SKY detection of chromosome rearrangements in two cases of tMDS with a complex karyotype

Complex karyotype in myelodysplastic syndromes: Diagnostic procedure and prognostic susceptibility

Complex karyotype (CK) is a poor prognosis factor in hematological malignancies. Studies have shown that the presence of CK in myelodysplastic syndrome (MDS) can be associated with MDS progression to acute myeloid leukemia. The goal of this review was to examine the relationship between different types of CK with MDS, as well as its possible role in the deterioration and progression of MDS to leukemia. The content used in this paper has been obtained by a PubMed and Google Scholar search of English language papers (1975-2018) using the terms complex karyotype and myelodysplastic syndromes. A single independent abnormality can be associated with a good prognosis. However, the coexistence of a series of abnormalities can lead to CK, which is associated with the deterioration of MDS and its progression to leukemia. Therefore, CK may be referred to as a prognostic factor in MDS. The detection of independent cytogenetic disorders that altogether can result in CK could be used as a prognostic model for laboratory and clinical use.

Techniques for detecting chromosomal aberrations in myelodysplastic syndromes

Myelodysplastic syndromes (MDS) are a group of heterogeneous hematologic diseases. Chromosomal aberrations are important for the initiation, development, and progression of MDS. Detection of chromosomal abnormalities in MDS is important for categorization, risk stratification, therapeutic selection, and prognosis evaluation of the disease. Recent progress of multiple techniques has brought powerful molecular cytogenetic information to reveal copy number variation, uniparental disomy, and complex chromosomal aberrations in MDS. In this review, we will introduce some common chromosomal aberrations in MDS and their clinical significance. Then we will explain the application, advantages, and limitations of different techniques for detecting chromosomal abnormalities in MDS. The information in this review may be helpful for clinicians to select appropriate methods in patient-related decision making.

Detection of Inter-chromosomal Stable Aberrations by Multiple Fluorescence In Situ Hybridization (mFISH) and Spectral Karyotyping (SKY) in Irradiated Mice

Ionizing radiation (IR) induces numerous stable and unstable chromosomal aberrations. Unstable aberrations, where chromosome morphology is substantially compromised, can easily be identified by conventional chromosome staining techniques. However, detection of stable aberrations, which involve exchange or translocation of genetic materials without considerable modification in the chromosome morphology, requires sophisticated chromosome painting techniques that rely on in situ hybridization of fluorescently labeled DNA probes, a chromosome painting technique popularly known as fluorescence in situ hybridization (FISH). FISH probes can be specific for whole chromosome/s or precise sub-region on chromosome/s. The method not only allows visualization of stable aberrations, but it can also allow detection of the chromosome/s or specific DNA sequence/s involved in a particular aberration formation. A variety of chromosome painting techniques are available in cytogenetics; here two highly sensitive methods, multiple fluorescence in situ hybridization (mFISH) and spectral karyotyping (SKY), are discussed to identify inter-chromosomal stable aberrations that form in the bone marrow cells of mice after exposure to total body irradiation. Although both techniques rely on fluorescent labeled DNA probes, the method of detection and the process of image acquisition of the fluorescent signals are different. These two techniques have been used in various research areas, such as radiation biology, cancer cytogenetics, retrospective radiation biodosimetry, clinical cytogenetics, evolutionary cytogenetics, and comparative cytogenetics.

Molecular cytogenetic profiling of complex karyotypes in primary myelodysplastic syndromes and acute myeloid leukemia

Complex chromosomal aberrations are present in < or =30% of patients with primary myelodysplastic syndrome (MDS) or acute myeloid leukemia (AML) and are associated with a poor prognosis. Specific alterations in complex karyotypes are difficult to define by conventional cytogenetics alone. To obtain a more comprehensive view of the recurrent aberrations, we performed spectral karyotyping (SKY) and fluorescence in situ hybridization (FISH) with selected probes on bone marrow samples from 17 patients with primary MDS and 3 with primary AML. All cases had chromosome 5 alterations. Two different types of 5q loss were identified: unbalanced translocations and interstitial deletions, or del(5q), each occurring in 10 patients. The most frequent additional chromosome aberrations were -3/-3p/-3q, -7/7q-, +8, 13q-, -16, 17p-, -18/18p-, -20/20q-, and +21q, each occurring in 25%. In the five cases with gain of 21q, involvement of the AML1 gene was excluded. Unbalanced 5q translocations occurred more often in combination with monosomy 3 and 7 and with gain of 21q, whereas del(5q) was associated more often with -1p and trisomy 8. A detailed analysis of specific breakpoints and deletions revealed recurrent involvement of specific chromosomal bands harboring known tumor suppressor genes or oncogenes. Analysis of large numbers of MDS and AML cases in a similar detailed manner with SKY and FISH will reveal whether new subgroups can be identified according to their genetic alterations. Correlation with clinical parameters may reveal the prognostic significance of these genetic subgroups.

