Entrapped Molecule-Like Europium-Oxide Clusters in Zinc Oxide with Nearly Unaffected Host Structure

Nanocrystalline ZnO sponges doped with 5 mol% EuO_1.5 are obtained by heating metal-salt complex based precursor pastes at 200-900 °C for 3 min. X-ray diffraction, transmission electron microscopy, and extended X-ray absorption fine structure (EXAFS) show that phase separation into ZnO:Eu and c-Eu₂ O₃ takes place upon heating at 700 °C or higher. The unit cell of the clean oxide made at 600 °C shows only ≈0.4% volume increase versus undoped ZnO, and EXAFS shows a ZnO local structure that is little affected by the Eu-doping and an average Eu³⁺ ion coordination number of ≈5.2. Comparisons of 23 density functional theory-generated structures having differently sized Eu-oxide clusters embedded in ZnO identify three structures with four or eight Eu atoms as the most energetically favorable. These clusters exhibit the smallest volume increase compared to undoped ZnO and Eu coordination numbers of 5.2-5.5, all in excellent agreement with experimental data. ZnO defect states are crucial for efficient Eu³⁺ excitation, while c-Eu₂ O₃ phase separation results in loss of the characteristic Eu³⁺ photoluminescence. The formation of molecule-like Eu-oxide clusters, entrapped in ZnO, proposed here, may help in understanding the nature of the unexpected high doping levels of lanthanide ions in ZnO that occur virtually without significant change in ZnO unit cell dimensions.

Fast, Low-Cost Synthesis of ZnO:Eu Nanosponges and the Nature of Ln Doping in ZnO

A low-cost template-free solution chemical route to highly porous nanocrystalline sponges of ZnO-EuO_1.5 with 0-5 mol % Eu is presented. The process uses Zn- and Eu-acetate-nitrate and triethanolamine as precursors in methanol. After evaporation of the solvent and heating at 200 °C for 3 min, crystalline ZnO:Eu sponges with minor amounts of organic residues were obtained. Heating to 400 °C replaced the organics with carbonate, which in its turn was decomposed at temperatures below 600 °C, forming ZnO:Eu sponges. Samples heated to 200-1000 °C for 3 min were studied with XRD, SEM, TEM, TG, XPS, and IR spectroscopy. The ZnO:Eu crystallite sizes could be tuned from below 10 nm for sponges prepared at 200-500 °C, to over 100 nm range at 900 °C, without sintering of the overall microstructure. XRD showed the presence of hexagonal ZnO:Eu (or at 700-1000 °C, ZnO:Eu and cubic Eu₂O₃) as the only phases present. The ZnO:Eu had slightly larger unit cell dimensions than the literature value of ZnO for samples obtained at 200-600 °C, while the unit cells of samples obtained at higher temperatures were quite close to the value of undoped ZnO. XPS showed that Eu was mainly in its 3+ state and well-distributed within the sponges but segregated at the ZnO sponge surface upon heating at 700-1000 °C, in accordance with XRD studies showing Eu₂O₃ formation.

PTPRM, a candidate tumor suppressor gene in small intestinal neuroendocrine tumors

Small intestinal neuroendocrine tumors (SI-NETs) are small, slow growing neoplasms with loss of one copy of chromosome 18 as a common event. Frequently mutated genes on chromosome 18 or elsewhere have not been found so far. The aim of this study was to investigate a possible tumor suppressor role of the transmembrane receptor type tyrosine phosphatase PTPµ (PTPRM at 18p11) in SI-NETs. Immunohistochemistry, quantitative RT-PCR, colony formation assay and quantitative CpG methylation analysis by pyrosequencing were performed. Undetectable/very low levels of PTPRM or aberrant pattern of immunostaining, with both negative and positive areas, were detected in the majority of tumors (33/40), and a significantly reduced mRNA expression in metastases compared to primary tumors was observed. Both the DNA methylation inhibitor 5-aza-2'-deoxycytidine and the S-adenosylhomocysteine hydrolase inhibitor 3-deazaneplanocin A (DZNep) induced PTPRM expression in CNDT2.5 and KRJ-I SI-NET cells. CpG methylation of upstream regulatory regions, the promoter region and the exon 1/intron 1 boundary was detected by pyrosequencing analysis of the two cell lines and not in the analyzed SI-NETs. Overexpression of PTPRM in the SI-NET cell lines reduced cell growth and cell proliferation and induced apoptosis. The tyrosine phosphatase activity of PTPRM was not involved in cell growth inhibition. The results support a role for PTPRM as a dysregulated candidate tumor suppressor gene in SI-NETs and further analyses of the involved mechanisms are warranted.

Lignin Valorization by Cobalt-Catalyzed Fractionation of Lignocellulose to Yield Monophenolic Compounds

Herein, a catalytic reductive fractionation of lignocellulose is presented using a heterogeneous cobalt catalyst and formic acid or formate as a hydrogen donor. The catalytic reductive fractionation of untreated birch wood yields monophenolic compounds in up to 34 wt % yield of total lignin, which corresponds to 76 % of the theoretical maximum yield. Model compound studies revealed that the main role of the cobalt catalyst is to stabilize the reactive intermediates formed during the organosolv pulping by transfer hydrogenation and hydrogenolysis reactions. Additionally, the cobalt catalyst is responsible for depolymerization reactions of lignin fragments through transfer hydrogenolysis reactions, which target the β-O-4' bond. The catalyst could be recycled three times with only negligible decrease in efficiency, showing the robustness of the system.

Decrease of 5-hydroxymethylcytosine and TET1 with nuclear exclusion of TET2 in small intestinal neuroendocrine tumors

BACKGROUND

Small intestinal neuroendocrine tumors (SI-NETs) originate from enterochromaffin cells scattered in the intestinal mucosa of the ileum and jejunum. Loss of one copy of chromosome 18 is the most frequent observed aberration in primary tumors and metastases. The aim of this study was to investigate possible involvement of 5-hydroxymethylcytosine (5hmC), TET1 and TET2 in SI-NETs.

METHODS

The analysis was conducted using 40 primary tumors and corresponding 47 metastases. The level of 5hmC, TET1 and TET2 was analyzed by DNA immune-dot blot assay and immunohistochemistry. Other methods included a colony forming assay, western blotting analysis, and quantitative bisulfite pyrosequencing analysis. The effect of the exportin-1 nuclear transport machinery inhibitors on cell proliferation and apoptosis was also explored using two SI-NET cell lines.

RESULTS

Variable levels of 5hmC and a mosaic staining appearance with a mixture of positive and negative cell nuclei, regardless of cell number and staining strength, was observed overall both in primary tumors and metastases. Similarly aberrant staining pattern was observed for TET1 and TET2. In a number of tumors (15/32) mosaic pattern together with areas of negative staining was also observed for TET1. Abolished expression of TET1 in the tumors did not seem to involve hypermethylation of the TET1 promoter region. Overexpression of TET1 in a colony forming assay supported a function as cell growth regulator. In contrast to 5hmC and TET1, TET2 was also observed in the cytoplasm of all the analyzed SI-NETs regardless of nuclear localization. Treatment of CNDT2.5 and KRJ-I cells with the exportin-1 (XPO1/CRM1) inhibitor, leptomycin B, induced reduction in the cytoplasm and nuclear retention of TET2. Aberrant partitioning of TET2 from the nucleus to the cytoplasm seemed therefore to involve the exportin-1 nuclear transport machinery. Reduced cell proliferation and induction of apoptosis were observed after treatment of CNDT2.5 and KRJ-I cells with leptomycin B or KPT-330 (selinexor).

CONCLUSIONS

SI-NETs are epigenetically dysregulated at the level of 5-hydroxymethylcytosine/ TET1/TET2. We suggest that KPT-330/selinexor or future developments should be considered and evaluated for single treatment of patients with SI-NET disease and also in combinations with somatostatin analogues, peptide receptor radiotherapy, or everolimus.

