Mutational analysis of p27 (CDKN1B) and p18 (CDKN2C) in sporadic pancreatic endocrine tumors argues against tumor-suppressor function

Pancreatic endocrine tumors (PETs) arise sporadically or are associated with multiple endocrine neoplasia type 1 (MEN1) syndrome or von Hippel-Lindau syndrome. About 90% of patients with familial MEN1 display detectable MEN1 gene (menin) mutations. The cyclin-dependent kinase inhibitor p27 (CDKN1B) is a downstream target of menin and has been recently shown to be responsible for the multiple endocrine neoplasia-like syndrome in rats, where affected animals develop multiple tumors and hyperplasia in endocrine tissues, including the pancreatic islets of Langerhans. A germline nonsense truncation mutation of p27 has been recently described in a suspected MEN1 family without MEN1 mutation, raising the possibility that p27 mutation could be responsible for MEN1 phenotype. Somatic MEN1 mutations occur at low frequency in sporadic PETs; here, we subjected p27 to mutational analysis in 27 sporadic PETs. As an additional menin target, analysis of the p18 (CDKN2C) gene was included. In the p27 gene, one common polymorphism (V109G) and one novel polymorphism (g/a) in the noncoding part of exon 2 were identified. Three known polymorphisms were found in the p18 gene. These data suggest that p27 and p18 are unlikely to present classic tumor-suppressor genes in sporadic PETs.

Fibroblast growth factor-23 regulates parathyroid hormone and 1alpha-hydroxylase expression in cultured bovine parathyroid cells

Fibroblast growth factor-23 (FGF23) is a circulating factor that decreases serum levels of inorganic phosphate (Pi) as well as 1,25-dihydroxyvitamin D(3). Recent studies also suggest a correlation between serum levels of FGF23 and parathyroid hormone (PTH) in patients with chronic kidney disease. It is, however, unknown whether FGF23 directly modulates PTH expression, or whether the correlation is secondary to abnormalities in Pi and vitamin D metabolism. The objective of the current study was therefore to elucidate possible direct effects of FGF23 on bovine parathyroid cells in vitro. Treatment of parathyroid cells with a stabilized form of recombinant FGF23 (FGF23(R176Q)) induced a rise in early response gene-1 mRNA transcripts, a marker of FGF23 signaling. FGF23(R176Q) potently and dose-dependently decreased the PTH mRNA level within 12 h. In agreement, FGF23(R176Q) also decreased PTH secretion into conditioned media. In contrast, FGF23(R176Q) dose-dependently increased 1alpha-hydroxylase expression within 3 h. FGF23 (R176Q) did not affect cell viability nor induce apoptosis, whereas a small but significant increase in cell proliferation was found. We conclude that FGF23 is a negative regulator of PTH mRNA expression and secretion in vitro. Our data suggest that FGF23 may be a physiologically relevant regulator of PTH. This defines a novel function of FGF23 in addition to the previously established roles in controlling vitamin D and Pi metabolism.

Potentiating effects of nonactive/active vitamin D analogues and ketoconazole in parathyroid cells

BACKGROUND AND OBJECTIVE

1,25-dihydroxyvitamin D(3)[1alpha,25(OH)(2)D(3), calcitriol], and its less calcaemic synthetic analogues have therapeutic potential in several diseases, including hyperparathyroidism (HPT). We have suggested that non-1alpha-hydroxylated (nonactive) vitamin D analogues may present an alternative in tumour cells expressing 25-hydroxyvitamin D(3) 1alpha-hydroxylase (1alpha-hydroxylase). The aim of this study was to investigate biological effects of a non-1alpha-hydroxylated vitamin D analogue in normal and tumour parathyroid cells.

PATIENTS AND METHODS

Effects of vitamin D analogues and ketoconazole on parathyroid hormone (PTH) secretion (radioimmunoassay) and PTH mRNA expression (reverse transcription-polymerase chain reaction) were studied in primary bovine parathyroid cells. Proliferation of tumour cells isolated from HPT patients was determined by thymidine incorporation.

RESULTS

EB1285, non-1alpha-hydroxylated precursor of the vitamin D analogue EB1089, suppressed PTH secretion and PTH mRNA level as well as increased expression of 25-hydroxyvitamin D(3)-24-hydroxylase (24-hydroxylase) in bovine parathyroid cells. EB1285 also inhibited cell proliferation of parathyroid tumour cells from primary (pHPT) and secondary HPT (sHPT) patients. Combined treatment with the cytochrome P450-dependent enzyme inhibitor ketoconazole and EB1285 or with active vitamin D compounds potentiated the suppressive effect on PTH secretion from bovine parathyroid cells. Ketaconazole alone displayed PTH suppression and increased 24-hydroxylase expression.

