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R F Gagel

Publications and source records attributed to R F Gagel.

At least 73 records · Page 4Linked to original sources
PubMed1995

Putting the bits and pieces of the RET proto-oncogene puzzle together.

The RET proto-oncogene has been implicated in the causation of papillary thyroid carcinoma, multiple endocrine neoplasia types 2A (MEN 2A) and 2B (MEN 2B), and Hirschsprung's disease. The mutations in these syndromes can be categorized into activating or inactivating mutations. Activating mutations of a cysteine-rich extracellular region cause enhanced dimerization of the RET tyrosine kinase receptor and autophosphorylation, and are causative for MEN 2A and familial medullary thyroid carcinoma (FMTC). An activating mutation of the tyrosine kinase domain causes increased autophosphorylation but does not affect the state of dimerization. A variety of inactivating mutations of the RET proto-oncogene, which result in defective protein formation, are causative for Hirschsprung's disease.

Amino Acid Sequence↗
PubMed1995

Surgical management, DNA content, and patient survival in adrenal cortical carcinoma.

BACKGROUND: Surgical resection is the only potentially curative treatment for adrenal cortical carcinoma, yet the value of extended resection, palliative resection, and tumor DNA analysis remains unclear. METHODS: The records of 23 patients with adrenal cortical carcinoma who underwent primary surgical resection at our institution were retrospectively reviewed. Flow cytometric DNA analysis was performed on primary tumor tissue from 14 patients. RESULTS: Sixteen of 23 patients underwent complete resection. For these 16 patients the median follow-up was 43 months, the actuarial median survival was 46 months, and the actuarial 5-year survival rate was 46%. The seven patients who underwent incomplete resection all died of disease with a median survival of 8.5 months. Isolated local recurrence as the first site of failure occurred in two patients. Only completeness of resection (p = 0.004) and stage at presentation (p = 0.006) were significant prognostic indicators. None of the following predicted a poor prognosis in patients who underwent complete resection: (1) need for extended resection, (2) presence of renal vein or inferior vena cava tumor thrombus, or (3) tumor aneuploidy (14 of 14 tumors were aneuploid). CONCLUSIONS: Long-term survival is possible in patients with adrenal cortical carcinoma if complete, margin-negative tumor resection can be achieved. Isolated local recurrence is uncommon after complete resection. Because adrenal cortical carcinomas are consistently aneuploid, tumor DNA content is not a useful prognostic factor.

Adenoma↗
PubMed1995

RET proto-oncogene mutations in multiple endocrine neoplasia type 2 and medullary thyroid carcinoma.

The identification of RET proto-oncogene mutations in patients with MEN2 2 years ago was a watershed event in the management of this genetic cancer syndrome. The identification of a finite number of mutations that together causes more than 95% of hereditary and 15-25% of sporadic MTC has made it possible to develop simple and definitive tests to screen individuals at risk for this tumour syndrome. The impact of this technology is enormous. It is now possible to reassure 50% of family members at risk that they, and their children, do not have to worry about developing MTC. In the other 50% who are gene carriers, it is now possible to approach clinical management with greater certainty and plot strategies that are likely to result in a greater percentage of curative therapy. It seems likely that this technology will also have an impact on the management of sporadic MTC, although it is still too early to define a specific role for mutational analysis in these patients, except to exclude hereditary disease. The identification of specific mutations causative for MTC makes it possible to conceive future strategies for the treatment or prevention of MTC and to further extend the impact of these exciting findings.

Carcinoma, Medullary↗
PubMed1995

Clinical use of molecular information in the management of multiple endocrine neoplasia type 2A.

One hundred and ninety-seven members of 28 kindreds with multiple endocrine neoplasia type 2A (MEN 2A) were screened for RET proto-oncogene exon 10 and 11 mutations. Seventy-one known affected individuals had mutations of codons 609, 618, 620 or 634, whereas 53 unaffected individuals had no abnormalities. Nineteen out of 54 individuals of unknown status, mostly children, had RET mutations. Four of these children had thyroidectomy based on this analysis and were found to have C-cell abnormalities. We identified one false negative mutation analysis because of a codon 691 polymorphism. We conclude that RET mutational analysis is a cost-effective and accurate method for determination of gene carrier status in MEN 2A.

Amino Acid Sequence↗
PubMed1995

Genotype-phenotype correlation in multiple endocrine neoplasia type 2: report of the International RET Mutation Consortium.