A role for TET2 in parathyroid carcinoma

Primary hyperparathyroidism (pHPT) is rarely caused by parathyroid carcinoma (PC, <1-5% of pHPT cases). The TET proteins oxidize the epigenetic mark 5-methylcytosine to 5-hydroxymethylcytosine (5hmC) and inactivation by mutation or epigenetic deregulation of TET1 and TET2 play important roles in various cancers. Recently, we found that 5hmC was severely reduced in all of the analyzed PCs and with deranged expression of TET1 for the majority of PCs. Here, we have examined the expression of the TET2 protein in 15 5hmC-negative PCs from patients who had local invasion or metastases. Cell growth and cell migratory roles for TET2 as well as epigenetic deregulated expression were addressed. Immunohistochemistry revealed very low/undetectable expression of TET2 in all PCs and verified for two PCs that were available for western blotting analysis. Knockdown of TET2 in the parathyroid cell line sHPT-1 resulted in increased cell growth and increased cell migration. DNA sequencing of TET2 in PCs revealed two common variants and no obvious inactivating mutations. Quantitative bisulfite pyrosequencing analysis of the TET2 promoter CpG island revealed higher CpG methylation level in the PCs compared to that in normal tissues and treatment of a PC primary cell culture with the DNA methylation inhibitor 5-aza-2'-deoxycytidine caused increased expression of the methylated TET2 gene. Hence, the data suggest that deregulated expression of TET2 by DNA hypermethylation may contribute to the aberrantly low level of 5hmC in PCs and further that TET2 plays a cell growth and cell migratory regulatory role and may constitute a parathyroid tumor suppressor gene.

DcR3, TFF3, and Midkine Are Novel Serum Biomarkers in Small Intestinal Neuroendocrine Tumors

Small intestinal neuroendocrine tumors (SI-NETs) are amine- and peptide-producing neoplasms. Most patients display metastases at the time of diagnosis; they have an unpredictable individual disease course and the tumors are often therapy resistant. Chromogranin A and 5-hydroxyindoleacetic acid are the biomarkers clinically used most often today, but there is a great need for novel diagnostic and prognostic biomarkers and new therapeutic targets. Sixty-nine biomarkers were screened in serum from 23 SI-NET patients and 23 healthy controls using the multiplex proximity ligation assay (PLA). A refined method, the proximity extension assay (PEA), was used to analyze 76 additional biomarkers. Statistical testing and multivariate classification were performed. Immunohistochemistry and ELISA were performed in an extended cohort. Using PLA, 19 biomarkers showed a significant difference in serum concentrations between patients and controls, and PEA revealed a difference in the concentrations of 17 proteins. Multivariate classification analysis revealed decoy receptor 3 (DcR3), trefoil factor 3 (TFF3), and midkine to be good biomarkers for the disease, which was confirmed by ELISA analysis. All 3 biomarkers were expressed in tumor tissue. DcR3 concentrations were elevated in patients with stage IV disease. High concentrations of DcR3 and TFF3 were correlated to poor survival. DcR3, TFF3, and midkine exhibited elevated serum concentrations in SI-NET patients compared to healthy controls, and DcR3 and TFF3 were associated with poor survival. DcR3 seems to be a marker for liver metastases, while TFF3 and midkine may be new diagnostic biomarkers for SI-NETs.

Genetics and epigenetics in small intestinal neuroendocrine tumours

Neuroendocrine tumour of the small intestine (SI-NET), formerly known as midgut carcinoid tumour, is the most common small intestinal malignancy. The incidence is rising, with recent reports of 0.67 per 100 000 in the USA and 1.12 per 100 000 in Sweden. SI-NETs often present a challenge in terms of diagnosis and treatment, as patients often have widespread disease and are beyond cure by surgery. Somatostatin analogues provide the mainstay of medical treatment to control hormonal excess and increase the time to progression. Despite overall favourable prognosis (5-year overall survival of 65%), there is a need to find markers to identify both patients with worse outcome and new targets for therapy. Loss on chromosome 18 has been reported in 60-90% of SI-NETs, but mutated genes on this chromosome have failed detection. Recently, a putative tumour suppressor role has been suggested for TCEB3C occurring at 18q21 (encoding elongin A3), which may undergo epigenetic repression. CDKN1B has recently been revealed as the only recurrently mutated gene in SI-NETs but, with a frequency as low as 8%, its role as a driver in SI-NET development may be questioned. Integrated genomewide analysis including exome and whole-genome sequencing, gene expression, DNA methylation and copy number analysis has identified three novel molecular subtypes of SI-NET with differing clinical outcome. DNA methylation analysis has demonstrated that SI-NETs have significant epigenetic dysregulation in 70-80% of tumours. In this review, we focus on understanding of the genetic, epigenetic and molecular events that lead to development and progression of SI-NETs.

Molecular genetics and epigenetics of nonfamilial (sporadic) parathyroid tumours

Primary hyperparathyroidism (pHPT) is a common endocrine disease characterized by excessive secretion of parathyroid hormone and an increased level of serum calcium. Overall, 80-85% of pHPT cases are due to a benign, single parathyroid adenoma (PA), and 15% to multiglandular disease (multiple adenomas/hyperplasia). Parathyroid carcinoma (PC) is rare, accounting for <0.5-1% of pHPT cases. Secondary hyperparathyroidism (sHPT) is a complication of renal failure, with the development of parathyroid tumours and hypercalcaemia. Recurrent mutations in the MEN1 gene have been confirmed by the whole-exome sequencing in 35% of PAs, suggesting that non-protein-coding genes, regulatory elements or epigenetic derangements may also have roles in the majority of PAs. DNA translocations with cyclin D1 overexpression occur in PAs (8%). In PCs, mutations in CDC73/HRPT2 are common. Activation of the WNT/β-catenin signalling pathway (accumulation of nonphosphorylated β-catenin) by an aberrantly truncated LRP5 receptor has been seen for the majority of investigated PAs and sHPT tumours, and possibly by APC inactivation through promoter methylation in PCs. Promoter methylation of several other genes and repressive histone H3 lysine 27 trimethylation by EZH2 of the HIC1 gene may also contribute to parathyroid tumorigenesis. It is possible that a common pathway exists for parathyroid tumour development. CCND1 (cyclin D1) and EZH2 overexpression, accumulation of nonphosphorylated β-catenin and repression of HIC1 have all been observed to occur in PAs, PCs and sHPT tumours. In addition, hypermethylation has been observed for the same genes in PAs and PCs (e.g. SFRP1, CDKN2A and WT1). Whether β-catenin represents a 'hub' in parathyroid tumour development will be discussed.

A plausible role for actin gamma smooth muscle 2 (ACTG2) in small intestinal neuroendocrine tumorigenesis

BACKGROUND

Small intestinal neuroendocrine tumors (SI-NETs) originate from the enterochromaffin cells in the ileum and jejunum. The knowledge about genetic and epigenetic abnormalities is limited. Low mRNA expression levels of actin gamma smooth muscle 2 (ACTG2) have been demonstrated in metastases relative to primary SI-NETs. ACTG2 and microRNA-145 (miR-145) are aberrantly expressed in other cancers and ACTG2 can be induced by miR-145. The aim of this study was to investigate the role of ACTG2 in small intestinal neuroendocrine tumorigenesis.

METHODS

Protein expression was analyzed in SI-NETs (n = 24) and in enterochromaffin cells by immunohistochemistry. The cell line CNDT2.5 was treated with the histone methyltransferase inhibitor 3-deazaneplanocin A (DZNep), the selective EZH2 inhibitor EPZ-6438, or 5-aza-2'-deoxycytidine, a DNA hypomethylating agent. Cells were transfected with ACTG2 expression plasmid or miR-145. Western blotting analysis, quantitative RT-PCR, colony formation- and viability assays were performed. miR-145 expression levels were measured in tumors.

RESULTS

Eight primary tumors and two lymph node metastases displayed variable levels of positive staining. Fourteen SI-NETs and normal enterochromaffin cells stained negatively. Overexpression of ACTG2 significantly inhibited CNDT2.5 cell growth. Treatment with DZNep or transfection with miR-145 induced ACTG2 expression (>10-fold), but no effects were detected after treatment with EPZ-6438 or 5-aza-2'-deoxycytidine. DZNep also induced miR-145 expression. SI-NETs expressed relatively low levels of miR-145, with reduced expression in metastases compared to primary tumors.

CONCLUSIONS

ACTG2 is expressed in a fraction of SI-NETs, can inhibit cell growth in vitro, and is positively regulated by miR-145. Theoretical therapeutic strategies based on these results are discussed.

