Lack of islet amyloid polypeptide/amylin-immunoreactivity in urine collected from healthy volunteers after ingestion of a carbohydrate-rich meal

Islet amyloid polypeptide (IAPP), or amylin, is synthesized by beta cells in the islets of Langerhans of the pancreas. Plasma IAPP levels are highly elevated in patients with advanced renal failure. To investigate the involvement of the kidney in the clearance of IAPP, the response of plasma and urinary IAPP to a carbohydrate-rich meal was investigated in 14 healthy volunteers. Although plasma IAPP levels increased severalfold after the meal, no IAPP-immunoreactivity was detected in the urine samples up to 4 hours after the meal. This might be due to the fact that urinary IAPP levels are under the detection limit of the assay or, assuming the presence of IAPP in the primary urine, immunoreactive IAPP molecules may be processed by renal mechanisms in such a way that they are no longer recognized by the antibodies used in the radioimmunoassay. Processed IAPP molecules may be reabsorbed in the proximal tubules of the kidney and/or excreted.

Counselling in multiple endocrine neoplasia syndromes: from individual experience to general guidelines

Counselling of patients and closely related family members has to take a central place in management of hereditary diseases, like multiple endocrine neoplasia (MEN) syndromes including von Hippel-Lindau (VHL) disease. In the strategy of health care, preventive medicine such as periodic clinical examination of families at-risk needs a high priority, because in general it is assumed that continuity in attendance is cost-effective. Counselling has to be based on individual medical experience of the doctor, adjusted to common guidelines and the findings in the family. Information leaflets, appropriate outpatient departments and an extensive network of specialists will facilitate continuity in care. Flow diagrams involving practical guidelines for diagnosis, treatment and follow up need to be applicable and after adjustment, should be accepted generally. Specially trained paramedics for counselling are required as a network that will guarantee periodic clinical examination and secure optimal prevention. Such paramedics will coordinate nationwide multidisciplinary guidance, and organize preventive and emergency cure for these patients. They will be supervised by expert clinicians in the field, and collaborate with specialists for social and psychological issues, patient organizations and clinical genetic centres. All of these professionals are responsible together for providing patients with up to date clinical information (via newsletters, Internet, etc.). Recently, in the Netherlands, a project was initiated to guarantee continuity in care and study the delivery of care. In order to realize this plan, funding has to be provided in the current research programme. In a future system support has to be obtained on a continuous base, preferably by the government and health care insurers and supervised by the national institute for health care.

Guidelines for diagnosis and therapy of MEN type 1 and type 2

This is a consensus statement from an international group, mostly of clinical endocrinologists. MEN1 and MEN2 are hereditary cancer syndromes. The commonest tumors secrete PTH or gastrin in MEN1, and calcitonin or catecholamines in MEN2. Management strategies improved after the discoveries of their genes. MEN1 has no clear syndromic variants. Tumor monitoring in MEN1 carriers includes biochemical tests yearly and imaging tests less often. Neck surgery includes subtotal or total parathyroidectomy, parathyroid cryopreservation, and thymectomy. Proton pump inhibitors or somatostatin analogs are the main management for oversecretion of entero-pancreatic hormones, except insulin. The roles for surgery of most entero-pancreatic tumors present several controversies: exclusion of most operations on gastrinomas and indications for surgery on other tumors. Each MEN1 family probably has an inactivating MEN1 germline mutation. Testing for a germline MEN1 mutation gives useful information, but rarely mandates an intervention. The most distinctive MEN2 variants are MEN2A, MEN2B, and familial medullary thyroid cancer (MTC). They vary in aggressiveness of MTC and spectrum of disturbed organs. Mortality in MEN2 is greater from MTC than from pheochromocytoma. Thyroidectomy, during childhood if possible, is the goal in all MEN2 carriers to prevent or cure MTC. Each MEN2 index case probably has an activating germline RET mutation. RET testing has replaced calcitonin testing to diagnose the MEN2 carrier state. The specific RET codon mutation correlates with the MEN2 syndromic variant, the age of onset of MTC, and the aggressiveness of MTC; consequently, that mutation should guide major management decisions, such as whether and when to perform thyroidectomy.