The International RET Mutation Consortium was first convened as part of the Fifth International Workshop on Multiple Endocrine Neoplasia, Stockholm, Sweden, in an attempt to analyse the relationship of RET mutation and disease phenotype in the autosomal dominantly inherited multiple endocrine neoplasia type 2 (MEN 2) syndromes. Out of 361 families studied, 41% had MEN 2A, 17.7% MEN 2B, 6.4% FMTC and the remaining subjects were unclassified. RET mutations were detected in 87.3% of families overall. Over 93% of MEN 2B families had the RET 918 ATG-->ACG mutation, while the most frequent mutation detected in MEN 2A families was cysteine codon 634 (87% of all mutations).

Carcinoma, Medullary↗
PubMed1995

An intron enhancer containing a 5' splice site sequence in the human calcitonin/calcitonin gene-related peptide gene.

Regulation of calcitonin (CT)/calcitonin gene-related peptide (CGRP) RNA processing involves the use of alternative 3' terminal exons. In most tissues and cell lines, the CT terminal exon is recognized. In an attempt to define regulatory sequences involved in the utilization of the CT-specific terminal exon, we performed deletion and mutation analyses of a mini-gene construct that contains the CT terminal exon and mimics the CT processing choice in vivo. These studies identified a 127-nucleotide intron enhancer located approximately 150 nucleotides downstream of the CT exon poly(A) cleavage site that is required for recognition of the exon. The enhancer contains an essential and conserved 5' splice site sequence. Mutation of the splice site resulted in diminished utilization of the CT-specific terminal exon and increased skipping of the CT exon in both the mini-gene and in the natural CT/CGRP gene. Other components of the intron enhancer modified utilization of the CT-specific terminal exon and were necessary to prevent utilization of the 5' splice site within the intron enhancer as an actual splice site directing cryptic splicing. Conservation of the intron enhancer in three mammalian species suggests an important role for this intron element in the regulation of CT/CGRP processing and an expanded role for intronic 5' splice site sequences in the regulation of RNA processing.

Alternative Splicing↗
PubMed1995

Calcitonin-secreting cells of the thyroid express an extracellular calcium receptor gene.

Calcitonin (CT) secretion by parafollicular cells of the thyroid (C cells) is regulated by small changes in the concentration of extracellular calcium ([Ca2+]e). Elevation of [Ca2+]e elicits a rise in the C cell cytoplasmic calcium concentration and stimulates CT release. The molecular entity through which C cells detect changes in [Ca2+]e and modulate hormone secretion is unknown. Recently, an extracellular calcium-sensing receptor (CaR) complementary DNA was isolated from bovine parathyroid gland. To assess whether parathyroid cells and C cells use similar mechanisms to detect changes in ambient Ca2+, rat, human, and sheep C cells were examined for expression of the parathyroid CaR or a related receptor isoform. Reverse transcription-polymerase chain reaction analysis identified CaR transcripts in rat and human thyroid gland. Northern blot analysis demonstrated CaR messenger RNA (mRNA) in rat thyroid gland, a human medullary thyroid carcinoma (MTC) isolate, and a highly enriched preparation of sheep C cells. Rat MTC 44-2 cells, a cell line responsive to changes in [Ca2+]e, express abundant levels of CaR mRNA. Human TT cells, a C cell line lacking the extracellular calcium-sensing function, have undetectable levels of CaR mRNA by Northern blot analysis. Western blot analysis, using antiserum specific to the parathyroid CaR, detected CaR protein in rMTC 44-2, but not TT cells. Immunostaining of both dispersed sheep C cells and rat thyroid gland sections identified C cell-specific expression of the CaR protein, and in situ hybridization analysis confirmed the C cell-specific expression of CaR mRNA in the intact rat thyroid. The nucleotide sequence of the coding region of the rMTC 44-2 CaR transcripts was found to encode the same CaR protein as that expressed in the parathyroid and kidney. The results demonstrate that C cells express the same extracellular calcium-sensing receptor that is found in parathyroid and kidney, and the presence of this receptor protein in C cell lines correlates with the extracellular calcium-sensing function. This CaR is likely to represent the primary molecular entity through which C cells detect changes in [Ca2+]e and control CT release, suggesting that activation of the same receptor can either stimulate or inhibit hormone secretion in different cell types.

Amino Acid Sequence↗
PubMed1995

Safety and efficacy of long-term octreotide therapy of acromegaly: results of a multicenter trial in 103 patients--a clinical research center study.

