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S Ezzat

Publications and source records attributed to S Ezzat.

At least 37 records · Page 2Linked to original sources
PubMed2000

Molecular basis off hurthle cell papillary thyroid carcinoma.

Among thyroid neoplasms, Hurthle cell tumors (HCTs) have traditionally been a distinct diagnostic category. Hurthle cell adenomas are encapsulated follicular lesions with benign behavior. Hurthle cell carcinomas exhibit unequivocal capsular and/or vascular invasion; they are aggressive tumors with a poor prognosis. Recently, Hurthle cell papillary thyroid carcinomas (PTCs) have been identified on morphological grounds. We hypothesize that a subset of HCTs represent PTC with clinical, histological, and immunohistochemical features based on specific molecular events. ret/PTC gene rearrangements give rise to novel oncogenes that are unique to PTC. We studied a group (n = 50) of HCTs for ret/PTC gene rearrangements. Tumors were examined for papillary differentiation by light microscopic evaluation of nuclear features, by RT-PCR for ret/PTC gene rearrangements, and by immunohistochemistry for ret. Among 24 noninvasive tumors, 13 contained ribonucleic acid for ret/PTC-1, -2, or -3, and 9 of these were immunoreactive for ret. Among 19 Hurthle cell carcinomas, 15 had focal nuclear hypochromasia with grooves and/or inclusions; expressed transcripts of ret/PTC-1, -2, or-3; and exhibited ret positivity. Tumors with ret/PTC gene rearrangements tended to have lymph node metastases rather than hematogenous spread. Our results indicate that a subset of HCTs exhibit features of PTC that are attributable to specific gene rearrangements, resulting in expression of ret/PTC oncogenes. These data support subclassification of HCTs into three groups: Hurthle cell adenomas, Hurthle cell carcinomas, and Hurthle cell PTC.

Adenocarcinoma, Papillary↗
PubMed2000

Myostatin and insulin-like growth factor-I and -II expression in the muscle of rats exposed to the microgravity environment of the NeuroLab space shuttle flight.

The mechanism of the loss of skeletal muscle mass that occurs during spaceflight is not well understood. Myostatin has been proposed as a negative modulator of muscle mass, and IGF-I and IGF-II are known positive regulators of muscle differentiation and growth. We investigated whether muscle loss associated with spaceflight is accompanied by increased levels of myostatin and a reduction in IGF-I and -II levels in the muscle, and whether these changes correlate with an increase in muscle proteolysis and apoptosis. Twelve male adult rats sent on the 17-day NASA STS-90 NeuroLab space flight were divided upon return to earth into two groups, and killed either 1 day later (R1) or after 13 days of acclimatization (R13). Ground-based control rats were maintained for the same periods in either vivarium (R3 and R15, respectively), or flight-simulated cages (R5 and R17, respectively). RNA and protein were isolated from the tibialis anterior, biceps femoris, quadriceps, and gastrocnemius muscles. Myostatin, IGF-I, IGF-II and proteasome 2c mRNA concentrations were determined by reverse transcription/PCR; myostatin and ubiquitin mRNA were also measured by Northern blot analysis; myostatin protein was estimated by immunohistochemistry; the apoptotic index and the release of 3-methylhistidine were determined respectively by the TUNEL assay and by HPLC. Muscle weights were 19-24% lower in the R1 rats compared with the control R3 and R5 rats, but were not significantly different after the recovery period. The myostatin/beta-actin mRNA ratios (means+/-s.e.m. ) were higher in the muscles of the R1 rats compared with the control R5 rats: 5.0-fold in tibialis (5.35 +/- 1.85 vs 1.07 +/- 0.26), 3.0-fold in biceps (2.46+/-0.70 vs 0.81 +/- 0.04), 1.9-fold in quadriceps (7.84 +/- 1.73 vs 4.08 +/- 0.52), and 2.2-fold in gastrocnemius (0.99 +/- 0.35 vs 0.44 +/- 0.17). These values also normalized upon acclimatization. Our antibody against a myostatin peptide was validated by detection of the recombinant human myostatin protein on Western blots, which also showed that myostatin immunostaining was increased in muscle sections from R1 rats, compared with control R3 rats, and normalized upon acclimatization. In contrast, IGF-II mRNA concentrations in the muscles from R1 rats were 64-89% lower than those in R3 animals. With the exception of the gastrocnemius, IGF-II was also decreased in R5 animals maintained in flight-simulated cages, and normalized upon acclimatization. The intramuscular IGF-I mRNA levels were not significantly different between the spaceflight rats and the controls. No increase was found in the proteolysis markers 3-methyl histidine, ubiquitin mRNA, and proteasome 2C mRNA. In conclusion, the loss of skeletal muscle mass that occurs during spaceflight is associated with increased myostatin mRNA and protein levels in the skeletal muscle, and a decrease in IGF-II mRNA levels. These alterations are normalized upon restoration of normal gravity and caging conditions. These data suggest that reciprocal changes in the expression of myostatin and IGF-II may contribute to the multifactorial pathophysiology of muscle atrophy that occurs during spaceflight.