[Lump in the neck: 4 patients with a medullary thyroid carcinoma]

In a 25-year-old man, medullary thyroid carcinoma (probably a solitary sporadic form) was diagnosed following investigation of a small lump in the patient's neck. This was removed and followed up with further treatment. In a 27-year-old man, episodes of headache, palpitations and excessive perspiration (due to a pheochromocytoma) and a positive family history of thyroid problems led to further investigations and the subsequent diagnosis of multiple endocrine neoplasia (MEN) type 2A. The patient died at 48 years of age as the result of liver metastases. A total thyroidectomy had been carried out on a 19-year-old man with familial medullary thyroid carcinoma. The calcitonin levels remained elevated, but no tumour residues could be found. A 16-year-old girl with MEN type 2B had also previously undergone surgery. Her main complaint consisted of persistent constipation. Thyroid carcinomas usually present as a nodule in the neck. In 25% of cases, medullary thyroid carcinoma is part of the MEN2 syndrome. The clinical approach for medullary thyroid carcinoma is based on pathological findings following fine needle aspiration biopsy. The results of DNA tests determine the course of treatment and the need for family testing. In families with a hereditary form, there is a clear genotype-phenotype correlation. Early diagnosis and treatment can improve life expectancy.

[From gene to disease; from the RET gene to multiple endocrine neoplasia types 2A and 2B, sporadic and familial medullary thyroid carcinoma, Hirschsprung disease and papillary thyroid carcinoma]

The RET gene encodes a receptor tyrosine kinase involved in normal and neoplastic development of neural crest cell lineages. Activating RET mutations are present in patients with multiple endocrine neoplasia types 2A and 2B (MEN2A, 2B) and in familial medullary thyroid carcinoma (FMTC) patients, whereas inactivating RET mutations are found in patients with Hirschsprung (HSCR) disease. In particular for MEN2A and FMTC, the clinical management largely depends on the specific mutation found.

Clinical management of Von Hippel-Lindau (VHL) disease

Von Hippel-Lindau (VHL) disease is an autosomal, dominant inherited tumour syndrome with an estimated prevalence of 2-3 per 100,000 persons. A germline mutation in the VHL gene predisposes carriers to tumours in multiple organs. These tumours may include haemangioblastoma in the retina and central nervous system (CNS), renal cell carcinoma, phaeochromocytoma, islet cell tumours of the pancreas, and endolymphatic sac tumours, as well as cysts and cystadenoma in the kidney, pancreas, epididymis and broad ligament. Penetrance of VHL disease is high, most carriers of a VHL germline mutation develop one or more tumours by the age of 60 years. The most common symptoms include: loss of vision, raised intracranial pressure, neurological deficits, paroxysmal raised blood pressure and local pain. At present, metastases from renal cell carcinoma and neurological complications from cerebellar haemangioblastoma are the most common causes of death. However, it is anticipated that intensive radiological and clinical monitoring, and advanced operation techniques will reduce both morbidity and mortality in patients with VHL disease.

Molecular genetic aspects of Von Hippel-Lindau (VHL) disease and criteria for DNA analysis in subjects at risk

Von Hippel-Lindau (VHL) disease is an autosomal, dominantly inherited tumour syndrome. Carriers of a germline mutation in the VHL tumour suppressor gene tumours are predisposed to develop tumours that are multicentric or bilateral, and manifest at a younger age than in situations without a VHL germline mutation. The mutation spectrum is heterogeneous, with mutations scattered throughout most of the VHL gene. Although some recurrent mutations have been reported, most families have their own unique germline mutation. Tested individuals are no longer uncertain regarding their risk for developing the disease and family members who are non-carriers are relieved of the burden of repeated clinical monitoring.VHL germline mutations are identified in virtually all families and sporadic patients with classic VHL disease, but also in patients who do not meet clinical diagnostic criteria. The chance of finding a VHL germline mutation in (apparently) sporadic patients not fulfilling the criteria increases with: young age at diagnosis, the presence of multi-centric or bilateral tumours, involvement of multiple organs and a positive family history of VHL associated tumours.