CONCLUSION

The results support the idea that a non-1alpha-hydroxylated vitamin D analogue may elicit vitamin D receptor (VDR) effects in 1alpha-hydroxylase expressing parathyroid tumour cells. Further studies are warranted to elucidate whether precursor vitamin D analogues as well as inhibitors of 24-hydroxylase present therapeutic alternatives in patients suffering from HPT.

Activated β-catenin in the novel human parathyroid tumor cell line sHPT-1

Misregulation of the Wnt/beta-catenin signalling pathway is involved in the development and progression of many cancers. Recently, we presented evidence for aberrant accumulation of non-phosphorylated (stabilized) beta-catenin in benign parathyroid tumors from patients with primary hyperparathyroidism (pHPT) or HPT secondary to uremia (sHPT). Here we have used a human parathyroid hormone (PTH)-producing cell line (sHPT-1), established from a hyperplastic parathyroid gland removed at operation of a patient with sHPT, to further investigate the potential importance of beta-catenin in parathyroid tumorigenesis. Our studies demonstrate that efficient and specific knockdown of beta-catenin by small interfering RNA (siRNA) markedly decreased endogenous beta-catenin transcriptional activity as well as expression of the Wnt/beta-catenin target genes cyclin D1 and c-myc, known to be overexpressed in a substantial fraction of parathyroid tumors. Furthermore, siRNA to beta-catenin inhibited cellular growth and induced cell death. Growth and survival of the parathyroid tumor cells are thus dependent on maintained expression level of beta-catenin. The Wnt/beta-catenin signalling pathway, and beta-catenin in particular, presents a potential therapeutic target for HPT.

Cyclin-dependent kinase 4 (CDK4) expression in pancreatic endocrine tumors

BACKGROUND/AIMS

Pancreatic endocrine tumors (PETs) occur sporadically, in association with the multiple endocrine neoplasia type 1 (MEN1) and the von Hippel-Lindau syndromes. CDK4 is central to the cell cycle control in pancreatic beta cells, and we have assessed whether CDK4 expression is deregulated in 18 human sporadic or familial PETs.

METHODS

Real-time quantitative PCR, immunohistochemistry, DNA sequencing, and Western blot analysis were used.

RESULTS

CDK4 mRNA was expressed in all PETs within the range of the arbitrary control. CDK4 protein was absent in normal pancreatic islets but distinctly expressed in all PETs as determined by immunohistochemistry. CDK4 expression was confirmed by Western blot analysis. No significant differences of CDK4 expression were observed between the groups of benign and malignant PETs or between tumors with or without MEN1 gene mutations. CDK4 expression was not due to gene amplification, and no mutations were identified in coding exons and RNA splice sites. c-Myc is known to be overexpressed in PETs and directly augments CDK4 expression in other cell types. Analysis of consecutive tissue sections for CDK4 and c-Myc showed overlapping homo- or heterogeneous immunostaining in all 18 PETs.

CONCLUSION

We conclude that CDK4 and c-Myc is generally expressed in benign and malignant PETs, and regardless of MEN1 mutational status. Targeting of CDK4 may present an alternative to traditional chemotherapy of PETs in the future.

Mutational analyses of WNT7A and HDAC11 as candidate tumour suppressor genes in sporadic malignant pancreatic endocrine tumours

OBJECTIVE

We and others have reported loss of heterozygosity (LOH) on chromosome 3p25 in sporadic malignant pancreatic endocrine tumours (PETs). A common region of deletion on chromosome 3p25 contains numerous genes, including VHL and PPARgamma, that have been excluded previously as candidate tumour suppressor genes by DNA sequencing analysis. We have analysed whether WNT7A or HDAC11 was biallelically inactivated in a group of well-characterized PETs.

PATIENTS AND DESIGN

Ten PETs from eight patients were selected from a previous study, where LOH on chromosome 3p25 was found in 11 out of 22 sporadic PETs. These tumours were examined for inactivating mutations of WNT7A and HDAC11 by direct sequencing of all exons and intron-exon boundaries. Inactivation of WNT7A expression by aberrant CpG island methylation and WNT7A protein expression were evaluated by methylation-specific polymerase chain reaction (PCR) and immunohistochemistry, respectively. HDAC11 protein expression was also examined.

RESULTS

No point mutations, deletion or insertions were detected in either WNT7A or HDAC11 in any of the PETs. Two polymorphisms were identified in the third exon of the WNT7A gene. CpG methylation of the WNT7A gene was not detected and the WNT7A and HDAC11 proteins were normally expressed.

