| 1. |
- Hjälm, Göran, et al.
(författare)
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Cloning and sequencing of human gp330, a Ca2+ -binding receptor with potential intracellular signaling properties
- 1996
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Ingår i: European Journal of Biochemistry. - : Wiley. - 0014-2956 .- 1432-1033. ; 239:1, s. 132-137
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Tidskriftsartikel (refereegranskat)abstract
- We present here the complete primary structure of human gp330, the human variant of the principal kidney autoantigen causing Heymann membranous glomerulonephritis in rats. The deduced 4655 amino acid residues give a calculated molecular mass of 519636 Da for the mature protein and consists of a probable 25-amino-acid N-terminal signal peptide sequence, an extracellular region of 4398 amino acids, a single transmembrane-spanning domain of 23 amino acids, and an intracellular C-terminal region of 209 amino acid residues. Three types of cysteine-rich repeats characteristic of the low density lipoprotein receptor (LDLR) superfamily are present in human gp330. In the extracellular region, there are a total of 36 LDLR ligand-binding repeats, comprising four distinct domains, 16 growth factor repeats separated by eight YWTD spacer regions, and one epidermal growth factor-like repeat. No consensus cleavage sequence for the processing endoprotease furin is detected in human gp330. The intracellular tail contains not only two copies of the F(X)NPXY coated-pit mediated internalization signal characteristic of LDLR superfamily members, but also intriguing and potentially functional motifs including several Src-homology 3 recognition motifs, one Src-homology 2 recognition motif for the p85 regulatory subunit of phosphatidylinositol 3-kinase, and additional sites for protein kinase C, casein kinase II and cAMP-/cGMP-dependent protein kinase. There is approximately 77% amino acid identity between human and rat gp330 with minor differences between the extracellular and intracellular regions. Recently gp330 has been implicated in Ca2+ regulation in the parathyroid, the placenta, and the renal tubule, but its overall physiological and pathological role still remains uncertain.
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| 2. |
- Lundgren, Stefan, et al.
(författare)
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Tissue distribution of human gp330/megalin, a putative Ca2+-sensing protein
- 1997
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Ingår i: Journal of Histochemistry and Cytochemistry. - : SAGE Publications. - 0022-1554 .- 1551-5044. ; 45:3, s. 383-392
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Tidskriftsartikel (refereegranskat)abstract
- We used riboprobes and monoclonal antibodies to characterize tissue distribution of the human 550-kD homologue to gp330/megalin, primarily identified in the rat kidney. Human gp330/megalin mRNA and protein are readily identified in human parathyroid cells, placental cytotrophoblasts, kidney proximal tubule cells, and epididymal epithelial cells. The immunoreactivity is found on the surface of the cells and is heterogeneously downregulated in parathyroid hyperplasia and adenomas. Cells of the proximal kidney tubule and epididymis express the protein on their luminal aspect. Moreover, the protein is expressed in Type II pneumocytes, mammary epithelial and thyroid follicular cells, and the ciliary body of the eye. Sequence analysis of cDNA fragments, obtained by RT-PCR, revealed identical nucleotide sequences in parathyroid, kidney, placenta, epididymis, and lung. Immunohistochemistry for parathyroid hormone-related protein (PTHrP) revealed partial co-expression with human gp330/megalin in parathyroid, placenta, and mammary gland. The findings substantiate human gp330/megalin expression in a variety of human tissues expected to possess calcium-sensing functions. It may constitute a protein of utmost importance to adult and fetal calcium homeostasis, although other important functions may also be coupled to this exceptionally large protein with highly restricted tissue distribution.
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| 3. |
- Åkerström, Tobias, et al.
(författare)
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Comprehensive Re-Sequencing of Adrenal Aldosterone Producing Lesions Reveal Three Somatic Mutations near the KCNJ5 Potassium Channel Selectivity Filter.
- 2012
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Ingår i: PloS one. - : Public Library of Science (PLoS). - 1932-6203. ; 7:7
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Tidskriftsartikel (refereegranskat)abstract
- 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.
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| 4. |
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| 5. |
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| 6. |
- Alimohammadi, Mohammad, et al.