Acute dyspnoea resulting from pulmonary oedema as the first sign of a phaeochromocytoma

The day after undergoing neck dissection, a 42-year-old woman developed acute dyspnoea due to pulmonary oedema. Measurements with a Swan-Ganz catheter revealed not only cardiac depression but also a greatly increased peripheral vascular resistance: 5,400 dyn x s x cm(-5)/m2. A phaeochromocytoma with acute cardiac failure leading to pulmonary oedema was considered. Treatment with alpha- and beta-blockers was complicated by severe hypotension and later ventricular fibrillation. Mechanical ventilation was required for 6 days following resuscitation. Investigation of the urine subsequently showed greatly increased catecholamine concentrations, while imaging revealed bilateral adrenal tumours. Our case history shows that acute pulmonary oedema may be the presenting manifestation of a phaeochromocytoma. The pulmonary oedema resulted partly from backward failure following tachycardia, myocyte necrosis and the greatly increased peripheral vascular resistance, and partly from increased permeability of the capillary network in the lungs.

Medullary thyroid carcinoma: role of genetic testing and calcitonin measurement

All patients with a thyroid nodule should have their plasma CT measured. Stimulated CT is generally better than basal, but in the lower ranges false negatives and false positives still occur. In families with hereditary MTC, RET gene mutation analysis has superseded measurement of plasma CT in the detection of asymptomatic disease gene carriers. All individuals with apparently sporadic MTC, but in whom there is some suspicion of familial disease, should also have RET genetic analysis. A negative DNA result practically excludes the possibility of hereditary MTC in families where an index case has been investigated and obviates the need for further biochemical evaluation. Disease gene carriers may be divided into three distinct risk groups depending on the specific RET gene mutation in the family. The age at which presymptomatic surgery has to be performed depends on the risk group to which the patient belongs. Compared with the results of DNA analysis, the results of CT stimulation tests have become less important in the assessment of timing of surgery. During follow-up of patients who underwent surgery, measurement of plasma basal CT is still useful. The high sensitivity of measuring stimulated CT levels does not outweigh the burden of life-long periodic stimulation tests and the limited clinical consequences of slightly elevated levels. Stimulation tests are inevitable for persons at risk who prefer not to have genetic testing.

Efficacy of high therapeutic doses of iodine-131 in patients with differentiated thyroid cancer and detectable serum thyroglobulin

Serum thyroglobulin (Tg) is usually the best marker of residual or metastatic disease after treatment of differentiated thyroid cancer. We evaluated the effect of so-called blind therapeutic doses of iodine-131 in patients with detectable Tg during suppressive levothyroxine treatment (Tg-on), and in patients with a negative diagnostic scintigram but detectable Tg during the hypothyroid phase (Tg-off). Twenty-two patients with differentiated thyroid carcinoma underwent total thyroidectomy and radioiodine ablation. During the follow-up, six patients with detectable Tg-on and 16 patients with detectable Tg-off were identified. All patients were treated with a blind therapeutic dose of 7,400 MBq iodine-131. Diagnostic scintigrams were compared with post-treatment scintigrams. Tg-off was measured in 16 cases, 1 year after the administration of the blind therapeutic dose, at the time of the follow-up diagnostic scintigram. Six patients were followed up by Tg-on only. Post-therapy scintigrams revealed previously undiagnosed local recurrence or distant metastases in 13/22 cases (59%); the remaining nine post-therapy scintigrams were negative. At the time of the blind therapeutic doses, Tg-off values ranged from 8 to 608 microg/l. After 1 year of follow-up, Tg-off decreased in 14/16 (88%) patients. In all patients who were followed by Tg-on only (n=6), a decrease in Tg values was measured. It is concluded that blind therapeutic doses resulted in a decrease in Tg levels in the majority of patients with suspected recurrence or metastases. The post-treatment scintigrams revealed pathological uptake in 59% of patients.