CONCLUSION

The absence of tumour-specific somatic events in WNT7A and HDAC11 suggests that these genes are unlikely to have a classical tumour suppressor gene role in sporadic malignant PETs. The putative 3p25 tumour suppressor remains to be identified.

Accumulation of nonphosphorylated beta-catenin and c-myc in primary and uremic secondary hyperparathyroid tumors

CONTEXT

Primary hyperparathyroidism (pHPT) resulting from parathyroid tumors is a common endocrine disorder with incompletely understood etiology, affecting about 1% of the adult population, with an even higher prevalence for elderly individuals. In renal failure, secondary hyperparathyroidism (sHPT) occurs with multiple tumor development as a result of calcium and vitamin D regulatory disturbance.

OBJECTIVE

Aberrant Wnt/beta-catenin signaling with accumulation of beta-catenin in the cytoplasm/nucleus is involved in the development of a variety of neoplasms. The aim of this study was to evaluate whether the Wnt/beta-catenin signaling pathway is activated in parathyroid adenomas of pHPT and in hyperplastic glands from uremic patients with sHPT.

DESIGN

Immunohistochemistry, Western blotting, real-time quantitative RT-PCR, and DNA sequencing were performed.

RESULTS

beta-Catenin was accumulated in all analyzed parathyroid tumors (n = 47) from patients with pHPT and from patients with HPT secondary to uremia. The accumulation included nonphosphorylated, stabilized (transcriptionally active) beta-catenin. The overexpression was not related to increased beta-catenin mRNA levels. A protein-stabilizing mutation in exon 3 of beta-catenin (S37A) was detected in three of 20 pHPT tumors (15%). No mutation was detected in secondary hyperplastic glands (n = 20), and no evidence for truncated adenomatosis polyposis coli proteins was found in adenomas and secondary hyperplastic glands. Mutations in other Wnt signaling components leading to beta-catenin accumulation, other than in beta-catenin itself, are therefore anticipated. The beta-catenin target gene c-myc was overexpressed in a substantial fraction of the parathyroid tumors.

CONCLUSION

Our results strongly suggest that modifications in the Wnt/beta-catenin signaling pathway may be involved in the development of hyperparathyroidism.

Parathyroid glands in calcium regulation and human disease

In humans and other land-living vertebrates, the parathyroids are known to have an overall regulatory role with action as a thermostat in the systemic calcium homeostasis to ensure tight regulation of serum calcium concentrations and appropriate skeletal mineralization. Parathyroid hormone (PTH) is an 84-amino-acid peptide, synthesized and released by parathyroid chief cells in response to hypocalcemia. PTH mobilizes calcium by increasing calcium resorption from bone and by raising calcium reabsorption in the proximal kidney tubule. Treatment with active vitamin D can increase vitamin D receptor expression, inhibit growth of parathyroid tumors, and reduce PTH levels in patients with hyperparathyroidism (HPT). Newly developed vitamin D analogues with reduced calcemic effects and with more pronounced antiproliferative effect may provide new favorable treatment for reversal of HPT.

Adsorption and Solar Light Decomposition of Acetone on Anatase TiO2 and Niobium Doped TiO2 Thin Films

Adsorption and solar light decomposition of acetone was studied on nanostructured anatase TiO2 and Nb-doped TiO2 films made by sol-gel methods (10 and 20 mol % NbO2.5). A detailed characterization of the film materials show that films contain only nanoparticles with the anatase modification with pentavalent Nb oxide dissolved into the anatase structure, which is interpreted as formation of substituted Nb=O clusters in the anatase lattice. The Nb-doped films displayed a slight yellow color and an enhanced the visible light absorption with a red-shift of the optical absorption edge from 394 nm for the pure TiO2 film to 411 nm for 20 mol % NbO2.5. In-situ Fourier transform infrared (FTIR) transmission spectroscopy shows that acetone adsorbs associatively with eta1-coordination to the surface cations on all films. On Nb-doped TiO2 films, the carbonyl bonding to the surface is stabilized, which is evidenced by a lowering of the nu(C=O) frequency by about 20 cm(-1) to 1672 cm(-1). Upon solar light illumination acetone is readily decomposed on TiO2, and stable surface coordinated intermediates are formed. The decomposition rate is an order of magnitude smaller on the Nb-doped films despite an enhanced visible light absorption in these materials. The quantum yield is determined to be 0.053, 0.004 and 0.002 for the pure, 10% Nb:TiO2, and 20%Nb:TiO2, respectively. Using an interplay between FTIR and DFT calculations we show that the key surface intermediates are bidentate bridged formate and carbonate, and H-bonded bicarbonate, respectively, whose concentration on the surface can be correlated with their heats of formation and bond strength to coordinatively unsaturated surface Ti and Nb atoms at the surface. The oxidation rate of these intermediates is substantially slower than the initial acetone decomposition rate, and limits the total oxidation rate at t>7 min on TiO2, while no decrease of the rate is observed on the Nb-doped films. The rate of degradation of key surface intermediates is different on pure TiO2 and Nb-doped TiO2, but cannot explain the overall lower total oxidation rate for the Nb-doped films. Instead the inferior photocatalytic activity in Nb-doped TiO2 is attributed to an enhanced electron-hole pair recombination rate due to Nb=O cluster and cation vacancy formation.

