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- Gisselsson Nord, David, et al.
(author)
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Generation of trisomies in cancer cells by multipolar mitosis and incomplete cytokinesis.
- 2010
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In: Proceedings of the National Academy of Sciences. - : Proceedings of the National Academy of Sciences. - 1091-6490 .- 0027-8424. ; 107:47, s. 20489-20493
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Journal article (peer-reviewed)abstract
- One extra chromosome copy (i.e., trisomy) is the most common type of chromosome aberration in cancer cells. The mechanisms behind the generation of trisomies in tumor cells are largely unknown, although it has been suggested that dysfunction of the spindle assembly checkpoint (SAC) leads to an accumulation of trisomies through failure to correctly segregate sister chromatids in successive cell divisions. By using Wilms tumor as a model for cancers with trisomies, we now show that trisomic cells can form even in the presence of a functional SAC through tripolar cell divisions in which sister chromatid separation proceeds in a regular fashion, but cytokinesis failure nevertheless leads to an asymmetrical segregation of chromosomes into two daughter cells. A model for the generation of trisomies by such asymmetrical cell division accurately predicted several features of clones having extra chromosomes in vivo, including the ratio between trisomies and tetrasomies and the observation that different trisomies found in the same tumor occupy identical proportions of cells and colocalize in tumor tissue. Our findings provide an experimentally validated model explaining how multiple trisomies can occur in tumor cells that still maintain accurate sister chromatid separation at metaphase-anaphase transition and thereby physiologically satisfy the SAC.
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- Lundberg, Gisela, et al.
(author)
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Alternative lengthening of telomeres--an enhanced chromosomal instability in aggressive non-MYCN amplified and telomere elongated neuroblastomas.
- 2011
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In: Genes, chromosomes & cancer. - : Wiley. - 1098-2264 .- 1045-2257. ; 50:4, s. 250-62
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Journal article (peer-reviewed)abstract
- Telomere length alterations are known to cause genomic instability and influence clinical course in several tumor types, but have been little investigated in neuroblastoma (NB), one of the most common childhood tumors. In the present study, telomere-dependent chromosomal instability and telomere length were determined in six NB cell lines and fifty tumor biopsies. The alternative lengthening of telomeres (ALT) pathway was assayed by scoring ALT-associated promyelocytic leukemia (PML) bodies (APBs). We found a reduced probability of overall survival for tumors with increased telomere length compared to cases with reduced or unchanged telomere length. In non-MYCN amplified tumors, a reduced or unchanged telomere length was associated with 100% overall survival. Tumor cells with increased telomere length had an elevated frequency of APBs, consistent with activation of the ALT pathway. The vast majority of tumor biopsies and cell lines exhibited an elevated rate of anaphase bridges, suggesting telomere-dependent chromosomal instability. This was more pronounced in tumors with increased telomere length. In cell lines, there was a close correlation between lack of telomere-protective TTAGGG-repeats, anaphase bridging, and remodeling of oncogene sequences. Thus, telomere-dependent chromosomal instability is highly prevalent in NB, and may contribute to the complexity of genomic alterations as well as therapy resistance in the absence of MYCN amplification and in this tumor type.
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| 4. |
- Lundberg, Gisela, et al.
(author)
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Intratumour diversity of chromosome copy numbers in neuroblastoma mediated by on-going chromosome loss from a polyploid state.
- 2013
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In: PLoS ONE. - : Public Library of Science (PLoS). - 1932-6203. ; 8:3
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Journal article (peer-reviewed)abstract
- Neuroblastomas (NBs) are tumours of the sympathetic nervous system accounting for 8-10% of paediatric cancers. NBs exhibit extensive intertumour genetic heterogeneity, but their extent of intratumour genetic diversity has remained unexplored. We aimed to assess intratumour genetic variation in NBs with a focus on whole chromosome changes and their underlying mechanism. Allelic ratios obtained by SNP-array data from 30 aneuploid primary NBs and NB cell lines were used to quantify the size of clones harbouring specific genomic imbalances. In 13 cases, this was supplemented by fluorescence in situ hybridisation to assess copy number diversity in detail. Computer simulations of different mitotic segregation errors, single cell cloning, analysis of mitotic figures, and time lapse imaging of dividing NB cells were used to infer the most likely mechanism behind intratumour variation in chromosome number. Combined SNP array and FISH analyses showed that all cases exhibited higher inter-cellular copy number variation than non-neoplastic control tissue, with up to 75% of tumour cells showing non-modal chromosome copy numbers. Comparisons of copy number profiles, resulting from simulations of different segregation errors to genomic profiles of 120 NBs indicated that loss of chromosomes from a tetraploid state was more likely than other mechanisms to explain numerical aberrations in NB. This was supported by a high frequency of lagging chromosomes at anaphase and polyploidisation events in growing NB cells. The dynamic nature of numerical aberrations was corroborated further by detecting substantial copy number diversity in cell populations grown from single NB cells. We conclude that aneuploid NBs typically show extensive intratumour chromosome copy number diversity, and that this phenomenon is most likely explained by continuous loss of chromosomes from a polyploid state.