5-Hydroxymethylcytosine discriminates between parathyroid adenoma and carcinoma

Background

Primary hyperparathyroidism is characterized by enlarged parathyroid glands due to an adenoma (80–85 %) or multiglandular disease (~15 %) causing hypersecretion of parathyroid hormone (PTH) and generally hypercalcemia. Parathyroid cancer is rare (<1–5 %). The epigenetic mark 5-hydroxymethylcytosine (5hmC) is reduced in various cancers, and this may involve reduced expression of the ten-eleven translocation 1 (TET1) enzyme. Here, we have performed novel experiments to determine the 5hmC level and TET1 protein expression in 43 parathyroid adenomas (PAs) and 17 parathyroid carcinomas (PCs) from patients who had local invasion or metastases and to address a potential growth regulatory role of TET1.

Results

The global 5hmC level was determined by a semi-quantitative DNA immune-dot blot assay in a smaller number of tumors. The global 5hmC level was reduced in nine PCs and 15 PAs compared to four normal tissue samples (p < 0.05), and it was most severely reduced in the PCs. By immunohistochemistry, all 17 PCs stained negatively for 5hmC and TET1 showed negative or variably heterogeneous staining for the majority. All 43 PAs displayed positive 5hmC staining, and a similar aberrant staining pattern of 5hmC and TET1 was seen in about half of the PAs. Western blotting analysis of two PCs and nine PAs showed variable TET1 protein expression levels. A significantly higher tumor weight was associated to PAs displaying a more severe aberrant staining pattern of 5hmC and TET1. Overexpression of TET1 in a colony forming assay inhibited parathyroid tumor cell growth.

Conclusions

5hmC can discriminate between PAs and PCs. Whether 5hmC represents a novel marker for malignancy warrants further analysis in additional parathyroid tumor cohorts. The results support a growth regulatory role of TET1 in parathyroid tissue.

Electronic supplementary material

The online version of this article (doi:10.1186/s13148-016-0197-2) contains supplementary material, which is available to authorized users.

Novel somatic mutations and distinct molecular signature in aldosterone-producing adenomas

Aldosterone-producing adenomas (APAs) are found in 1.5-3.0% of hypertensive patients in primary care and can be cured by surgery. Elucidation of genetic events may improve our understanding of these tumors and ultimately improve patient care. Approximately 40% of APAs harbor a missense mutation in the KCNJ5 gene. More recently, somatic mutations in CACNA1D, ATP1A1 and ATP2B3, also important for membrane potential/intracellular Ca(2) (+) regulation, were observed in APAs. In this study, we analyzed 165 APAs for mutations in selected regions of these genes. We then correlated mutational findings with clinical and molecular phenotype using transcriptome analysis, immunohistochemistry and semiquantitative PCR. Somatic mutations in CACNA1D in 3.0% (one novel mutation), ATP1A1 in 6.1% (six novel mutations) and ATP2B3 in 3.0% (two novel mutations) were detected. All observed mutations were located in previously described hotspot regions. Patients with tumors harboring mutations in CACNA1D, ATP1A1 and ATP2B3 were operated at an older age, were more often male and had tumors that were smaller than those in patients with KCNJ5 mutated tumors. Microarray transcriptome analysis segregated KCNJ5 mutated tumors from ATP1A1/ATP2B3 mutated tumors and those without mutation. We observed significant transcription upregulation of CYP11B2, as well as the previously described glomerulosa-specific gene NPNT, in ATP1A1/ATP2B3 mutated tumors compared to KCNJ5 mutated tumors. In summary, we describe novel somatic mutations in proteins regulating the membrane potential/intracellular Ca(2) (+) levels, and also a distinct mRNA and clinical signature, dependent on genetic alteration.

Exome Sequencing and CNV Analysis on Chromosome 18 in Small Intestinal Neuroendocrine Tumors: Ruling Out a Suspect?

The genetic background in small intestinal neuroendocrine tumors is poorly understood, but several studies have revealed numerical imbalances. Loss of one copy of chromosome 18 is the most frequent genetic aberration in this tumor type, which indirectly suggests that a driver mutation may be present in the remaining allele. The aim of this study was to evaluate the mutation status on chromosome 18 in small intestinal neuroendocrine tumors. DNAs from 7 small intestinal neuroendocrine tumors were subjected to whole exome capture, followed by next generation sequencing and high resolution SNP array followed by copy number variation analysis. Exome capture sequencing generated an average coverage of 50.6-138.2. Only 19 genes were covered less than 8X. No tumor-specific somatic mutation was identified. Genomic profiling revealed loss of chromosome 18 in 5 out of 7 small intestinal neuroendocrine tumors and a number of other aberrancies. Loss of chromosome 18 is the most frequent genetic aberration in small intestinal neuroendocrine tumors, but no evidence for eventual mutations in the remaining allele. This suggests involvement of other mechanisms than point mutations in small intestinal neuroendocrine tumors tumorigenesis.

A review on management discussions of small intestinal neuroendocrine tumors ‘midgut carcinoids’

European Neuroendocrine Tumor Society staging, together with the Ki67 grading system, has appeared as superior for classification of neuroendocrine tumors (NET). The management of small intestinal NET (SI-NET) has been overall controversial. Mesenteric metastases occur also with the smallest SI-NET, and the majority of patients risk to ultimately progress with liver metastases. 68Gallium (somatostatin receptor)/PET/CT has appeared as most sensitive for imaging, and fluorodeoxyglucose-PET is recommended to identify lesions with high proliferation. Our treatment policy for SI-NET is to initiate somatostatin analog treatment, and in order to prevent abdominal complications we recommend early intestinal resection for removal of primary tumors and clearance of lymph node metastases. Liver metastases are liberally treated by resection (or ablation), as this can efficiently palliate carcinoid syndrome-associated symptoms.

Somatic Mutations and Genetic Heterogeneity at the CDKN1B Locus in Small Intestinal Neuroendocrine Tumors

BACKGROUND

Until recently, the genetic landscape of small intestinal neuroendocrine tumors (SI-NETs) was limited to recurrent copy number alterations, most commonly a loss on chromosome 18. Intertumor heterogeneity with nonconcordant genotype in paired primary and metastatic lesions also is described, further contributing to the difficulty of unraveling the genetic enigma of SI-NETs. A recent study analyzing 55 SI-NET exomes nominated CDKN1B (p27) as a haploinsufficient tumor suppressor gene.

METHODS

This study aimed to determine the frequency of CDKN1B inactivation and to investigate genotype-phenotype correlations. It investigated 362 tumors from 200 patients. All samples were resequenced for mutations in CDKN1B using automated Sanger sequencing. The expression of p27 was investigated in 12 CDKN1B mutant and nine wild type tumors.

RESULTS

Some 8.5 % (17/200) of patients had tumors with pathogenic mutations in CDKN1B including 13 insertion deletions, four nonsense variants, and one stop-loss variant. All variants with available nontumoral DNA were classified as somatic. Inter- and intratumor heterogeneity at the CDKN1B locus was detected respectively in six of ten and two of ten patients. Patients with CDKN1B mutated tumors had both heterogeneous disease presentation and diverse prognosis. Expression of the p27 protein did not correlate with CDKN1B mutation status, and no differences in the clinical characteristics between CDKN1B mutated and CDKN1B wild type tumor carriers were found.

CONCLUSION

This study corroborates the finding of CDKN1B as a potential haplo-insufficient tumor suppressor gene characterized by inter- and intratumor heterogeneity in SI-NETs.

Peritoneal carcinomatosis from small intestinal neuroendocrine tumors: Clinical course and genetic profiling

BACKGROUND

One-fifth of all patients with small-intestinal neuroendocrine tumors (SI-NETs) present with or develop peritoneal carcinomatosis (PC). Our aim was to determine the prognosis and genetic profiles of tumors in patients with PC compared with tumors in patients without PC.

METHODS

We included SI-NET patients (cases with PC, n = 73, and controls without PC, n = 468) who underwent operation between 1985 and 2012. The Lyon prognostic index was used to correlate the amount of PC to survival. DNA samples from patients with (n = 8) and without (n = 7) PC were analyzed with a single-nucleotide polymorphism array (HumanOmni2.5 BeadChip, Illumina) to investigate genetic disparities between groups.

RESULTS

Patients with PC had poorer survival (median 5.1 years) than controls (11.1 years). An advanced postoperative Lyon prognostic index was a negative prognostic marker for survival by multivariable analysis (P = .042). Patients with and without PC clustered differently based on loss of heterozygosity and copy number variation data from single-nucleotide polymorphism array of the primary tumors (P = .042).