25-hydroxyvitamin D3 1alpha-hydroxylase and vitamin D receptor expression in papillary thyroid carcinoma

Vitamin D receptor (VDR) and 25-hydroxyvitamin D3 1-alpha-hydroxylase expression have recently been shown to be upregulated in several tumors and thought to represent an important endogenous response to tumor progression. Little is known about the expression of these proteins in thyroid carcinoma, although previous reports have documented evidence of the biological effect of vitamin D in thyroid cells. Using paraffin-embedded and frozen sections of papillary thyroid carcinoma, we utilized real-time quantitative RT-PCR and immunohistochemistry to characterize the expression of VDR and 1-alpha-hydroxylase in thyroid follicular cells, with special emphasis on papillary thyroid carcinoma (PTC). VDR and 1-alpha-hydroxylase expression were increased in PTC compared with normal thyroid tissue and especially high in areas of lymphocyte infiltration. Expression of VDR and 1-alpha-hydroxylase in PTC may be compatible with an overall favorable prognosis for this tumor type and may constitute important prerequisites for using vitamin D and/or vitamin D analogs in the treatment of PTC.

25-Hydroxyvitamin D3 1alpha-hydroxylase expression in breast cancer and use of non-1alpha-hydroxylated vitamin D analogue

Introduction

The cytochrome P450 mitochondrial enzyme 25-hydroxyvitamin D₃ 1α-hydroxylase (1α-hydroxylase) of renal tubule cells hydroxylates the major circulating form of vitamin D (25(OH)D₃) to the active systemic hormone 1,25(OH)₂D₃. Local production of 1,25(OH)₂D₃ appears to occur also at other sites where 1α-hydroxylase is expressed for autocrine/paracrine regulation. To reduce risks of hypercalcemia during treatment with vitamin D, we have previously suggested use of non-1α-hydroxylated vitamin D analogues to target tissues where 1α-hydroxylase is expressed, including the parathyroid glands in secondary hyperparathyroidism. The present study was undertaken to examine expression of 1α-hydroxylase in breast cancer and to investigate whether a non-1α-hydroxylated vitamin D analogue displayed biological function. In addition, expression of the 25-hydroxyvitamin D₃ 24-hydroxylase (24-hydroxylase) and the vitamin D receptor (VDR) was investigated.

Methods

The expression of 1α-hydroxylase, 24-hydroxylase and VDR was investigated in breast cancer specimens (n = 19) and normal breast tissues (n = 10) by immunohistochemistry and/or RT-PCR. Consecutive cryosections of 6 μm essentially free of immune cells were used in the analyses. The effect of vitamin D analogues on transcriptional activation was analyzed in transiently transfected MCF-7 breast cancer cells.

Results

1α-hydroxylase protein was demonstrated in 79% and 100% of breast cancer specimens and normal breast, respectively. The overall relative mRNA levels of 1α-hydroxylase and 24-hydroxylase in normal breast compared to breast tumors were: 1α-hydroxylase, 1 ± 0.07 versus 0.7 ± 0.05, respectively (p < 0.001); 24-hydroxylase, 1 ± 0.08 verus 2.1 ± 0.2, respectively (p < 0.001). The VDR was expressed in 95% of the tumors as expected, with mRNA levels of 1 ± 0.09 and 1.4 ± 0.12 (p < 0.05) in breast cancer and normal breast, respectively. The ketoconazole-sensitive transcription activation potential of the non-1α-hydroxylated vitamin D analogue prodrug of EB1089 (EB1285) was demonstrated in MCF-7 cells, which express 1α-hydroxylase. The activity of EB1285 was about 20% of 1,25(OH)₂D₃.

Conclusion

These results demonstrate nearly normal expression levels of 1α-hydroxylase, 24-hydroxylase and VDR in the majority of investigated breast cancer specimens. A non-1α-hydroxylated vitamin D analogue displayed activity in breast cancer cells. Such analogues may present future therapeutic options for proliferative disorders where 1α-hydroxylase is expressed.

