Biomedical subjects

G Westin

Publications and source records attributed to G Westin.

At least 19 recordsLinked to original sources

PubMed2006

Activated beta-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.

Cell Line↗

PubMed2005

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 1-alpha-Hydroxylase↗

PubMed2002

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.

Journal Article↗

PubMed2001

Chromosome 18 deletions are common events in classical midgut carcinoid tumors.

Classical midgut carcinoids are rare intestinal neuroendocrine tumors that often present with metastases at diagnosis. In contrast to foregut carcinoids, midgut carcinoids are not related to the multiple endocrine neoplasia type 1 syndrome, and the mechanisms involved in their tumorigenesis are unknown. Eight classical midgut carcinoids were analyzed by genome-wide screening for loss of heterozygosity. Deletions on chromosome 18 were found in 88% of the tumors. DNA sequencing and immunohistochemical staining for Smad4/DPC4, which often is homozygously mutated in pancreatic and colon carcinomas, revealed no aberrations. In 1 tumor, a region telomeric to the Smad4/DPC4/DCC genes at 18q21 was deleted. Other chromosomes were affected in 3 lesions only. The high frequency of chromosome 18 deletions strongly indicates a genetic alteration of importance in classical midgut carcinoid tumorigenesis, apparently not involving the Smad4/DPC4 gene.

Adult↗

PubMed2001

Nd[Al(iPrO)4]3, a novel tetranuclear alkoxide forming merohedrally twinned crystals.

The new tetranuclear alkoxide hexa-mu(2)-isopropoxy-1:2kappa(4)O;1:3kappa(4)O;1:4kappa(4)O-hexaisopropoxy-2kappa(2)O,3kappa(2)O,4kappa(2)O-trialuminium(III) neodymium(III), [Nd[Al(C(3)H(7)O)(4)](3)], has a metal-oxygen NdAl(3)O(12) core which consists of four metal atoms arranged in an approximately planar triangular geometry. The central Nd atom is six-coordinated by O atoms and the Al atoms are four-coordinated by O atoms.

Journal Article↗

PubMed2001

The NeiI polymorphism in the cyclin D1 gene and sporadic primary hyperparathyroidism.

OBJECTIVES: The cell cycle regulator cyclin D1 plays an important role in parathyroid tumourigenesis. The NciI polymorphism in exon 4 has recently been associated with early onset of hereditary nonpolyposis colorectal cancer and is a prognostic indicator of nonsmall cell lung cancer and squamous cell carcinomas. Furthermore, a limited study of 28 primary hyperparathyroidism (pHPT) patients displayed a tendency of NciI influence on HPT development. We hypothesized that the NciI polymorphism may relate to a risk of developing pHPT. DESIGN, SETTING AND SUBJECTS: We genotyped 182 patients with sporadic pHPT and matched controls for the cyclin D1 polymorphism. A total of 88 pHPT patients and controls were recruited via a health-screening. RESULTS: The frequency distribution of the NciI genotypes NN, Ni, and ii were in pHPT patients and controls 22, 44 and 34%, and 26, 49 and 25%, respectively. The calculated allele frequencies were A = 0.56; G = 0.44 in cases and A = 0.49; G = 0.51 in controls. The frequency distributions did not differ comparing cases and controls when subgrouped after age and menopausal status. The NciI genotypes were not significantly associated with age of the individuals, serum (s)-calcium, s-parathyroid hormone (PTH), bone mineral density (BMD) or parathyroid tumour weight in any of the groups of pHPT patients or controls. CONCLUSIONS: No significant differences in distribution of the genotypes could be detected between the groups, suggesting that the polymorphism has minor or no pathogenic importance in the development of pHPT. Our results suggest that determination of the NciI polymorphism in the cyclin D1 gene is not a clinically useful tool for prediction of pHPT.

Aged↗

PubMed2001

Multiple allelic deletions and intratumoral genetic heterogeneity in men1 pancreatic tumors.

