Germline and somatic mutations in an oncogene: RET mutations in inherited medullary thyroid carcinoma.

Inherited cancer syndromes predispose an individual to development of specific tumors. Somatic and germline mutations in the same tumor suppressor gene, as described in Knudson's two-mutation model, are well recognized. Inherited mutations in the RET proto-oncogene, which encodes a receptor tyrosine kinase, predispose individuals to the multiple endocrine neoplasia type 2 (MEN 2) cancer syndromes. The major component tumor of these syndromes is medullary thyroid carcinoma (MTC). To date, somatic mutations in RET have not been identified in tumors from individuals with MEN 2, although they have been well documented in sporadic MEN 2-related tumors. We have identified, among 16 MEN 2 cases with well-defined RET germline mutations, a somatic missense mutation at codon 918 of RET in 3 of 15 MTCs and in a sample with hyperplastic C-cells (presumed precursor to hereditary MTC). We suggest that the presence of a somatic mutation, in addition to the preexisting germline mutation in hereditary MTCs, may contribute to tumorigenesis in vivo.

Does iron affect osteoblast function? Studies in vitro and in patients with chronic liver disease.

In order to study the role of trace elements as potential osteoblastic toxins, we measured bone aluminum, copper, and iron in 106 ambulant patients with histologically proven liver disease. We used analytical and histochemical methods and we correlated our results with serum biochemistry, forearm and spinal bone density, and dynamic bone histomorphometry. Patients with chronic liver disease had higher iron-stained perimeters than control subjects (P less than 0.001). However, the mean iron-stained perimeter was no greater than 5% of the total mineralized bone perimeter and did not correlate significantly with either the osteoblast perimeters or bone formation rates. The mean concentration of bone iron were 2.5 times (P less than 0.01) greater in the patients than in the controls although 80% of the patients fell within the normal range. There was a weak negative correlation between bone iron and the osteoblast perimeters (R = 0.18, P = ns) and between bone iron and bone formation (R = -0.30, P less than 0.05). There were 57 patients (56% of the total) with diminished bone formation, but only 16 had elevated bone iron concentrations. In a regression analysis, age, hypogonadism, and serum albumin concentrations were the most important predictors of osteoblast perimeters and bone formation rates. In vitro experiments using rat osteoblast-like osteosarcoma cells showed that an iron concentration of 400 mumol/liter was required to diminish cellular proliferation and function. Iron concentrations are elevated in the bones of patients with chronic liver disease. However, there is at present insufficient evidence that this metal is responsible for the osteoblast dysfunction seen in these patients.(ABSTRACT TRUNCATED AT 250 WORDS)

Exercise-related changes in plasma levels of 15-keto-13,14-dihydro-prostaglandin F2alpha and noradrenaline in asthmatic and normal subjects.

In an attempt to elucidate the roles of prostaglandin F2alpha and noradrenaline in exercise-induced asthma, plasma levels of these substances were measured at rest, during and after exercise in normal and asthmatic subjects. Changes in airways resistance were assessed by measuring the peak expiratory flow rate. Plasma levels of 15-keto-13,14-dihydro-prostaglandin F2alpha (a relatively stable metabolite of prostaglandin F2alpha) and noradrenaline, at rest, and the changes that occurred during and after exercise, were similar in both the normal and asthmatic subjects. Exercise-induced broncho-constriction occurred in all asthmatic subjects following exercise while no significant change occurred in the peak expiratory flow rates of the normal subjects. At this time, in both groups of subjects, the levels of 15-keto-13,14-dihydro-prostaglandin F2alpha were lower than at rest. The level of noradrenaline observed following exercise were lower than during exercise in all but one subject. It would appear that neither noradrenaline nor prostaglandin F2alpha (or its metabolites) play a significant role in the aetiology of exercise-induced asthma.

Carboxyhemoglobin, cotinine, and thiocyanate assay compared for distinguishing smokers from non-smokers.