Analysis of Variance↗
PubMed2000

Guidelines for the diagnosis and treatment of acromegaly: a Canadian perspective.

Acromegaly is a chronic, debilitating condition caused by excessive secretion of growth hormone (GH). In the majority of cases the condition results from benign pituitary adenomas or, rarely, from ectopic production of GH-releasing hormone. Regardless of the cause, excess GH results in physical disfigurement associated with arthropathy, diabetes, hypertension, cardiac dysfunction, obstructive sleep apnea and colonic neoplasia. The death rate for acromegalic patients is 2 to 3 times higher than that of the general population, but with appropriate reduction of GH hypersecretion it tends to shift into the normal range. Treatment is thus aimed at normalizing GH secretion; eradicating or stabilizing the pituitary tumour while preserving normal pituitary function, and managing the associated complications. The treatment modalities available to achieve these objectives include transsphenoidal surgery, pharmacotherapy and radiation, or various combinations of these. This review provides an update on our current understanding of the pathophysiology of GH hypersecretion in acromegaly, the newly defined diagnostic criteria and the end point for a cure for acromegaly, and on new developments in drug treatment with the advent of slow-release forms of somatostatin analogues and the longer-acting dopamine receptor agonists, as well as in the area of radiotherapy. Its main purpose is to guide any physician involved in the diagnosis and management of patients with acromegaly.

Acromegaly↗
PubMed1999

Molecular determinants of pituitary cytodifferentiation.

The pituitary is a complex gland and is composed of several cell types, each responsible for the production of specific hormones. In the past, it was thought that one cell could make only one hormone; the concept of plurihormonality was poorly understood. Plurihormonal adenomas were thought to be either composed of multiple cell types, each producing one hormone (plurimorphous adenomas) or composed of poorly differentiated cells that exhibited abnormal production of multiple hormones. However, the molecular factors that determine hormone production have now been identified as transcription factors that target specific hormone genes. These factors have clarified three main pathways of cell differentiation. ACTH-producing corticotrophs are determined by corticotropin upstream transcription-binding element (CUTE) proteins including neuroD1/beta 2. Bihormonal gonadotrophs require expression of steroidgenic factor (SF)-1. The complex family of Pit-1 expressing cells can mature into somatotrophs, mammosomatotrophs, lactotrophs or thyrotrophs with the additional expression of estrogen receptor (ER) alpha, which enhances PRL secretion, or thyrotroph embryonic factor (TEF) which stimulates TSH-beta production. The recognition of these molecular determinants of adenohypophysial cytodifferentiation has clarified the patterns of plurihormonality which have been recognized in pituitary adenomas and provide a framework for classification of these tumors.

Adenoma↗
PubMed1999

Cystic lesions of the pituitary: clinicopathological features distinguishing craniopharyngioma, Rathke's cleft cyst, and arachnoid cyst.