Multiple endocrine neoplasia type 1 (MEN1) is an inherited syndrome with multiple tumors of the endocrine pancreas, the parathyroid, the pituitary, and other tissues. The MEN1 gene at 11q13 is homozygously mutated in the majority of MEN1 tumors. Here we present a genome-wide loss of heterozygosity (LOH) screening of 23 pancreatic lesions, one duodenal tumor, and one thymic carcinoid from 13 MEN1 patients. Multiple allelic deletions were found. Fractional allelic loss varied from 6-75%, mean 31%. All pancreatic tumors displayed LOH on chromosome 11, whereas the frequency of losses for chromosomes 3, 6, 8, 10, 18, and 21 was over 30%. Different lesions from individual patients had discrepant patterns of LOH. Intratumoral heterogeneity was revealed, with chromosome 6 and 11 deletions in most tumor cells, whereas other chromosomal loci were deleted in portions of the analyzed tumor. Chromosome 6 deletions were mainly found in lesions from patients with malignant features. Fractional allelic loss did not correlate to malignancy or to tumor size. Our findings indicate that MEN1 pancreatic tumors fail to maintain DNA integrity and demonstrate signs of chromosomal instability.

Adult↗

PubMed2000

Downstream promoter sequences facilitate the formation of a specific transcription factor IID-promoter complex topology required for efficient transcription from the megalin/low density lipoprotein receptor-related protein 2 promoter.

Megalin/low density lipoprotein receptor-related protein 2 (LRP-2) is an endocytic receptor expressed in highly specialized cell types such as parathyroid cells and epithelia of the kidney. Previous experiments identified a nonconsensus TATA element, with the sequence TAGAAAA, as crucial for accurate and efficient transcription from the LRP-2 promoter. Here we show that, in addition to the TAGA element, promoter sequences downstream of the transcription start site contribute significantly to transcription both in vitro and in transfected cells. Deletion and point mutational analyses reveal that the promoter region located between positions +5 and +11 (sequence TTTTGGC) is of particular importance. Complementation experiments in nuclear extracts lacking transcription factor IID (TFIID) activity show that TATA-binding protein-associated factors of TFIID are essential for the function of LRP-2 downstream promoter sequences. Interestingly, DNase I footprinting studies show that the downstream region between positions +5 and +11 does not significantly affect overall TFIID affinity to the promoter but that it profoundly affects the topology of the TFIID x promoter complex not only downstream of the transcription start site, but in particular in the TATA box region. Our observations suggest a model for a novel downstream sequence function, in which TATA-binding protein-associated factor-promoter interactions downstream of the transcription start site modulate TFIID-DNA interactions in the TATA box region.

Base Sequence↗

PubMed2000

Familial hypercalcemia and hypercalciuria caused by a novel mutation in the cytoplasmic tail of the calcium receptor.

Familial hyperparathyroidism (HPT), characterized by hypercalcemia and hypercalciuria, and familial benign hypocalciuric hypercalcemia (FHH) are the most common causes of hereditary hypercalcemia. The calcium-sensing receptor (CaR) regulates PTH secretion and renal calcium excretion. Heterozygous inactivating mutations of the gene cause FHH, whereas CaR gene mutations have not been demonstrated in HPT. In a kindred with 20 affected individuals, the hypercalcemic disorder segregated with inappropriately higher serum PTH and magnesium levels and urinary calcium levels than in unaffected members. Subtotal parathyroidectomy revealed parathyroid gland hyperplasia/adenoma and corrected the biochemical signs of the disorder in seven of nine individuals. Linkage analysis mapped the condition to markers flanking the CaR gene on chromosome 3q. Sequence analysis revealed a mutation changing phenylalanine to leucine at codon 881 of the CaR gene, representing the first identified point mutation located within the cytoplasmic tail of the CaR. A construct of the mutant receptor (F881L) was expressed in human embryonic kidney cells (HEK 293), and demonstrated a right-shifted dose-response relationship between the extracellular and intracellular calcium concentrations. The hypercalcemic disorder of the present family is caused by an inactivating point mutation in the cytoplasmic tail of the CaR and displays clinical characteristics atypical of FHH and primary HPT.

Adult↗

PubMed2000

Reduced parathyroid vitamin D receptor messenger ribonucleic acid levels in primary and secondary hyperparathyroidism.

