Aysegul Ilhan

Immunohistochemical testing of BRAF V600E status in 1,120 tumor tissue samples of patients with brain metastases

Brain metastases (BM) are frequent and carry a dismal prognosis. BRAF V600E mutations are found in a broad range of tumor types and specific inhibitors targeting BRAF V600E protein exist. We analyzed tumoral BRAF V600E-mutant protein expression using the novel mutation-specific antibody VE1 in a series of 1,120 tumor specimens (885 BM, 157 primary tumors, 78 extra-cranial metastases) of 874 BM patients. In 85 cases, we performed validation of immunohistochemical results by BRAF exon 15 gene sequencing. BRAF V600E protein was expressed in BM of 42/76 (55.3%) melanomas, 1/15 (6.7%) ovarian cancers, 4/72 (5.5%) colorectal cancers, 1/355 (0.3%) lung cancers, 2/6 thyroid cancers and 1/2 choriocarcinomas. BRAF V600E expression showed high intra-tumoral homogeneity and was similar in different tumor manifestations of individual patients. VE1 immunohistochemistry and BRAF exon 15 sequencing were congruent in 68/70 (97.1%) cases, but VE1 immunostaining identified small BRAF V600E expressing tumor cell aggregates in 10 cases with inconclusive genetic results. Melanoma patients with BRAF V600E mutant protein expressing tumors were significantly younger at diagnosis of the primary tumor and at operation of BM than patients with non-mutated tumors. In conclusion, expression of BRAF V600E mutant protein occurs in approximately 6% of BM and is consistent in different tumor manifestations of the same patient. Thus, BRAF V600E inhibiting therapies seem feasible in selected BM patients. Immunohistochemical visualization of V600E-mutant BRAF protein is a promising tool for patient stratification. An integrated approach combining both, VE1 immunohistochemistry and genetic analysis may increase the diagnostic accuracy of BRAF mutation analysis.

Expression of TAU in insulin-secreting cells and its interaction with the calcium-binding protein secretagogin

Tauopathies have been associated with Alzheimers disease (AD), which frequently manifests together with diabetes mellitus type 2. Calcium-binding proteins such as the recently identified secretagogin (SCGN) might exert protective effects. As pancreatic beta-cells and neurons share common electrophysiological properties, we investigated the appearance of TAU (listed as MAPT in the HUGO and MGI Databases) protein at the islets of Langerhans and beta-cell-derived cell lines which highly express the neuroendocrine-specific protein SCGN. Six predominant TAU isoforms could be identified by immunoblotting, which formed TAU deposits detectable by immunofluorescence and sarkosyl-insoluble pellets. Using GST-SCGN pull-down assays, a calcium-dependent SCGN-TAU interaction was found. In this line, sucrose density gradient fractionation and differential ultracentrifugation studies of TAU and SCGN revealed co-appearance of both proteins. Co-localization of TAU and SCGN within insulinoma cells and islets of Langerhans mainly restricted to insulin-positive beta-cells was demonstrated by confocal microscopy. Motivated by these findings, we looked if SCGN overexpression could exert protective function on Rin-5F cells, which showed differences in TAU levels. Testing the vulnerability of Rin-5F clones by MTT assay, we revealed that high TAU levels going along with highest TAU aggregates could not be antagonized by high levels of SCGN protein. Our findings demonstrated for the first time the association of TAU and the calcium-binding protein SCGN and support earlier results implicating that beta-cells might represent an extra cerebral site of tauopathy.

Circulating angiopoietin-2 and soluble Tie-2 in type 2 diabetes mellitus: a cross-sectional study

BackgroundType 2 diabetes is associated with increased levels of Angiopoietin-2 (Ang-2) and soluble Tie-2 (sTie-2), but its impact on vascular disease is still unknown. This study aimed to further explore the associations of Ang-2 and sTie-2 with metabolic control and diabetic complications.MethodsIn a cross-sectional designed study, levels of Ang-2 and sTie-2 as well as their relationships to cardiometabolic parameters were determined in 80 type 2 diabetic subjects (age 65 ± 7 years, female 47.4%).ResultsAfter controlling for age and BMI, Ang-2 levels were associated with levels of sTie-2, diastolic blood pressure, plasma insulin, homeostasis model assessment of insulin resistance (HOMA-IR), creatinine, glomerular filtration rate (GFR), and gamma-glutamyl transferase (GGT) (all p < 0.02). Presence of diabetic macrovascular complications, polyneuropathy and insulin therapy were associated with higher Ang-2 levels (p < 0.05). Conversely, sTie-2 levels were associated with glycated hemoglobin (HbA1c), fasting plasma glucose and insulin, HOMA-IR, triglyceride, and liver function parameters (all p < 0.03). Multiple linear regression analysis showed that Ang-2 remained significantly associated only with levels of GGT (p < 0.04), whereas sTie-2 remained significantly associated with HbA1c, insulin levels, and HOMA-IR (p < 0.03). No differences in Ang-2 and sTie-2 levels were observed with regard to gender of participants.ConclusionsAng-2 is independently associated with levels of GGT while sTie-2 is independently associated with levels of HbA1c, plasma insulin and HOMA-IR in type 2 diabetic subjects. Therefore we suggest that the associations of Ang-2 and sTie-2 with type 2 diabetes are based on different patho-physiological mechanisms.