CONCLUSION

SI-NET patients with PC have poor survival, which diminishes with increasing PC load after surgery. Clustering based on copy number variation and loss of heterozygosity data suggests different genotypes in primary tumors comparing patients with and without PC.

TCEB3C a putative tumor suppressor gene of small intestinal neuroendocrine tumors

Small intestinal neuroendocrine tumors (SI-NETs), formerly known as midgut carcinoids, are rare and slow-growing neoplasms. Frequent loss of one copy of chromosome 18 in primary tumors and metastases has been observed. The aim of the study was to investigate a possible role of TCEB3C (Elongin A3), currently the only imprinted gene on chromosome 18, as a tumor suppressor gene in SI-NETs, and whether its expression is epigenetically regulated. Primary tumors, metastases, the human SI-NET cell line CNDT2.5, and two other cell lines were included. Immunohistochemistry, gene copy number determination by PCR, colony formation assay, western blotting, real-time quantitative RT-PCR, RNA interference, and quantitative CpG methylation analysis by pyrosequencing were performed. A large majority of tumors (33/43) showed very low to undetectable Elongin A3 expression and as expected 89% (40/45) displayed one gene copy of TCEB3C. The DNA hypomethylating agent 5-aza-2'-deoxycytidine induced TCEB3C expression in CNDT2.5 cells, in primary SI-NET cells prepared directly after surgery, but not in two other cell lines. Also siRNA to DNMT1 and treatment with the general histone methyltransferase inhibitor 3-deazaneplanocin A induced TCEB3C expression in a cell type-specific way. CpG methylation at the TCEB3C promoter was observed in all analyzed tissues and thus not related to expression. Overexpression of TCEB3C resulted in a 50% decrease in clonogenic survival of CNDT2.5 cells, but not of control cells. The results support a putative role of TCEB3C as a tumor suppressor gene in SI-NETs. Epigenetic repression of TCEB3C seems to be tumor cell type-specific and involves both DNA and histone methylation.

The histone methyltransferase EZH2, an oncogene common to benign and malignant parathyroid tumors

Primary hyperparathyroidism (pHPT) resulting from parathyroid tumors is a common endocrine disorder with incompletely understood etiology. In renal failure, secondary hyperparathyroidism (sHPT) occurs with multiple tumor development as a result of calcium and vitamin D regulatory disturbance. The aim of this study was to investigate a potential role of the histone 3 lysine 27 methyltransferase EZH2 in parathyroid tumorigenesis. Parathyroid tumors from patients with pHPT included adenomas and carcinomas. Hyperplastic parathyroid glands from patients with HPT secondary to uremia and normal parathyroid tissue specimens were included in this study. Quantitative RT-PCR, western blotting, bisulfite pyrosequencing, colony formation assay, and RNA interference were used. EZH2 was overexpressed in a subset of the benign and in all malignant parathyroid tumors as determined by quantitative RT-PCR and western blotting analyses. Overexpression was explained by EZH2 gene amplification in a large fraction of tumors. EZH2 depletion by RNA interference inhibited sHPT-1 parathyroid cell line proliferation as determined by tritium-thymidine incorporation and colony formation assays. EZH2 depletion also interfered with the Wnt/β-catenin signaling pathway by increased expression of growth-suppressive AXIN2, a negative regulator of β-catenin stability. Indeed, EZH2 contributed to the total level of aberrantly accumulated transcriptionally active (nonphosphoylated) β-catenin in the parathyroid tumor cells. To our knowledge EZH2 gene amplification presents the first genetic aberration common to parathyroid adenomas, secondary hyperplastic parathyroid glands, and parathyroid carcinomas. This supports the possibility of a common pathway in parathyroid tumor development.

Somatic and germline CACNA1D calcium channel mutations in aldosterone-producing adenomas and primary aldosteronism

Adrenal aldosterone-producing adenomas (APAs) constitutively produce the salt-retaining hormone aldosterone and are a common cause of severe hypertension. Recurrent mutations in the potassium channel KCNJ5 that result in cell depolarization and Ca²⁺ influx cause ~40% of these tumors¹. We found five somatic mutations (four altering glycine 403, one altering isoleucine 770) in CACNA1D, encoding a voltage-gated calcium channel, among 43 non-KCNJ5-mutant APAs. These mutations lie in S6 segments that line the channel pore. Both result in channel activation at less depolarized potentials, and glycine 403 mutations also impair channel inactivation. These effects are inferred to cause increased Ca²⁺ influx, the sufficient stimulus for aldosterone production and cell proliferation in adrenal glomerulosa². Remarkably, we identified de novo mutations at the identical positions in two children with a previously undescribed syndrome featuring primary aldosteronism and neuromuscular abnormalities. These findings implicate gain of function Ca²⁺ channel mutations in aldosterone-producing adenomas and primary aldosteronism.

Abstract 1982: TCEB3C (Elongin A3) on chromosome 18 presents a putative tumor suppressor gene of small intestine neuroendocrine tumors

Small intestine neuroendocrine tumors (SI-NETs) arise from the enterochromaffin cells and produce hormones which can cause the carcinoid syndrome. The incidence is increasing and the five-year survival rate is 60-80 %. Loss of one copy of chromosome 18 is a very frequent event in these tumors, supporting the presence of a crucial tumor suppressor gene. This study investigated whether TCEB3C, encoding Elongin A3, presents a putative tumor suppressor gene in SI-NETs. This gene is currently the only known imprinted gene on chromosome 18, requiring only one gene copy inactivation event to fulfill the Knudson hypothesis.

Elongin A3 expression in SI-NETs (n=47) was heterogeneous and negative in most cells. 5-Aza-2’-deoxycytidine induced expression of Elongin A3 in a carcinoid tumor cell line and in tumor derived primary cell cultures, but not in a control cell line. Also the general histone methyltransferase inhibitor 3-deazaneplanocin A induced TCEB3C expression in the carcinoid tumor cell line, but not in control cells suggesting further that the TCEB3C gene was epigenetically suppressed in neuroendocrine tumor cells. The TCEB3C gene encompasses an CpG island and quantitative cytosine CpG methylation analysis will be presented. Furthermore, overexpression of Elongin A3 led to a decrease in clonogenic survival of carcinoid tumor cells, but not of control cells strongly supporting a growth-regulatory role. These results support a putative tumor suppressor role of TCEB3C in neuroendocrine cells of the small intestine.

Citation Format: Katarina Edfeldt, Tanvver Ahmad, Göran Åkerström, Eva Tiensuu Janson, Per Hellman, Peter Stålberg, Peyman Björklund, Gunnar Westin. TCEB3C (Elongin A3) on chromosome 18 presents a putative tumor suppressor gene of small intestine neuroendocrine tumors. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 1982. doi:10.1158/1538-7445.AM2013-1982

Evidence of a stabilizing mutation of β-catenin encoded by CTNNB1 exon 3 in a large series of sporadic parathyroid adenomas

Aberrant accumulation of β-catenin plays an important role in a variety of human neoplasms. This can be caused by stabilizing mutation of β-catenin (CTNNB1, exon 3) or by mutation or deregulated expression of other components of the WNT/β-catenin signaling pathway. Accumulation of non-phosphorylated active β-catenin has been reported to commonly occur in parathyroid adenomas from patients with primary hyperparathyroidism (pHPT), either due to the aberrantly spliced internally truncated WNT receptor LRP5 (LRP5Δ) or to a stabilizing mutation of β-catenin. The S37A mutation was reported to occur in 7.3 % in a single study of parathyroid adenomas, while in other studies no stabilizing mutations of β-catenin exon 3 were identified. The aim of this study was to determine the mutational frequency of the CTNNB1 gene, specifically exon 3 in a large series of parathyroid adenomas. One hundred and eighty sporadic parathyroid adenomas were examined for mutations in exon 3 of CTNNB1 by direct DNA sequencing, utilizing previously published primer sequences. The mutation S33C (TCT>TGT) was detected by direct-DNA sequencing of PCR fragments in 1 out of 180 sporadic parathyroid adenomas (0.68 %). Like serine 37, mutations of serine 33 have been reported in many neoplasms with resulting β-catenin stabilization, enhanced transcription, and oncogenic activities. Immunohistochemical analysis revealed an overexpression of the β-catenin protein in the lone mutant tumor. Taking also previous studies into account we conclude that activating mutations of the regulatory GSK-3β phosphorylation sites serine 33 and 37, encoded by CTNNB1 exon 3, rarely occur in parathyroid adenomas from patients with pHPT.

