold decreased plasma insulin and up to 2-fold decreased plasma IAPP levels were present in all hamsters. Remarkably, both in azaserine-treated rats on high-fat and in BOP-treated hamsters, decreased insulin levels and elevated IAPP/insulin ratios are not associated with hyperglycaemia. In contrast to humans with pancreatic cancer, IAPP over-production and hyperglycaemia do not develop in rats and hamsters with (pre-)neoplastic pancreatic lesions.

Acute liver necrosis induced by iodine-131-MIBG in the treatment of metastatic carcinoid tumors

Iodine-131-metaiodobenzylguanidine (MIBG) is used in the treatment of carcinoid tumors. Temporary palliation with complete subjective symptomatic response has been reported in these patients. This treatment is usually well tolerated and side-effects are generally limited to nausea, mild hepatic toxicity with spontaneous recovery and temporary myelosuppression. Our case report shows that repeated treatment with [131I]MIBG in a patient with extensive carcinoid liver metastasis may cause severe hepatic toxicity leading to death. Factors such as concomitant use of 5-fluorouracil and the progressive nature of the disease may have contributed to this event.

Identification of the multiple endocrine neoplasia type 1 (MEN1) gene. The European Consortium on MEN1

Multiple endocrine neoplasia type 1 (MEN1) is an autosomal dominant disorder characterised by tumours of the parathyroids, pancreas and anterior pituitary that represents one of the familial cancer syndromes. The MEN1 locus has been previously localised to chromosome 11q13, and a <300 kb gene-rich region flanked centromerically by PYGM and telomerically by D11S1783 defined by combined meiotic and tumour deletion mapping studies. Two candidate genes, ZFM1 and PPP2R5B, from this region have been previously excluded, and in order to identify additional candidate genes we used a BAC to isolate cDNAs from a bovine parathyroid cDNA library by direct selection. One of the novel genes that we identified, SCG2, proved to be identical to the recently published MEN1 gene, which is likely to be a tumour suppressor gene. The SCG2 transcript was 2.9 kb in all tissues with an additional 4.2 kb transcript also being present in the pancreas and thymus. Mutational analysis of SCG2 in 10 unrelated MEN1 families identified one polymorphism and nine different heterozygous mutations (one missense, four non-sense, one insertional and three deletional frameshifts) that segregated with the disease, hence providing an independent confirmation for the identification of the MEN1 gene.

Germline and somatic mutations in the tyrosine kinase domain of the MET proto-oncogene in papillary renal carcinomas

Hereditary papillary renal carcinoma (HPRC) is a recently recognized form of inherited kidney cancer characterized by a predisposition to develop multiple, bilateral papillary renal tumours. The pattern of inheritance of HPRC is consistent with autosomal dominant transmission with reduced penetrance. HPRC is histologically and genetically distinct from two other causes of inherited renal carcinoma, von Hippel-Lindau disease (VHL) and the chromosome translocation (3;8). Malignant papillary renal carcinomas are characterized by trisomy of chromosomes 7, 16 and 17, and in men, by loss of the Y chromosome. Inherited and sporadic clear cell renal carcinomas are characterized by inactivation of both copies of the VHL gene by mutation, and/or by hypermethylation. We found that the HPRC gene was located at chromosome 7q31.1-34 in a 27-centimorgan (cM) interval between D7S496 and D7S1837. We identified missense mutations located in the tyrosine kinase domain of the MET gene in the germline of affected members of HPRC families and in a subset of sporadic papillary renal carcinomas. Three mutations in the MET gene are located in codons that are homologous to those in c-kit and RET, proto-oncogenes that are targets of naturally-occurring mutations. The results suggest that missense mutations located in the MET proto-oncogene lead to constitutive activation of the MET protein and papillary renal carcinomas.