Vitamin D, via its receptor (VDR), inhibits the hormone secretion and proliferation of parathyroid cells. Vitamin D deficiency and reduced parathyroid VDR expression has been associated with development of hyperparathyroidism (HPT) secondary to uremia. VDR polymorphisms may influence VDR messenger RNA (mRNA) levels and have been coupled to an increased risk of parathyroid adenoma of primary HPT. VDR mRNA relative to glyceraldehyde-3-phosphate dehydrogenase mRNA levels were determined by RNase protection assay in 42 single parathyroid adenomas of patients with primary HPT, 23 hyperplastic glands of eight patients with uremic HPT, and 15 normal human parathyroid glands. The adenomas and hyperplasias demonstrated similar VDR mRNA levels, which were reduced (42 +/- 2.8% and 44 +/- 4.0%) compared with the normal glands (P < 0.0001). Comparison of parathyroid adenoma with a normal-sized parathyroid gland of the same individual (n = 3 pairs) showed a 20-58% reduction in the tumor. Nodularly enlarged glands represent a more advanced form of secondary HPT and showed greater reduction in the VDR mRNA levels than the diffusely enlarged glands (P < 0.005). The reduced VDR expression is likely to impair the 1,25(OH)2D3-mediated control of parathyroid functions, and to be of importance for the pathogenesis of not only uremic but also primary HPT. Circulating factors like calcium, PTH, and 1,25(OH)2D3 seem to be less likely candidates mediating the decreased VDR gene expression in HPT.

Adenoma↗

PubMed1999

Menin represses JunD-activated transcription by a histone deacetylase-dependent mechanism.

Recently the multiple endocrine neoplasia type 1 (MEN-1) tumor suppressor gene was cloned. MEN-1 encodes a nuclear protein, called menin, of hitherto unknown function. In order to investigate the biological function of menin we employed the yeast two-hybrid system to identify menin-interacting proteins. Here we report that menin functions as a transcriptional repressor through interaction with the transcription factor JunD. The interaction is mediated via the N-terminal transcription activation domain of JunD, and the C-terminal part of menin. In transient co-transfection experiments, expression of menin leads to specific repression of JunD transcriptional activity, which is dependent on the integrity of the menin C-terminal region. C-Terminal truncations of the protein not only abolish repression, but increase JunD transcriptional activity, implying the existence of a functional domain separate from the JunD-binding region. Menin-mediated repression is relieved by the histone deacetylase inhibitor trichostatin A, indicating that deacetylation of histones is an essential component of this repression mechanism, as has recently been demonstrated for the retinoblastoma protein. Missense, in-frame deletions, frameshift and nonsense mutations lead to inactivation of menin or possibly to truncated proteins. This would result in loss of repression of menin/JunD target genes, as well as non-target genes through indirect mechanisms, deregulation of cellular growth control and endocrine tumorigenesis.

Down-Regulation↗

PubMed1999

The vitamin D receptor (VDR) start codon polymorphism in primary hyperparathyroidism and parathyroid VDR messenger ribonucleic acid levels.

Vitamin D regulates parathyroid cell proliferation and secretion of PTH. Increased prevalence of the polymorphic vitamin D receptor (VDR) alleles b, a, and T has been reported in sporadic primary hyperparathyroidism (PHPT), suggesting that these genetic variants may predispose to the disease. Recently, another polymorphism in the VDR gene was related to bone mineral density, and this VDR-FokI polymorphism causes different lengths of the VDR, implying possible functional consequences. The VDR-FokI polymorphism was studied in 182 postmenopausal women with sporadic PHPT and in matched controls. No significant differences in distribution of the VDR-FokI genotypes could be detected between the groups, although there was a tendency toward overrepresentation of the F allele in the PHPT patients (P = 0.05). There were no significant associations with age, serum calcium, serum PTH, bone mineral density, or parathyroid tumor weight. The VDR genotypes were unrelated to VDR and PTH messenger ribonucleic acid levels in the parathyroid adenomas of 42 PHPT patients. In 23 PHPT patients, the Ca2+-PTH set-points were determined in vivo and were unrelated to the VDR alleles. We suggest that the VDR-FokI polymorphism has at most a minor pathogenic importance in the development of PHPT.

