| 1. |
- Asp, Julia, 1973, et al.
(författare)
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Alterations in the regulatory pathway involving p16, pRb and cdk4 in human chondrosarcoma.
- 2001
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Ingår i: Journal of orthopaedic research : official publication of the Orthopaedic Research Society. - 0736-0266. ; 19:1, s. 149-54
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Tidskriftsartikel (refereegranskat)abstract
- The G1 regulatory pathway involving p16, pRb and cdk4 in the cell cycle has been investigated in human chondrosarcoma. The protein expression of p16, pRb and cdk4 was analyzed by Western blot in cultured cells from eight chondrosarcomas and in two chondrosarcoma cell lines. Both cell lines and one other sample were negative for p16. Moreover, one of the cell lines was pRb-negative and showed a high expression of cdk4 as well. In the other cell line and in three other samples pRb of expected size were detected in addition to a shorter form of the protein. To further investigate the reasons for down-regulation of the p16 protein, the p16-coding gene CDKN2 was analyzed by polymerase chain reaction (PCR), methyl-specific PCR (MSP) and sequencing in all tumor samples as well as in corresponding tumor tissues from three of the samples. The p16-negative samples were all found to have homozygous deletion of CDKN2. Another sample showed partial gene methylation and a heterozygous position in codon 148 was detected in one sample. The same base substitution was also found in two of the tissue samples. Finally, cytogenetic analysis of the samples with homozygously deleted CDKN2 revealed multiple structural abnormalities in all three cases. In conclusion, the p16/pRb/cdk4 pathway may play an important role in the pathogenesis of some chondrosarcomas.
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| 2. |
- Asp, Julia, 1973
(författare)
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Cell cycle genes in chondrosarcoma. Involvement of the Id1 and p16 pathways
- 2002
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Chondrosarcoma is a malignant, cartilaginous tumour arising from bone. The wide variationin morphology, behaviour and clinical outcome raise the question whether chondrosarcomasare several different but closely related tumours rather than a single entity. On the cellularlevel, little is known about the molecular events responsible for the development andprogression of chondrosarcoma. The aim of this thesis was to investigate if the tumoursuppressor p16 and the helix-loop-helix (HLH) transcription factor Id1 and their regulatorypathways in the G1 phase of the cell cycle were affected in chondrosarcoma.Cultured cells and tissue from 34 human chondrosarcomas were investigated for geneticdefects by polymerase chain reaction (PCR) based methods and for changes in expressionpatterns of p16, p14ARF, p53, pRb, cdk4, Id1, Id3, E12 and MIDA1.While a structurally unchanged p53-gene was revealed in all samples analysed and only onehomozygous deletion of the p14ARF gene was found, the p16 gene showed homozygousdeletion, methylation and sequence deviations in preferable high-grade tumour tissue fromnine of 22 chondrosarcomas and in three of eight cultures of chondrosarcoma cells as well asin two chondrosarcoma cell lines. The protein expression of p16, pRb and cdk4 was analysedby Western blot in the cultured cells and several changes in the expression was detected incells from four of the eight tumours and in both cell lines. The expression and localisation ofId1 and Id3, as well as localisation of the E12-protein in cultured cells were studied byribonuclease protection assay, Western blot and immunohistochemistry. Id1 demonstrated astrong expression in chondrosarcoma cells also after serum withdrawal from the culturemedia, in contrast to normal chondrocytes where the expression was down-regulated.Moreover, antisense oligonucleotides directed against Id1 and Id3 decreased the mitoticactivity as measured by BrdU-labelling in both cell types. E12 had a nuclear localisation inchondrocytes and non-confluent tumour cells but in confluent tumour cells, E12 was found inthe cytoplasm. A previously unreported splicing form of MIDA1, a non-HLH protein bindingto Id1, was also found. The expression of MIDA1, Id1 and p16 studied by real-time PCRshowed that the expression levels of MIDA1 were rather constant between samples, while theexpressions of Id1 and p16 varied. The lowest levels of p16 expression were found inchondrosarcomas with worse prognosis, suggesting a possible role for p16 expression as aprognostic factor.The results from this thesis show that important genes in the G1 regulation of the cell cycleare changed in chondrosarcoma. Different defects in tumours with the same histological gradesupport the theory that chondrosarcomas may be several closely related tumours.
