Ret oncogene signal transduction via a IRS-2/PI 3-kinase/PKB and a SHC/Grb-2 dependent pathway: possible implication for transforming activity in NIH3T3 cells.

Multiple endocrine neoplasia 2A (MEN 2A) is an inherited disease caused by mutations of the Ret proto-oncogene. Although many different Ret mutations have been described, little is known about the signaling pathways triggered by the Ret oncogene. In this study, we have determined the signaling properties of a Ret-9bp duplication encoding amino acids 634-636, which was recently identified in a patient with all clinical features of the MEN 2A syndrome. The Ret-9bp duplication leads to constitutive activation of the Ret tyrosine kinase. Furthermore, Ret-9bp increased mitogenic and transforming activity demonstrated by thymidine incorporation as well as colony formation in soft agar. Studying intracellular signaling pathways, which may be involved in malignant transformation of Ret-9bp expressing NIH3T3 cells, we could demonstrate Ret-9bp dependent phosphorylation of insulin receptor substrate-2 (IRS-2) with consecutive activation of phosphatidylinositol 3-kinase (PI 3-kinase) and protein kinase B (PKB/AKT). Moreover, Ret-9bp induces phosphorylation of SHC resulting in growth factor receptor binding protein-2 (Grb-2) binding and activation of the mitogen activating protein (MAP) kinase pathway. In addition to these postreceptor cytoplasmic signaling events, we have studied nuclear signal by Ret-9bp and found activation of c-jun and jun-D, two members of the jun/AP-1 family of transcription factors. In summary, an oncogenic 9bp duplication of Ret causes Ret dimer formation and ligand independent activation of the tyrosine kinase. Besides the signaling steps leading to MAPK activation, we could demonstrate that Ret-9bp induced constitutive activation of a signaling pathway involving IRS-2, PI 3-kinase and PKB/AKT which could transduce the oncogenic Ret signal to increased gene transcription via activation of the jun/AP-1 transcription factor family.

[The unmasking of secondary adrenal insufficiency and central diabetes insipidus by a highly febrile acute Hantaan virus infection]. / Demaskierung einer sekundären Nebennierenrindeninsuffizienz und eines Diabetes insipidus centralis durch eine hochfieberhafte akute Hantaan-Virus-Infektion.

CASE REPORT: A 32-year-old obese patient was admitted to our hospital as an emergency with very severe abdominal pain. Routine examinations initially failed to establish a diagnosis. The patient then went on to develop a high fever that was associated with polydipsia and polyuria. Serological studies revealed an acute infection with the Hantaan virus. Laboratory investigations showed hypofunction of the anterior and posterior lobes of the pituitary, with complete absence of ACTH, which was caused by two germinomas located intracranially. CONCLUSION: The clinical symptoms had thus been the result of acute secondary insufficiency of the adrenal cortex, which was unmasked by the acute, highly febrile Hantaan viral infection.

Upregulation of cholesterol synthesis after acute reduction of low density lipoprotein by apheresis in normocholesterolaemic subjects: evidence for a threshold effect.

The influence of low density lipoproteins (LDL) in the plasma on the regulation of cholesterol biosynthesis is not clear. We studied the changes in plasma mevalonic acid (MVA) concentration and the lathosterol/cholesterol (L/C) ratio, which are well established indices of whole body cholesterol synthesis, in four normocholesterolaemic subjects after each had undergone LDL apheresis on two occasions. LDL apheresis of 75% of the calculated plasma volume reduced LDL-cholesterol by 44% to 1.5 +/- 0.2 mmol/l without changing plasma MVA levels or L/C ratios. Apheresis of 125% of the calculated plasma volume decreased plasma LDL-cholesterol by 69% to 0.9 +/- 0.2 mmol/l, with significant increases in plasma MVA and L/C ratio on the day after the procedure. These results imply that LDL-cholesterol is an integral part of the sterol regulatory pool and suggest that plasma levels cannot be lowered below 1-1.4 mmol/l in normal subjects without upregulating cholesterol biosynthesis.

