[Show abstract][Hide abstract] ABSTRACT: Most soft tissue sarcomas are characterized by genetic instability and frequent genomic copy number aberrations that are not subtype-specific. Oligonucleotide microarray-based Comparative Genomic Hybridisation (array CGH) is an important technique used to map genome-wide copy number aberrations, but the traditional requirement for high-quality DNA typically obtained from fresh tissue has limited its use in sarcomas. Although large archives of Formalin-fixed Paraffin-embedded (FFPE) tumour samples are available for research, the degradative effects of formalin on DNA from these tissues has made labelling and analysis by array CGH technically challenging. The Universal Linkage System (ULS) may be used for a one-step chemical labelling of such degraded DNA. We have optimised the ULS labelling protocol to perform aCGH on archived FFPE leiomyosarcoma tissues using the 180k Agilent platform. Preservation age of samples ranged from a few months to seventeen years and the DNA showed a wide range of degradation (when visualised on agarose gels). Consistently high DNA labelling efficiency and low microarray probe-to-probe variation (as measured by the derivative log ratio spread) was seen. Comparison of paired fresh and FFPE samples from identical tumours showed good correlation of CNAs detected. Furthermore, the ability to macro-dissect FFPE samples permitted the detection of CNAs that were masked in fresh tissue. Aberrations were visually confirmed using Fluorescence in situ Hybridisation. These results suggest that archival FFPE tissue, with its relative abundance and attendant clinical data may be used for effective mapping for genomic copy number aberrations in such rare tumours as leiomyosarcoma and potentially unravel clues to tumour origins, progression and ultimately, targeted treatment.
[Show abstract][Hide abstract] ABSTRACT: Uveal melanoma (UM) is the most common primary intraocular cancer of adults and is characterized by several well-established chromosomal changes. More recently, a specific mutation of guanine nucleotide binding protein Gq alpha subunit (GNAQ) has also been identified in a proportion of UM. Although some of these alterations have been suggested to be early changes, the genetic alterations responsible for the development of UM have yet to be clearly determined. Cancers are characterized by increased genetic instability, and analysis of established cancer cell lines and blood from cancer patients has universally been associated with an increased level of sister chromatid exchange (SCE). We have observed that the spontaneous frequency of SCE in primary cultures of UM and UM-derived cell lines is decreased below normal baseline levels, a phenomenon unique to UM when compared with multiple other cancers. This finding was specific to the tumor and not found in lymphocytes from the patients. Although we cannot exclude the possibility that low SCE (LSCE) is peculiar to the uveal melanocytes lineage, as it was consistently observed in all UM studied, regardless of other genetic defects, we propose that this phenomenon contributes to the molecular pathogenesis of UM.
No preview · Article · Jan 2011 · Genes Chromosomes and Cancer
[Show abstract][Hide abstract] ABSTRACT: Gastrointestinal stromal tumours (GISTs) are the most common mesenchymal tumours of the gastrointestinal tract. Formerly GISTs were commonly classified histologically as leiomyosarcomas; however, they are now known to arise from the interstitial cells of Cajal. Majority of GISTs overexpress KIT and have characteristic mutations within the gene, which are the targets of drug treatment with tyrosine kinase inhibitors. Leiomyosarcoma is a malignant tumour of smooth muscle differentiation and falls into a group of sarcomas that show complex karyotypic changes with no consistent recurrent genetic abnormality. We have used comparative genomic hybridization in combination with fluorescence in situ hybridization to determine genetic differences between the tumour types. We found leiomyosarcomas and GISTs share common regions of chromosomal 13q and 11q imbalance, in addition to more specific 1p and 8p losses in leiomyosarcoma and 15q and 22q losses in GISTs. More importantly, we have shown for the first time a deletion in the ataxia telangiectasia mutated (ATM) gene locus with decreased/absent expression of ATM protein, and amplification in the region 13q21-q32 in both tumour types, suggesting both regions may play a role in leiomyosarcoma and GIST biology.
Full-text · Article · Oct 2009 · International Journal of Experimental Pathology
[Show abstract][Hide abstract] ABSTRACT: Ideopathic myelofibrosis (IMF) is a chronic myeloproliferative disorder resulting in bone marrow fibrosis as a consequence of growth factor release from clonal haematopoiesis. Conventional cytogenetic analysis identifies abnormalities in approximately a third of cases at diagnosis, although rarely uncovers unique, primary genetic events. We have used comparative genomic hybridization (CGH) to study 25 IMF cases and have compared the results with conventional cytogenetics. Metaphase cells were available for analysis in 13 cases, of which seven showed an abnormal karyotype. CGH chromosomal profiles showed imbalances in 21 of 25 cases. The most frequent aberrations were gains of 9p (12 cases), 2q (seven cases), 3p (seven cases), chromosome 4 (seven cases), 12q (seven cases), 13q (eight cases). The main losses were at 17q and occurred in six cases. The results for CGH and cytogenetics were matched for one case only. Investigation of IMF by CGH suggests that genomic aberrations are much more common than has been previously indicated by conventional cytogenetic analysis and occur in the majority of cases. Gains of 9p were the most frequent finding, occurring in 50% of patients and suggests that genes on 9p may play a crucial role in the pathogenesis of IMF.
Full-text · Article · May 2005 · British Journal of Haematology