Exclusion of the nuclear factor-kappa B3 (REL A) gene as candidate for the multiple endocrine neoplasia type 1 (MEN 1) gene

Multiple endocrine neoplasia type 1 (MEN 1) is inherited as an autosomal dominant disorder, characterized by neoplasia and hyperplasia in specific endocrine organs. The MEN 1 gene, which is most probably a tumor suppressor gene, has been localized to a region of approximately 900 kb on chromosome 11q13. The nuclear factor-kappa B (NF-kappa B) is a transcription factor with pleiotropic expression, which is involved in the regulation of expression of many cellular genes. The p50/p65 heterodimer is the most abundant form of NF-kappa B. The gene encoding the p65 subunit (NF-kappa B3/REL A) was recently localized in the 900-kb MEN 1 region and was considered a good candidate gene for MEN 1. The structure and nucleotide sequence of the NF-kappa B3 coding region in MEN 1 patients were compared with those of non-MEN 1 subjects, to determine the potential role of this gene in MEN 1 tumorigenesis. Southern blot analysis with constitutional DNA from probands of 14 independent MEN 1 families and DNA from four MEN 1 tumor specimens did not reveal any structural abnormality of the NF-kappa B3 gene. Direct sequencing of cDNAs from two affected subjects from 2 different MEN 1 families, as well as nucleotide sequence analysis of exon/intron boundaries in these patients, did not reveal MEN 1-specific point mutations or other small structural aberrations in the NF-kappa B3 gene. These results make it very unlikely that the NF-kappa B3 gene is the gene responsible for the development of MEN 1.

Exclusion of the phosphatidylinositol-specific phospholipase C beta 3 (PLC beta 3) gene as candidate for the multiple endocrine neoplasia type 1 (MEN 1) gene

Multiple endocrine neoplasia type 1 (MEN 1) is inherited as an autosomal dominant disorder, characterized by hyperplasia and neoplasia in several endocrine organs. The MEN 1 gene, which is most probably a tumor suppressor gene, has been localized to a 900-kb region on chromosome 11q13. The human phosphatidylinositol-specific phospholipase C beta 3 (PLC beta 3) gene, which is located within this region, was considered to be a good candidate for the MEN 1 gene. In this study, the structure and expression of the PLC beta 3 gene in MEN 1 patients were investigated in more detail, to determine its potential role in MEN 1 tumorigenesis. Southern blot analysis, using blood and tumor DNA from affected persons from seven different MEN 1 families, did not reveal structural abnormalities in the PLC beta 3 gene. To detect possible point mutations, or other small structural aberrations, direct sequencing of PLC beta 3 cDNAs from two affected persons from two different MEN 1 families was performed, but no MEN 1-specific abnormalities were revealed. Several common nucleotide sequence polymorphisms were detected in these cDNAs, proving that both alleles of the PLC beta 3 gene were expressed and analyzed. In conclusion, these results exclude the PLC beta 3 gene as a candidate gene for MEN 1.

Biologically active human islet amyloid polypeptide/amylin in transgenic mice

OBJECTIVE

Human islet amyloid polypeptide (hIAPP), also named amylin, is a pancreatic beta cell protein implicated in the pathogenesis of pancreatic islet amyloid formation and type 2 diabetes mellitus. To study the (patho)physiological roles of hIAPP, we have generated transgenic mice that overexpress hIAPP mRNA, in relation to endogenous mouse IAPP (mIAPP) mRNA, in pancreatic beta cells. The biological activity of human and mouse IAPP derived from pancreatic extracts was determined.

METHODS

Pancreatic and plasma extracts of transgenic and control mice were analyzed by reversed-phase high-performance liquid chromatography (HPLC) and radioimmunoassay, yielding a separation of hIAPP from mIAPP. Biological activity of immunoreactive human and mouse IAPP components derived from pancreatic extracts was assessed by calcitonin receptor-mediated stimulation of cyclic AMP accumulation in T47D human breast carcinoma cells.

RESULTS

The predominant immunoreactive human and mouse IAPP gene products had the retention times on HPLC analysis of the corresponding synthetic peptides. The ratio of bioactive over immunoreactive hIAPP and mIAPP was 0.93 +/- 0.18 and 1.19 +/- 0.56 respectively. In extracts of two plasma pools from 4 transgenic animals, hIAPP was 4.6- to 7-fold more abundant than mIAPP.

CONCLUSION

This study has shown that correctly processed hIAPP produced in transgenic mouse pancreatic beta cells exhibits full biological activity. The results validate these transgenic mice for the study of (patho)physiological roles of hIAPP in vivo.