Plasma neuropeptide Y levels differ in distinct diabetic conditions

Neuropeptide Y (NPY) is an important hormone in appetite regulation. Although the contribution of NPY to metabolic disease has been previously demonstrated, there are only a few reports addressing NPY plasma levels under distinct diabetic conditions. In this study we evaluated NPY plasma levels in diabetes mellitus type 2 (DM2) patients with (n=34) and without (n=34) diabetic polyneuropathy (PNP) and compared these with age and gender matched healthy controls (n=34). We also analyzed NPY plasma levels in gestational diabetes mellitus (GDM) patients with age and pregnancy-week matched controls with normal glucose tolerance (NGT). NPY concentration was determined using a commercially available radioimmunoassay kit. In addition, metabolic parameters of DM2 and GDM patients were recorded. One-way ANOVA tests with appropriate post hoc corrections showed elevated levels of NPY in DM2 patients with and without PNP when compared with those of healthy controls (122.32±40.86 and 117.33±29.92 vs. 84.65±52.17 pmol/L; p<0.001, p<0.005, respectively). No significant difference was observed between diabetic patients with and without PNP. The NPY levels were similar in the GDM group and in pregnant women with NGT (74.87±14.36 vs. 84.82±51.13 pmol/L, respectively). Notably, the NPY concentration correlated positively with insulin levels in DM2 patients (R=0.35, p<0.01). Our data suggest a potential involvement of circulating NPY in DM2 pathology.

Diabetic polyneuropathy relates to bone metabolism and markers of bone turnover in elderly patients with type 2 diabetes: greater effects in male patients.

BACKGROUND There is evidence that diabetic polyneuropathy (PNP) is associated with reduced bone mineral density (BMD) in type 1 diabetes but little is known about the impact of diabetic PNP on bone metabolism in type 2 diabetes. OBJECTIVES The aim of this study was to evaluate differences in bone metabolism by measuring markers of bone turnover and BMD in men and postmenopausal women with type 2 diabetes and diabetic PNP compared with those without PNP. Gender differences were analyzed for both groups of patients. METHODS One hundred twenty patients with type 2 diabetes, 68 without PNP (43 men, 25 women, mean age 62 [8] years) and 52 with PNP (28 men, 24 women, mean age 64 [8] years) were studied. Clinical parameters with bone turnover biomarkers such as osteocalcin, bone alkaline phosphatase, procollagen type 1 amino-terminal propeptide, and carboxy-terminal telopeptide of type 1 collagen were measured in all patients. Dual energy x-ray absorptiometry to evaluate BMD was performed in a subgroup of patients. RESULTS After controlling for age, body mass index, duration of diabetes, smoking, glycosylated hemoglobin, homeostasis model assessment index for insulin resistance, serum C-reactive protein, creatinine, calcium, gamma-glutamyltransferase, parathyroid and sex hormones levels, presence of micro/macrovascular complications, statin- as well as diabetes-related therapies, levels of carboxy-terminal telopeptide of type 1 collagen and procollagen type 1 amino-terminal propeptide were significantly higher among patients with PNP when compared with patients without PNP (P = 0.01 and P = 0.03, respectively). Differences in bone biomarkers were more pronounced among men with diabetes. BMD did not differ significantly between patients with and without PNP, independent of gender. CONCLUSIONS Male patients with PNP exhibit a higher rate of bone turnover than men without PNP. High rate of bone turnover increases the susceptibility for developing osteoporosis. Prevention of diabetic PNP might also reduce the incidence of osteoporosis and fractures in patients with type 2 diabetes.

Levels of fetuin‐A relate to the levels of bone turnover biomarkers in male and female patients with type 2 diabetes

Objective  To evaluate the relationship of plasma fetuin‐A levels with markers of bone turnover in male and female type 2 diabetic subjects.

Elevated blood markers 1 year before manifestation of malignant glioma

We detected distinct plasma concentration profiles of S100B, neuropeptide Y, and secretagogin in 3 of 191 patients enrolled in a previous study investigating brain-tissue-related markers in the blood of patients with atrial fibrillation. Intriguingly, 2 of these 3 patients, both of whom were without neurological symptoms at the time of blood sampling, were diagnosed with malignant glioma (MG) approximately 1 year later. To our knowledge, this is the first report indicating that distinct blood biomarker profiles may be detected long before clinical manifestation of MG.

