Detailed molecular cytogenetic characterisation of the myeloid cell line U937 reveals the fate of homologous chromosomes and shows that centromere capture is a feature of genome instability.

Background: The U937 cell line is widely employed as a research tool. It has a complex karyotype. A PICALM-MLLT10 fusion gene formed by the recurrent t(10;11) translocation is present, and the myeloid common deleted region at 20q12 has been lost from its near-triploid karyotype.

BCL-XL inhibition by BH3-mimetic drugs induces apoptosis in models of Epstein-Barr virus-associated T/NK-cell lymphoma.

Epstein-Barr virus (EBV)-associated T- and natural killer (NK)-cell malignancies, such as extranodal NK-/T-cell lymphoma (ENKTL), exhibit high chemoresistance and, accordingly, such patients have a poor prognosis. The rare nature of such cancers and nonmalignant T/NK lymphoproliferative disorders, such as chronic active EBV (CAEBV), has limited our understanding of the pathogenesis of these diseases. Here, we characterize a panel of ENKTL- and CAEBV-derived cell lines that had been established from human tumors to be used as preclinical models of these diseases.

Hemopoietic Cell Kinase amplification with Protein Tyrosine Phosphatase Receptor T depletion leads to polycythemia, aberrant marrow erythoid maturation, and splenomegaly.

Deletion of long arm of chromosome 20 [del(20q)] is the second most frequent recurrent chromosomal abnormality in hematological malignancies. It is detected in 10% of myeloproliferative neoplasms, 4-5% of myelodysplastic syndromes, and 1-2% of acute myeloid leukaemia. Recurrent, non-random occurrence of del(20q) indicates that it is a pathogenic driver in myeloid malignancies.

Haploinsufficiency Impairs Catalytic Activity of PARP1 and Promotes Chromosome Instability and Growth of Intestinal Tumors.

ADP-ribosylation is an important posttranslational protein modification that regulates diverse biological processes, controlled by dedicated transferases and hydrolases. Here, we show that frequent deletions (∼30%) of the mono-ADP-ribosylhydrolase locus in human colorectal cancer cause impaired PARP1 transferase activity in a gene dosage-dependent manner. haploinsufficiency alters DNA repair and sensitivity to DNA damage and results in chromosome instability.

Analysis of Chromothripsis by Combined FISH and Microarray Analysis.

Fluorescence in situ hybridization (FISH) to metaphase chromosomes, in conjunction with SNP array, array CGH, or whole genome sequencing, can help determine the organization of abnormal genomes after chromothripsis and other types of complex genome rearrangement. DNA microarrays can identify the changes in copy number, but they do not give information on the organization of the abnormal chromosomes, balanced rearrangements, or abnormalities of the centromeres and other regions comprised of highly repetitive DNA. Many of these details can be determined by the strategic use of metaphase FISH.

The Dicentric Chromosome dic(20;22) Is a Recurrent Abnormality in Myelodysplastic Syndromes and Is a Product of Telomere Fusion.

We describe a recurrent dicentric chromosome formed by telomere fusion between chromosome 20 and chromosome 22 in 4 cases of myelodysplastic syndromes (MDS) or acute myeloid leukaemia (AML). In particular, the presence of residual telomere sequences at the site of translocation in 3 of the 4 cases makes a compelling case for telomere fusion. This is the first description of a recurrent telomere fusion event in any malignant condition.

Active centromere and chromosome identification in fixed cell lines.

Background: The centromere plays a crucial role in ensuring the fidelity of chromosome segregation during cell divisions. However, in cancer and constitutional disorders, the presence of more than one active centromere on a chromosome may be a contributing factor to chromosome instability and could also have predictive value in disease progression, making the detection of properly functioning centromeres important. Thus far, antibodies that are widely used for functional centromere detection mainly work on freshly harvested cells whereas most cytogenetic samples are stored long-term in methanol-acetic acid fixative.

Src family kinases and their role in hematological malignancies.

The Src family protein tyrosine kinases (SFKs) are non-receptor intracellular kinases that have important roles in both hematopoiesis and leukemogenesis. The derangement of their expression or activation has been demonstrated to contribute to hematological malignancies. This review first examines the mechanisms of SFK overexpression and hyperactivation, emphasizing the dysregulation of the upstream modulators.

Genome organization and the role of centromeres in evolution of the erythroleukaemia cell line HEL.

Background And Objectives: The human erythroleukaemia (HEL) cell line has a highly rearranged genome. We matched whole chromosome analysis with cytogenomic microarray data to build a detailed description of these rearrangements.

Methodology: We used a combination of single nucleotide polymorphism array and multiple fluorescence in situ hybridization approaches, and compared our array data with publicly available data for different sublines of HEL.

Chromothripsis under the microscope: a cytogenetic perspective of two cases of AML with catastrophic chromosome rearrangement.