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| 3. |
- Asp, Julia, 1973, et al.
(författare)
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Changes in p14(ARF) do not play a primary role in human chondrosarcoma tissues.
- 2001
-
Ingår i: International journal of cancer. Journal international du cancer. - 0020-7136. ; 93:5, s. 703-5
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Tidskriftsartikel (refereegranskat)abstract
- The locus encoding the tumor suppressor p16 has been found to code for a second, different protein. This protein, p14(ARF), has been shown to protect p53 from degradation. Like p16, its gene is often altered in different cancers. In this study, the first unique exon, exon 1 beta, of p14(ARF), has been studied in 22 chondrosarcoma tissues using polymerase chain reaction, DNA sequencing and methylation-specific polymerase chain reaction. One chondrosarcoma was found to have exon 1 beta homozygously deleted, but neither mutations nor methylations were found in any of the chondrosarcomas. This indicates that genetic changes of p14(ARF) are a rare event in chondrosarcoma.
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| 4. |
- Asp, Julia, 1973, et al.
(författare)
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Changes of the p16 gene but not the p53 gene in human chondrosarcoma tissues.
- 2000
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Ingår i: International journal of cancer. Journal international du cancer. - 0020-7136. ; 85:6, s. 782-6
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Tidskriftsartikel (refereegranskat)abstract
- The role of two important tumour suppressor genes, p16 and p53, was evaluated in cartilaginous tumour tissues. Genomic DNA from 22 chondrosarcomas, 5 benign chondroid tumours, 1 sample of reactive proliferative cartilage and 2 samples of normal cartilage were analysed using polymerase chain reaction, single strand conformational polymorphism, DNA sequencing and methylation-specific polymerase chain reaction. The p16 gene was found to be partly methylated in 5 high-grade chondrosarcomas and homozygously deleted in 1 chondrosarcoma. Moreover, a polymorphism was detected in 3 malignant tumours, but not in benign tumours or normal cartilage. Analysis of the p53 gene revealed an unchanged structure in all samples. These findings show a role for p16, but not p53, in chondrosarcoma.
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| 5. |
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| 6. |
- Ropero, Santiago, et al.
(författare)
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Epigenetic loss of the familial tumor-suppressor gene exostosin-1 (EXT1) disrupts heparan sulfate synthesis in cancer cells.
- 2004
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Ingår i: Human molecular genetics. - : Oxford University Press (OUP). - 0964-6906 .- 1460-2083. ; 13:22, s. 2753-65
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Tidskriftsartikel (refereegranskat)abstract
- Germline mutations in the Exostoses-1 gene (EXT1) are found in hereditary multiple exostoses syndrome, which is characterized by the formation of osteochondromas and an increased risk of chondrosarcomas and osteosarcomas. However, despite its putative tumor-suppressor function, little is known of the contribution of EXT1 to human sporadic malignancies. Here, we report that EXT1 function is abrogated in human cancer cells by transcriptional silencing associated with CpG island promoter hypermethylation. We also show that, at the biochemical and cellular levels, the epigenetic inactivation of EXT1, a glycosyltransferase, leads to the loss of heparan sulfate (HS) synthesis. Reduced HS production can be reversed by the use of a DNA demethylating agent. Furthermore, the re-introduction of EXT1 into cancer cell lines displaying methylation-dependent silencing of EXT1 induces tumor-suppressor-like features, e.g. reduced colony formation density and tumor growth in nude mouse xenograft models. Screening a large collection of human cancer cell lines (n=79) and primary tumors (n=454) from different cell types, we found that EXT1 CpG island hypermethylation was common in leukemia, especially acute promyelocytic leukemia and acute lymphoblastic leukemia, and non-melanoma skin cancer. These findings highlight the importance of EXT1 epigenetic inactivation, leading to an abrogation of HS biosynthesis, in the processes of tumor onset and progression.
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