Biomedical subjects

M Eszlinger

Publications and source records attributed to M Eszlinger.

9 recordsLinked to original sources

PubMed2006

Cytology and mRNA expression analysis of fine needle aspirates of thyroid nodules in an East German region with borderline iodine deficiency.

Fine needle aspiration cytology (FNAC) is widely recommended as an important tool for pre-operative identification of malignancy in patients with nodular thyroid disease. To assess the diagnostic contribution of FNAC and the potential of quantitative mRNA analysis in fine needle aspirates in daily practice, we conducted a prospective study in thyroid clinics (n=2) and endocrine practices (n=3), respectively in an East German region with borderline iodine deficiency. Two-hundred and forty-four consecutive FNACs were obtained over a period of 2 years (2002-2004) from euthyroid patients presenting for first evaluation of a solitary thyroid nodule. The mean nodule size for FNAC was 27 mm (range: 10-79 mm). In 55% of patients FNAC was performed after scintiscan detection of a cold or normal functioning thyroid nodule (CTN), while in the remainder FNAC was performed as a primary investigation. FNAC outcomes were: 57.8% benign, 22.1% indeterminate, 2.5% suspicious for malignancy, 17.6% non-diagnostic. Messenger RNA levels for a house keeping gene (beta-actin) and a thyroid specific marker (thyroglobulin, Tg) were studied as basic molecular markers using real-time PCR. Both in the IN VIVO and EX VIVO FNA series, beta-actin and Tg mRNA levels were positively correlated with the thyrocyte cell yield/respective FNA smear. However, subgroup analysis showed that FNAC with histologically confirmed follicular thyroid cancer and/or microfollicular adenoma exhibited significantly lower Tg mRNA expression despite high beta-actin levels. Sufficient mRNA quantities were obtained in >90% of FNA specimen to allow quantitative mRNA analysis of at least 5 further genes. In conclusion, quantitative mRNA analysis is feasible in FNA on a routine basis and provides a perspective for a molecular distinction of thyroid nodules, once specific marker genes have been defined for benign and malignant thyroid tumours respectively.

Actins↗

PubMed2005

Increased power of microarray analysis by use of an algorithm based on a multivariate procedure.

MOTIVATION: The power of microarray analyses to detect differential gene expression strongly depends on the statistical and bioinformatical approaches used for data analysis. Moreover, the simultaneous testing of tens of thousands of genes for differential expression raises the 'multiple testing problem', increasing the probability of obtaining false positive test results. To achieve more reliable results, it is, therefore, necessary to apply adjustment procedures to restrict the family-wise type I error rate (FWE) or the false discovery rate. However, for the biologist the statistical power of such procedures often remains abstract, unless validated by an alternative experimental approach. RESULTS: In the present study, we discuss a multiplicity adjustment procedure applied to classical univariate as well as to recently proposed multivariate gene-expression scores. All procedures strictly control the FWE. We demonstrate that the use of multivariate scores leads to a more efficient identification of differentially expressed genes than the widely used MAS5 approach provided by the Affymetrix software tools (Affymetrix Microarray Suite 5 or GeneChip Operating Software). The practical importance of this finding is successfully validated using real time quantitative PCR and data from spike-in experiments. AVAILABILITY: The R-code of the statistical routines can be obtained from the corresponding author. CONTACT: Schuster@imise.uni-leipzig.de

Algorithms↗

PubMed2005

Evaluation of peroxisome proliferator-activated receptor-gamma expression in benign and malignant thyroid pathologies.