Detailed assessment of chromosome 22 aberrations in sporadic pheochromocytoma using array-CGH

Pheochromocytoma is a predominantly sporadic neuroendocrine tumor derived from the adrenal medulla. Previous low resolution LOH and metaphase-CGH studies reported the loss of chromosomes 1p, 3q, 17p and 22q at various frequencies. However, the molecular mechanism(s) behind development of sporadic pheochromocytoma remains largely unknown. We have applied high-resolution tiling-path microarray-CGH with the primary aim to characterize copy number imbalances affecting chromosome 22 in 66 sporadic pheochromocytomas. We detected copy number alterations on 22q at a frequency of 44%. The predominant finding was monosomy 22 (30%), followed by terminal deletions in 8 samples (12%) and a single interstitial deletion. We further applied a chromosome 1 tiling-path array in 7 tumors with terminal deletions of 22q and found deletions of 1p in all cases. Our overall results suggest that at least 2 distinct regions on both 22q and 1p are important in the tumorigenesis of sporadic pheochromocytoma. A large proportion of pheochromocytomas also displayed indications of cellular heterogeneity. Our study is to our knowledge the first array-CGH study of sporadic pheochromocytoma. Future analysis of this tumor type should preferably be performed in the context of the entire human genome using genome-wide array-CGH, which is a superior methodological approach. Supplemental material for this article can be found on the International Journal of Cancer website at http://www.interscience.wiley.com/jpages/0020-7136/suppmat/index.html.

Vitamin D in normal and pathological parathyroid glands: new prospects for treating hyperparathyroidism (review)

The secosteroid hormone active vitamin D [1,25(OH)2D3] is a key player in the regulation of calcium homeostasis and bone mineralization. In addition, it has antiproliferative and prodifferentiating effects on various cells in vitro and in vivo. The action of 1,25(OH)2D3 is mediated through the vitamin D receptor (VDR), which belongs to the superfamily of steroid/thyroid hormone nuclear receptors. VDR is expressed in the intestine, bone, kidney, parathyroid glands, and in many other tissues and cell types. In the parathyroid glands, 1,25(OH)2D3 markedly decreases parathyroid hormone gene transcription and parathyroid cell proliferation and induces parathyroid cell differentiation. Diminished VDR expression is frequent in parathyroid tumors and probably contributes to parathyroid tumorigenesis. The enzyme responsible for catalyzing synthesis of 1,25(OH)2D3 (1alpha-hydroxylase) has lately been demonstrated in the parathyroid glands. This indicates a new role for 1alpha-hydroxylase as an intracrine modulator of vitamin D function in non-renal tissues, which recently has been recognized as crucial in parathyroid tumor development. The growth-inhibitory properties of 1,25(OH)2D3 are prospects for treatment of hyperparathyroidism.

Activated Neu/ErbB-2 induces expression of the vascular endothelial growth factor gene by functional activation of the transcription factor Sp 1

The neu (c- erbB-2 or HER2 ) proto-oncogene which encodes a receptor protein homologous to the epidermal growth factor receptor is overexpressed in 20%-30% of human breast and ovarian cancers. Oncogenic activation of Neu can also occur through multiple molecular mechanisms, including a point mutation in the transmembrane domain, deletion of the extracellular domain and short in-frame deletions of 7-12 amino acids in the extracellular region proximal to the transmembrane domain. Because of the highly vascularized phenotype of breast and ovarian cancers and the contribution of the Neu receptor to the development and progression of these tumors, we investigated the effect of Neu on the expression of the tumor angiogenesis factor VEGF. Expression of various activated Neu receptors but not wild-type Neu in Rat-1 cells, leads to increased VEGF expression on mRNA as well as on protein level. This effect is mediated by transcriptional activation of the VEGF promoter via a cluster of Sp 1 binding sites. Molecular analysis of the activation mechanism of Sp 1 revealed that neither the VEGF promoter binding activity of Sp 1 nor the expression of Sp 1 is affected by Neu transformation of the cells. Instead, functional Neu-induced transactivation of Sp 1 was observed by using a GAL4-based transactivation assay. These results demonstrate that functional changes of the transcription factor Sp 1 mediates a Neu-signaling cascade leading to VEGF promoter activation.