One hundred and three acromegalic patients from 14 medical centers were enrolled in this study to determine the efficacy and safety of the somatostatin analog, octreotide acetate, during long term treatment. Seventy percent of the patients had undergone previous surgery or radiation treatment. Octreotide was initiated at a dose of 100 micrograms, sc, every 8 h and gradually increased to a maximum of 1500 micrograms daily depending upon the individual patient's clinical and biochemical response [GH and insulin-like growth factor I (IGF-I) reduction]. The mean duration of treatment was 24 months (range, 3-30 months). However, most patients were treated for a mean of 30 months, because this study took place after an initial 6-month study previously reported. Mean serum GH fell from 30.9 micrograms/L (range, 2.7-350) to 5.7 micrograms/L (range, 0.6-59) at the 3 months visit and remained suppressed (P < 0.001). Plasma IGF-I concentrations were also significantly reduced and remained in the normal range for at least half of the treatment visits in 56 of 87 patients (64%) treated for 12-30 months. Patients with higher initial GH concentrations were less likely to normalize IGF-I concentrations during treatment (P < 0.001). There was no evidence of drug tachyphylaxis in those patients who continued taking stable doses of medication. With some exceptions, dose increments above 800 micrograms daily in 31 patients did not provide additional benefit in terms of GH and IGF-I reduction. Headache, excessive perspiration, fatigue, and joint pain were ameliorated in 83-95% of patients. Mean finger circumference was decreased significantly at the 12 month visit (P < 0.05). The most common adverse events reported were diarrhea, abdominal discomfort, loose stools, and nausea; these symptoms usually disappeared within 3 months of treatment. Five patients discontinued octreotide because of adverse events. Of 102 patients with normal baseline ultrasound examinations of the gallbladder, 24 patients (23.5%) developed gallstones (usually during the first year of treatment), and 21 patients developed sludge alone. Gallstone formation was not related to the dose of octreotide. Most patients with cholelithiasis were asymptomatic, and none developed cholecystitis. These observations suggest that octreotide is a valuable long term medical treatment for acromegaly.

Acromegaly↗
PubMed1995

Cell type-specific regulation of transcription by cyclic adenosine 3,'5'-monophosphate-responsive elements within the calcitonin promoter.

A cAMP-induced enhancer was previously mapped to nucleotides -255 to -85 of the calcitonin (CT) gene 5'-flanking DNA. To determine the functional cis-acting elements within this region, we transfected medullary thyroid carcinoma (MTC) cells with CT 5'-flanking DNA/GH fusion genes containing potential cAMP-responsive elements and assessed their transcriptional activities with and without cAMP. In CT-expressing MTC cells (the TT line), we identified by deletions and point mutations three transcriptionally active motifs: a cAMP-responsive element (CRE), TGACGTCA, at -253 to -246, and a hybrid site containing a CRE-like element (CREL; TGACCTCA, -169 to -162) adjacent to an equally transcriptionally active octamer (O) sequence (ATG-CAAAT, -161 to -154). These three motifs acted synergistically and their transcriptional activity was completely dependent on cAMP. In HeLa cells their synergistic activity was more constitutive than cAMP induced, whereas in CT-negative MTC cells (the RO-D81-1 line) these motifs were inactive. Gel mobility shift assays with antibodies against CRE-binding protein (CREB) and activating transcription factor 1 (ATF-1) showed that both CREB and ATF-1 interacted with the CRE in MTC cells, whereas in HeLa cells only ATF-1 bound to the CRE. Specific binding to the CREL/O motif was detectable in extracts from tumors induced by injection of TT cells but not in extracts from any of the three cultured cell lines. We conclude that cAMP-induced transcription of the CT gene is modulated in a cell-specific manner by the CRE and the CREL/O elements.

Base Sequence↗
PubMed1994

Calcitriol production in hypercalcemic and normocalcemic patients with non-Hodgkin lymphoma.

OBJECTIVE: To determine the following: a reference range for serum calcitriol during hypercalcemia in a control group of patients with myeloma in whom calcitriol production is known to be appropriately suppressed; the incidence of elevated serum calcitriol levels in hypercalcemic patients with non-Hodgkin lymphoma according to this derived reference range; and the incidence of abnormal calcium metabolism in normocalcemic patients with non-Hodgkin lymphoma. DESIGN: Prospective clinical study. SETTING: Referral cancer center. PATIENTS: 2 groups of hypercalcemic patients: 16 control patients with myeloma and 22 patients with non-Hodgkin lymphoma divided into those with elevated or normal serum calcitriol levels; 1 group of 22 normocalcemic patients with non-Hodgkin lymphoma. MEASUREMENTS: Serum chemistries and intact parathyroid hormone, calcitriol, parathyroid hormone-related protein, and urinary electrolyte levels. RESULTS: On the basis of the mean serum calcitriol level of the control group plus 3 standard deviations, the reference range for serum calcitriol during hypercalcemia was defined as less than 42 pg/mL. Although serum calcium and parathyroid hormone levels in the study patients were similar to those in controls, 12 of the 22 hypercalcemic patients with non-Hodgkin lymphoma (55%) had serum calcitriol levels greater than 42 pg/mL (range, 51 to 170 pg/mL). No features distinguished the patients with elevated serum calcitriol levels from those with normal levels. Seventy-one percent of normocalcemic patients with non-Hodgkin lymphoma were hypercalciuric, and 18% had serum calcitriol levels greater than the normocalcemic reference range (20 to 76 pg/mL). CONCLUSIONS: Serum calcitriol levels are elevated in most hypercalcemic patients with non-Hodgkin lymphoma in the absence of elevated serum levels of parathyroid hormone, which implicates extrarenal calcitriol production in the pathogenesis of this syndrome. Abnormal calcium metabolism, hypercalciuria, and dysregulated calcitriol production are also common in normocalcemic patients with non-Hodgkin lymphoma.

