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- Lindberg, Daniel, et al.
(författare)
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Evaluation of CDKN2C/p18, CDKN1B/p27, and CDKN2B/p15 mRNA expression and CpG methylation status in sporadic and MEN1-associated pancreatic endocrine tumors
- 2008
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Ingår i: Clinical Endocrinology. - : Wiley. - 0300-0664 .- 1365-2265. ; 68:2, s. 271-278
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Tidskriftsartikel (refereegranskat)abstract
- Objective Menin, encoded by the multiple endocrine neoplasia type 1 (MEN1) gene at 11q13, enhances transcription of the cyclin-dependent kinase inhibitors (CDIs), CDKN2C (p18) and CDKN1B (p27) in mouse pancreatic islets, and inactivation of menin reduced CDKN2B (p15) expression in this mouse model. Here, we have compared the relative mRNA expression level and CpG methylation status of p18, p27 and p15 in 18 pancreatic endocrine tumours (PETs) with or without MEN1 gene mutations. Design Real-time quantitative PCR, DNA sequencing and pyro-sequencing methylation analysis were employed. Results The p18 gene was expressed in 15 out of the 18 analysed PETs. The expression level was within the range of the normal pancreatic tissues or higher. Of the three remaining tumours with no expression, two displayed loss of heterozygocity (LOH) at 11q13, one derived from a MEN1 patient. The p27 gene was expressed in all PETs at a level higher than the normal pancreatic tissues, except for one tumour. Promoter methylation was not detected for p18 and p27. p15 expression was undetectable in 8/18 (44%) of the PETs, and no general relations to tumour syndrome, malignancy or MEN1 gene mutations were evident. This was not due to homozygous gene deletions, but the p15 promoter was hypermethylated in two insulinomas. No mutations were found in the pl5 gene. Conclusions Expression of p15, p18 and p27 was not generally related to the MEN1 gene mutational status of the investigated 18 PETs. The p15 gene was silenced by promoter hypermethylation in two tumours. Dysregulation of menin and the CDIs are important in PET tumorigenesis, and their interrelations remain to be elucidated.
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- Lindberg, Daniel, et al.
(författare)
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Mutational analyses of WNT7A and HDAC11 as candidate tumour suppressor genes in sporadic malignant pancreatic endocrine tumours
- 2007
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Ingår i: Clinical Endocrinology. - : Wiley. - 0300-0664 .- 1365-2265. ; 66:1, s. 110-114
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Tidskriftsartikel (refereegranskat)abstract
- 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 PPARγ, 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.
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- Segersten, Ulrika, et al.
(författare)
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Potentiating effects of non-active/active vitamin D analogues and ketoconazole in parathyroid cells
- 2007
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Ingår i: Clinical Endocrinology. - : Wiley. - 0300-0664 .- 1365-2265. ; 66:3, s. 399-404
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Tidskriftsartikel (refereegranskat)abstract
- Background and objective: 1,25-dihydroxyvitamin D3 [1α,25(OH)2D3, calcitriol], and its less calcaemic synthetic analogues have therapeutic potential in several diseases, including hyperparathyroidism (HPT). We have suggested that non-1α-hydroxylated (nonactive) vitamin D analogues may present an alternative in tumour cells expressing 25-hydroxyvitamin D3 1α-hydroxylase (1α-hydroxylase). The aim of this study was to investigate biological effects of a non-1α-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-1α-hydroxylated precursor of the vitamin D analogue EB1089, suppressed PTH secretion and PTH mRNA level as well as increased expression of 25-hydroxyvitamin D3-24-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-1α-hydroxylated vitamin D analogue may elicit vitamin D receptor (VDR) effects in 1α-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.
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