The distinction among craniopharyngioma (CR), Rathke's cleft cyst (RCC), and intrasellar arachnoid cyst (AC) remains a difficult preoperative problem. Accurate diagnosis of these rare pituitary lesions is important to determine the type of treatment and predict prognostic outcome. The majority of the literature describes the clinical manifestations and management of only one of CR, RCC, or AC, rendering comparisons difficult. We conducted a study to 1) investigate distinguishing preoperative clinical, biochemical, and radiographic features of patients with CR, RCC, and AC; and 2) identify clinicopathological features that independently predict recurrence in CR and RCC in adults. Fifty-two adult patients included 21 patients with CR (mean age at initial surgery, 35 +/- 14 yr), 26 patients with RCC (mean age, 37 +/- 14 yr), and 5 patients with AC (mean age, 53 +/- 12 yr). Mean follow-up duration was 70 +/- 13 months. Patients with CR presented with hypopituitarism in 95% of cases and hyperprolactinemia in 38%. These patients also had more preoperative neurological deficits (67%), ophthalmological complaints (67%), and significantly higher psychiatric manifestations (33%; P = 0.003) than those with RCC or AC. Patients with AC presented with headaches (60%), visual field deficits (60%), or impotence (50%) in the absence of other specific endocrine dysfunction symptoms. Using biochemical criteria, the percentage of patients with two or more pituitary hormonal axes impaired preoperatively was 67% for CR and 62% for RCC, significantly greater (P = 0.03) than that for the AC patients who had pituitary dysfunction of only one axis. The composition of CR lesions was cystic (38%), solid (10%), or mixed solid and cystic (43%). Patients with RCC or AC groups had a significantly greater proportion (P = 0.006) of purely cystic lesions (88% and 100%, respectively). Calcification detectable on computed tomographic scanning was present in 87% of patients with CR, a significantly greater proportion (P < 0.001) compared to those with RCC (13%) or AC (0%). No significant differences were found between the groups based on computed tomography density, the presence of postcontrast enhancement, or magnetic resonance imaging. Recurrence rate was 62% for CR, 19% for RCC, and 20% for AC. Surgical intervention statistically improved most neurological, ophthalmological, and psychiatric manifestations; in contrast, galactorrhea, menstrual dysfunction, and diabetes insipidus (52% CR; 31% RCC) did not improve or became worse postoperatively. A significantly higher percentage of patients with CR required postoperative hormone replacement. Similarly, there was a biochemical trend suggesting that a smaller proportion of patients with CR improved in at least one pituitary axis after surgery (P = 0.08) compared to those with RCC or AC. There was a positive correlation between cyst size and recurrence rate (r = 0.689; P < 0.01) and between cyst size and time to recurrence (r = 0.582; P = 0.037) for all three groups. We describe the largest clinical, biochemical, radiographic, and histological series of adult patients with cystic disease of the sella turcica. Patients with AC tended to be older at initial diagnosis than CR or RCC patients. Mass effects, such as visual problems and headaches, are common symptoms of all three cystic lesions, but psychiatric deficits favor a diagnosis of CR. Calcification or solid components on neuroimaging characterize CR. Endocrinological deficits, especially diabetes insipidus, had the worst prognosis after surgery. Low recurrence rates can be expected for RCC and AC. These data have direct implications for the management and monitoring of patients with cystic lesions of the sella turcica.

Adult↗
PubMed1999

Measures of submaximal aerobic performance evaluate and predict functional response to growth hormone (GH) treatment in GH-deficient adults.

The impact of GH on functional performance in GH-deficient adults is not well understood. To investigate the effects of GH on skeletal muscle, physical, and functional capacity, we randomized 28 GH-deficient adults to receive 3 months of recombinant human GH [rhGH: somatotropin, 6.25 microg/kg lean body mass (LBM) for 1 month, 12.5 microg/kg LBM thereafter] in a double-blind placebo-controlled crossover trial. We measured muscle fiber type, size, and insulin-like growth factor I messenger RNA, aerobic capacity [maximal oxygen uptake (VO2max), ventilation threshold (VeT)], isokinetic strength, oxygen-cost-of-walking at normal and fast speeds, and fatigue determined by the profile of mood states questionnaire. As expected, GH treatment decreased body fat, increased LBM, increased muscle fiber size, and increased muscle insulin-like growth factor-I messenger RNA 5-fold; however, muscle strength remained unchanged. At baseline, VeT occurred at a high percentage of maximal VO2max (73.3% +/-2.6) because of low VO2max (1.74+/-0.1 L/min or 20.7+/-1.3 mL/ kg x min). Walking required high oxygen consumptions representing from 83+/-4% of VeT at normal speeds to 120+/-5% of VeT at fast speeds. After rhGH, there was a significant (P = 0.03) increase in VeT (18%), compared with placebo. This was paralleled by a nonsignificant rise in VO2max. Functionally, rhGH treatment decreased the oxygen cost of walking, relative to VeT, at normal (14% decrease, P = 0.019) and fast (21% decrease, P = 0.004) SPW speeds. A 3-variable model (baseline fast SPW speed, VeT/VO2max, and VeT) accounted for 39% of the variance of change in self-reported fatigue. These data indicate that GH-deficient adults require a high fraction of VeT for daily activities, explaining the perception of increased fatigue and impaired physical performance. The actions ofrhGH on muscle fiber size translate into physiological improvement in submaximal aerobic capacity and result in functional improvement in walking ability but do not necessarily alter strength. Thus, measures of effort-independent submaximal aerobic performance provide novel objective determinants of functional impairment and fatigue and can be used to evaluate and predict response to GH treatment.

