Non random distribution of genomic features in breakpoint regions involved in chronic myeloid leukemia cases with variant t(9;22) or additional chromosomal rearrangements

<p>Abstract</p> <p>Background</p> <p>The t(9;22)(q34;q11), generating the Philadelphia (Ph) chromosome, is found in more than 90% of patients with chronic myeloid leukemia (CML). As a result of the translocation, the 3' portion of the <it>ABL1 </it>oncogene is transposed from 9q34 to the 5' portion of the <it>BCR </it>gene on chromosome 22 to form the <it>BCR</it>/<it>ABL1 </it>fusion gene. At diagnosis, in 5-10% of CML patients the Ph chromosome is derived from variant translocations other than the standard t(9;22).</p> <p>Results</p> <p>We report a molecular cytogenetic study of 452 consecutive CML patients at diagnosis, that revealed 50 cases identifying three main subgroups: i) cases with variant chromosomal rearrangements other than the classic t(9;22)(q34;q11) (9.5%); ii) cases with cryptic insertions of <it>ABL1 </it>into <it>BCR</it>, or vice versa (1.3%); iii) cases bearing additional chromosomal rearrangements concomitant to the t(9;22) (1.1%). For each cytogenetic group, the mechanism at the basis of the rearrangement is discussed.</p> <p>All breakpoints on other chromosomes involved in variant t(9;22) and in additional rearrangements have been characterized for the first time by Fluorescence In Situ Hybridization (FISH) experiments and bioinformatic analyses. This study revealed a high content of <it>Alu </it>repeats, genes density, GC frequency, and miRNAs in the great majority of the analyzed breakpoints.</p> <p>Conclusions</p> <p>Taken together with literature data about CML with variant t(9;22), our findings identified several new cytogenetic breakpoints as hotspots for recombination, demonstrating that the involvement of chromosomes other than 9 and 22 is not a random event but could depend on specific genomic features. The presence of several genes and/or miRNAs at the identified breakpoints suggests their potential involvement in the CML pathogenesis.</p

Reciprocal t(9;22) ABL/BCR fusion proteins: leukemogenic potential and effects on B cell commitment

Background: t(9;22) is a balanced translocation, and the chromosome 22 breakpoints (Philadelphia chromosome – Ph+) determine formation of different fusion genes that are associated with either Ph+ acute lymphatic leukemia (Ph+ ALL) or chronic myeloid leukemia (CML). The "minor" breakpoint in Ph+ ALL encodes p185BCR/ABL from der22 and p96ABL/BCR from der9. The "major" breakpoint in CML encodes p210BCR/ABL and p40ABL/BCR. Herein, we investigated the leukemogenic potential of the der9-associated p96ABL/BCR and p40ABL/BCR fusion proteins and their roles in the lineage commitment of hematopoietic stem cells in comparison to BCR/ABL. Methodology: All t(9;22) derived proteins were retrovirally expressed in murine hematopoietic stem cells (SL cells) and human umbilical cord blood cells (UCBC). Stem cell potential was determined by replating efficiency, colony forming - spleen and competitive repopulating assays. The leukemic potential of the ABL/BCR fusion proteins was assessed by in a transduction/transplantation model. Effects on the lineage commitment and differentiation were investigated by culturing the cells under conditions driving either myeloid or lymphoid commitment. Expression of key factors of the B-cell differentiation and components of the preB-cell receptor were determined by qRT-PCR. Principal Findings: Both p96ABL/BCR and p40ABL/BCR increased proliferation of early progenitors and the short term stem cell capacity of SL-cells and exhibited own leukemogenic potential. Interestingly, BCR/ABL gave origin exclusively to a myeloid phenotype independently from the culture conditions whereas p96ABL/BCR and to a minor extent p40ABL/BCR forced the B-cell commitment of SL-cells and UCBC. Conclusions/Significance: Our here presented data establish the reciprocal ABL/BCR fusion proteins as second oncogenes encoded by the t(9;22) in addition to BCR/ABL and suggest that ABL/BCR contribute to the determination of the leukemic phenotype through their influence on the lineage commitment

Chromosome Abnormalities and Hematopoietic Stem Cell Transplantation in Acute Leukemias

The chapter considers specific treatment options, including allogeneic hematopoietic stem cell transplantation (allo‐HSCT) in acute myeloid leukemia (AML) and acute lymphoblastic leukemia (ALL), in patients with some prognostically proven cytogenetic variants as monosomal ones, complex and hyperdiploid karyotypes, like chromosomal translocations t(v;11)(v;q23), t(3;3)/inv(3); t(8;21), t(9;22), etc. Important prognostic role of additional chromosome abnormalities was shown for the patients with t(8;21) and t(9;22). Hence, it is evident that allo‐HSCT in patients with poor risk cytogenetic variant must be performed as early as possible, i.e., during first complete remission

Chromosomal in situ suppression hybridization of immunologically classified mitotic cells in hematologic malignancies

Chromosomal in situ suppression (CISS) hybridization was performed with library DNA from sorted human chromosomes 8, 9, 15, 17, 21, and 22 on immunologically stained bone marrow cells of four patients with a hematologic neoplasm, including two patients with myelodysplastic syndrome and trisomy 8, one patient with promyelocytic leukemia bearing the translocation t(15;17)(q22;q11-12), and one patient with chronic myeloid leukemia and the translocation t(9;22)(q34;q11). In all patients, the results of conventional karyotype analysis could be confirmed by one- or two-color CISS hybridization using the appropriate chromosome-specific libraries. Our results show that CISS hybridization can detect both numerical and structural chromosome changes in immunologically classified cells with high specificity and reliability. The fact that chromosome spreads of very poor quality can now be included in such analyses is a decisive advantage of this approach. In addition, the suitability of this approach for interphase cytogenetics is discussed