Comprehensive re-sequencing of adrenal aldosterone producing lesions reveal three somatic mutations near the KCNJ5 potassium channel selectivity filter

Background

Aldosterone producing lesions are a common cause of hypertension, but genetic alterations for tumorigenesis have been unclear. Recently, either of two recurrent somatic missense mutations (G151R or L168R) was found in the potassium channel KCNJ5 gene in aldosterone producing adenomas. These mutations alter the channel selectivity filter and result in Na⁺ conductance and cell depolarization, stimulating aldosterone production and cell proliferation. Because a similar mutation occurs in a Mendelian form of primary aldosteronism, these mutations appear to be sufficient for cell proliferation and aldosterone production. The prevalence and spectrum of KCNJ5 mutations in different entities of adrenocortical lesions remain to be defined.

Materials and Methods

The coding region and flanking intronic segments of KCNJ5 were subjected to Sanger DNA sequencing in 351 aldosterone producing lesions, from patients with primary aldosteronism and 130 other adrenocortical lesions. The specimens had been collected from 10 different worldwide referral centers.

Results

G151R or L168R somatic mutations were identified in 47% of aldosterone producing adenomas, each with similar frequency. A previously unreported somatic mutation near the selectivity filter, E145Q, was observed twice. Somatic G151R or L168R mutations were also found in 40% of aldosterone producing adenomas associated with marked hyperplasia, but not in specimens with merely unilateral hyperplasia. Mutations were absent in 130 non-aldosterone secreting lesions.

KCNJ5 mutations were overrepresented in aldosterone producing adenomas from female compared to male patients (63 vs. 24%). Males with KCNJ5 mutations were significantly younger than those without (45 vs. 54, respectively; p<0.005) and their APAs with KCNJ5 mutations were larger than those without (27.1 mm vs. 17.1 mm; p<0.005).

Discussion

Either of two somatic KCNJ5 mutations are highly prevalent and specific for aldosterone producing lesions. These findings provide new insight into the pathogenesis of primary aldosteronism.

Hypermethylated in cancer 1 (HIC1), a tumor suppressor gene epigenetically deregulated in hyperparathyroid tumors by histone H3 lysine modification

CONTEXT

Primary hyperparathyroidism (pHPT) resulting from parathyroid tumors is a common endocrine disorder with incompletely understood etiology. In renal failure, secondary hyperparathyroidism (sHPT) occurs with multiple tumor development as a result of calcium and vitamin D regulatory disturbance.

OBJECTIVE

The aim of the study was to investigate whether HIC1 may act as a tumor suppressor in the parathyroid glands and whether deregulated expression involves epigenetic mechanisms.

PATIENTS AND METHODS

Parathyroid tumors from patients with pHPT included single adenomas, multiple tumors from the same patient, and cancer. Hyperplastic parathyroid glands from patients with sHPT and hypercalcemia and normal parathyroid tissue specimens were included in the study. Quantitative RT-PCR, bisulfite pyrosequencing, colony formation assay, chromatin immunoprecipitation, and RNA interference was used.

RESULTS

HIC1 was generally underexpressed regardless of the hyperparathyroid disease state including multiple parathyroid tumors from the same patient, and overexpression of HIC1 led to a decrease in clonogenic survival of parathyroid tumor cells. Only the carcinomas showed a high methylation level and reduced HIC1 expression. Cell culture experiments, including use of primary parathyroid tumor cells prepared directly after operation, the general histone methyltransferase inhibitor 3-deazaneplanocin A, chromatin immunoprecipitation, and RNA interference of DNA methyltransferases and EZH2 (enhancer of zeste homolog 2), supported a role of repressive histone H3 modifications (H3K27me2/3) rather than DNA methylation in repression of HIC1.

CONCLUSIONS

The results strongly support a growth-regulatory role of HIC1 in the parathyroid glands and suggest that perturbed expression of HIC1 may represent an early event during tumor development. Repressive histone modification H3K27me2/3 is involved in repression of HIC1 expression in hyperparathyroid tumors.

Comprehensive DNA methylation analysis of benign and malignant adrenocortical tumors

The molecular pathogenesis of benign and malignant adrenocortical tumors (ACT) is incompletely clarified. The role of DNA methylation in adrenocortical tumorigenesis has not been analyzed in an unbiased, systematic fashion. Using the Infinium HumanMethylation27 BeadChip, the DNA methylation levels of 27,578 CpG sites were investigated in bisulfite-modified DNA from 6 normal adrenocortical tissue samples, 27 adrenocortical adenomas (ACA), and 15 adrenocortical carcinomas (ACC). Genes involved in cell cycle regulation, apoptosis, and transcriptional regulation of known or putative importance in the development of adrenal tumors showed significant and frequent hypermethylation. Such genes included CDKN2A, GATA4, BCL2, DLEC1, HDAC10, PYCARD, and SCGB3A1/HIN1. Comparing benign versus malignant ACT, a total of 212 CpG islands were identified as significantly hypermethylated in ACC. Gene expression studies of selected hypermethylated genes (CDKN2A, GATA4, DLEC1, HDAC10, PYCARD, SCGB3A1/HIN1) in 6 normal and 16 neoplastic adrenocortical tissues (10 ACA and 6 ACC), displayed reduced gene expression in benign and malignant ACT versus normal adrenocortical tissue. Treatment with 5-aza-2'-deoxycytidine of adrenocortical cancer H-295R cells increased expression of the hypermethylated genes CDKN2A, GATA4, DLEC1, HDAC10, PYCARD, and SCGB3A1/HIN1. In conclusion, the current study represents the first unbiased, quantitative, genome-wide study of adrenocortical tumor DNA methylation. Genes with altered DNA methylation patterns were identified of putative importance to benign and malignant adrenocortical tumor development.

Different gene expression profiles in metastasizing midgut carcinoid tumors

The genetic events leading the progression of midgut carcinoid tumors are largely unknown. The disease course varies from patient to patient, and there is a lack of reliable prognostic markers. In order to identify genes involved in tumor progression, gene expression profiling was performed on tumor specimens. Samples comprised 18 primary tumors, 17 lymph node (LN) metastases, and seven liver metastases from a total of 19 patients. Patients were grouped according to clinical data and histopathology into indolent or progressive course. RNA was subjected to a spotted oligo microarray and B-statistics were performed. Differentially expressed genes were verified using quantitative real-time PCR. Self-organizing maps demonstrated three clusters: 11 primary tumors separated in one cluster, five LN metastases in another cluster, whereas all seven liver metastases, seven primary, and 12 LN metastases formed a third cluster. There was no correlation between indolent and progressive behavior. The primary tumors with Ki67 >5%, with low frequency of the carcinoid syndrome, and a tendency toward shorter survival grouped together. Primary tumors differed in expression profile from their associated LN metastases; thus, there is evidence for genetic changes from primary tumors to metastases. ACTG2, GREM2, REG3A, TUSC2, RUNX1, TPH1, TGFBR2, and CDH6 were differentially expressed between clusters and subgroups of tumors. The expression profile that assembles tumors as being genetically similar on the RNA expression level may not be concordant with the clinical disease course. This study reveals differences in gene expression profiles and novel genes that may be of importance in midgut carcinoid tumor progression.

The DNA methylome of benign and malignant parathyroid tumors

The role of DNA methylation of CpG islands in parathyroid tumorigenesis has not been analyzed in an unbiased, systematic fashion. DNA was isolated from normal and pathologic parathyroid tissues, bisulphite modified and analyzed using the Infinium HumanMethylation27 BeadChip. Distinct hierarchical clustering of genes with altered DNA methylation profiles in normal and pathologic parathyroid tissue was evident. Comparing normal parathyroid tissue with parathyroid adenomas, 367 genes were significantly altered, while 175 genes significantly differed when comparing parathyroid carcinomas and normal parathyroid tissues. A comparison between parathyroid adenomas and parathyroid carcinomas identified 263 genes with significantly distinct methylation levels. Results were confirmed for certain genes in a validation cohort of 40 parathyroid adenomas by methylation-specific PCR. Genes of known or putative importance in the development of parathyroid tumors showed significant and frequent hypermethylation. DNA hypermethylation of CDKN2B, CDKN2A, WT1, SFRP1, SFRP2, and SFRP4 was associated with reduced gene expression in both benign and malignant parathyroid tumors. Treatment with 5-aza-2'-deoxycytidine of primary cell cultures restores expression of hypermethylated genes in benign and malignant parathyroid tumors. In conclusion, the unbiased, genome-wide study of the parathyroid tumor DNA methylome identified a number of genes with altered DNA methylation patterns of putative importance to benign and malignant parathyroid tumorigenesis.