[Diverse expression of multiple endocrine neoplasia type 1]

MEN-1 is an autosomal dominantly inherited disorder, characterised by the occurrence of multiple tumours, particularly in the parathyroid glands, the pancreatic islets, the pituitary gland and the adrenal glands, as well as by neuroendocrine carcinoid tumours. Various clinical manifestations are presented by description of three patients harbouring a MEN1 gene germline mutation. A 44-year-old man had symptoms of hyperparathyroidism and in addition to parathyroid adenomas proved to have tumours in the thymus, adrenal and pituitary glands. A 48-year-old woman from a family with MEN-1 had suffered since her 40th year from headache and heartburn; she appeared to have adenomas in the parathyroid glands and gastrinomas in the pancreas, leading to a Zollinger-Ellison syndrome. One of her relatives, a man aged 29, had suffered from childhood from convulsions due to attacks of hypoglycaemia, and an insulinoma was assessed. In all patients, surgical and/or medical treatment alleviated symptoms. Clearly, the position or nature of the mutations in the MEN1 gene do not correlate with the clinical expression of the disease. Family investigation, DNA analysis and periodic examination improve quality of life and the life expectancy.

[Multiple endocrine neoplasia type 1: recent developments and guidelines for DNA diagnosis and periodic clinical monitoring]

Multiple endocrine neoplasia type 1 (MEN-1) is an autosomal dominantly inherited disorder, characterised by the occurrence of multiple tumours, particularly in the parathyroid glands, the pancreatic islets, the pituitary gland, the adrenal glands, as well as neuroendocrine carcinoid tumours. Since the identification of the responsible gene in 1997, the diagnosis MEN-1 can be assessed easily, and even presymptomatically, by DNA analysis. An early diagnosis is of importance because through periodic clinical monitoring of (putative) MEN1 gene germline mutation carriers, tumour development can be detected and treated at an early stage. Eligible for DNA analysis are MEN-1 patients and their family members, as well as patients with seemingly sporadic MEN-1 related tumours in whom on clinical grounds carriership of a MEN1 gene germline mutation is suspected. Eligible for periodic clinical monitoring are putative and confirmed carriers of a MEN1 germline mutation from the age of 5.

Growth hormone overproduction in a patient with multiple endocrine neoplasia type I

In a 69-year-old woman with a complicated history of multiple endocrine neoplasia type I (MEN 1), growth hormone overproduction was found without clinical features of acromegaly. Zollinger-Ellison syndrome was diagnosed at the age of 36 years. Total gastrectomy and partial pancreatectomy were performed. Two years later hypercalcaemia occurred, hyperparathyroidism was suspected and three hyperplastic parathyroid glands were removed. In 1994 the plasma gastrin level was elevated and a computerized tomography of the abdomen revealed a 1.5-cm large pancreatic tumour. Screening of the pituitary functions was unremarkable and a magnetic resonance scan of the pituitary gland showed no abnormalities. In 1995 type II diabetes mellitus was diagnosed. In 1997 basal plasma growth hormone levels were raised and plasma IGF-I levels were alternately high and normal. The patient had no clinical signs of acromegaly, but glucose tolerance testing resulted in a paradoxical rise in growth hormone concentration compatible with the diagnosis of growth hormone overproduction. Magnetic resonance imaging of the pituitary gland revealed a microadenoma.

Cryptic von Hippel-Lindau disease: germline mutations in patients with haemangioblastoma only

OBJECTIVES

Central nervous system haemangioblastoma (HAB) is a major feature of von Hippel-Lindau (VHL) disease, and it is estimated that about 30% of HAB patients have VHL disease. Consequently, it is widely recommended that sporadic HAB patients are screened for clinical and radiological features of VHL disease because of the risk of multiple tumours. We investigated the frequency of VHL germline mutations in patients with HAB only with no clinical or radiological evidence of VHL disease to define the role of molecular genetic analysis in the management of such patients.

METHODS

Eighty four patients with a single HAB (23 Dutch, 61 UK) and four with multiple HAB (two Dutch, two UK) were studied by direct sequencing of the coding region and quantitative Southern blotting.

RESULTS

A VHL germline mutation was found in three of 69 (4.3%) single HAB patients aged 50 years or less (three of 84 (3.6%) total single HAB patients). A germline VHL mutation was detected in a 44 year old woman with a solitary cerebellar HAB, as well as in four clinically unaffected close relatives, and in two single HAB cases presenting at the ages of 29 and 36 years. Germline VHL mutations were detected in two of four cases with multiple HAB.