First Example of Low-Valence Ion Substitution in Ln5O(OPri)13: Mixed-Valence Europium Oxoalkoxide [EuIII4EuIIO(OPri)12(HOPri)]*HOPri

The novel mixed-valence alkoxide [Eu3+(4)Eu2+O(OPri)12(HOPri)]HOPri (1) has been prepared and structurally and spectroscopically characterized. The three synthesis routes (i) metathesis of 4EuCl3, EuI2, and 14KOPri combined with hydrolysis with 1H2O, (ii) oxidation of 5[Eu4(OPri)10(HOPri)3]2HOPri with 1.5O2, and (iii) reduction of Eu5O(OPri)13 with 0.8[Eu4(OPri)10(HOPri)3]2HOPri all yielded pure 1, whereas (iv) reduction of Eu5O(OPri)13 with 0.36-0.5 mol of europium metal produced impure 1. The compound, having the average Eu oxidation number +2.8, is very sensitive toward further oxidation to Eu5O(OPri)13 and is part of a redox series of europium 2-propoxides with average oxidation states +2.5, +2.8, and +3. The square pyramidal molecular structure, containing an oxo-oxygen atom in the basal plane, is similar to that of the well-known Ln5O(OPri)13; the main difference is the substitution of an Eu3+(-)OPri pair for an Eu2+(-)HOPri pair in the basal plane. Fourier transform infrared (FT-IR) and UV-visible spectroscopy showed that the solid-state structure was retained on dissolution in hexane and toluene-HOPri. The compound was further characterized by differential scanning calorimetry and solubility studies.

Transfection of the multiple endocrine neoplasia type 1 gene to a human endocrine pancreatic tumor cell line inhibits cell growth and affects expression of JunD, delta-like protein 1/preadipocyte factor-1, proliferating cell nuclear antigen, and QM/Jif-1

In the absence of metastases or overgrowth to adjacent organs, the lack of reliable markers for malignancy is a well-recognized problem for clinicians managing patients with endocrine tumors. Apart from inactivation of the multiple endocrine neoplasia type 1 (MEN1) gene, the molecular mechanisms involved in tumorigenesis of the endocrine organs and MEN1-associated nonendocrine lesions are vastly unknown. To try to learn more about down-stream effects on MEN1 gene inactivation, we used the BON1 cells, showing low levels of endogenous menin, and transfected them with a MEN1 gene construct. On restoring the menin expression, we recorded inhibition of cell growth. We also performed macroarray and present data on differentially expressed genes in the transfected cells, after corroboration by Northern blots and quantitative PCR. JunD was up-regulated in menin-expressing clones, whereas delta-like protein 1/preadipocyte factor-1 (involved in differentiation and growth of the pancreatic endocrine cells), proliferating cell nuclear antigen, and QM/Jif-1 (a negative regulator of c-Jun) became down-regulated. These findings might contribute to the understanding of the tissue-specific features of MEN1. We also show that homozygous inactivation of the MEN1 gene statistically correlates to higher expression of delta-like protein 1/preadipocyte factor-1, proliferating cell nuclear antigen, and QM/Jif-1, as well as lower MEN1 expression, in a limited sample of malignant endocrine pancreatic tumors.

Reduced p18INK4c, p21CIP1/WAF1 and p27KIP1 mRNA levels in tumours of primary and secondary hyperparathyroidism

OBJECTIVE

Hyperparathyroidism (HPT) refers to states of excessive production of parathyroid hormone (PTH). The eukaryotic cell cycle is driven forward by cyclins and their cyclin-dependent kinase (CDK) partners. Cyclin-dependent kinase inhibitors (CKIs), which generally inhibit cell cycle progression, modulate the activity of cyclin-CDK complexes.

DESIGN

In order to quantify the expression of the CKI genes p18, p21, and p27 semiquantitative RT-PCR with mRNA specific-primers was performed on four normal parathyroid biopsies, 31 parathyroid adenomas of primary HPT and 13 hyperplastic glands from uraemic patients with secondary HPT.

PATIENTS

Parathyroid adenomas and secondary hyperplastic glands were obtained from 31 and 13 randomly selected patients undergoing parathyroidectomy in the clinical routine, respectively. Four normal parathyroid gland biopsies were obtained at surgery for pHPT or from normocalcemic patients undergoing thyroidectomy for goitre.

RESULTS

The relative p27 expression (p27/GAPDH) was significantly reduced in parathyroid adenomas compared to normal parathyroid gland biopsies. Furthermore, 42% and 53% of the parathyroid adenomas displayed undetectable p18 and p21 expression levels, respectively. All 13 adenomas that lacked p18 expression showed undetectable p21 expression. The p18 expression was significantly lower in tumours of uraemic sHPT as compared to normal parathyroids and an undetectable expression level was observed for p21 and p27 in 61% and 53%, respectively.

CONCLUSION

Parathyroid adenomas and secondary hyperplastic glands exhibit aberrant reduced expression of the CKIs p18, p21, and p27. This suggests that deranged collaboration of different CKIs may contribute to the development of both primary and secondary HPT.