Adolescent↗
PubMed1999

Oncogene profile of papillary thyroid carcinoma.

BACKGROUND: Our purpose was to study the expression of multiple oncogenes in papillary thyroid cancer for possible interactions and prognostic significance. METHODS: Twenty papillary thyroid carcinomas were studied for expression/mutation of 3 oncogenes: ras, ret/PTC, and erbB-2/neu. H, N, and K ras codons were examined by polymerase chain reaction (PCR), single-stranded conformation polymorphism, and sequencing. The thyroid oncogene ret/PTC was identified by reverse transcription (RT)-PCR. Gene amplification of erbB-2/neu was analyzed by differential PCR. The transmembrane domain of erbB-2/neu was sequenced for activating mutations. Quantitation of erbB-2/neu mRNA was evaluated by competitive RT-PCR, and protein expression was determined by immunohistochemistry. RESULTS: Among 20 tumors, 3 had insular/anaplastic dedifferentiation, 13 were intrathyroidal, and 7 were metastatic to cervical lymph nodes (6) or lung (1). An H-ras 13 mutation was found in 1 metastatic tumor and an N-ras 61 mutation in 1 intrathyroidal tumor. ret/PTC was identified in 3 intrathyroidal and 5 metastatic tumors. No erbB-2/neu DNA amplification or mutations were identified, although 4 tumors had elevated erbB-2/neu mRNA levels. Three of 20 patients had abnormalities detected in multiple oncogenes; 2 had elevated erbB-2/neu mRNA and ret/PTC rearrangements, and 1 of these had pulmonary metastasis. An intrathyroidal papillary cancer had an N61 ras mutation and a ret/PTC gene rearrangement. CONCLUSIONS: ret/PTC rearrangements are present in 40% of papillary thyroid carcinomas and may play a role in metastatic behavior. In contrast, ras mutations are rare (10%). erbB-2/neu gene amplification and activating mutations are not detected, although elevated mRNA levels were found in 20% of papillary carcinomas. The lack of correlation among the 3 oncogenes in 17 of 20 (85%) papillary thyroid carcinomas suggests that they were not cumulative factors in the pathogenesis of these tumors.

Adult↗
PubMed1998

Organization of the human myostatin gene and expression in healthy men and HIV-infected men with muscle wasting.

Myostatin, a member of the transforming growth factor-beta superfamily, is a genetic determinant of skeletal muscle growth. Mice and cattle with inactivating mutations of myostatin have marked muscle hypertrophy. However, it is not known whether myostatin regulates skeletal muscle growth in adult men and whether increased myostatin expression contributes to wasting in chronic illness. We examined the hypothesis that myostatin expression correlates inversely with fat-free mass in humans and that increased expression of the myostatin gene is associated with weight loss in men with AIDS wasting syndrome. We therefore cloned the human myostatin gene and cDNA and examined the gene's expression in the skeletal muscle and serum of healthy and HIV-infected men. The myostatin gene comprises three exons and two introns, maps to chromosomal region 2q33.2, has three putative transcription initiation sites, and is transcribed as a 3.1-kb mRNA species that encodes a 375-aa precursor protein. Myostatin is expressed uniquely in the human skeletal muscle as a 26-kDa mature glycoprotein (myostatin-immunoreactive protein) and secreted into the plasma. Myostatin immunoreactivity is detectable in human skeletal muscle in both type 1 and 2 fibers. The serum and intramuscular concentrations of myostatin-immunoreactive protein are increased in HIV-infected men with weight loss compared with healthy men and correlate inversely with fat-free mass index. These data support the hypothesis that myostatin is an attenuator of skeletal muscle growth in adult men and contributes to muscle wasting in HIV-infected men.