CONCLUSIONS

Early detection of VHL disease is important to reduce morbidity and mortality and therefore we recommend that, in addition to conventional clinical and radiological investigations, VHL gene mutation analysis should be offered to all HAB patients younger than 50 years. HAB patients aged >50 years will have a lower a priori risk of VHL disease and further data are required to evaluate the role of routine molecular genetic investigations in late onset HAB cases. The failure to detect germline VHL mutations in some patients with multiple HAB may indicate the presence of somatic mosaicism or additional HAB susceptibility genes.

[Islet amyloid and diabetes mellitus type 2]

Type 2 diabetes mellitus is a heterogeneous and multifactorial disorder accompanied by severe complications and a reduced life expectancy. Histopathologically, it is characterized by deposition of protein in the islets of Langerhans in the pancreas ('islet amyloid'). The 37 amino acids 'islet amyloid polypeptide' (IAPP) was discovered in 1986 as the building block of islet amyloid. The identification of IAPP caused an intensification of research on islet amyloid. In the past few years, particularly transgenic mouse technology has shown that islet amyloidosis is a consequence as well as an (additional) cause in the pathogenesis of type 2 diabetes. Islet amyloid has turned out to be a pathogenic factor, which is accompanied by death of beta-cells and reduction of the insulin producing capacity. This knowledge offers opportunities for the development of novel (preventive) therapy and thus for a better life expectancy of persons which develop type 2 diabetes.

Parents' responses to disclosure of genetic test results of their children

The psychological reactions of 22 parental couples and 3 single parents were investigated after disclosure of genetic test results of their children. The children were tested for the early-onset, monogenetic cancer disorder multiple endocrine neoplasia type 2. Participants came from 13 different families and were aged between 28 and 47 years. Parents who were informed that their child was a gene carrier reacted with resignation, showed moderate to high levels of test-related and general anxiety, but few psychological complaints. Daily activities were disturbed in 43% of the parents with carrier-children. There was little disruption of the parents' future perspective, apart from some socioeconomic disadvantages and increased parental concern for the carrier-children. Most parents with carrier-children showed restraint with respect to short-term prophylactic treatment. Parents with favorable test results showed significantly less anxiety and no disturbance in their daily activities. They did not, however, seem to be reassured by the DNA test result. These parents questioned the reliability of the DNA test, wanted confirmation of the test results, and were eager to continue screening of their noncarrier children. Parents, especially those with a lower level of education and/or a pessimistic view of the future, were distressed by unfavorable test results. Additional counseling is advised to prevent parents of carrier-children worrying unnecessarily, or parents with children in whom the disease gene was not found being not reassured. Am. J. Med. Genet. 94:316-323, 2000.

Multiple endocrine neoplasia type 2B mutation in human RET oncogene induces medullary thyroid carcinoma in transgenic mice

Multiple endocrine neoplasia type 2B (MEN 2B) is a familial cancer syndrome, in which the cardinal feature is medullary thyroid carcinoma (MTC), a malignant tumor arising from the calcitonin producing thyroid C-cells. MEN 2B is associated with a germline point mutation in the RET proto-oncogene, leading to a Met-->Thr substitution at codon 918 in the kinase domain, which alters the substrate specificity of the protein. We used the human calcitonin gene (CALC-I) promoter to generate transgenic mice expressing either the human RET oncogene with the MEN2B-specific 918 Met-->Thr mutation (CALC-MEN2B-RET) or the human non-mutated RET proto-oncogene (CALC-WT-RET) in the C-cells. At 20 - 22 months of age three out of eight CALC-MEN2B-RET transgenic founders presented with macroscopic bilateral MTC. In two founders nodular C-cell hyperplasia (CCH) was observed. Thyroid abnormalities were never observed in CALC-WT-RET transgenic mice or control non-transgenic mice analysed at this age. In some mice from established CALC-MEN2B-RET transgenic lines nodular CCH was observed from 8 months on whereas MTC was detected in 13% of mice from one CALC-MEN2B-RET line, from the age of 11 months on. These results show for the first time that the MEN2B mutation in the RET oncogene predisposes mice for MTC.