Adult↗
PubMed1994

The calcitonin exon and its flanking intronic sequences are sufficient for the regulation of human calcitonin/calcitonin gene-related peptide alternative RNA splicing.

The primary transcript of the calcitonin (CT)/calcitonin gene-related peptide (CGRP) is alternatively spliced in a cell-specific fashion to produce CT in thyroid C cells and CGRP in neuronal cells. The key step in this regulatory process is the recognition and inclusion of exon 4 to produce CT mRNA or nonrecognition and exclusion of exon 4 to produce CGRP mRNA. To determine whether inclusion/exclusion of CT exon is regulated independently of its position, we created a series of minigene constructs containing decreasing amounts of CT gene sequence. A human glioblastoma cell line, T98G, was tested and used as a CT exon exclusion cell line, while HeLa cells were used as a CT exon inclusion cell line. CT exon inclusion/exclusion was regulated when either the relative position of exon 4 within the CT gene was changed or when the exon with flanking sequence was inserted into a completely heterologous gene. Our results demonstrate that CT exon functions as a unit in a position-independent fashion in regulating its own inclusion/exclusion. We believe that the heterologous fusion gene containing only exon 4 and part of its flanking intron sequences will be useful for further defining the sequence elements involved in the regulation of CT/CGRP splicing.

Alternative Splicing↗
PubMed1993

Single-dose intravenous therapy with pamidronate for the treatment of hypercalcemia of malignancy: comparison of 30-, 60-, and 90-mg dosages.

PURPOSE: To determine the efficacy, dose-response relationship, and safety of 30, 60, and 90 mg of a single intravenous dose of an aminobisphosphonate, pamidronate (APD), for the treatment of moderate to severe hypercalcemia of malignancy. PATIENTS AND METHODS: Patients with histologically proven cancer and a corrected serum calcium level of at least 12.0 mg/dL after 48 hours of normal saline hydration were enrolled in a double-blind, multicenter, randomized clinical trial. Pamidronate in 30-, 60-, or 90-mg doses was administered as a single 24-hour infusion. Serum calcium corrected for albumin, urine hydroxyproline, and calcium excretion, and serum parathyroid hormone (PTH) (1-84) were determined before and after pamidronate therapy. RESULTS: Thirty-two men and 18 women entered the study. A dose-response relationship for normalization of corrected serum calcium was seen after pamidronate administration. Corrected serum calcium normalized in 40% of patients who received 30 mg, in 61% of patients who received 60 mg, and in 100% of patients who received 90 mg of pamidronate. The decline in the serum calcium level was associated with decreased osteoclastic skeletal resorption evidenced by a decrease in urine calcium and hydroxyproline excretion. Among those with a normalized corrected serum calcium level, the mean (median) duration of normalization of the corrected serum calcium value was 9.2 (4), 13.3 (5), and 10.8 (6) days in the 30-, 60-, and 90-mg treatment groups, respectively. The response of hypercalcemia to pamidronate was not significantly influenced by the presence of skeletal metastases. PTH 1-84, suppressed in patients on entry into this study, increased to a greater extent in those patients with osteolytic skeletal metastases compared with those with humoral hypercalcemia of malignancy. Clinical improvement, including improved mental status and decreased anorexia, accompanied the decline in the corrected serum calcium level in all three treatment groups. Side effects included low-grade fever, asymptomatic hypocalcemia, hypomagnesemia, and hypophosphatemia. CONCLUSIONS: A single-dose infusion of 60 to 90 mg of pamidronate was highly effective and well tolerated and normalized corrected serum calcium in nearly all patients (61% to 100%) with hypercalcemia of malignancy.

Aged↗
PubMed1993

The role of genetic screening in the management of hereditary malignancy.

The identification of closely linked markers for several genetic syndromes has resulted in the routine identification of gene carriers for these disorders before the development of disease manifestations. The experiences with the multiple endocrine neoplasia syndromes, multiple endocrine neoplasia type 2 in particular, provide one example of how genetic testing can be combined with ongoing screening, treatment and support mechanisms to help families cope with the treatment realities and the psychosocial aspects of genetic disease.

Genetic Testing↗