| 41. |
- Gisselsson Nord, David, et al.
(författare)
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Interphase chromosomal abnormalities and mitotic missegregation of hypomethylated sequences in ICF syndrome cells
- 2005
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Ingår i: Chromosoma. - : Springer Science and Business Media LLC. - 0009-5915 .- 1432-0886. ; 114:2, s. 118-126
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Tidskriftsartikel (refereegranskat)abstract
- The immunodeficiency, centromeric region instability, facial anomalies (ICF) syndrome is a rare autosomal recessive disease. Usually, it is caused by mutations in the DNA methyltransferase 3B gene, which result in decreased methylation of satellite DNA in the juxtacentromeric heterochromatin at 1qh, 16qh, and 9qh. Satellite II-rich 1qh and 16qh display high frequencies of abnormalities in mitogen-stimulated ICF lymphocytes without these cells being prone to aneuploidy. Here we show that in lymphoblastoid cell lines from four ICF patients, there was increased colocalization of the hypomethylated 1qh and 16qh sequences in interphase, abnormal looping of pericentromeric DNA sequences at metaphase, formation of bridges at anaphase, chromosome 1 and 16 fragmentation at the telophase-interphase transition, and, in apoptotic cells, micronuclei with overrepresentation of chromosome 1 and 16 material. Another source of anaphase bridging in the ICF cells was random telomeric associations between chromosomes. Our results elucidate the mechanism of formation of ICF chromosome anomalies and suggest that 1qh-16qh associations in interphase can lead to disturbances of mitotic segregation, resulting in micronucleus formation and sometimes apoptosis. This can help explain why specific types of 1qh and 16qh rearrangements are not present at high frequencies in ICF lymphoid cells despite diverse 1qh and 16qh aberrations continuously being generated.
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| 42. |
- Gisselsson Nord, David
(författare)
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Intratumor diversity and clonal evolution in cancer-a skeptical standpoint.
- 2011
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Ingår i: Advances in Cancer Research. - 0065-230X. ; 112, s. 1-9
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Tidskriftsartikel (refereegranskat)abstract
- Clonal evolution in cancer is intimately linked to the concept of intratumor cellular diversity, as the latter is a prerequisite for Darwinian selection at the micro-level. It has been frequently suggested in the literature that clonal evolution can be promoted by an elevated rate of mutation in tumor cells, so-called genomic instability, the mechanisms of which are now becoming increasingly well characterized. However, several issues need clarification before the presumably complex relationship between mutation rate, intratumor diversity, and clonal evolution can be understood sufficiently well to translate into models that predict the course of tumor disease. In particular, it has to be clarified which of the proposed mechanisms for genomic instability that are able to generate daughter cells with sufficient viability to form novel clones, how clones with different genomic changes differ phenotypically from each other, and what the selective forces are that guide competition among diverse clones in different microenvironments. Furthermore, standardized measurements of mutation rates at the chromosome level, as well as genotypic and phenotypic diversity, are essential to compare data from different studies. Finally, the relationship between clonal variation brought about by genomic instability, on the one hand, and cellular differentiation hierarchies, on the other hand, should be explored to put genomic instability in the context of the tumor stem cell hypothesis.
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| 43. |
- Gisselsson Nord, David, et al.
(författare)
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Locus-specific multifluor FISH analysis allows physical characterization of complex chromosome abnormalities in neoplasia
- 2000
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Ingår i: Genes, Chromosomes and Cancer. - 1045-2257. ; 28:3, s. 347-352
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Tidskriftsartikel (refereegranskat)abstract
- Novel techniques in molecular cytogenetics have radically improved the ability to characterize genetic changes in neoplastic cells. In parallel, a rapid development in high-throughput genomics has resulted in detailed physical maps of the human genome. Combining these two fields, we have developed a method for the simultaneous visualization of several physically defined segments along a chromosome. Seven YAC clones and one subtelomeric cosmid clone from chromosome 12 were labeled with unique combinations of four fluors and hybridized to metaphase chromosomes from neoplastic cells. In a uterine leiomyoma and a myxoid liposarcoma with translocations 12;14 and 12;16, the breakpoints in chromosome 12 could be localized to the HMGIC and CHOP regions, respectively. In the other tumors, more complex aberrations were visualized, including two inversions in 12q with a common breakpoint between MDM2 and D12S332 in a pleomorphic adenoma, amplification of MDM2 and CDK4 in ring chromosomes from a malignant fibrous histiocytoma, and amplification of KRAS2 together with other unbalanced rearrangements in two pancreatic adenocarcinomas. Combinatorially labeled single-copy probes may thus simultaneously provide physical localization of breakpoints and an overview of complex structural rearrangements.
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| 44. |
- Gisselsson Nord, David
(författare)
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Mechanisms of Whole Chromosome Gains in Tumors - Many Answers to a Simple Question.
- 2011
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Ingår i: Cytogenetic and Genome Research. - : S. Karger AG. - 1424-859X .- 1424-8581. ; 133, s. 190-201
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Tidskriftsartikel (refereegranskat)abstract
- Whole chromosome gain is the most common type of gross genomic abnormality observed in human tumors. It is particularly frequent in lympho-haematopoietic and embryonic neoplasms, where trisomies and tetrasomies are typically present together with few or no other cytogenetic imbalances, resulting in hyperdiploid chromosome numbers. Despite the high prevalence of whole chromosome gains in neoplastic cells, their mechanism of origin remains disputed. Here, 4 potential models for the generation of whole chromosome gains are reviewed: (1) loss of chromosomes from the tetraploid level, (2) sequential sister chromatid non-disjunction, (3) multipolar mitosis coupled to sister chromatid non-disjunction, and (4) multipolar mitosis coupled to incomplete cytokinesis. Each of these mechanisms may in theory result in the generation of hyperdiploid neoplastic clones, but none of them were single-handedly able to reproduce the scenario of chromosome copy number alterations in tumors when cell populations resulting from these models were simulated in silico and compared to published cytogenetic data. To develop models for the generation of whole chromosome gains further, it is critical to improve our knowledge of the principles of clonal selection in tumors and of the baseline rate of chromosome segregation errors in human cells. To illustrate this, a model combining multipolar mitosis coupled to incomplete cytokinesis with a low rate of baseline sister chromatid non-disjunction was shown readily to reproduce copy number distributions in hyperdiploid karyotypes from human tumors.