Adult↗
PubMed1998

Insulin and related factors in premenopausal breast cancer risk.

BACKGROUND: Insulin and insulin-like growth factor I (IGF-I) are important mitogens in vitro and in vivo. It has been hypothesized that these factors may play an important role in the development of breast cancer. METHODS: A case-control study comparing plasma insulin levels in 99 premenopausal women with newly diagnosed node-negative invasive carcinoma of the breast and 99 age-matched controls with incident biopsied non-proliferative breast disease (NP) was conducted. Women with known diabetes were excluded. RESULTS: For the entire study group, mean age was 42.6 +/- 5.1 years and mean weight was 62.9 +/- 10.3 kg. After adjustment for age and weight, elevated insulin levels were significantly associated with breast cancer, Odds Ratio (OR) for women in the highest insulin quintile versus the lowest quintile = 2.83 (95% Confidence Interval [CI] 1.22-6.58). There were no statistically significant differences between cases and controls for IGF-I and IGFBP-1 levels. However, after adjustment for age, the association between plasma levels of insulin-like growth factor binding protein 3 (IGFBP-3) and breast cancer approached statistical significance; OR for highest quintile versus lowest quintile of IGFBP-3 being 2.05 (95% CI, 0.93-4.53). All results were independent of diet and other known risk factors for breast cancer. CONCLUSION: Circulating insulin levels and possibly IGFBP-3 levels are elevated in women with premenopausal breast cancer. This association may reflect an underlying syndrome of insulin resistance that is independent of obesity.

Adult↗
PubMed1998

Cytoplasmic staining of erbB-2 but not mRNA levels correlates with differentiation in human thyroid neoplasia.

OBJECTIVE: Amplification and overexpression of the erbB-2 proto-oncogene in human carcinomas may have prognostic significance. Its role in thyroid carcinoma is controversial. We investigated human thyroid tumours for erbB-2 gene amplification, activating mutations in the transmembrane domain, quantitative mRNA expression and protein expression. MATERIALS AND METHODS: DNA and mRNA were extracted from 47 morphologically characterized, frozen thyroid tumours including 10 nodular hyperplasias, 3 follicular carcinomas and 34 papillary carcinomas (4 with tall-cell features, 2 with insular and 2 with anaplastic de-differentiation). DNA amplification was analysed by differential PCR. The transmembrane domain of erbB-2 was sequenced in all tumours for activating mutations in position 659. Levels of mRNA expression were determined by competitive mRNA RT-PCR. Immunohistochemistry (IHC) for erbB-2 protein expression in corresponding paraffin-embedded samples was evaluated. RESULTS: Our results showed no DNA amplification of erbB-2. Sequencing of the transmembrane domain of erbB-2 revealed no activating mutations. The level of mRNA expression was variable, 11 papillary carcinomas showing statistically significant elevated mRNA levels compared with corresponding normal thyroid tissue; however, this did not correlate with other indicators of poor prognosis. In contrast to elevated mRNA levels in tumours, the level of protein staining correlated with degree of differentiation, normal and hyperplastic tissue being strongly positive and poorly differentiated tumours negative. CONCLUSION: There are no mutations or amplifications of the erbB-2 gene in human thyroid tumours. Elevated erbB-2 mRNA expression in some thyroid tumours is not associated with clinical features of poor prognosis; however, the significance of the elevated mRNA levels is unclear, as it did not result in protein overexpression. Instead, cytoplasmic erbB-2 protein detection by IHC correlates with differentiation of human thyroid tumours and may be a feature of good prognosis.

Carcinoma, Papillary↗
PubMed1998

Psychological features of acromegaly.

Acromegaly is a serious but often undiagnosed condition that is often unrecognized for many years. The delay from onset of symptoms until the time of diagnosis results in a unique constellation of physical and mental problems for patients and health care professionals. The purpose of this chapter is to identify the psychological consequences experienced by individuals affected with pituitary tumors which alter growth hormone release. As little research has been completed on the subject, very little is known, or has been applied, in the treatment of these patients. To identify the presence of psychological features, the research which exists and an in-depth qualitative analysis of the personal experience of one of the author (K.F.), having suffered a pituitary macroadenoma with accompanying acromegaly, is described. Our findings are compared with those from an earlier series and the few published reports.