Adult↗

PubMed1999

Vitamin D and retinoids in parathyroid glands (review).

Vitamin D and retinoids are important regulators of differentiation and proliferation in a number of tissues, and have been implicated as chemopreventive agents in several different tumors. While vitamin D is known to be important for regulation of parathyroid function and proliferation, it has recently been established that parathyroid cells also are targets for retinoids. Hyperparathyroidism (HPT) is a common disorder, and evaluation of the disease has indicated high prevalence of subclinical disease, as well as clear benefits of offering treatment for the disease. This review summarizes the data so far gathered concerning parathyroid cells, vitamin D and retinoids, with clear implication on prospects of possible medical treatment of hyperparathyroidism.

Animals↗

PubMed1999

Genetic alterations on 3p, 11q13, and 18q in nonfamilial and MEN 1-associated pancreatic endocrine tumors.

Pancreatic endocrine tumors occur sporadically and as part of the multiple endocrine neoplasia type 1 (MEN 1) and von Hippel-Lindau (VHL) syndromes. The MEN1 locus on 11q13 and a candidate tumor suppressor locus on 3p are known to be hemi- or homozygously mutated in a subset of these tumors. Chromosome arm 18q harbors the SMAD4/DPC4 tumor suppressor gene that is frequently deleted and inactivated in tumors of the exocrine pancreas. We have analyzed 22 nonfamilial and 16 MEN 1-associated pancreatic endocrine tumors for loss of heterozygosity (LOH) at 3p, 11q13, and 18q. LOH at 3p was revealed in 45% and 36% of tumors from 31 patients with nonfamilial and MEN 1-associated disease, respectively. The corresponding proportions for 11q13 were 55% and 91%, and for 18q 27% and 25%, respectively. A striking relation between LOH at 11q13 and 3p and a malignant phenotype was found for the nonfamilial tumors. None of the six benign tumors (all of them insulinomas) had allelic loss at 3p or 11q13, whereas 92% (P < 0.01) of the malignant tumors (including malignant insulinomas) had such deletions. Besides the 11q13 abnormality, more than half of the MEN 1-associated tumors had additional genetic lesions affecting 3p or 18q. LOH analysis of several tumors from two MEN 1 patients suggested different clonal origin of the lesions. Sequencing of the SMAD4/DPC4 gene did not identify mutations in coding regions or at exon/intron boundaries in tumors with LOH at 18q. The data indicate involvement of tumor suppressor genes on 3p and 18q, in addition to the MEN1 gene at 11q13, in the tumorigenesis of both nonfamilial and MEN 1-associated pancreatic endocrine tumors.

Biomarkers, Tumor↗

PubMed1998

Mutation of the multiple endocrine neoplasia type 1 gene in nonfamilial, malignant tumors of the endocrine pancreas.

Endocrine pancreatic tumors are rare neoplasms that occur sporadically or as part of a multiple endocrine neoplasia type 1 (MEN1) syndrome. Germ-line mutations of the MEN1 gene, located at 11q13, have been demonstrated in MEN1 kindreds, and loss of heterozygosity (LOH) on 11q13 together with somatic MEN1 mutations have been detected in 20% of nonfamilial parathyroid tumors. Here, we examine 11 non-MEN1 malignant tumors of the endocrine pancreas, 9 nonfunctioning tumors, and 2 glucagonomas. LOH of at least one informative locus on 11q13 was found in 70% of the tumors. Three tumors displayed somatic mutations of the MEN1 gene together with LOH on 11q13, whereas the corresponding germ-line DNA was normal. These findings support the hypothesis that MEN1 gene mutations contribute to the tumorigenesis of nonfamilial, malignant endocrine pancreatic tumors.

Adult↗

PubMed1998

Characterization of the human Megalin/LRP-2 promoter in vitro and in primary parathyroid cells.