Impairment of peroxisome proliferator-activated receptor-gamma (PPAR-gamma) function through a dominant negative PAX-8/PPAR-gamma fusion gene or other events resulting in wild-type PPAR-gamma downregulation has been implicated in malignant thyroid cell transformation. The aim of our study was to perform a systematic evaluation of PPAR-gamma mRNA and protein expression in normal thyroid tissue as opposed to benign thyroid pathologies of different functional status and thyroid malignancy, to gain further insights into a putative physiological role of PPAR-gamma in the thyroid and to define whether PPAR-gamma could serve as a marker of thyroid cell differentiation. Ten cold benign (CTN) and 10 toxic (TTN) thyroid nodules and corresponding normal thyroid tissues, 10 follicular thyroid cancers (FTC), 10 papillary thyroid cancers (PTC) and 8 Graves' disease (GD) thyroids were studied by real-time polymerase chain reaction (PCR), immunohistochemistry and reverse transcriptase (RT)-PCR (PAX-8/PPAR-gamma fusion gene). PPAR-gamma mRNA expression was demonstrated in all samples. When comparing benign nodular and normal thyroid tissue of the same patient no significant difference in PPAR-gamma mRNA expression was observed. PPAR-gamma mRNA levels were similar in CTN and FTC. In contrast, PPAR-gamma mRNA expression was downregulated in 9 of 10 PTC and all GD samples, whereby at least 4 fold downregulation (compared with normal and benign nodular thyroid tissues) was observed in the latter. Immunohistochemistry showed an increased, patchy PPAR-gamma nuclear staining in CTNs and TTNs and only faint staining in the corresponding normal thyroid tissues. A diffuse and weak PPAR-gamma staining pattern was observed in all GD samples. No PAX-8/PPAR-gamma rearrangements were detected in any of the 68 thyroid tissue samples. In conclusion PPAR-gamma mRNA and protein expression levels are not concordant in benign thyroid nodular disease. Furthermore there is no clear-cut association of PPAR-gamma mRNA expression with follicular thyroid tumorigenesis. Absence of a PAX-8/PPAR-gamma fusion gene in the series of 68 thyroid samples is in agreement with the suggestion of PAX-8/PPAR-gamma rearrangement being restricted to a subset of follicular thyroid cancers. The marked downregulation of PPAR-gamma in GD warrants further investigation and could be linked, for example, with changes in apoptosis.

Adenoma↗

PubMed2005

Evaluation of insulin-like growth factor II, cyclooxygenase-2, ets-1 and thyroid-specific thyroglobulin mRNA expression in benign and malignant thyroid tumours.

OBJECTIVE: We evaluated three markers (insulin-like growth factor II (IGF-II), cyclooxygenase-2 (COX-2) and ets-1) of thyroid growth stimulation and cell transformation together with a thyroid-specific marker (thyroglobulin (Tg)) for their potential to differentiate benign and malignant follicular thyroid neoplasia (FN). DESIGN AND METHODS: mRNA expression levels were determined by real-time PCR in 100 snap-frozen thyroid samples: 36 benign thyroid nodules with different histology and function (19 cold (CTN) and 17 toxic thyroid nodules (TTN)), 36 corresponding normal thyroid tissues of the same patients, eight Graves' disease (GD) thyroids, 10 follicular thyroid carcinomas (FTC) and 10 papillary thyroid carcinomas (PTC). RESULTS: Mean IGF-II and COX-2 levels were not significantly altered between benign and malignant thyroid nodules (IGF-II) or nodular (FTC, TTN, CTN) and normal thyroid tissues (COX-2). In contrast, eight- to tenfold upregulation of ets-1 was observed in PTC and three- to fourfold upregulation of ets-1 was observed in FTC (and GD) compared with benign thyroid nodules and normal thyroid tissues. In addition, thyroglobulin mRNA expression was markedly downregulated (50- to 100-fold) in FTC, PTC and GD samples compared with benign nodular and normal thyroid tissues. Hence an ets-1/Tg ratio >20 distinguished differentiated thyroid cancer from benign nodular or normal thyroid tissue. We then studied ets1- and Tg mRNA expression levels in fine needle aspiration cytology (FNAC) samples. However, in a consecutive series of 40 FNAC samples only equivocal results were obtained on 38 benign and two malignant (FTC) thyroid tumour samples. CONCLUSIONS: Upregulation of ets-1 and downregulation of Tg mRNA expression occur in differentiated thyroid cancer and may facilitate pre-operative identification of thyroid malignancy depending on further evaluation of these potentially promising markers in a larger series of benign and malignant thyroid tumours and their FNAC samples.

Adenoma↗

PubMed2001

Tumor necrosis factor alpha is a negative regulator of resistin gene expression and secretion in 3T3-L1 adipocytes.