Familial medullary thyroid carcinoma: not a distinct entity? Genotype-phenotype correlation in a large family

BACKGROUND

Multiple endocrine neoplasia type 2A (MEN 2A) is a hereditary syndrome characterized by medullary thyroid carcinoma (MTC), pheochromocytoma, and hyperparathyroidism. Familial MTC (FMTC) is characterized by MTC only. Both MEN 2A and FMTC are caused by germline mutations of the RET proto-oncogene.

PURPOSE

To assess genotype/phenotype correlations, large families have to be examined periodically over a long period using an extensive screening program.

PATIENTS AND METHODS

Since 1973, we screened a large family with hereditary C cell carcinoma for MTC, pheochromocytoma, and parathyroid disease by clinical tests and imaging methods. A germline codon Cys618 to Ser mutation in the RET proto-oncogene was recently identified in this family. The disease phenotype associated with this mutation was compared with that of Cys634 mutations in some other large MEN 2A families.

RESULTS

The distinct course of disease in the family described here is similar to that in other FMTC families and MEN 2A families with a Cys618 mutation of the RET gene, but clearly different from that in families with a Cys634 mutation. The frequency of pheochromocytomas and parathyroid disease is clearly lower, whereas cure rates and life expectancy are higher. However, in families with a Cys618 mutation, pheochromocytoma and parathyroid disease do occur.

CONCLUSION

In FMTC families with cysteine codon mutations of the RET proto-oncogene, screening for other endocrinopathies is mandatory, since these may not be MTC-only families. Therefore, we suggest that MEN 2A families should not be subclassified into MEN 2A and FMTC, but rather according to their specific mutation in the RET protein (i.e., for this family MEN 2A RET C618S).

The relationship between specific RET proto-oncogene mutations and disease phenotype in multiple endocrine neoplasia type 2. International RET mutation consortium analysis

OBJECTIVE

Multiple endocrine neoplasia type 2 (MEN 2) is an autosomal dominant disorder. The 3 recognized subtypes include MEN 2A, characterized by medullary thyroid carcinoma (MTC), pheochromocytoma (pheo), and hyperparathyroidism (HPT); MEN 2B, by MTC, pheo, and characteristic stigmata; and familial MTC (FMTC), by the presence of MTC only. The purpose of this study was to establish the relationship between specific mutations and the presence of certain disease features in MEN 2 which could help in clinical decision making.

DESIGN

Correlative survey study of 477 MEN 2 families.

SETTING

Eighteen tertiary referral centers worldwide.

PATIENTS

A total of 477 independent MEN 2 families.

MAIN OUTCOME MEASURES

Association between the position and type of germline mutation in the RET proto-oncogene and the presence or absence of MTC, pheo, HPT, and/or other features in a family.

RESULTS

There is a statistically significant association between the presence of any mutation at a specific position (codon 634) and the presence of pheo and HPT. The presence of a specific mutation, CGC at codon 634, has yet to be associated with FMTC. Conversely, mutations at codons 768 and 804 are thus far seen only with FMTC, while codon 918 mutation is MEN 2B--specific. Rare families with both MEN 2 and Hirschsprung disease were found to have MEN 2-specific codon mutations. Patients with Hirschsprung disease presenting with such mutations should be monitored for the possible development of MEN 2 tumors.

CONCLUSIONS

This consortium analysis suggests that genotype-phenotype correlations do exist and, if made reliably absolute, could prove useful in the future in clinical management with respect to screening, surveillance, and prophylaxis, as well as provide insight into the genetic effects of particular mutations.

Somatic mutations of the RET proto-oncogene are not required for tumor development in multiple endocrine neoplasia type 2 (MEN 2) gene carriers

Germ line mutations in one allele of the RET proto-oncogene predispose to the multiple endocrine neoplasia type 2 (MEN 2) syndromes. To investigate whether these inherited mutations alone can cause the development of tumors in vivo (oncogene model) or whether somatic mutations in the homologous RET allele are required for tumorigenesis (tumor suppressor gene model), we analyzed the entire coding region of both alleles of the RET gene in two MEN 2A and two MEN 2B tumors by reverse transcription-PCR and direct sequencing. No tumor-specific mutations could be detected in either allele of the RET gene in these tumors. Unlike the molecular mechanism in other hereditary tumor syndromes, somatic mutations in the homologous allele are apparently not required in MEN 2 tumorigenesis. Thus, RET genes with MEN 2-specific germ line mutations act as dominantly transforming oncogenes in vivo.