The gp330/Megalin/LRP-2 protein belongs to the low-density lipoprotein receptor gene family and is believed to function as an endocytic receptor for the uptake of lipoproteins and many other ligands. Other functions of this protein may include a role in calcium sensing in the parathyroid glands and other tissues. In order to study the transcriptional regulation of the human LRP-2 gene, a clone containing the 5'-flanking region was isolated from a genomic DNA library, and a transient transfection protocol for primary bovine parathyroid cells was established. RNA mapping techniques located the transcriptional start site 136 bp upstream of the initiation codon. Transient expression in several cell types, including primary parathyroid cells, and in vitro transcription in HeLa cell nuclear extracts showed that sequences between -120 and -35 were important for activated transcription. This region contains consensus binding sites (GC boxes) for transcription factor Sp1. Mutation of the GC boxes abolished binding of Sp1 in vitro and resulted in reduced transcription in vitro and in transfected cells. Furthermore, Sp1 stimulated transcription when tethered to the LRP-2 core promoter through a heterologous DNA-binding domain. Through site-directed mutagenesis, we identified a novel atypical TATA element with the sequence TAGAAAA. Intriguingly, this sequence motif was shown previously not to mediate transcription in a systematic mutational analysis of the TATA motif. Possible roles of this novel TATA element in the regulation of transcription initiation are discussed. The isolation and characterization of the LRP-2 promoter and the 5'-flanking region and the establishment of a transient expression assay in primary parathyroid cells will facilitate studies on the regulatory mechanisms of the LRP-2 gene and of other genes expressed in the parathyroid glands.

Animals↗

PubMed1998

Vitamin D receptor (VDR) and parathyroid hormone messenger ribonucleic acid levels correspond to polymorphic VDR alleles in human parathyroid tumors.

Calcitriol, via its receptor (VDR) is a main regulator of PTH secretion and parathyroid cell proliferation. Recently, marked overrepresentation of the polymorphic VDR alleles b, a, and T was found in patients with primary hyperparathyroidism (pHPT), which suggests pathogenic importance in the disease. Using the ribonuclease protection assay, relative VDR and PTH messenger ribonucleic acid (mRNA) levels of parathyroid adenomas from 42 patients with sporadic pHPT were related to these VDR polymorphisms. The tumors of patients homozygous for the b, a, or T alleles demonstrated significantly lower VDR and higher PTH mRNA levels than those exhibiting the BB, AA, or tt genotypes (P < 0.0001-0.02), whereas heterozygotes had intermediate values. A similar discrepancy was found when comparing the baT and non-baT haplotypes (0.042 +/- 0.005 vs. 0.064 +/- 0.004 for VDR; 34.4 +/- 3.7 vs. 21.6 +/- 2.2 for PTH; both P < 0.005). The lower VDR mRNA levels associated with the b, a, and T alleles may affect the calcitriol-mediated control of parathyroid function and thereby contribute to the development of sporadic pHPT.

Adenoma↗

PubMed1998

Parathyroid MEN1 gene mutations in relation to clinical characteristics of nonfamilial primary hyperparathyroidism.

Biochemical signs and severity of symptoms of primary hyperparathyroidism (pHPT) differ among patients, and little is known of any coupling of clinical characteristics of nonfamilial pHPT to genetic abnormalities in the parathyroid tumors. Mutations in the recently identified MEN1 gene at chromosome 11q13 have been found in parathyroid tumors of nonfamilial pHPT. Using microsatellite analysis for loss of heterozygosity (LOH) at 11q13 and DNA sequencing of coding exons, the MEN1 gene was studied in 49 parathyroid lesions of patients with divergent symptoms, operative findings, histopathological diagnosis, and biochemical signs of nonfamilial pHPT. Allelic loss at 11q13 was detected in 13 tumors, and 6 of them demonstrated previously unrecognized somatic missense and frameshift deletion mutations of the MEN1 gene. Many of the detected mutations would most likely result in a nonfunctional menin protein, consistent with a tumor suppressor mechanism. Clinical and biochemical characteristics of HPT were apparently unrelated to the presence or absence of LOH and the MEN1 gene mutations. However, the demonstration of LOH at 11q13 and MEN1 gene mutations in small parathyroid adenomas of patients with slight hypercalcemia and normal serum PTH levels suggest that altered MEN1 gene function may also be important for the development of mild sporadic pHPT.

Adenoma↗