Department of Cytogenetics

The IHBT Cytogenetic laboratory performs diagnostic and research work on chromosomes of bone marrow and blood cells of the patients with hematologic malignancies (pathological chromosomes of bone marrow cell in a woman with acute myeloid leukemia are shown in figure No 1). Conventional chromosome banding techniques are used together with molecular cytogenetic methods with all known modifications which are in principle the fluorescence in situ hybridization – FISH.                                                                                                              Figure 1

For studies of structural chromosomal changes multicolor FISH (mFISH) and multicolor banding with high resolution (mBAND) are routinely used. By these techniques the sensitivity and precision of examinations was highly increased and the results of such analyses are shown in figures No 2 and 3.

        Figure 2                                                            Figure 3

For monitoring the success of bone marrow transplantations and/or to follow pathological leukemic clones after chemotherapy interphase FISH with locus specific probes is used. To determine the presence of residual leukemic cells after chemotherapy cosmids and centromeric probes are utilized, for the mapping of genes the BAC (Bacterial Artificial Chromosomes) clones are employed.

The aim of the research studies are molecular-cytogenetic analyses of cryptic deletions and rearrangements of chromosomes in bone marrow and blood cells of patients with preleukemia and myeloid leukemias. By means of molecular techniques the exact breakpoints are located and corresponding genes mapped in the deleted region. The relationship of missing genes with hematopoiesis could be the step forward to better understanding of neoplasia and hopefully, in the near future, can help to determine individual treatment of the patient (translation medicine).

Part of our research was focused on dicentric chromosomes (figure No 4). They are well known features of cancer cells, highly relevant to genome instability. Monosomies, which can be consequently detected in karyotype of these cells, are indicators of the worst prognosis in myeloid diseases.

Classical cytogenetic analysis is not always sufficient to reveal the presence of dicentric chromosomes and monosomies, especially in cases when intercentromeric distance is too small or the part of chromosome remains in the karyotype forming marker chromosome or other type of aberration. Using molecular cytogenetic (FISH) and molecular genetic techniques (aCGH/SNP) we can detect hidden dicentrics, total and partial monosomies, primary or secondary, which have arisen as a result of centromere deletion of primary dicentric chromosomes.

Evaluation of the presence of various types of dicentric chromosomes and monosomies at diagnosis and during the course of the disease contribute to better characterization of different patient subgroups, understanding of unclear mechanisms involved in development and progression of leukemic transformation and point out to the prognostic significance of dicentric chromosomes as biomarkers in myeloid diseases.