Vitamin D3 polyunsaturated side-chain analogues (EB1089, GS1590) and the 20-epi-vitamin D3 analogue CB1393 suppress parathyroid hormone secretion and mRNA level in bovine parathyroid cells

Several vitamin D analogues, with reduced hypercalcemic and hyperphosphatemic toxicity at therapeutic dosages, are in clinical use for prevention and treatment of secondary hyperparathyroidism (HPT) in chronic renal failure. We have performed a first in vitro evaluation of five vitamin D analogues displaying less calcemic activity in normal rats, considerably more antiproliferative ability and higher transcription activation potential than 1,25-dihydroxyvitamin D(3) (1,25(OH)(2)D(3)), with the future prospects in mind to identify even more effective and less calcemic vitamin D analogues for treatment of HPT. The vitamin D analogues EB1089 and GS1590 have polyunsaturated side-chains, whereas HEP187, MC1598 and CB1393 display altered stereochemistry at carbon 20. In primary cultures of bovine parathyroid cells EB1089, GS1590, CB1393 and MC1598 as well as the comparative controls 1,25(OH)(2)D(3), 22-oxacalcitriol (OCT, maxacalcitol), 19-nor-1,25(OH)(2)D(2) (paricalcitol) and 1alpha(OH)D(2) (doxercalciferol) significantly suppressed PTH secretion or reduced PTH mRNA level at 10(-8), 10(-10), and 10(-11)M for all compounds except for MC1598 at the lowest concentration. The analogue HEP187 displayed no PTH suppressive activity. We conclude that the vitamin D analogues EB1089, GS1590 and CB1393 may be suitable for treatment of hyperparathyroidism secondary to uremia and that further evaluation in vivo should be considered.

Increased 25-hydroxyvitamin D3 1alpha-hydroxylase and reduced 25-hydroxyvitamin D3 24-hydroxylase expression in parathyroid tumors--new prospects for treatment of hyperparathyroidism with vitamin d

Vitamin D analogues are in clinical use for prevention and treatment of secondary hyperparathyroidism (HPT) in chronic renal failure. Despite recent advances there is a need for vitamin D derivatives with maintained parathyroid hormone suppressive activity and less hypercalcemic and hyperphosphatemic toxicity. Here we show coincident increased expression of the vitamin D activating enzyme 25-hydroxyvitamin D(3) 1alpha-hydroxylase (1alpha-hydroxylase) and reduced expressions of the 1,25(OH)(2)D(3) catabolizing enzyme 25-hydroxyvitamin D(3) 1alpha-hydroxylase (1alpha-hydroxylase) in the majority of investigated parathyroid adenomas and secondary hyperplastic glands. In addition, this relationship was found for the mitochondrial CYP27A enzyme (25-hydroxylase), a potential physiological vitamin D(3) 25-hydroxylase. These findings should be considered in future development of vitamin D analogues for treatment of HPT.

Exclusive underexpression of vitamin D receptor exon 1f transcripts in tumors of primary hyperparathyroidism

OBJECTIVE

Primary hyperparathyroidism (pHPT) is characterized by excessive production of parathyroid hormone (PTH) due to parathyroid adenomas while uremic secondary HPT (sHPT) is caused by parathyroid hyperplasia in response to renal failure. Active vitamin D, 1,25-dihydroxyvitamin D(3) (1,25-(OH)(2)D(3)), with the vitamin D receptor (VDR) is involved in regulation of the calcium homeostasis together with PTH. In a feedback loop, 1,25-(OH)(2)D(3) has a direct action on the parathyroid gland to regulate PTH transcription, PTH secretion and cell proliferation. We have previously demonstrated reduced VDR mRNA expression in parathyroid adenomas and hyperplasia of sHPT using a probe detecting all 14 variant VDR transcripts expressed in parathyroid cells. Here we have assessed which of the 5'-terminal exon 1a, 1d and 1f variant VDR transcripts are reduced in pathological parathyroid glands.

METHODS

The relative VDR/glyceraldehyde-3-phosphate dehydrogenase mRNA levels for each VDR exon were determined by real-time quantitative RT-PCR in five normal parathyroid glands, seventeen parathyroid adenomas and ten hyperplastic glands of sHPT.

RESULTS

The results demonstrated exclusive underexpression of VDR exon 1f transcripts in parathyroid adenoma, while all measured VDR transcripts were reduced in secondary hyperplasia.

CONCLUSIONS

We suggest that exclusive underexpression of VDR exon 1f transcripts in adenomas of pHPT, which derive from a distal promoter active in tIssues involved in calcium regulation by 1,25-(OH)(2)D(3), may either reflect a defective cell type-specific transcription factor or other physiologically important pathway(s) for tIssue-specific VDR gene expression.