(författare)
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Autoimmune Polyendocrine Syndrome Type 1 : NALP5 in Autoimmune Polyendocrine Syndrome Type 1
- 2006
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Ingår i: The New England Journal of Medicine. ; 358:10, s. 1018-28
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Tidskriftsartikel (refereegranskat)abstract
- 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.
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| 7. |
- Alimohammadi, Mohammad, et al.
(författare)
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Autoimmune polyendocrine syndrome type 1 and NALP5, a parathyroid autoantigen
- 2008
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Ingår i: New England Journal of Medicine. - 0028-4793 .- 1533-4406. ; 358:10, s. 1018-1028
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Tidskriftsartikel (refereegranskat)abstract
- 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.
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| 8. |
- Ander, Stefan
(författare)
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Preservation of parathyroid function in thyroid and parathyroid surgery
- 1998
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Preservation of normal parathyroid function and calcium homeostasis after operations on the thyroid and parathyroid glands is a difficult assignment in endocrine surgery, and it is crucial to minimise the risks of permanent postoperative hypoparathyroidism. The aim of this thesis was to study the vascular supply of the parathyroid glands and the revascularisation, growth, and function of transplanted parathyroid tissue, in order to add new information about parathyroid preservation.The microcirculation and blood supply of normal, hyperplas~c and adenomatous parathyroid glands were studied with laser Doppler flowmetry in 103 patients during operations on the thyroid and parathyroid glands. In normal parathyroid glands the blood flow was higher compared with that in hyperplastic glands and adenomas. Occlusion of the main trunks of the inferior and superior thyroid arteries reduced the blood flow by 35% and 25%, respectively. The reduction was similar in normal, hyperplastic, and adenomatous parathyroid glands. In 12 patients with single parathyroid adenomas, the increased concentration of parathyroid hormone (PTH) remained mainly unchanged despite appreciable reduction in blood flow. In 16 patients the microcirculation and macroscopic appearance of normal parathyroid glands located anteriorly on the thyroid lobe were analysed before and after dissection for in situ preservation. There was a poor correlation between reduction in blood flow and macroscopic appearance of the glands. Laser Doppler flowmetry (LDF) showed that the disturbed microcirculation often recovered 30-60 minutes after dissection for preservation.Parathyroid tissue obtained from 47 patients operated on for hyperparathyroidism was implanted subcutaneously in athymic mice. The processes of revascularisation, morphology, cell proliferation, and function of normal, hyperplastic, and adenomatous parathyroid tissue were studied at 2 and 4 days and 1, 4, 7 and 12 weeks after transplantation. Vessels were detected by monoclonal antibodies specific for mouse and human endothelial cells. The transplanted tissues were examined by light and electron microscopy and by autoradiography after continuous infusion of tritiated thymidine. The relative amount of viable tissue was assessed with a computer image-analysing program. Graft function was judged by measuring human iPTH in mouse serum.Over 90% of the transplants took and the original structure of the tissue was well preserved. Confluent areas of parathyroid tissue could be seen in 80% of the transplants. The mean loss of viable tissue in all three groups was 45%.Immunohistochemical examination showed ingrowth of vessels from the host into the transplant. The sprouts matured gradually into vessels with thin endothelial linings and capillary fenestrations in adenomatous and hyperplastic transplants but not in transplants of normal tissue.In normal parathyroid tissue the proliferation of parathyroid parenchyma! cells increased only slightly in contrast to the advancing proliferative capacity in adenomatous tissue. In contrast to adenomas, parenchyma! cell proliferative capacity in hyperplastic tissue decreased at 12 week.Concentrations of iPTH were raised at one week in hyperplastic and adenomatous tissue. Twelve weeks after transplantation iPTH concentrations in relation to the amount of transplanted tissue and relative area of viable tissue were comparable in all three groups of transplanted tissue.We conclude that, LDF is a feasible method to study physiological blood flow in human parathyroid glands. Parathyroid blood supply is not as dependent on the inferior thyroid artery as was previously suggested. LDF showed that blood flow recovered in parathyroid glands dissected for in situ preservation and any decision about autografting should be delayed until the end of the operation. Parathyroid transplants re vascularise from host vessels and this is more pronounced and proceeds faster in hyperplastic and adenomatous tissue than in normal transplants. In contrast to nonnal and hyperplastic transplants, adenomatous tissue has a greater and increasing proliferative capacity. The iPTH concentration as an expression of parathyroid function correlates poorly with parenchyma! cell proliferation.