We compared cotinine, carboxyhemoglobin, and thiocyanate concentrations in blood sampled from 187 cigarette smokers and 181 non-smokers. All three differed significantly between smokers and non-smokers. Cotinine performed best as a test for assessing smoking status, with a sensitivity of 98% as compared with 94% for carboxyhemoglobin and 80% for thiocyanate, all at a specificity of 95%. These differences were statistically significant. Results by none of these three methods correlated well with number of cigarettes smoked per day.

A rapid screening method for the detection of mutations in the RET proto-oncogene in multiple endocrine neoplasia type 2A and familial medullary thyroid carcinoma families.

Multiple endocrine neoplasia type 2A (MEN2A) and familial medullary thyroid carcinoma (FMTC) are autosomal dominant inherited cancer syndromes with incomplete penetrance. Following the identification of mutations in the RET proto-oncogene that segregate with the disease phenotype in MEN2A, MEN2B, and FMTC, genetic screening of individuals with mutations in RET may be performed. We have employed restriction endonuclease digestion of polymerase chain reaction products as an alternative to sequence analysis for rapid identification of mutant gene carriers in families in which MEN2A and FMTC are segregating. Twenty-one Australasian MEN2A and FMTC families have been screened for mutations in a cysteine-rich region of the RET proto-oncogene. Seven independent mutations were identified in key individuals in 16 of these families. We have identified a mutation in codon 620, 2053 T-->C (Cys620Arg), and two mutations in codon 634 of exon 11 of RET, 2095 T-->C (Cys634Arg) and 2096 G-->A (Cys634Tyr), all three of which were present in both MEN2A and FMTC families.

Somatic mutations in the RET proto-oncogene in sporadic medullary thyroid carcinoma.

OBJECTIVE: We have determined the frequency of specific mutations in the RET proto-oncogene in sporadic medullary thyroid carcinomas (MTCs) and correlated the presence or absence of a codon 918 mutation with the clinical characteristics of these tumours. DESIGN: Thirty paraffin-embedded sporadic MTCs and two frozen MTCs were collected for analysis of specific mutations in the RET proto-oncogene in codons 609, 611, 618 and 620 (exon 10); 630 and 634 (exon 11); 768 (exon 13); 883 (exon 15) and 918 (exon 16). A novel primer was designed which introduced a restriction site for Rsal in the presence of the specific codon 918 mutation (ATG-->ACG) in these tumour samples. A 'clinical-genetic' correlation was performed comparing the presence of absence of the codon 918 mutation with the following clinical characteristics: age at diagnosis, tumour size, presence or absence of metastases, MTC related morbidity, and base line calcitonin levels at diagnosis or most recent follow-up. PATIENTS: Patients were classified as having sporadic MTC if there was no family history of C-cell hyperplasia, MTC, phaeochromocytoma or parathyroid disease. Retrospective review of patient records enabled complete clinical data to be obtained in 28 of 32 patients. MEASUREMENTS: Base line calcitonin levels were measured by radioimmunoassay or calcitonin enzyme linked immunoassay. Cysteine codons in exons 10 and 11, specifically codons 609, 611, 618, 620, 630 and 634, were screened for the presence of mutations by sequence analysis. Specific mutations occurring at codons 768, 883 and 918 were screened for by restriction endonuclease digestion of PCR products. RESULTS: The mutation at codon 918ATG-->ACG was found in 21 of 32 (66%) MTCs and the mutation at codon 883GCT-->TTT was found in one of 32 MTCs. Where possible, the presence of 'germline-type' mutations in codons 609, 611, 618, 620, 630 and 634 were excluded. Ten MTCs did not have a mutation in codons 768, 883 or 918 of the RET proto-oncogene. The presence or absence of the somatic mutation at codon 918 did not correlate with any of the above clinical characteristics. CONCLUSION: Somatic mutations in the RET protooncogene occur frequently in sporadic MTCs.