Criteria for mutation analysis in MEN 1-suspected patients: MEN 1 case-finding

BACKGROUND

Multiple endocrine neoplasia type 1 (MEN 1) is an autosomal, dominantly inherited cancer syndrome, with tumours in various endocrine glands. In 1997 the responsible tumour suppressor gene was identified. MEN1 gene germ-line mutations are detected in the vast majority of MEN 1 patients, however, with regard to case-finding, unfortunately only at a very low frequency in patients with apparently sporadic MEN 1-related tumours. In order to increase the detection rate of disease gene carriers among patients with apparently sporadic MEN 1-related tumours, clinical criteria were needed.

DESIGN AND RESULTS

In this study MEN1 gene germ-line mutations were revealed in 16/16 MEN 1 patients/families (100%). Based on our clinical experience with MEN 1 patients/families we formulated clinical criteria to identify disease gene carriers among patients with apparently sporadic MEN 1-related tumours. The criteria for MEN 1-suspected patients are: young age at onset (< 35 years) and/or multiple MEN 1-related lesions in a single organ or two distinct organs affected. Application of these criteria yielded MEN1 gene germ-line mutations in nine of 15 MEN 1-suspected patients (60%), thus identifying novel MEN 1 families. Follow up was also guaranteed for patients not fulfilling these criteria.

CONCLUSIONS

The clinical criteria for MEN 1-suspected patients increase the detection rate of germ-line MEN1 gene mutations among patients with apparently sporadic MEN 1-related tumours. These criteria may be used for (presymptomatic) identification of MEN 1 disease gene-carriers, thus enabling early detection of tumour development and timely treatment, as well as genetic counselling.

Internally shortened menin protein as a consequence of alternative RNA splicing due to a germline deletion in the multiple endocrine neoplasia type 1 gene

Multiple endocrine neoplasia type 1 (MEN 1) is an autosomal dominantly inherited cancer syndrome (OMIM 131100), with tumours in several endocrine glands. In 1997 the responsible tumour suppressor gene was identified and recently it was shown that menin, its encoded protein, represses JunD-activated gene expression. Although many MEN 1 patients have been investigated both clinically and genetically, no genotype-phenotype correlation has been found yet. The vast majority of MEN1 gene mutations involve point mutations. We describe a patient in whom a 26 base pair deletion in the MEN1 gene, comprising part of exon 3 and part of intron 3, causes activation of a cryptic donor splice site at the beginning of exon 3. This germline mutation results in an in frame deletion of 105 nucleotides in MEN1 gene mRNA, i.e. an internal deletion of 35 amino acids in the menin protein. Since the deleted region of menin has been implicated in binding to JunD, this may explain the tumourigenic effect of this mutation. The knowledge of this MEN1 gene germline defect, may be used for presymptomatic identification of MEN 1 disease gene-carriers among family-members of this proband. This enables early detection of tumour development, timely treatment and genetic counseling.

A genotypic and histopathological study of a large Dutch kindred with hyperparathyroidism-jaw tumor syndrome

Familial primary hyperparathyroidism is the main feature of 2 familial endocrine neoplasia syndromes: multiple endocrine neoplasia type 1 (MEN 1) and hyperparathyroidism-jaw tumor syndrome (HPT-JT). The latter is a recently described syndrome that has been associated with ossifying fibroma of the jaw and various types of renal lesions, including benign cysts, Wilms' tumor, and hamartomas. To further illustrate the natural history of this syndrome, we describe a large, previously unreported Dutch kindred in which 13 affected members presented with either parathyroid adenoma or carcinoma; in 5 affected individuals, cystic kidney disease was found. Additionally, pancreatic adenocarcinoma, renal cortical adenoma, papillary renal cell carcinoma, testicular mixed germ cell tumor with major seminoma component, and Hürthle cell thyroid adenoma were also identified. Linkage analysis of the family using MEN1-linked microsatellite markers and mutation analysis excluded the involvement of the MEN1 gene. Using markers from the HPT-JT region in 1q2531, cosegregation with the disease was found, with a maximum logarithm of odds score of 2.41 obtained for 6 markers using the most conservative calculation. Meiotic telomeric recombination between D1S413 and D1S477 was identified in 3 affected individuals, and when combined with previous reports, delineated the HPT-JT region to 14 centimorgan. Combined comparative genomic hybridization and loss of heterozygosity data revealed complex genetic abnormalities in the tumors, suggesting different possible genetic mechanisms for the disease. In conclusion, we report a family with hyperparathyroidism linked to chromosome 1q, and exhibiting several types of renal and endocrine tumors that have not been previously described.