Acromegaly↗
PubMed1998

Distinct multiple RET/PTC gene rearrangements in multifocal papillary thyroid neoplasia.

Rearrangements involving the RET protooncogene have been implicated in the development of papillary thyroid carcinoma (PC). Transgenic mice, expressing thyroid-targeted RET/PTC-1, develop PC; but the clinical significance of this oncogene remains uncertain. We examined the expression of RET/PTC-1, -2, and -3 in human thyroid microcarcinomas and clinically evident PC to determine its role in early stage vs. developed PC and to examine the diversity of RET/PTC in multifocal disease. RNA was extracted from paraffin-embedded microcarcinomas and clinically evident PCs; the results obtained from paraffin-embedded tissue were confirmed on RNA from corresponding snap-frozen tissue of clinically evident PCs. RT and PCR was performed using primers for RET/PTC-1, -2, and -3; PGK-1 (the housekeeping gene) analysis was used to ensure integrity of the RNA and efficiency of the RT reaction. PCR products were resolved by gel electrophoresis, and Southern hybridization was performed with RET/PTC-1, -2, and -3 probes. A polyclonal antibody to the carboxyterminus of RET was used for immunohistochemistry on paraffin sections. Thirty-nine occult papillary thyroid microcarcinomas from 21 patients were analyzed. Of the 30 tumors (77%) positive for RET/PTC rearrangements, 12 were positive for RET/PTC-1, 3 for RET/ PTC-2, 6 for RET/PTC-3, and 9 for multiple RET/PTC oncogenes. In clinically evident tumors, 47% had RET/PTC rearrangements. Immunohistochemistry demonstrated close correlation with RT-PCR-derived findings. RET/PTC expression is highly prevalent in microcarcinoma and occurs more frequently than in clinically evident PC (P < 0.005). Multifocal disease, identified in 17 of the 21 patients, exhibited identical RET/PTC rearrangements within multiple tumors in only 2 patients; the other 15 patients had diverse rearrangements in individual tumors. Our results indicate that RET/PTC oncogene rearrangements may play a role in early-stage papillary thyroid carcinogenesis, but they seem to be less important in determining progression to clinically-evident disease. In multifocal disease, the diversity of RET/PTC profiles, in the majority of cases, suggests that individual tumors arise independently in a background of genetic or environmental susceptibility.

Carcinoma, Papillary↗
PubMed1998

Improved diagnostic accuracy of inferior petrosal sinus sampling over imaging for localizing pituitary pathology in patients with Cushing's disease.

The majority of patients with Cushing's disease can be cured by transsphenoidal microsurgery; however, precise localization of the pituitary source of ACTH is not always possible by standard imaging techniques. Bilateral venous sampling from the inferior petrosal sinuses (IPSS) is also useful for diagnosing Cushing's disease, but the interpretation of discordant findings between IPSS and imaging remains problematic. We tested the ability of imaging and IPSS to localize an ACTH-secreting pituitary lesion in comparison to definitive histopathological examination of the pituitary in patients with Cushing's disease (n = 37). Bilateral IPS catheterization was technically feasible in 32 patients and provided evidence of lateralization in 31 patients. Histological examination confirmed a corticotropic adenoma in 28 patients and corticotropic hyperplasia in 2 patients; Crooke's hyaline change was found in 7 patients, among whom 1 subsequently was found to have an ectopic sphenoid corticotropic adenoma, and the remainder had suspected microadenomas that were not identified microscopically. Accurate localization of the pituitary lesion was more frequent when based on IPSS results than on imaging studies (70% vs. 49%, P < 0.06). The 2 tests provided directly discrepant results for 8 patients; among these, IPSS was more likely than imaging to agree with final pathology (63% vs. 13%, P < 0.10). Imaging was entirely normal for another 9 patients, in whom IPSS accurately localized the lesion for the majority (89%; 95% confidence interval: 50-99%). We suggest that IPSS is an effective tool for localizing pituitary pathology and planning surgery for patients with Cushing's disease.

Adrenocorticotropic Hormone↗
PubMed1998

The MEN-1 gene is rarely down-regulated in pituitary adenomas.