Detection of the apolipoprotein B-100 arg(3500) > gl mutation in familial defective apoB-100 by temperature-gradient gel electrophoresis.

Familial defective apolipoprotein B-100 (FDB) is caused by a point mutation in exon 26 of the apolipoprotein B gene leading to a decreased binding to the LDL-receptor. Patients with FDB have hypercholesterolemia and atherosclerotic disease. Since other mutations of apoB-100 could also cause binding abnormalities we established a temperature-gradient gel electrophoresis (TGGE) method and started to screen hypercholesterolemic patients for the presence of point mutations in this region. 4 of 43 patients were positive according to TGGE and subsequent sequencing showed the familiar guanine to adenine transition in codon 3500 in all cases.

Analysis of thyroid stimulating hormone-receptor mutations by temperature-gradient gel electrophoresis.

Somatic mutations in the genes for G-protein-coupled receptors which regulate intracellular levels of cyclic AMP have been found in several regions coding for the receptors of melanocyte-stimulating hormone, adrenaline, luteinizing hormone, rhodopsin and thyrotropin. The mutations found in the thyroid-stimulating hormone (TSH) receptor are restricted to cells of hyperfunctioning thyroid adenomas and other thyroid tumors. They are thought to lead to a constitutive activation of the receptor independent of TSH. We have developed a temperature-gradient gel electrophoresis (TGGE) assay starting with the amplification of a part of exon 10 of the TSH-receptor gene to screen tissue of thyroid tumours. TGGE allows the detection of point mutations even if there are only a few cells with somatic mutations in tissue sections.

Spontaneous transient remission of disseminated histiocytosis X during pregnancy.

Disseminated histiocytosis X with cutaneous and lymph node involvement was diagnosed in a 25-year-old women. The diagnosis was established on the basis of a positive cell-surface staining with OKT 6 and typical signs on electron microscopy. Both the specific skin rash and lymph node swelling completely disappeared during pregnancy, but recurred 2 weeks before delivery. Therapeutic trials with 0.25 mg ethinylestradiol/day and a later application of human chorionic gonadotropin up to 5000 IU i.m. twice weekly as well as prednisolone 25 mg three times per day were unsuccessful. A second pregnancy was not desired. Polychemotherapy with initial high-dose prednisolone plus vincristine and a consolidation therapy with 5-mercaptopurine 300 mg/day led to full recovery. The observation of transient remission of histiocytosis X during pregnancy suggests that at least some forms of this disease may have prevailing immunological features where an immunosuppressive effect of pregnancy could be beneficial.

Ectopic ACTH secretion due to a bronchopulmonary carcinoid localized by somatostatin receptor scintigraphy.

We present the case of a 65-year-old woman with an adrenocorticotropic hormone (ACTH) secreting bronchopulmonary carcinoid. This patient showed the typical long history of Cushing's syndrome, including hypokaliemia, impaired glucose tolerance, high levels of ACTH and beta-endorphin, and coproduction of other peptides. At the onset of clinical symptoms in 1979 an adrenal adenoma was suspected, and left-sided adrenalectomy was performed. The symptoms soon recurred, and the diagnosis of ACTH-dependent Cushing's syndrome was made. As no ACTH-secreting tumor was found, the right adrenal was resected, and the patient was followed up regularly. Fourteen years later chest roentgenography and computed tomography revealed a para-aortic pulmonary lesion, which was suspicious for a bronchopulmonary carcinoid. ACTH and beta-endorphin were excessively, pancreatic polypeptide slightly elevated at that time. The final diagnosis was made using somatostatin receptor scintigraphy which confirmed the hormonal activity of the suspicious lesion; no additional focus was found. This method turned out to be not only a useful additional localization technique but also a promising tool for characterization and staging of a suspected ACTH-producing carcinoid. The tumor was resected curatively, and the diagnosis was confirmed histologically.