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| 45. |
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| 46. |
- Gisselsson Nord, David
(författare)
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Mitotic instability in cancer - Is there method in the madness?
- 2005
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Ingår i: Cell Cycle. - 1551-4005. ; 4:8, s. 1007-1010
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Tidskriftsartikel (refereegranskat)abstract
- It has been known for more than a century that neoplastic cells often exhibit disturbances of the mitotic process, but the causes have only recently been thoroughly explored. In many cancers, a combination of cell cycle checkpoint deficiency and abnormal shortening of telomeres predisposes to unbalanced chromosome segregation at cell division and the development of complex genomic rearrangements. Shortening of telomeric repeats beyond normal limits leads to fusion of chromosome ends and the formation of chromatin bridges at anaphase. In turn, these bridges may trigger at least three types of chromosomes mutation: ( 1) structural rearrangements of chromosomes through extensive chromatin fragmentation beyond the centromeric sequences, typically leading to the formation of isochromosomes and whole-arm translocations, ( 2) loss of whole chromosomes through mechanical detachment from the mitotic spindle machinery, and ( 3) failure of cytokinesis, leading to polyploidisation and supernumerary centrosomes, which may in turn orchestrate multipolar spindle configurations at a subsequent mitosis. Anaphase bridging rarely hinders further survival of tumor daughter cells. In contrast, multipolar mitoses may lead to extensive reshuffling of chromosome copies that compromise further clonal expansion. The telomere-dependent instability can be partly counteracted by expression of telomerase during tumor progression, but genomic stabilisation is rarely, if ever, complete.
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| 47. |
- Gisselsson Nord, David, et al.
(författare)
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PLAG1 alterations in lipoblastoma: involvement in varied mesenchymal cell types and evidence for alternative oncogenic mechanisms
- 2001
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Ingår i: American Journal of Pathology. - 1525-2191. ; 159:3, s. 955-962
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Tidskriftsartikel (refereegranskat)abstract
- Lipoblastomas are rare soft tissue tumors that occur primarily in young children. They typically contain variably differentiated adipocytes, primitive mesenchymal cells, myxoid matrix, and fibrous trabeculae. Abnormalities in chromosome 8, leading to rearrangements of the PLAG1 gene, were demonstrated recently in four lipoblastomas. In the present report, we determine the frequency of PLAG1 alterations in 16 lipoblastomas from children aged 13 years or younger, and we also evaluate the stages of lipoblastoma differentiation at which PLAG1 genomic alterations are found. Eleven lipoblastomas (69%), including those with either classic or lipoma-like histology, had rearrangements of the 8q12 PLAG1 region. Another three lipoblastomas had polysomy for chromosome 8 in the absence of PLAG1 rearrangement. Only two cases (13%) lacked a chromosome 8 abnormality. Notably, the lipoblastomas with chromosome 8 polysomy had up to five copies of chromosome 8 as an isolated cytogenetic finding in an otherwise diploid cell. We also demonstrate that PLAG1 alterations are found in a spectrum of mesenchymal cell types in lipoblastomas, including lipoblasts, mature adipocytes, primitive mesenchymal cells, and fibroblast-like cells. This finding is consistent with neoplastic origin in a primitive mesenchymal precursor and with variable differentiation to a mature adipocyte end-point. Hence, our studies provide biological validation for the clinical observation that lipoblastomas can evolve into mature, lipoma-like, lesions. They also suggest that PLAG1 dosage alterations caused by polysomy 8 might represent an alternative oncogenic mechanism in lipoblastoma.
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| 48. |
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| 49. |
- Gisselsson Nord, David
(författare)
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Refined characterisation of chromosome aberrations in tumours by multicolour banding and electronic mapping resources
- 2001
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Ingår i: Methods in cell science: an official journal of the Society for In Vitro Biology. - 1381-5741. ; 23:1-3, s. 23-28
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Tidskriftsartikel (refereegranskat)abstract
- Acquired chromosome abnormalities in tumours often reflect pathogenetic events at the gene level. Multicolour fluorescence in situ hybridisation (FISH) with single-copy probes offers extensive possibilities to characterise chromosome breakpoints in relation to the physical map of the human genome. This approach is based on the construction of comprehensive EST- based maps, combinatorial labelling of probes, and tumour cell preparations optimised for metaphase FISH. Information from several electronically available databases is combined into an integrated physical map, to which clones carrying yeast and bacterial artificial chromosomes are anchored. Extracted DNA or PCR products from these clones are then fluorescently labelled by one or several fluors, allowing simultaneous FISH detection of multiple loci. To improve hybridisation efficiency and reduce background fluorescence, standard methods for chromosome preparation from cultured tumour cells are complemented with a prolonged trypsin treatment to obtain complete disaggregation of cells, and exposure of the metaphase spreads to detergent and saline at high temperature, followed by pepsin digestion to remove extracellular matrix and cytoplasmic debris. The resulting colour-banding allows the characterisation of chromosome abnormalities in relation to expressed sequences, even in tumours exhibiting highly complex rearrangements.
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| 50. |
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