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| 9. |
- Backlin, Carin, et al.
(författare)
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Immunohistochemical expression of insulin-like growth factor 1 and its receptor in normal and neoplastic human adrenal cortex
- 1995
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Ingår i: Anticancer Research. - 0250-7005 .- 1791-7530. ; 15:6B, s. 2453-2459
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Tidskriftsartikel (refereegranskat)abstract
- BACKGROUND:Insulin-like growth factor 1 (IGF-1) may influence cellular growth, differentiation and secretion.MATERIAL AND METHODS:Cryosectioned normal human adrenal glands (n = 6), cortical adenoma (n = 21), and carcinoma (n = 17) were stained immunohistochemically for IGF-1 and its receptor, and human adrenocortical cancer cells expressing the receptor were analysed for influences on proliferation.RESULTS:Normal cortical parenchyma generally displayed faint IGF-1 reactivity and intracellular receptor staining. Similar labelling encompassed the adenomas, but only 6 of them were receptor reactive. IGF-1 expression was conspicuous in 11 carcinomas, and 6 of them displayed cell surface receptor reactivity. All aldosterone producing lesions were receptor antibody unreactive. Recombinant IGF-1 dose-dependently stimulated the cell proliferation, and this effect was reversed by the receptor antibody.CONCLUSION:IGF-1 may interact with function and proliferation of the human adrenal cortex with particular reference to cortical carcinomas lacking discernible aldosterone excess.
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| 10. |
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| 11. |
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| 12. |
- Bergström, Mats, et al.
(författare)
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PET imaging of adrenal cortical tumors with the 11beta-hydroxylase tracer 11C-metomidate
- 2000
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Ingår i: Journal of Nuclear Medicine. - 0161-5505 .- 1535-5667. ; 41:2, s. 275-282
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Tidskriftsartikel (refereegranskat)abstract
- The purpose of the study was to evaluate PET with the tracer 11C-metomidate as a method to identify adrenal cortical lesions.METHODS:PET with 11C-metomidate was performed in 15 patients with unilateral adrenal mass confirmed by CT. All patients subsequently underwent surgery, except 2 who underwent biopsy only. The lesions were histopathologically examined and diagnosed as adrenal cortical adenoma (n = 6; 3 nonfunctioning), adrenocortical carcinoma (n = 2), and nodular hyperplasia (n = 1). The remaining were noncortical lesions, including 1 pheochromocytoma, 1 myelolipoma, 2 adrenal cysts, and 2 metastases.RESULTS:All cortical lesions were easily identified because of exceedingly high uptake of 11C-metomidate, whereas the noncortical lesions showed very low uptake. High uptake was also seen in normal adrenal glands and in the stomach. The uptake was intermediate in the liver and low in other abdominal organs. Images obtained immediately after tracer injection displayed high uptake in the renal cortex and spleen. The tracer uptake in the cortical lesions increased throughout the examination. For quantitative evaluation of tracer binding in individual lesions, a model with the splenic radioactivity concentration assigned to represent nonspecific uptake was applied. Values derived with this method, however, did show the same specificity as the simpler standardized uptake value concept, with similar difference observed for cortical versus noncortical lesions.CONCLUSION:PET with 11C-metomidate has the potential to be an attractive method for the characterization of adrenal masses with the ability to discriminate lesions of adrenal cortical origin from noncortical lesions.
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| 13. |
- Björklund, Peyman, et al.
(författare)
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A LRP5 receptor with internal deletion in hyperparathyroid tumors with implications for deregulated Wnt/β-catenin signaling
- 2007
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Ingår i: PLoS Medicine. - : Public Library of Science (PLoS). - 1549-1277 .- 1549-1676. ; 4:11, s. 1829-1841
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Tidskriftsartikel (refereegranskat)abstract
- 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.