Resistin has recently been implicated as an adipocytokine leading to insulin resistance and, therefore, potentially linking obesity and diabetes. To further characterize the regulation of this fat-secreted protein by insulin sensitivity-modulating hormones, 3T3-L1 adipocytes were treated with tumor necrosis factor (TNF) alpha, angiotensin (AT) 2, as well as growth hormone (GH), and resistin gene expression and protein secretion were determined by quantitative real-time reverse transcription-polymerase chain reaction and Western blotting. Interestingly, both, resistin mRNA expression and protein secretion, were inhibited by 70-90% after TNFalpha-treatment whereas AT2 and GH did not have any effect. The inhibitory effect of TNFalpha was time- and dose-dependent with significant inhibition occurring as early as 4 h after effector addition and at concentrations as low as 1 ng/ml TNFalpha. Pharmacological inhibition of protein kinase A (PKA), p44/42, and p38 mitogen-activated protein (MAP) kinase did not reverse the inhibitory effect of TNFalpha suggesting that neither of these signaling molecules is involved in suppression of resistin gene expression by TNFalpha. Furthermore, suppression of resistin mRNA levels could be completely reversed to control levels by withdrawal of TNFalpha for 24 h. Taken together, these results suggest that TNFalpha is a pivotal negative regulator of resistin gene expression. This may have important implications for the pathogenesis of insulin resistance and its link to obesity.

3T3 Cells↗

PubMed2001

Adiponectin gene expression is inhibited by beta-adrenergic stimulation via protein kinase A in 3T3-L1 adipocytes.

Recently, it has been shown that the fat-derived factor adiponectin is downregulated in insulin resistance and obesity and that replenishment of this adipocytokine reverses insulin resistance in mice. Growing evidence, on the other hand, suggests that raised levels of catecholamines due to increased activity of the sympathetic nervous system are an integral part in the development of insulin resistance. To clarify whether catecholamines might exert their insulin resistance-inducing effects at least partly via downregulation of adiponectin gene expression, 3T3-L1 adipocytes were treated with isoproterenol, and adiponectin mRNA was measured by quantitative real-time reverse transcription-polymerase chain reaction. In fact, isoproterenol treatment reduced the level of adiponectin mRNA by about 75% in a dose-dependent fashion with significant inhibition detectable at concentrations as low as 10 nM isoproterenol. Furthermore, the inhibitory effect of isoproterenol was almost completely reversed by pretreatment of 3T3-L1 cells with the beta-adrenergic antagonist propranolol and the protein kinase A (PKA) inhibitor H-89. Moreover, the effects of isoproterenol could be mimicked by stimulation of stimulatory guanine nucleotide-binding (G(S))-proteins with cholera toxin and adenylyl cyclase with forskolin. Thus, our results suggest that adiponectin gene expression is severely suppressed by beta-adrenergic agents via activation of a G(S)-protein-PKA-dependent pathway. The data support a possible role of adiponectin in catecholamine-induced insulin resistance.

3T3 Cells↗

PubMed2001

Isoproterenol inhibits resistin gene expression through a G(S)-protein-coupled pathway in 3T3-L1 adipocytes.

Resistin was recently identified as a hormone secreted by adipocytes which leads to insulin resistance in vivo and in vitro and might therefore be an important link between obesity and diabetes. To clarify the regulation of resistin gene expression, 3T3-L1 adipocytes were treated with various agents known to modulate insulin sensitivity, and resistin mRNA was measured by quantitative real-time reverse transcription-polymerase chain reaction. Interestingly, isoproterenol treatment reduced the level of resistin mRNA to 20% of non-treated control cells. This effect was dose-dependent with significant inhibition occurring at concentrations as low as 10 nM isoproterenol. Moreover, pretreatment of adipocytes with the beta-adrenergic antagonist propranolol almost completely reversed the inhibitory effect of isoproterenol, whereas addition of the alpha-adrenergic antagonist phentolamine did not have any effect. Furthermore, the effect of isoproterenol could be mimicked by activation of G(S)-proteins and adenylyl cyclase. Thus, both cholera toxin and forskolin decreased resistin mRNA expression in a dose-dependent fashion by up to 90% of control levels. Taken together, these results suggest that resistin gene expression is regulated by a protein kinase A-dependent pathway in 3T3-L1 adipocytes.

3T3 Cells↗

PubMed2001

Growth factor expression in cold and hot thyroid nodules.