Cloning and molecular characterization of Dashurin encoded by C20orf116, a PCI-domain containing protein

BACKGROUND Characterization of gene products originating from undefined open reading frames and delineation of biological functions has become the task after the human genome has been decoded. METHODS We cloned the human C20orf 116 and defined its transcript in liver, kidney and various brain regions by Northern analysis. Antibodies against recombinant protein used for immunofluorescence and immunoblots confirmed its expression in these tissues. With the focus on kidney, its tubular expression and presence in glomerula were shown. RESULTS A 28 aa long signal peptide predicted by in silico analysis is reflected by visualization of size variants of approximately 3kDa difference suggesting a signal peptidase cleavage of the proform. Cell compartment separation confirmed the presence of Dashurin in peroxisomes/mitochondria, microsomes, cytosol and nucleus. This is in line with green fluorescent protein (GFP)-Dashurin fusion protein shuttling between cytosol and nucleus. Luciferase reporter studies revealed a 2-3 fold increase of promoter activities upon over-expression. Bioinformatic analysis identified a PCI-domain at the C-terminus providing protein-protein interaction capabilities. CONCLUSION Our present findings suggest the involvement of Dashurin in gene transcription or mRNA translation. GENERAL SIGNIFICANCE Dashurin shares the PCI-domain with three multisubunit protein complexes (26S proteasome, COP9 signalosome and eIF3 translation initiation factor).

Localization and characterization of the novel protein encoded by C20orf3

In the present study, we characterized the gene product of open reading frame 3 encoded at human chromosome 20 (C20orf3), which represents a member of the lactonohydrolase super family. Multiple-tissue Northern blot analysis showed ubiquitous expression of the 2.4 kb transcript coding for 416 amino acids, with highest levels in human liver, placenta and kidney. After recombinant production of protein variants in Escherichia coli and insect cells, antibodies directed against different epitopes within the C20orf3 gene product were generated. Using these immunoreagents, protein expression was demonstrated in the liver, and glomerular and tubular structures of the kidney, as well as in endothelial cells and arterial wall. Positive staining was also observed at the pancreatic islets of Langerhans. Using immunoblotting, we identified three size variants. In line with the results of in silico analysis demonstrating a single transmembrane sequence (amino acids 40-61) at the N-terminus of the full-length protein, FACS cell-surface staining confirmed a mainly extracellular localization of the full-length protein. Sucrose density gradient cell fractionation revealed membrane association of the dominant 50 kDa variant in HepG2 and Rin-5F cells. The finding of a strong arylesterase activity with beta-naphthyl acetate and phenyl acetate of the C20orf3 protein-containing fractions suggests potential involvement of this protein in enzymatic processes. C20orf3 promoter-driven reporter assays, which were verified by gene-specific RT-qPCR (real-time quantitative PCR) showed a strong inhibitory effect of human serum on transcription using the HEK-293 human embryonic kidney cell line. In conclusion, we characterized the structure and expression pattern of the C20orf3 gene product. According to a series of analogies with PON (paraoxonase) family members, we speculate that the C20orf3 gene product represents a new member of this important protein family present at the cellular level.

Relations of adiponectin to levels of metabolic parameters and sexual hormones in elderly type 2 diabetic patients.

BACKGROUND Despite the effective role of adiponectin levels in the predisposition to type 2 diabetes mellitus, the potential impact of adiponectin in manifest type 2 diabetes is less studied. OBJECTIVES This study aimed to determine gender-specific differences regarding the relationship between adiponectin levels and metabolic parameters as well as sex hormones in elderly type 2 diabetics. METHODS Sixty-two elderly type 2 diabetic men (mean age 60 [9] years) and 38 postmenopausal type 2 diabetic women (mean age 64 [9] years) were evaluated in a cross-sectional study. Glycemic control, lipids, sex hormones, adiponectin, and anthropometric parameters were measured in all participants. RESULTS Serum adiponectin was higher in women than in men (P < 0.006). After controlling for age and body mass index, adiponectin concentrations showed a positive correlation with sex hormone-binding globulin and high-density lipoprotein levels (P < 0.001) and a negative correlation with glycated hemoglobin, homeostasis model assessment index for insulin resistance, glucose, C-peptide, and triglyceride levels (P < 0.05) in all patients. In men, adiponectin significantly correlated with serum levels of testosterone (r = 0.420; P < 0.002). In women, negative correlations were observed between adiponectin levels and the fatty liver index (r = -0.492; P < 0.006) and γ-glutamyltransferase (r = -0.432; P < 0.01). CONCLUSIONS High serum adiponectin is a feature of better metabolic control and lipid profile, whereas low adiponectin levels are associated with fatty liver disease in women and low testosterone levels in men with type 2 diabetes.