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| 14. |
- Björklund, Peyman, et al.
(författare)
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Accumulation of nonphosphorylated β-catenin and c-myc in primary and uremic secondary hyperparathyroid tumors
- 2007
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Ingår i: Journal of Clinical Endocrinology and Metabolism. - : The Endocrine Society. - 0021-972X .- 1945-7197. ; 92:1, s. 338-344
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Tidskriftsartikel (refereegranskat)abstract
- 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.
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| 15. |
- Björklund, Peyman, et al.
(författare)
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Activated β-catenin in the novel human parathyroid tumor cell line sHPT-1
- 2007
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Ingår i: Biochemical and Biophysical Research Communications - BBRC. - : Elsevier BV. - 0006-291X .- 1090-2104. ; 352:2, s. 532-536
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Tidskriftsartikel (refereegranskat)abstract
- 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.
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| 16. |
- Björklund, Peyman, et al.
(författare)
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Stabilizing mutation of CTNNB1/beta-catenin and protein accumulation analyzed in a large series of parathyroid tumors of Swedish patients
- 2008
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Ingår i: Molecular Cancer. - : Springer Science and Business Media LLC. - 1476-4598. ; 7, s. 53-
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Tidskriftsartikel (refereegranskat)abstract
- BACKGROUND: Aberrant accumulation of beta-catenin plays an important role in a variety of human neoplasms. We recently reported accumulation of beta-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 beta-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 beta-catenin accumulation. Western blotting revealed a slightly higher expression level of beta-catenin and nonphosphorylated active beta-catenin in tumors with mutation compared to those without. Presence of the mutation was not related to distinct clinical characteristics. CONCLUSION: Aberrant accumulation of beta-catenin is very common in parathyroid tumors, and is caused by stabilizing homozygous mutation in 7.3% of Swedish pHPT patients.
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| 17. |
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| 18. |
- Björklund, Peyman, et al.
(författare)
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Stathmin as a Marker for Malignancy in Pheochromocytomas
- 2010
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Ingår i: Experimental and clinical endocrinology & diabetes. - : Georg Thieme Verlag KG. - 0947-7349 .- 1439-3646. ; 118:1, s. 27-30
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Tidskriftsartikel (refereegranskat)abstract
- 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.
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| 19. |
- Björklund, Peyman, et al.
(författare)
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The internally truncated LRP5 receptor presents a therapeutic target in breast cancer
- 2009
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Ingår i: PloS one. - : Public Library of Science (PLoS). - 1932-6203. ; 4:1, s. e4243-
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Tidskriftsartikel (refereegranskat)abstract
- 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/beta-catenin signaling with accumulation of beta-catenin is common in breast tumors, but mutations in WNT signaling pathway components have been rare. An aberrantly spliced internally truncated LRP5 receptor (LRP5Delta666-809, LRP5Delta) was shown recently to be resistant to DKK1 inhibition, and was required for beta-catenin accumulation in hyperparathyroid tumors and parathyroid tumor growth. METHODOLOGY/PRINCIPAL FINDINGS: Here we show, by reverse transcription PCR and Western blot analysis, that LRP5Delta is frequently expressed in breast tumors of different cancer stage (58-100%), including carcinoma in situ and metastatic carcinoma. LRP5Delta was required in MCF7 breast cancer cells for the non-phosphorylated active beta-catenin level, transcription activity of beta-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 beta-catenin activity of MCF7 cells in a DKK1-insensitive manner. Furthermore, an anti-LRP5 antibody attenuated beta-catenin activity, inhibited cell growth, and induced apoptosis in LRP5Delta-positive MCF7 and T-47D breast cancer cells, but not in control cells. CONCLUSIONS/SIGNIFICANCE: Our results suggest that the LRP5Delta 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.
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| 20. |
- Björklund, Peyman, et al.