Chromothripsis is a recently described phenomenon identified in cancer cells that produces catastrophic chromosome reorganization of one or a small number of chromosomes. It has been proposed that the multiple breakage events occur at a single point in time. Here we introduce the term anachromosome to describe an abnormal chromosome produced by chromothripsis.

CGH and SNP array using DNA extracted from fixed cytogenetic preparations and long-term refrigerated bone marrow specimens.

Background: The analysis of nucleic acids is limited by the availability of archival specimens and the quality and amount of the extracted material. Archived cytogenetic preparations are stored in many laboratories and are a potential source of total genomic DNA for array karyotyping and other applications. Array CGH using DNA from fixed cytogenetic preparations has been described, but it is not known whether it can be used for SNP arrays.

A cryptic deletion in 5q31.2 provides further evidence for a minimally deleted region in myelodysplastic syndromes.

Recurrent deletions of 5q in myeloid malignancies encompass two separate regions: deletion of 5q33, which is associated with the 5q− syndrome and haploinsufficiency of RPS14, and deletion of a more proximal locus at 5q31. We present a case with a cryptic 1.3 Mb deletion in 5q31.

Unbalanced translocations of 20q in AML and MDS often involve interstitial rather than terminal deletions of 20q.

Dicentric chromosomes can occur in myelodysplastic syndromes and acute myeloid leukemia. As these unbalanced rearrangements often combine two recurrent deletions, they could be an efficient mechanism for the loss of two tumor suppressor genes in a single step. We report here that dicentric chromosomes involving chromosome 20 with loss of the 20q12 putative tumor suppressor gene are often the result of more complex rearrangements, with the 20q12 region being lost by an interstitial deletion independent of the site of translocation.

The use of M-FISH and M-BAND to define chromosome abnormalities.

Multicolour fluorescence in situ hybridisation (M-FISH) and multicolour banding (M-BAND) are advanced chromosome painting techniques combining multiple chromosome- or region-specific paints in one step. M-FISH identifies all chromosomes or chromosome arms at once, whereas M-BAND identifies the different regions of a single chromosome. The use of either or both can improve the accuracy of karyotyping and help identify cryptic chromosome rearrangements.

The role of dicentric chromosome formation and secondary centromere deletion in the evolution of myeloid malignancy.

Dicentric chromosomes have been identified as instigators of the genome instability associated with cancer, but this instability is often resolved by one of a number of different secondary events. These include centromere inactivation, inversion, and intercentromeric deletion. Deletion or excision of one of the centromeres may be a significant occurrence in myeloid malignancy and other malignancies but has not previously been widely recognized, and our reports are the first describing centromere deletion in cancer cells.

The paradox of 20q11.21 amplification in a subset of cases of myeloid malignancy with chromosome 20 deletion.

Deletion of the long arm of one chromosome 20 (del(20q)) is a well-recognized abnormality in acute myeloid leukemia (AML) and myelodysplastic syndromes (MDS) and is presumed to cause loss of a tumor suppressor gene at 20q12. In a previously published series of MDS and AML cases, which had lost this region via unbalanced translocation, around 40% of cases were shown to have additional copies of the chromosome 20 abnormalities, with resulting gain or amplification of the retained parts of chromosome 20, most often 20q11.2.

A FISH comparison of variant derivatives of the recurrent dic(17;20) of myelodysplastic syndromes and acute myeloid leukemia: Obligatory retention of genes on 17p and 20q may explain the formation of dicentric chromosomes.

The dic(17;20) is a recurrent unbalanced translocation occurring rarely in myelodysplastic syndromes and acute myeloid leukemia. We have studied eleven cases with the dic(17;20) or a more complex derivative, all of which showed deletion of 17p and 20q material. The tumor suppressor gene TP53 was not always lost, supporting a more distal gene as the target of these 17p deletions.

A comparison of two contrasting recurrent isochromosomes 20 found in myelodysplastic syndromes suggests that retention of proximal 20q is a significant factor in myeloid malignancies.

We compare two different isochromosomes of chromosome 20 in myelodysplastic syndromes (MDS): an isochromosome of the short arm of chromosome 20, idic(20)(q11), and an isochromosome of the long arm of a deleted chromosome 20, ider(20)(q10)del(20)(q11.2). The isochromosomes are of contrasting morphology, because opposite arms are duplicated, but they both show loss of the critical region at 20q12, as well as retention and duplication of the centromere and proximal long arm (20q11).

Recurrent duplication of Xq27-qter in hematological malignancies revealed by multicolor fluorescence in situ hybridization and multicolor banding.

Multicolor fluorescence in situ hybridization (M-FISH) experiments were performed to determine the composition of abnormal complex karyotypes in 15 cases of hematological malignancy. Four cases were found to have unsuspected unbalanced X chromosome translocations, which resulted in the presence of extra X chromosome material. We determined the identity of the duplicated chromosome regions using the multicolor banding (mBAND) technique.