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- Sehic, Daniel, et al.
(author)
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Absence of Epstein-Barr and Cytomegalovirus Infection in Neuroblastoma Cells by Standard Detection Methodologies.
- 2013
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In: Pediatric Blood & Cancer. - : Wiley. - 1545-5017 .- 1545-5009. ; 60:9, s. 91-93
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Journal article (peer-reviewed)abstract
- Indications exist in the scientific literature that infection with human herpes family viruses may contribute to the pathogenesis of neuroblastoma (NB). However, systematic investigations regarding viral presence in NB cells have been scarcely reported. Here, the presence of DNA from Epstein-Barr virus (EBV) and human cytomegalovirus (HCMV) was assessed by PCR in 12 NBs, supplemented with RNA in situ hybridization, immunohistochemical detection, and high-throughput DNA sequencing. These standard methods did not detect infection by EBV or HCMV in NB cells in any tumor, while occasional immune cells were positive for EBV RNA or HCMV protein in four cases. Pediatr Blood Cancer © 2013 Wiley Periodicals, Inc.
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- Sehic, Daniel
(author)
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Identification, Validation and Implementation of Blastemal Biomarkers in Wilms Tumour
- 2014
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Doctoral thesis (other academic/artistic)abstract
- The aim of this thesis has been to establish biomarkers for the blastemal element in Wilms tumour (WT) – the most common paediatric kidney cancer. Blastema is, together with epithelium and stroma, one of the three common histological elements of WT. WTs dominated by blastema after preoperative chemotherapy are classified as high risk tumours. According to the SIOP2001 protocol used in most European countries today, there is no recommendation of using molecular markers for WT risk stratification and this assessment is based on clinico-histological parameters alone. Patients with high risk tumours receive an extensive treatment, which may results in severe long term side effects. To secure an accurate estimation of the amount of blastemal elements a marker for detection of WT blastemal cells could be a useful tool, indirectly leading to a more precise risk estimation. Literature studies and gene expression data were used to identify potential markers for WT blastema. The protein expressions for candidate markers were evaluated by immunofluorescence on WT cell lines and paraffin-embedded WT tissue sections. Tissue microarrays were constructed to improve the efficiency of this process and the most prominent marker was also validated by immunohistochemical protein staining, to prepare it for clinical use. The two proteins found to have the most specific expression in blastemal cells were SIX1 and CITED1. These proteins are transcription factors expressed during kidney development and both were shown to be highly expressed in the blastemal element of WT (89% and 100%, of WT cases, respectively). SIX1 and CITED1 also displayed some expression in the epithelial (25% and 64%, respectively) and stromal (52% and 48%, respectively) elements. Since particularly CITED1 was highly expressed in epithelial components, SIX1 was selected for further clinical evaluation. In summary, SIX1 appeared to be a useful marker for defining blastemal elements in WT. SIX1 does not replace a pathologist’s evaluation and should only be used as a tool to help give a more accurate estimation of the extent of the blastemal elements in WT.
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| 8. |
- Sehic, Daniel, et al.
(author)
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SIX1 protein expression selectively identifies blastemal elements in Wilms tumor.
- 2012
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In: Pediatric Blood & Cancer. - : Wiley. - 1545-5017 .- 1545-5009. ; 59:1, s. 62-68
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Journal article (peer-reviewed)abstract
- BACKGROUND: Wilms tumor (WT) is the most common renal neoplasm in children. Histologically, most WTs consist of three tissue elements: blastema, epithelium, and stroma. Some cases also show diffuse or focal anaplastic features. Previous studies have shown that a predominance of blastemal cells in post-chemotherapy WT specimens is associated with a poor clinical course. However, there is currently no molecular marker for blastemal cells, and risk stratification for post-nephrectomy treatment is therefore often based on clinico-histological parameters alone. PROCEDURE: In the present study, three public gene expression microarray datasets, including 82 WTs and 8 normal fetal kidneys, were used to establish a consensus gene expression profile of WT. By bioinformatic analyses, 17 genes overexpressed in WT compared to fetal kidney were then selected for evaluation of their protein expression in WT cell lines and in the different histological components in paraffin-embedded WT tissue sections by immunofluorescence. RESULTS: Most of the evaluated proteins were expressed in all three common histological components. A prominent exception was SIX1, being expressed predominantly in blastemal elements in 24/25 pediatric cases containing blastema. Anaplastic elements exhibited highly variable SIX1-positivity. The SIX2 protein, known to be co-expressed with SIX1 during nephrogenesis, only exhibited blastemal-predominant expression in half of the SIX2 evaluated cases. CONCLUSIONS: Genes highly expressed in WT compared to fetal kidney are generally overexpressed in all of the three common WT tissue elements. An exception is the predominant expression of SIX1 in blastemal cells, hereby identifying this protein as a candidate marker for blastema. Pediatr Blood Cancer © 2011 Wiley Periodicals, Inc.
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