A novel t(8;18)(q13;q21) in acute monocytic leukemia evolving from constitutional trisomy 8 mosaicism

The epigenetic landscape of aneuploidy: constitutional mosaicism leading the way?

The role of structural genetic changes in human disease has received substantial attention in recent decades, but surprisingly little is known about numerical chromosomal abnormalities, even though they have been recognized since the days of Boveri as partaking in different cellular pathophysiological processes such as cancer and genomic disorders. The current knowledge of the genetic and epigenetic consequences of aneuploidy is reviewed herein, with a special focus on using mosaic genetic syndromes to study the DNA methylation footprints and expressional effects associated with whole-chromosomal gains. Recent progress in understanding the debated role of aneuploidy as a driver or passenger in malignant transformation, as well as how the cell responds to and regulates excess genetic material in experimental settings, is also discussed in detail.

New recurrent balanced translocations in acute myeloid leukemia and myelodysplastic syndromes: cancer and leukemia group B 8461

Acquired chromosome abnormalities in patients with acute myeloid leukemia (AML) and myelodysplastic syndromes (MDS) are among the most valuable determinants of diagnosis and prognosis. In search of new recurrent balanced translocations, we reviewed the Cancer and Leukemia Group B (CALGB) cytogenetics database containing pretreatment and relapse karyotypes of 4,701 adults with AML and 565 with MDS who were treated on CALGB trials. We identified all cases with balanced structural rearrangements occurring as a sole abnormality or in addition to one other abnormality, excluded abnormalities known to be recurrent, and then reviewed the literature to determine whether any of what we considered unique, previously unknown abnormalities had been reported. As a result, we identified seven new recurrent balanced translocations in AML or MDS: t(7;11)(q22;p15.5), t(10;11)(q23;p15), t(2;12)(p13;p13), t(12;17)(p13;q12), t(2;3)(p21;p21), t(5;21)(q31;q22), and t(8;14)(q24.1;q32.2), and additionally, t(10;12)(p11;q15), a new translocation in AML previously reported in a case of acute lymphoblastic leukemia. Herein, we report hematologic and clinical characteristics and treatment outcomes of patients with these newly recognized recurrent translocations. We also report 52 unique balanced translocations, together with the clinical data of patients harboring them, which to our knowledge have not been previously published. We hope that once the awareness of their existence is increased, some of these translocations may become recognized as novel recurring abnormalities. Identification of additional cases with both the new recurrent and the unique balanced translocations will enable determination of their prognostic significance and help to provide insights into the mechanisms of disease pathogenesis in patients with these rare abnormalities.

Chromosomal characterization of cryopreserved mesenchymal stem cells from the human subendothelium umbilical cord vein

AIMS

To conduct a morphological, functional and chromosomal characterization of mesenchymal stem cell populations from the human subendothelium umbilical cord vein after cryopreservation.

MATERIAL & METHODS

Five human umbilical cords were processed in order to obtain mesenchymal stem cells. Flow cytometry, differentiation assays and cytogenetic analysis were carried out before and after the cryopreservation process.

RESULTS

Flow cytometry revealed that CD105, CD73 and CD90 markers were expressed by the cells, which lacked the expression of hematopoietic lineage markers, such as CD14, CD34 and CD45. The mesenchymal stem cells demonstrated capacity for osteogenic, adipogenic and chondrogenic differentiation. Chromosome analysis showed no clonal chromosome changes in the cells in either situation. However, a significant number of nonclonal chromosomal aberrations were apparent after cryopreservation, including monosomies and structural changes. Cells isolated from one umbilical cord exhibited a rare balanced paracentric inversion, likely a cytogenetic constitutional alteration. This was present both before and after experimental procedures.

CONCLUSION

These findings show that using mesenchymal stem cells for clinical approaches requires careful investigation and sensitive tests in order to ensure cellular therapy biosafety.

Mosaiktrisomie 8p11.21q11.21 als Prädisposition für myeloische Leukämien

Bei der juvenilen myelomonozytären Leukämie (JMML) handelt es sich um eine myeloproliferative Erkrankung der frühen Kindheit. Bei vielen Patienten lassen sich zugrunde liegende somatische, aber auch konstitutionelle Mutationen in NRAS, KRAS, PTPN11, NF1 und CBL nachweisen. Zur Identifizierung submikroskopischer Veränderungen, die für die leukämische Transformation von Bedeutung sein können, wurden 20 JMML-Proben mittels hochauflösender Oligo-Microarray-basierter komparativer genomischer Hybridisierung (aCGH) untersucht. Bei 2 von 10 Patienten mit submikroskopischen Aberrationen konnte ein nahezu identischer Zugewinn von Chromosom 8 gezeigt werden, der sich in weiteren Untersuchungen als konstitutionelles Mosaik darstellte. Eine Übersicht von 27 Patienten mit einem konstitutionellen Trisomie-8-Mosaik (cT8M) und maligner Neoplasie zeigte, dass es sich meist um myeloische Neoplasien, auch JMML, handelt. Durch unsere Untersuchungen konnte die kritische Region auf Chromosom 8, deren Loci mutmaßlich an der Leukämieentstehung und/oder Progression beteiligt sein können, dramatisch reduziert werden: 8p11.21q11.21. Es bleibt zu klären in welcher Form das partielle Trisomie-8-Mosaik an der Leukämieentstehung beteiligt ist und in welcher Weise dies für verschiedenen Mutationssubtypen der JMML eine Rolle spielt.

Constitutional trisomy 8p11.21-q11.21 mosaicism: a germline alteration predisposing to myeloid leukaemia

Juvenile myelomonocytic leukaemia (JMML) is a unique myeloproliferative disorder of early childhood. Frequently, mutations in NRAS, KRAS, PTPN11, NF1 or CBL are found in these patients. Monosomy 7 is the most common cytogenetic aberration. To identify submicroscopic genomic copy number alterations, 20 JMML samples were analysed by comparative genomic hybridization. Ten out of 20 samples displayed additional submicroscopic alterations. In two patients, an almost identical gain of chromosome 8 was identified. In both patients, fluorescence in situ hybridization confirmed a constitutional partial trisomy 8 mosaic (cT8M). A survey on 27 cT8M patients with neoplasms showed that 21 had myeloid malignancies, and five of these had a JMML. Notably, the region gained in our cases is the smallest gain of chromosome 8 reported in cT8M cases with malignancies so far. Our results dramatically reduce the critical region to 8p11.21q11.21 harbouring 31 protein coding genes and two non-coding RNAs, e.g. MYST3, IKBKB, UBE2V2, GOLGA7, FNTA and MIR486--a finding with potential implications for the role of somatic trisomy 8 in myeloid malignancies. Further investigations are required to more comprehensively determine how constitutional partial trisomy 8 mosaicisms may contribute to leukaemogenesis in different mutational subtypes of JMML and other myeloid malignancies.

Constitutional aneuploidy and cancer predisposition

Constitutional aneuploidies are rare syndromes associated with multiple developmental abnormalities and the alterations in the risk for specific cancers. Acquired somatic chromosomal aneuploidies are the most common genetic aberrations in sporadic cancers. Thus studies of these rare constitutional aneuploidy syndromes are important not only for patient counseling and clinical management, but also for deciphering the mechanisms by which chromosomal aneuploidy affect cancer initiation and progression. Here we review the major constitutional aneuploidy syndromes and suggest some general mechanisms for the associated cancer predisposition.