The gene for multiple endocrine neoplasia type 1 (MEN-1) has recently been cloned and encodes a putative tumor suppressor protein named menin. We have previously reported inactivating MEN-1 gene mutations associated with loss of heterozygosity (LOH) of the normal allele in tumors of patients with MEN-1 and in some sporadic pituitary tumors. These genetic alterations, however, are noted in no more than 10% of sporadic adenomas. To investigate whether other mechanisms may result in down-regulation of menin gene expression in pituitary adenomas, we examined menin gene expression by semiquantitative RT-PCR in 60 sporadic pituitary adenomas. Ribonucleic acid (RNA) was extracted from surgically resected, morphologically characterized tumors. Primers were designed to amplify a 257-bp fragment spanning exons 4-6 of the MEN-1 gene. A product of the predicted size was amplified from normal pituitary samples as well as from adenomas. Competitive PCR was performed with the housekeeping gene PGK-1 to quantitate menin gene expression. A comparable ratio of menin/PGK-1 messenger RNA was identified in all but three samples; in two tumors with LOH, menin expression was weak, and in one tumor, menin messenger RNA was undetectable, associated with LOH and mutation of the other allele. Reduced expression of menin in some sporadic adenomas is consistent with a putative tumor suppressor role for this gene product. However, lack of menin down-regulation in the majority of these tumors, which exhibit LOH at 11q13 in up to 20% of cases, provides compelling evidence for an additional tumor suppressor gene at this locus, which is more commonly involved in the pathogenesis of pituitary neoplasms.

Adenoma↗
PubMed1997

Insulin-like growth factor binding protein-1 is elevated in patients with polycythemia vera and stimulates erythroid burst formation in vitro.

Previously, we found that, in the myeloproliferative disorder polycythemia vera (PV), circulating erythroid progenitor cells were hypersensitive to insulin-like growth factor I (IGF-I), an effect shown to occur through the IGF-I receptor. Also, in cells of PV patients, the IGF-I receptor was hyperphosphorylated on tyrosine residues under basal conditions, and its tyrosine phosphorylation in response to exogenous IGF-I was strongly augmented. Thus, because IGF-I appeared to play a role in the pathogenesis of PV, we wished to assess its level in the circulation of these patients. Normally, most of the circulating IGF-I is bound to specific high-affinity IGF binding proteins that can regulate its activity. We determined the circulating levels of IGF-I and two of its key binding proteins, IGFBP-1 and IGFBP-3. In two separate experiments, plasma samples from a total of 23 PV patients age- and sex-matched with 41 normal individuals were compared by radioimmunoassay. The levels of IGFBP-1 in patients with PV (37.80 +/- 4.33 microg/L) were more than fourfold higher than in normals (9.34 +/- 1.34 microg/L) or patients with secondary erythrocytosis (9.47 +/- 1.96 microg/L), whereas the plasma concentrations of IGFBP-3 and IGF-I in these patients were similar to those of normal subjects. Because circulating IGFBP-1 levels may be influenced by insulin, we measured the concentrations of insulin in the same samples. Our data showed that the elevation of circulating IGFBP-1 in PV could not be attributed to low levels of insulin in these patients. The substantial increase in concentration of IGFBP-1 was confirmed on ligand blots performed with (125)I-IGF-I. IGFBP-1 can be either inhibitory or stimulatory to the action of IGF-I under different conditions. We reasoned that if IGFBP-1 were stimulatory for erythropoiesis, an elevated IGFBP-1 level could help to explain the increased sensitivity to IGF-I observed in PV. If IGFBP-1 were inhibitory, it might suggest a compensatory mechanism in which a hyperphosphorylated IGF-I receptor in PV might induce a negative modulator of IGF-I action, in this case IGFBP-1. To distinguish between these two hypotheses, we titrated the effect of IGFBP-1 in the presence of IGF-I with respect to erythroid burst formation and found that IGFBP-1 was strikingly stimulatory. The elevated level of IGFBP-1 coupled with its ability to stimulate erythroid burst formation provide an attractive mechanism to account for the increased sensitivity of erythroid progenitor cells to IGF-I and the consequent overproduction of red blood cells characteristic of PV.

Cells, Cultured↗
PubMed1997

Acromegaly.

Acromegaly can be a serious, chronic, debilitating condition. The disease is often missed for years, resulting in significantly delayed diagnosis. This article reviews recent advances in our understanding of acromegaly and the impact of current approaches on the diagnosis and monitoring of patients with this disorder.

Acromegaly↗