(författare)
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Type I membrane Klotho expression is decreased and inversely correlated to serum calcium in primary hyperparathyroidism
- 2008
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Ingår i: Journal of Clinical Endocrinology and Metabolism. - : The Endocrine Society. - 0021-972X .- 1945-7197. ; 93:10, s. 4152-4157
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Tidskriftsartikel (refereegranskat)abstract
- Context: The type I membrane protein Klotho was recently shownto mediate PTH secretion in parathyroid cells in response tolow extracellular calcium. In contrast, Klotho inhibits PTHsecretion indirectly through the action of fibroblast growthfactor-23. Abnormal Klotho expression in parathyroid disordersremains to be elucidated.Objective: The aim of the study was to determine: 1) Klothoexpression in parathyroid adenomas from patients with primaryhyperparathyroidism (pHPT) compared to normal tissue; and 2)its relation to the serum calcium and PTH levels.Design: Surgically removed parathyroid glands (n = 40) and fournormal parathyroid tissue specimens were analyzed for KlothomRNA and protein levels by quantitative real-time PCR and immunohistochemistry.In vitro effects of calcium on Klotho mRNA expression were studiedin bovine parathyroid cells.Results: Klotho mRNA levels were significantly decreased (n= 23) or undetectable (n = 17) in parathyroid adenomas comparedto normal tissues (P < 0.001). Reduced Klotho protein expressionwas confirmed by immunohistochemistry. Klotho mRNA levels wereinversely correlated to serum calcium (r = –0.97; P <0.0001), and calcium dose-dependently decreased Klotho mRNAexpression in normal parathyroid cells in vitro (P < 0.01).Serum calcium was the only significant marker of Klotho expressionin multivariate analysis with calcium, phosphate, PTH, and adenomaweight as independent variables.Conclusions: Parathyroid Klotho expression is decreased or undetectablein pHPT. We provide evidence that 1) serum calcium is stronglyassociated with parathyroid Klotho expression in pHPT; and 2)abnormal PTH secretion in hypercalcemic pHPT subjects is mediatedby Klotho-independent mechanisms.
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| 21. |
- Björklund, Peyman, 1965-
(författare)
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Wnt/β-Catenin Signalling in Parathyroid Tumours
- 2007
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Primary hyperparathyroidism (pHPT) due to parathyroid tumours with hypersecretion of parathyroid hormone and hypercalcaemia is a common disease with incompletely understood etiology affecting more than 1 % of the population, primarily postmenopausal women. In secondary hyperparathyroidism (sHPT), parathyroid tumours develop in response to calcium and vitamin D deficiency generally in patients with uraemia. HPT is usually treated by surgical removal of enlarged parathyroid glands.The aim of this thesis was to examine the Wnt/β-catenin signalling pathway in parathyroid tumours.Aberrantly accumulated β-catenin was found in all analysed pHPT and sHPT tumours, with a stabilising homozygous mutation (Ser37Ala) in 7.3% of the pHPT tumours. Truncation of the APC protein was not found. MYC, a β-catenin target gene was overexpressed in a substantial fraction of pHPT and sHPT parathyroid tumours. A parathyroid tumour cell line (sHPT-1) was established from a hyperplastic gland removed at operation of a patient with sHPT. The cells produced parathyroid hormone and grew with a doubling time of approximately 72 hours. Stabilised nonphosphorylated transcriptionally active β-catenin was expressed. Efficient transfection of siRNA against β-catenin decreased expression of cyclin D1 and MYC, and inhibited cell growth with ensuring cell death. The Wnt coreceptor LRP5 was found expressed with an internal deletion of 142 amino acids (LRP5Δ) in 86% and 100% of pHPT and sHPT tumours, respectively. Stabilising mutation of β-catenin and expression of LRP5Δ was mutually exclusive. Expression of LRP5Δ was required to maintain the nonphosphorylated transcriptionally active ß-catenin level, MYC expression, parathyroid cell growth in vitro, and tumour growth in transplanted SCID mice. Wnt3 ligand and LRP5Δ strongly activated transcription, and LRP5Δ was insensitive to inhibition by DKK1.Aberrant accumulation of β-catenin by stabilising mutation or expression of LRP5Δ appears as a common pathogenic pathway for hyperparathyroid disease. LRP5Δ in particular presents a potential target for therapeutic intervention.
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