Underexpression of Gcm2, a master regulatory gene of parathyroid gland development, in adenomas of primary hyperparathyroidism

OBJECTIVE

Glial cells missing (Gcm) was first identified as a binary switch between neuronal and glial determination in Drosophila. Two homologues of Drosophila Gcm have been identified in mice and humans, namely Gcm1 and Gcm2. Mouse Gcm2 is restricted to parathyroid tissues and Gcm2 was recently identified as a master regulatory gene of parathyroid gland development as Gcm2 knockout mice lack parathyroid glands.

DESIGN/PATIENTS

To identify Gcm2 transcripts in human non-neural tissues and to examine whether Gcm2 is involved in parathyroid gland tumorigenesis we analysed Gcm2 transcript levels in several non-neural tissues by reverse transcriptase polymerase chain reaction (RT-PCR) and performed real-time quantitative RT-PCR analysis on five normal glands, 15 parathyroid adenomas of primary hyperparathyroidism (HPT) and nine hyperplastic glands of secondary HPT.

RESULTS

We found high Gcm2 mRNA expression in human parathyroid glands in comparison with other non-neural tissues and underexpression in parathyroid adenomas but not in lesions of HPT secondary to uraemia.

CONCLUSION

Because adenomas demonstrate lower Gcm2 expression than normal glands we suggest that reduced expression of Gcm2 contributes to parathyroid gland tumorigenesis. We speculate that a proper expression level of the Gcm2 transcription factor could be important for maintaining a fully differentiated state of the parathyroid cell.

Multiple endocrine neoplasia type 1 polymorphism D418D is associated with sporadic primary hyperparathyroidism

BACKGROUND

Sporadic primary hyperparathyroidism (pHPT) occurs separately and in several hereditary disorders including multiple endocrine neoplasia type 1. Irradiation to the neck, female gender, and age are well-identified risk factors that predispose to pHPT. The multiple endocrine neoplasia type 1 gene is the most commonly deranged gene in parathyroid adenomas and contains several polymorphisms including D418D with a prevalence of roughly 50%.

METHODS

We genotyped 162 pHPT patients and control participants to evaluate if the D418D polymorphism is related to development of pHPT. One hundred fourteen of the pHPT patients and control participants were recruited from a health screening and were subjected to measurement of bone mineral density (BMD) at the lumbar spine, femoral neck, and total body.

RESULTS

The prevalence of each genotype (ie, MM, Mm, and mm) was for all pHPT patients: 62%, 29%, and 9%; and for all control participants: 32%, 43%, and 25% (P <.0004). For the screening-detected pHPT patients and control participants, the genotype distribution for MM, Mm, and mm was 60%, 30%, and 10%; and 31%, 44%, and 25%, respectively (P =.009). In the screening-recruited control participants, but not in pHPT patients, the MM genotype was also associated with higher total body BMD (P =.01) and BMD at the femoral neck (P =.02), whereas it failed to be significant for BMD at the lumbar spine (P =.08).

CONCLUSIONS

We report that the MM genotype was overrepresented in pHPT patients compared with control participants, suggesting a novel marker for pHPT. Furthermore, the MM genotype was associated with higher BMD at the femoral neck and in the total body in the screening-recruited control participants.

Synthesis, characterization, and properties of three europium 2-propoxides: [Eu(4)(OPr(i))(10)(HOPr(i))(3)]*2HOPr(i), Eu(5)O(OPr(i))(13), and EuAl(3)(OPr(i))(12)

The reaction of Eu metal with HOPr(i)/toluene solutions yielded the mixed Eu(2+)/Eu(3+) alkoxide [Eu(4)(OPr(i))(10)(HOPr(i))(3)] x 2HOPr(i) (1), in contrast to the other lanthanide metals, which exclusively yield trivalent lanthanide ions in the alkoxides formed. Metathesis between EuCl(3) and 3KOPr(i) and stoichiometric hydrolysis yielded the square-pyramidal Eu(5)O(OPr(i))(13) (2), and metathesis with EuCl(3) and 3KAl(OPr(i))(4) gave EuAl(3)(OPr(i))(12) (3). The structures of these compounds were determined by single-crystal X-ray diffraction. IR spectroscopic studies showed that the solid-state molecular structure of the three alkoxides remained close to intact in solution. Further characterizations were made with UV-vis spectroscopy, differential scanning calorimetry, and solubility studies. It was also found that 1 can be converted to 2 by oxidation with dioxygen, but 2 was not reduced by Eu metal to 1. The reactions of 2 and 1 with Al(4)(OPr(i))(12) in toluene/HOPr(i) solvent were studied by IR and UV-vis spectroscopy; 2 reacted completely to form 3 in 2 h at 75 degrees C, while 1 reacted to yield 3 and other unidentified Eu(2+) containing product(s) in the same time.