EVI1 activation in blast crisis CML due to juxtaposition to the rare 17q22 partner region as part of a 4-way variant translocation t(9;22)

<p>Abstract</p> <p>Background</p> <p>Variant translocations t(9;22) occur in 5 to 10% of newly diagnosed CMLs and additional genetic changes are present in 60–80% of patients in blast crisis (BC). Here, we report on a CML patient in blast crisis presenting with a four-way variant t(9;22) rearrangement involving the <it>EVI1 </it>locus.</p> <p>Methods</p> <p>Dual-colour Fluorescence In Situ Hybridisation was performed to unravel the different cytogenetic aberrations. Expression levels of <it>EVI1 </it>and <it>BCR/ABL1 </it>were investigated using real-time quantitative RT-PCR.</p> <p>Results</p> <p>In this paper we identified a patient with a complex 4-way t(3;9;17;22) which, in addition to <it>BCR/ABL1 </it>gene fusion, also resulted in <it>EVI1 </it>rearrangement and overexpression.</p> <p>Conclusion</p> <p>This report illustrates how a variant t(9;22) translocation can specifically target a second oncogene most likely contributing to the more aggressive phenotype of the disease. Molecular analysis of such variants is thus warranted to understand the phenotypic consequences and to open the way for combined molecular therapies in order to tackle the secondary oncogenic effect which is unresponsive to imatinib treatment.</p

Molecular mechanisms in haematological malignancies

Haematopoiesis requires the constant production of large numbers of peripheral blood cells. This process is under tight control of transcription factor networks as well as cytokines, growth factors and hormones. We will review the importance of transcription factors in programming the haematopoietic lineage commitment and the role of the microenvironment and the corresponding cellular sensitivity to ensure production of mature functional cells in response to the physiological demand. Understanding the molecular mechanism of this complex process gives the opportunity to identify the underlying molecular deregulation in haematopoietic malignancies. The different levels of deregulation include hyperproliferation, block in differentiation and sensitivity to growth factors. In this review, leukaemic transformation is selected to give evidence of cell signalling deregulation. The clinical implications will be reviewed in the context of the potential opportunities in the future to identify specific therapeutic patient groups that can be defined using prognostic and predictive biomarkers.peer-reviewe

t(9;22)(p24;q11.2)

Review on t(9;22)(p24;q11.2), with data on clinics, and the genes involved

Комплексні цитогенетичні аномалії при хронічній мієлоїдній лейкемії: опис випадку

Описано випадок множинних хромосомних аберацій у пацієнта в фазі акселерації ХМЛ. Цитогенетичне та молекулярно-цитогенетичне дослідження дозволили встановити наявність t(9;22)(q34;q11) та ідентифікувати додаткові аномалії t(1;2)(p36;p21), del(6)(q21), +del (8)(q22), del(18)(q21), +der(22), частина з яких не характерна для цієї патології. Розглядається кореляція отриманих результатів з літературними даними, обговорюється імовірний зв’язок виявлених змін з попередньо отриманим лікуванням та можливий вплив цих змін на прогресування ХМЛ.Описан случай множественных хромосомных аберраций у пациента в фазе акселерации ХМЛ. Цитогенетическое и молекулярно-цитогенетическое исследование позволили установить наличие t(9;22)(q34;q11) и идентифицировать дополнительные аномалии t(1;2) (p36;p21), del(6)(q21), +del(8)(q22), del(18)(q21), +der (22), часть из которых не характерна для этой патологии. Рассматривается корреляция полученных результатов с литературными данными, обсуждается вероятная связь выявленных изменений с предварительно полученным лечением и возможное влияние этих изменений на прогрессирование ХМЛ.In this article is presented a case of multiple chromosomal aberrations in a patient with CML accelerated phase. Cytogenetic and molecular cytogenetic studies allowed us to determine the presence of t(9;22)(q34;q11) and to identify additional abnormalities such as t(1;2)(p36;p21), del (6)(q21), +del(8)(q22), del(18)(q21), +der (22), some of which are not typical for this kind of neoplasia. This case is compared with publications of the same cases. Our data suggested that detected changes can be correlated with previous treatment regimens and the influence of these changes on progression of disease is discussed

Metaphase and Interphase Cytogenetics with Alu-PCR-amplified Yeast Artificial Chromosome Clones Containing the BCR Gene and the Protooncogenes c-raf-1, c-fms, and c-erbB-21

A human yeast artificial chromosome (YAC) library was screened by polymerase chain reaction with oligonucleotide primers defined for DNA sequences of the BCR gene and the protooncogenes c-raf-1, c-fms, and c-erB-2. Alu-PCR-generated human DNA sequences were obtained from the respective YAC clones and used for fluorescence in situ hybridization experiments under suppression conditions. After chromosomal in situ suppression hybridization to GTG-banded human prometaphase chromosomes, seven of nine initially isolated YAC clones yielded strong signals exclusively in the chromosome bands containing the respective genes. Two clones yielded additional signals on other chromosomes and were excluded from further tests. The band-specific YACs were successfully applied to visualize specific structural chromosome aberrations in peripheral blood cells from patients with myelodysplasia exhibiting del(5)(q13q34), chronic myeloid leukemia and acute lymphocytic leukemia with t(9;22)(q34;q11), acute promyelocytic leukemia (M3) with t(15;17)(q22;q21), and in a cell line established from a proband with the constitutional translocation t(3;8)(p14.2;q24). In addition to the analysis of metaphase spreads, we demonstrate the particular usefulness of these YAC clones in combination with whole chromosome painting to analyze specific chromosome aberrations directly in the interphase nucleus