[Diagnosis, therapy and screening of multiple endocrine neoplasia type I (MEN I) in four endocrinologic centers]. / Diagnostik, Therapie und Screening bei multipler endokriner Neoplasie Typ I (MEN I) in vier endokrinologischen Zentren.

BACKGROUND: Multiple endocrine neoplasia type I (MEN I) is a hereditary disease characterised by involvement of several endocrine organs (parathyroid, anterior pituitary, pancreatic islet cells and other). In order to build up a German MEN I-register a questionnaire was developed. PATIENTS: In four centres we diagnosed 29 cases of MEN I (average age 53 years, range 27 to 72 years, 21 women, eight men). RESULTS: In 25 patients (86%) we found a primary hyperparathyroidism, in 15 patients (52%) an adenoma of the anterior pituitary (seven patients with growth hormone-secreting adenomas, five patients with prolactinomas, two patients with hormone-inactive and one patient with an ACTH-secreting adenoma), in ten patients (34%) a neoplasm of the pancreatic islet cells (six patients with gastrinomas, four patients with insulinomas and two patients with multihormone tumors) and in ten patients (34%) other endocrine tumors (five carcinoid tumors, three adenomas of the adrenal cortex, one papillary thyroid carcinoma and one thymic tumor). In nine cases nephrolithiasis was the leading symptom of primary hyperparathyroidism. All female patients with prolactinomas developed secondary amenorrhea. In three cases gastrinomas caused duodenal ulcers and three insulinomas were detected by fasting hypoglycemia. A primary hyperparathyroidism was most frequently combined with an adenoma of the anterior pituitary (21%). Detailed screening of 13 families early revealed MEN I in eleven cases. CONCLUSIONS: The manifestation of an endocrine disease in MEN I should initiate further diagnostics. Having established the diagnosis of MEN I, a meticulous work-up of all family members is warranted. The set-up of a register by the successfully tested questionnaire will support these activities and facilitate further research of new genetic markers, follow-up and treatment.

The natural course of multiple endocrine neoplasia type IIb. A study of 18 cases.

BACKGROUND: Multiple endocrine neoplasia (MEN) type IIb is an autosomal dominantly inherited disorder associated with medullary thyroid cancer, pheochromocytoma, and a characteristic phenotype. The present study was performed to investigate the natural course of the syndrome and to describe its expression. METHODS: The medical records of 18 patients with MEN IIb, seven male and 11 female, were reviewed. RESULTS: The mean age at diagnosis of MEN IIb was 18 years (range, 8 to 41 years). All 18 patients had medullary thyroid cancer. In three patients, medullary thyroid cancer was diagnosed via screening. In two of these patients, the calcitonin value normalized after thyroidectomy. One patient died of metastases from medullary thyroid cancer at the age of 20 years (median duration of follow-up, 10 years). Eight of the 18 patients had pheochromocytomas. All of our patients had neuromas and bumpy lips, and all but one had a marfanoid habitus. A large proportion of the patients had intestinal abnormalities (75%), thickened corneal nerves (69%), skeletal abnormalities (87%), and delayed puberty (43%). CONCLUSIONS: The course of medullary thyroid cancer in MEN IIb is not always as aggressive as is generally thought. Periodic examination of relatives who are at risk may lead to early diagnosis and curative treatment. Intestinal abnormalities, skeletal abnormalities, and delayed puberty are commonly found in association with MEN IIb.

The importance of multiple endocrine neoplasia syndromes in differential diagnosis.

In the differential diagnosis of endocrine symptoms, the autosomal dominant multiple endocrine neoplasia (MEN) syndromes are rare but important. We found seven index cases of MEN-I in 176 patients with adenomas of the anterior pituitary and 26 patients with primary hyperparathyroidism. Of 23 cases of medullary thyroid carcinoma and eight cases of pheochromocytoma, 14 patients are classified as MEN-IIa and one as MEN-IIb. Family screening identified six MEN-I and seven MEN-II cases among 32 individuals examined. Because of autosomal dominant inheritance and sometimes-delayed manifestation of the complete syndrome, screening of healthy and affected family members should be repeated at least every other year.