Common pathogenetic mechanism involving human chromosome 18 in familial and sporadic ileal carcinoid tumors

Serotonin producing endocrine carcinoma of small intestine (ileal carcinoid) is a clinically distinct endocrine tumor. It is generally considered as a sporadic disease and its molecular etiology is poorly understood. We report comprehensive clinical and molecular studies of 55 sporadic and familial patients diagnosed with this condition. Nine pedigrees encompassing 23 affected subjects were established, consistent with autosomal dominant mode of inheritance. Familial and sporadic patients demonstrated indistinguishable clinical pictures. Molecular analyses of 61 tumors from 45 individuals, including eight familial and 37 sporadic patients, aimed at determination of global copy number aberrations using BAC and Illumina SNP arrays and gene expression profiling by Affymetrix chips. Chromosome 18 aberrations were identified in both sporadic and in familial tumors; 100% vs. 38%, respectively. Other, less frequent aberrations were also common for both groups. Global expression profiles revealed no differentially expressed genes. Frequent gain of chromosome 7 was exclusively observed in metastases, when patient matched primary tumors and metastases were compared. Notably, the latter aberration correlated with solid growth pattern morphology (P < 0.01), a histopathological feature that has previously been related to worse prognosis. The clinical and molecular similarities identified between sporadic and familial cases suggest a common pathogenetic mechanism involved in tumor initiation. The familial variant of ileal carcinoid represents a previously unrecognized autosomal dominant inherited tumor disease, which we propose to call Familial Ileal Endocrine Carcinoma (FIEC). Our findings indicate the location of a FIEC tumor suppressor gene near the telomere of 18q, involved in development of inherited and sporadic tumors.

K+ channel mutations in adrenal aldosterone-producing adenomas and hereditary hypertension

Endocrine tumors such as aldosterone-producing adrenal adenomas (APAs), a cause of severe hypertension, feature constitutive hormone production and unrestrained cell proliferation; the mechanisms linking these events are unknown. We identify two recurrent somatic mutations in and near the selectivity filter of the potassium (K(+)) channel KCNJ5 that are present in 8 of 22 human APAs studied. Both produce increased sodium (Na(+)) conductance and cell depolarization, which in adrenal glomerulosa cells produces calcium (Ca(2+)) entry, the signal for aldosterone production and cell proliferation. Similarly, we identify an inherited KCNJ5 mutation that produces increased Na(+) conductance in a Mendelian form of severe aldosteronism and massive bilateral adrenal hyperplasia. These findings explain pathogenesis in a subset of patients with severe hypertension and implicate loss of K(+) channel selectivity in constitutive cell proliferation and hormone production.

Integrative epigenomic and genomic analysis of malignant pheochromocytoma

Epigenomic and genomic changes affect gene expression and contribute to tumor development. The histone modifications trimethylated histone H3 lysine 4 (H3K4me3) and lysine 27 (H3K27me3) are epigenetic regulators associated to active and silenced genes, respectively and alterations of these modifications have been observed in cancer. Furthermore, genomic aberrations such as DNA copy number changes are common events in tumors. Pheochromocytoma is a rare endocrine tumor of the adrenal gland that mostly occurs sporadic with unknown epigenetic/genetic cause. The majority of cases are benign. Here we aimed to combine the genome-wide profiling of H3K4me3 and H3K27me3, obtained by the ChIP-chip methodology, and DNA copy number data with global gene expression examination in a malignant pheochromocytoma sample. The integrated analysis of the tumor expression levels, in relation to normal adrenal medulla, indicated that either histone modifications or chromosomal alterations, or both, have great impact on the expression of a substantial fraction of the genes in the investigated sample. Candidate tumor suppressor genes identified with decreased expression, a H3K27me3 mark and/or in regions of deletion were for instance TGIF1, DSC3, TNFRSF10B, RASSF2, HOXA9, PTPRE and CDH11. More genes were found with increased expression, a H3K4me3 mark, and/or in regions of gain. Potential oncogenes detected among those were GNAS, INSM1, DOK5, ETV1, RET, NTRK1, IGF2, and the H3K27 trimethylase gene EZH2. Our approach to associate histone methylations and DNA copy number changes to gene expression revealed apparent impact on global gene transcription, and enabled the identification of candidate tumor genes for further exploration.

Aberrant WNT/β-catenin signaling in parathyroid carcinoma

Background

Parathyroid carcinoma (PC) is a very rare malignancy with a high tendency to recur locally, and recurrent disease is difficult to eradicate. In most western European countries and United States, these malignant neoplasms cause less than 1% of the cases with primary hyperparathyroidism, whereas incidence as high as 5% have been reported from Italy, Japan, and India. The molecular etiology of PC is poorly understood.

Results

The APC (adenomatous polyposis coli) tumor suppressor gene was inactivated by DNA methylation in five analyzed PCs, as determined by RT-PCR, Western blotting, and quantitative bisulfite pyrosequencing analyses. This was accompanied by accumulation of stabilized active nonphosphorylated β-catenin, strongly suggesting aberrant activation of the WNT/β-catenin signaling pathway in these tumors. Treatment of a primary PC cell culture with the DNA hypomethylating agent 5-aza-2'-deoxycytidine (decitabine, Dacogen(r)) induced APC expression, reduced active nonphosphorylated β-catenin, inhibited cell growth, and caused apoptosis.

Conclusion

Aberrant WNT/β-catenin signaling by lost expression and DNA methylation of APC, and accumulation of active nonphosphorylated β-catenin was observed in the analyzed PCs. We suggest that adjuvant epigenetic therapy should be considered as an additional option in the treatment of patients with recurrent or metastatic parathyroid carcinoma.

MicroRNA profiling of benign and malignant pheochromocytomas identifies novel diagnostic and therapeutic targets

MicroRNAs (miRNAs) are small RNAs ( approximately 22 bp) that post-transcriptionally regulate protein expression and are found to be differentially expressed in a number of human cancers. There is increasing evidence to suggest that miRNAs could be useful in cancer diagnosis, prognosis, and therapy. We performed miRNA microarray expression profiling on a cohort of 12 benign and 12 malignant pheochromocytomas and identified a number of differentially expressed miRNAs. These results were validated in a separate cohort of ten benign and ten malignant samples using real-time quantitative RT-PCR; benign samples had a minimum follow-up of at least 2 years. It was found that IGF2 as well as its intronic miR-483-5p was over-expressed, while miR-15a and miR-16 were under-expressed in malignant tumours compared with benign tumours. These miRNAs were found to be diagnostic and prognostic markers for malignant pheochromocytoma. The functional role of miR-15a and miR-16 was investigated in vitro in the rat PC12 pheochromocytoma cell line, and these miRNAs were found to regulate cell proliferation via their effect on cyclin D1 and apoptosis. These data indicate that miRNAs play a pivotal role in the biology of malignant pheochromocytoma, and represent an important class of diagnostic and prognostic biomarkers and therapeutic targets warranting further investigation.