Hot thyroid nodules (HTNs) are predominantly caused by constitutively activating thyrotropin receptor (TSHR) mutations leading to an activation of the cyclic adenosine monophosphate (cAMP)-cascade that stimulates growth and function of thyroid epithelial cells and confers growth advantage. In contrast to HTNs, the molecular etiology of szintigraphically cold thyroid nodules (CTNs) is largely unknown. An increased prevalence of toxic multinodular goiters in iodine-deficient regions has been reported. Growth factors increase during early stages of iodine deficiency in rats. These growth factors could modulate the proliferation of thyrocytes. In order to determine if and which growth factors could modulate the increase in thyroid epithelial cell proliferation in late stages of CTNs and HTNs we investigated epidermal growth factor (EGF), transforming growth factor-alpha (TGF-alpha), and TGF-beta1 concentrations by enzyme-linked immunosorbant assay (ELISA) in CTNs (n = 7), HTNs (n = 9), and their normal surrounding tissue (ST). Insulin-like growth factor-1 (IGF-1) was determined in CTNs (n = 5) and HTNs (n = 10) and their surrounding tissues by radioimmunoassay (RIA). We found lower concentrations of all investigated growth factors and iodine in CTNs compared to surrounding normal tissues (ST). Only iodine showed a significant difference. Furthermore, we found significantly lower concentrations of EGF and TGF-beta1 concentration in HTNs compared to their STs. Differences of TGF-alpha and IGF-1 were not significant. In conclusion, low EGF, TGF-alpha, and IGF-1 concentrations in most CTNs in spite of low iodine concentrations argue against a pathophysiologic role of EGF, TGF-alpha, or IGF-1 in late stages of CTNs. The low EGF, TGF-alpha, and IGF-1 concentrations in HTNs irrespective of their clonal origin or the presence or absence of activating mutations argue for increased cAMP as the primary cause for thyroid epithelial cell proliferation in established HTNs. However, the pathophysiologic significance of low TGF-beta1 concentrations in CTNs and HTNs remains to be elucidated. It might be possible that growth factors like EGF, TGF-alpha, TGF-beta1, and IGF-1 play a more prominent role during early clonal expansion and that aberrant intrinsic signaling through a somatic mutation (e.g., TSHR for HTNs) confers the predominant selective growth advantage in later stages of HTNs or CTNs.

Epidermal Growth Factor↗

PubMed2001

Complementary DNA expression array analysis suggests a lower expression of signal transduction proteins and receptors in cold and hot thyroid nodules.

Autonomously functioning thyroid nodules are characterized by an increased proliferation and function, which is predominantly caused by constitutively activating TSH receptor mutations leading to an activation of cAMP. In contrast to autonomously functioning thyroid nodules, cold thyroid nodules are functionally inactive and less differentiated. Their molecular cause is still unknown. To further investigate the pathophysiological aspects of autonomously functioning thyroid nodules and to elucidate the molecular etiology of cold thyroid nodules, it is essential to identify genes with differential expression in autonomously functioning thyroid nodules and cold thyroid nodules and to compare this expression to that in normal surrounding tissue. The list of possible candidates for differential regulation ranges from growth factors and their receptors to transcription factors or oncogenes. Therefore, we evaluated the potential of cDNA arrays and studied the expression of 588 known genes from 6 different classes of proteins in thyroid nodules characterized for their function. Forty-seven genes showed a differential expression between nodular and surrounding tissue identified by the expression arrays. The differential expression of 15 transcripts was verified by real-time PCR. About 25% of the transcripts determined by LightCycler PCR are considered false positives because data from PCR and array analysis did not agree. This indicates the reliability of cDNA expression arrays to identify differentially expressed genes in thyroid nodules compared with their surrounding tissue. The 15 selected genes were additionally quantified by real-time PCR in 7 additional cold thyroid nodules, autonomously functioning thyroid nodules, and their surrounding tissues. The highest number of differentially expressed genes was in the group of signal transduction proteins (4 of 38 detectable genes) and extracellular cell signaling and communication proteins (2 of 62 detectable genes). In contrast, transcripts of other classes of proteins were unchanged (e.g. DNA-binding molecules and stress responses). Most of the transcripts were down-regulated in autonomously functioning thyroid nodule and cold thyroid nodule compared with the respective surrounding tissue. This finding could be the result of a dominant activation of a signal transduction pathway, with the cAMP pathway being the likely candidate for autonomously functioning thyroid nodules. The qualitatively similar pattern of changes in this limited number of genes in autonomously functioning thyroid nodules and cold thyroid nodules could suggest a similar dominant activation of a specific signaling cascade in cold thyroid nodules as the constitutively activating mutations in autonomously functioning thyroid nodules.

Adult↗