Distress in MEN 2 family members and partners prior to DNA test disclosure. Multiple endocrine neoplasia type 2

Multiple endocrine neoplasia type 2 (MEN 2) is an autosomal dominant early-onset cancer disorder. In the Netherlands presymptomatic genetic testing for MEN 2 is offered to testees from the age of five years. We report on adults requesting testing for themselves (n=90) and on parents who want an at-risk child to be tested (n=26). Sociodemographic, personality, and attitude characteristics, and levels of psychological distress, were determined for applicants and their partners in the predisclosure phase of testing. These participants showed only mildly increased levels of psychological distress, defined as heightened scores on measures of general and test-related anxiety, and of psychological complaints. Compared with a normal population, high levels of anxiety and health complaints were found in applicants who were younger than 25 years and single, and in persons who generally tended to react to distressful situations with anxiety or depression. These characteristics were particularly evident in young applicants (<25 years). Our study shows that people who feel ambivalent towards DNA testing and who are more vulnerable to psychological distress are more likely to agree to participate in the test as part of a collective application by members of a hereditary cancer family.

Pseudohypoparathyroidism type Ia. Albright hereditary osteodystrophy: a model for research on G protein-coupled receptors and genomic imprinting

Pseudohypoparathyroidism type Ia (PHP Ia) is a hereditary endocrine disorder, characterised by resistance to parathyroid hormone (PTH), causing disturbance of calcium homeostasis, and to several other polypeptide hormones. Patients with PHP Ia exhibit a complex of somatic abnormalities, termed Albright hereditary osteodystrophy (AHO). Treatment with vitamin D derivatives alleviates symptoms of hypocalcemia and may prevent bone demineralisation. PTH, like many polypeptide hormones, exerts its effects via a G protein-coupled cell surface receptor. PHP Ia is caused by a heterozygous, inactivating mutation in the gene for the alpha-subunit of the Gs protein, which disrupts Gs-protein-coupled signal transduction pathways. Several mutations have been described. When the mutation is inherited from the mother, the offspring will develop PHP Ia, i.e., both hormonal resistance and somatic abnormalities. When the mutation is derived from the father, children will have normal hormone responses while exhibiting the somatic features of AHO; this form of the disorder is called pseudopseudohypoparathyroidism (PPHP). A combination of tissue-specific genomic imprinting and haploinsufficiency may explain the occurrence of PPHP, and the fact that not all Gs-mediated polypeptide hormone actions are affected equally. PHP may therefore serve as a model in studying the pleiotropic consequences of impaired Gs-mediated signal transduction.

A patient with neurofibromatosis type 1 and watery diarrhoea syndrome due to a VIP-producing adrenal phaeochromocytoma

A patient with neurofibromatosis type 1 and watery diarrhoea syndrome due to a VIP-producing adrenal phaeochromocytoma (Case Report). J Intern Med 1999; 246: 231-234. A 43-year-old patient with neurofibromatosis type 1 suffered from watery diarrhoea syndrome induced by excessive production of vasoactive intestinal polypeptide (VIP) in an adrenal phaeochromocytoma. This case report emphasizes that patients with neurofibromatosis are prone to develop more than one disease induced by tumours originating from the neural crest. Since excessive VIP production in a phaeochromocytoma may mask the symptoms of catecholamine overproduction, and in view of the therapeutic consequences, neurofibromatosis patients with hyperVIP-aemia must be checked for the presence of a phaeochromocytoma.

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.