Recurrent genomic alterations in benign and malignant pheochromocytomas and paragangliomas revealed by whole-genome array comparative genomic hybridization analysis

Pheochromocytomas and abdominal paragangliomas are adrenal and extra-adrenal catecholamine-producing tumours. They arise due to heritable cancer syndromes, or more frequently occur sporadically due to an unknown genetic cause. The majority of cases are benign, but malignant tumours are observed. Previous comparative genomic hybridization (CGH) and loss of heterozygosity studies have shown frequent deletions of chromosome arms 1p, 3q and 22q in pheochromocytomas. We applied high-resolution whole-genome array CGH on 53 benign and malignant pheochromocytomas and paragangliomas to narrow down candidate regions as well as to identify chromosomal alterations more specific to malignant tumours. Minimal overlapping regions (MORs) were identified on 16 chromosomes, with the most frequent MORs of deletion (> or = 32%) occurring on chromosome arms 1p, 3q, 11p/q, 17p and 22q, while the chromosome arms 1q, 7p, 12q and 19p harboured the most common MORs of gain (> or = 14%). The most frequent MORs (61-75%) in the pheochromocytomas were identified at 1p, and the four regions of common losses encompassed 1p36, 1p32-31, 1p22-21 and 1p13. Tumours that did not show 1p loss generally demonstrated aberrations on chromosome 11. Gain of chromosomal material was significantly more frequent among the malignant cases. Moreover, gain at 19q, trisomy 12 and loss at 11q were positively associated with malignant pheochromocytomas, while 1q gain was commonly observed in the malignant paragangliomas. Our study revealed novel and narrow recurrent chromosomal regions of loss and gain at several autosomes, a prerequisite for identifying candidate tumour suppressor genes and oncogenes involved in the development of adrenal and extra-adrenal catecholamine-producing tumours.

Expression and association of TRPC subtypes with Orai1 and STIM1 in human parathyroid

The mechanism behind Ca(2)(+) entry into the parathyroid cells has been widely debated, and the molecular identities of the responsible ion channels have not been established yet. In this study, we show that the parathyroid cells lack voltage-operated Ca(2)(+) channels. Passive store depletion by thapsigargin, on the other hand, induces a large non-voltage-activated non-selective cation current. The increase in intracellular Ca(2)(+) caused by thapsigargin is attenuated by 2-aminoethoxydiphenyl borate, a blocker of store-operated Ca(2)(+) entry (SOCE). Candidate molecules for non-voltage-operated Ca(2)(+) signaling were investigated. These included members of the transient receptor potential canonical (TRPC) ion channel family, as well as Ca(2)(+) release-activated Ca(2)(+) modulator 1 (Orai1) and stromal interaction molecule 1 (STIM1) that are key proteins in the SOCE pathway. Using RT-PCR screening, quantitative real-time PCR, and western blot, we showed expression of TRPC1, TRPC4, and TRPC6; Orai1; and STIM1 genes and proteins in normal and adenomatous human parathyroid tissues. Furthermore, co-immunoprecipitation experiments demonstrated a ternary complex of TRPC1-Orai1-STIM1, supporting a physical interaction between these molecules in human parathyroid.

Identification of Achaete-scute complex-like 1 (ASCL1) target genes and evaluation of DKK1 and TPH1 expression in pancreatic endocrine tumours

Background

ASCL1 role in pancreatic endocrine tumourigenesis has not been established. Recently it was suggested that ASCL1 negatively controls expression of the Wnt signalling antagonist DKK1. Notch signalling regulates expression of TPH1, the rate limiting enzyme in the biosyntesis of serotonin. Understanding the development and proliferation of pancreatic endocrine tumours (PETs) is essential for the development of new therapies.

Methods

ASCL1 target genes in the pancreatic endocrine tumour cell line BON1 were identified by RNA interference and microarray expression analysis. Protein expressions of selected target genes in PETs were evaluated by immunohistochemistry.

Results

158 annotated ASCL1 target genes were identified in BON1 cells, among them DKK1 and TPH1 that were negatively regulated by ASCL1. An inverse relation of ASCL1 to DKK1 protein expression was observed for 15 out of 22 tumours (68%). Nine tumours displayed low ASCL1/high DKK1 and six tumours high ASCL1/low DKK1 expression. Remaining PETs showed high ASCL1/high DKK1 (n = 4) or low ASCL1/low DKK1 (n = 3) expression. Nine of twelve analysed PETs (75%) showed TPH1 expression with no relation to ASCL1.

Conclusion

A number of genes with potential importance for PET tumourigenesis have been identified. ASCL1 negatively regulated the Wnt signalling antagonist DKK1, and TPH1 expression in BON1 cells. In concordance with these findings DKK1 showed an inverse relation to ASCL1 expression in a subset of PETs, which may affect growth control by the Wnt signalling pathway.

Two polypyrimidine tracts in the nitric oxide synthase 2 gene: similar regulatory sequences with different properties

We reported previously that the polymorphic polypyrimidine CCTTT-microsatellite in the regulatory region of nitric oxide synthase 2 (NOS2) bound nuclear proteins in vitro. In the present work, we aimed to characterize and investigate a potential regulatory role of the CCTTT-microsatellite in NOS2 expression. Therefore, we performed gel-shift, S1-nuclease, and chromatin immunoprecipitation (ChIP) assays. In vitro experiments showed that the microsatellite formed triplex-DNA both with and without superhelical constraint. We also found that the CCTTT-microsatellite and an apparently similar CT-repeat in the first intron of NOS2 were specifically cleaved by S1-nuclease, when cloned into a supercoiled plasmid. In vitro data suggested that the CCTTT-microsatellite bound both polypyrimidine tract-binding protein (PTBP1) and heterogeneous nuclear ribonucleoprotein K (hnRNPK). On the contrary, ChIP revealed binding of PTBP1 and hnRNPK rather to the CT-repeat in the first intron than to the CCTTT-microsatellite. Enrichment for RNA polymerase II and acetylated histones H3 and H4 was also detected at the intronic site. We suggest that both PTBP1 and hnRNPK binds the single strand of the triplex-DNA formed at the CT-repeat in the first intron and that this interaction could be involved in the regulation of NOS2 expression.

Stathmin as a marker for malignancy in pheochromocytomas

Pheochromocytomas of the adrenal medulla may be life-threatening catecholamine-producing tumors which are malignant in about 10% of cases. Differential diagnosis between malignant and benign tumors is dependent on the development of metastasis or extensive local invasion. A number of genetic aberrations have been described in pheochromocytomas, but no marker associated to malignancy has been reported. We applied an expression microarray containing 7770 cDNA clones and analysed the expression profiles in eleven tumors compared to normal adrenal medulla. Stathmin (STMN1, Op18) was most conspiciously overexpressed among the differentially expressed genes. RT-PCR analysis further confirmed mRNA overexpression, 6 to 8-fold for benign and malignant tumors, and 16-fold for metastases. Stathmin protein overexpression was observed by immunohistochemistry, and distinct differential protein expression between benign and malignant/metastasis specimens was confirmed by Western blot analysis. The results introduce stathmin as a possible diagnostic marker for malignant pheochromocytomas, and further evaluations are warranted.

The internally truncated LRP5 receptor presents a therapeutic target in breast cancer

Background

Breast cancer is a common malignant disease, which may be caused by a number of genes deregulated by genomic or epigenomic events. Deregulated WNT/β-catenin signaling with accumulation of β-catenin is common in breast tumors, but mutations in WNT signaling pathway components have been rare. An aberrantly spliced internally truncated LRP5 receptor (LRP5Δ666–809, LRP5Δ) was shown recently to be resistant to DKK1 inhibition, and was required for β-catenin accumulation in hyperparathyroid tumors and parathyroid tumor growth.

Methodology/Principal Findings

Here we show, by reverse transcription PCR and Western blot analysis, that LRP5Δ is frequently expressed in breast tumors of different cancer stage (58–100%), including carcinoma in situ and metastatic carcinoma. LRP5Δ was required in MCF7 breast cancer cells for the non-phosphorylated active β-catenin level, transcription activity of β-catenin, cell growth in vitro, and breast tumor growth in a xenograft SCID mouse model. WNT3 ligand, but not WNT1 and WNT3A augmented the endogenous β-catenin activity of MCF7 cells in a DKK1-insensitive manner. Furthermore, an anti-LRP5 antibody attenuated β-catenin activity, inhibited cell growth, and induced apoptosis in LRP5Δ-positive MCF7 and T-47D breast cancer cells, but not in control cells.

Conclusions/Significance

Our results suggest that the LRP5Δ receptor is strongly implicated in mammary gland tumorigenesis and that its aberrant expression present an early event during disease progression. LRP5 antibody therapy may have a significant role in the treatment of breast cancer.

Type I membrane klotho expression is decreased and inversely correlated to serum calcium in primary hyperparathyroidism

CONTEXT

The type I membrane protein Klotho was recently shown to mediate PTH secretion in parathyroid cells in response to low extracellular calcium. In contrast, Klotho inhibits PTH secretion indirectly through the action of fibroblast growth factor-23. Abnormal Klotho expression in parathyroid disorders remains to be elucidated.

OBJECTIVE

The aim of the study was to determine: 1) Klotho expression in parathyroid adenomas from patients with primary hyperparathyroidism (pHPT) compared to normal tissue; and 2) its relation to the serum calcium and PTH levels.

DESIGN

Surgically removed parathyroid glands (n = 40) and four normal parathyroid tissue specimens were analyzed for Klotho mRNA and protein levels by quantitative real-time PCR and immunohistochemistry. In vitro effects of calcium on Klotho mRNA expression were studied in bovine parathyroid cells.

RESULTS

Klotho mRNA levels were significantly decreased (n = 23) or undetectable (n = 17) in parathyroid adenomas compared to normal tissues (P < 0.001). Reduced Klotho protein expression was confirmed by immunohistochemistry. Klotho mRNA levels were inversely correlated to serum calcium (r = -0.97; P < 0.0001), and calcium dose-dependently decreased Klotho mRNA expression in normal parathyroid cells in vitro (P < 0.01). Serum calcium was the only significant marker of Klotho expression in multivariate analysis with calcium, phosphate, PTH, and adenoma weight as independent variables.

CONCLUSIONS

Parathyroid Klotho expression is decreased or undetectable in pHPT. We provide evidence that 1) serum calcium is strongly associated with parathyroid Klotho expression in pHPT; and 2) abnormal PTH secretion in hypercalcemic pHPT subjects is mediated by Klotho-independent mechanisms.

Stabilizing mutation of CTNNB1/beta-catenin and protein accumulation analyzed in a large series of parathyroid tumors of Swedish patients

Background

Aberrant accumulation of β-catenin plays an important role in a variety of human neoplasms. We recently reported accumulation of β-catenin in parathyroid adenomas from patients with primary hyperparathyroidism (pHPT). In CTNNB1 exon 3, we detected a stabilizing mutation (S37A) in 3 out of 20 analyzed adenomas. The aim of the present study was to determine the frequency and zygosity of mutations in CTNNB1 exon 3, and β-catenin accumulation in a large series of parathyroid adenomas of Swedish patients.

Results

The mutation S37A (TCT > GCT) was detected by direct DNA sequencing of PCR fragments in 6 out of 104 sporadic parathyroid adenomas (5.8%). Taking our previous study into account, a total of 9 out of 124 (7.3%) adenomas displayed the same mutation. The mutations were homozygous by DNA sequencing, restriction enzyme cleavage, and gene copy number determination using the GeneChip 500 K Mapping Array Set. All tumors analyzed by immunohistochemistry, including those with mutation, displayed aberrant β-catenin accumulation. Western blotting revealed a slightly higher expression level of β-catenin and nonphosphorylated active β-catenin in tumors with mutation compared to those without. Presence of the mutation was not related to distinct clinical characteristics.

Conclusion

Aberrant accumulation of β-catenin is very common in parathyroid tumors, and is caused by stabilizing homozygous mutation in 7.3% of Swedish pHPT patients.

Autoimmune polyendocrine syndrome type 1 and NALP5, a parathyroid autoantigen

BACKGROUND

Autoimmune polyendocrine syndrome type 1 (APS-1) is a multiorgan autoimmune disorder caused by mutations in AIRE, the autoimmune regulator gene. Though recent studies concerning AIRE deficiency have begun to elucidate the molecular pathogenesis of organ-specific autoimmunity in patients with APS-1, the autoantigen responsible for hypoparathyroidism, a hallmark of APS-1 and its most common autoimmune endocrinopathy, has not yet been identified.

METHODS

We performed immunoscreening of a human parathyroid complementary DNA library, using serum samples from patients with APS-1 and hypoparathyroidism, to identify patients with reactivity to the NACHT leucine-rich-repeat protein 5 (NALP5). Subsequently, serum samples from 87 patients with APS-1 and 293 controls, including patients with other autoimmune disorders, were used to determine the frequency and specificity of autoantibodies against NALP5. In addition, the expression of NALP5 was investigated in various tissues.

RESULTS

NALP5-specific autoantibodies were detected in 49% of the patients with APS-1 and hypoparathyroidism but were absent in all patients with APS-1 but without hypoparathyroidism, in all patients with other autoimmune endocrine disorders, and in all healthy controls. NALP5 was predominantly expressed in the cytoplasm of parathyroid chief cells.

CONCLUSIONS

NALP5 appears to be a tissue-specific autoantigen involved in hypoparathyroidism in patients with APS-1. Autoantibodies against NALP5 appear to be highly specific and may be diagnostic for this prominent component of APS-1.

Evaluation of CDKN2C/p18, CDKN1B/p27 and CDKN2B/p15 mRNA expression, and CpG methylation status in sporadic and MEN1-associated pancreatic endocrine tumours

OBJECTIVE

Menin, encoded by the multiple endocrine neoplasia type 1 (MEN1) gene at 11q13, enhances transcription of the cyclin-dependent kinase inhibitors (CDIs), CDKN2C (p18) and CDKN1B (p27) in mouse pancreatic islets, and inactivation of menin reduced CDKN2B (p15) expression in this mouse model. Here, we have compared the relative mRNA expression level and CpG methylation status of p18, p27 and p15 in 18 pancreatic endocrine tumours (PETs) with or without MEN1 gene mutations.

DESIGN

Real-time quantitative PCR, DNA sequencing and pyrosequencing methylation analysis were employed.

RESULTS

The p18 gene was expressed in 15 out of the 18 analysed PETs. The expression level was within the range of the normal pancreatic tissues or higher. Of the three remaining tumours with no expression, two displayed loss of heterozygocity (LOH) at 11q13, one derived from a MEN1 patient. The p27 gene was expressed in all PETs at a level higher than the normal pancreatic tissues, except for one tumour. Promoter methylation was not detected for p18 and p27. p15 expression was undetectable in 8/18 (44%) of the PETs, and no general relations to tumour syndrome, malignancy or MEN1 gene mutations were evident. This was not due to homozygous gene deletions, but the p15 promoter was hypermethylated in two insulinomas. No mutations were found in the p15 gene.

CONCLUSIONS

Expression of p15, p18 and p27 was not generally related to the MEN1 gene mutational status of the investigated 18 PETs. The p15 gene was silenced by promoter hypermethylation in two tumours. Dysregulation of menin and the CDIs are important in PET tumorigenesis, and their interrelations remain to be elucidated.

An LRP5 receptor with internal deletion in hyperparathyroid tumors with implications for deregulated WNT/beta-catenin signaling

BACKGROUND

Hyperparathyroidism (HPT) is a common endocrine disorder with incompletely understood etiology, characterized by enlarged hyperactive parathyroid glands and increased serum concentrations of parathyroid hormone and ionized calcium. We have recently reported activation of the Wnt signaling pathway by accumulation of beta-catenin in all analyzed parathyroid tumors from patients with primary HPT (pHPT) and in hyperplastic parathyroid glands from patients with uremia secondary to HPT (sHPT). Mechanisms that may account for this activation have not been identified, except for a few cases of beta-catenin (CTNNB1) stabilizing mutation in pHPT tumors.

METHODS AND FINDINGS

Reverse transcription PCR and Western blot analysis showed expression of an aberrantly spliced internally truncated WNT coreceptor low-density lipoprotein receptor-related protein 5 (LRP5) in 32 out of 37 pHPT tumors (86%) and 20 out of 20 sHPT tumors (100%). Stabilizing mutation of CTNNB1 and expression of the internally truncated LRP5 receptor was mutually exclusive. Expression of the truncated LRP5 receptor was required to maintain the nonphosphorylated active beta-catenin level, transcription activity of beta-catenin, MYC expression, parathyroid cell growth in vitro, and parathyroid tumor growth in a xenograft severe combined immunodeficiency (SCID) mouse model. WNT3 ligand and the internally truncated LRP5 receptor strongly activated transcription, and the internally truncated LRP5 receptor was insensitive to inhibition by DKK1.

CONCLUSIONS

The internally truncated LRP5 receptor is strongly implicated in deregulated activation of the WNT/beta-catenin signaling pathway in hyperparathyroid tumors, and presents a potential target for therapeutic intervention.