Polysomy 8 defines a clinico-cytogenetic entity representing a subset of myeloid hematologic malignancies associated with a poor prognosis: report on a cohort of 12 patients and review of 105 published cases

Tetrasomy, pentasomy, and hexasomy 8 (polysomy 8) are relatively rare compared to trisomy 8. Here we report on a series of 12 patients with acute myeloid leukemia (AML), myelodysplastic syndrome (MDS), or myeloproliferative disorder (MPD) associated with polysomy 8 as detected by conventional cytogenetics and fluorescence in situ hybridization (FISH). In an attempt to better characterize the clinical and hematological profile of this cytogenetic entity, our data were combined with those of 105 published patients. Tetrasomy 8 was the most common presentation of polysomy 8. In 60.7% of patients, polysomy 8 occurred as part of complex changes (16.2% with 11q23 rearrangements). No cryptic MLL rearrangements were found in cases in which polysomy 8 was the only karyotypic change. Our study demonstrates the existence of a polysomy 8 syndrome, which represents a subtype of AML, MDS, and MPD characterized by a high incidence of secondary diseases, myelomonocytic or monocytic involvement in AML and poor overall survival (6 months). Age significantly reduced median survival, but associated cytogenetic abnormalities did not modify it. Cytogenetic results further demonstrate an in vitro preferential growth of the cells with a high level of aneuploidy suggesting a selective advantage for polysomy 8 cells.

Genetic testing in the myelodysplastic syndromes: molecular insights into hematologic diversity

The myelodysplastic syndromes (MDS) are associated with a diverse set of acquired somatic genetic abnormalities. Bone marrow karyotyping provides important diagnostic and prognostic information and should be attempted in all patients who are suspected of having MDS. Fluorescent in situ hybridization (FISH) studies on blood or marrow may also be valuable in selected cases, such as patients who may have 5q- syndrome or those who have undergone hematopoletic stem cell transplantation. The MDS-associated cytogenetic abnormalities that have been defined by karyotyping and FISH studies have already contributed substantially to our current understanding of the biology of malignant myeloid disorders, but the pathobiological meaning of common, recurrent chromosomal lesions such as del(5q), del(20q), and monosomy 7 is still unknown. The great diversity of the cytogenetic findings described in MDS highlights the molecular heterogeneity of this cluster of diseases. We review the common and pathophysiologically interesting genetic abnormalities associated with MDS, focusing on the clinical utility of conventional cytogenetic assays and selected FISH studies. In addition, we discuss a series of well-defined MDS-associated point mutations and outline the potential for further insights from newer techniques such as global gene expression profiling and array-based comparative genomic hybridization.

Role of multiplex FISH in identifying chromosome involvement in myelodysplastic syndromes and acute myeloid leukemias with complex karyotypes: a report on 28 cases

Chromosomal abnormalities are found by conventional cytogenetic (CC) analysis in about 50% of myelodysplastic syndromes (MDS) and 70% of acute myeloid leukemias (AML). When cytogenetic abnormalities are complex, multiplex fluorescence in situ hybridization (M-FISH) can help clarify complex chromosomal abnormalities and identify rearrangements with prognostic value or cryptic translocations, which could be preliminary steps in identifying new genes. We studied by M-FISH 28 cases of MDS and AML with complex chromosomal abnormalities, 10 of them were therapy-related. M-FISH allowed the characterization of unidentified chromosomal material in 26 cases (93%). One or several unbalanced rearrangements were observed in 27 cases (96%), generally interpreted as deletions or additional material by CC. Among those translocations, 4 involved 3 chromosomes. Eighteen cryptic translocations undetected by CC were found in 13 cases. By FISH analysis using locus specific probes, TP53 deletion, additional copies of MLL, and additional copies or deletions of RUNX1/AML1 were observed in 16, 4, and 3 cases, respectively. Thus, M-FISH is an important tool to characterize complex chromosomal abnormalities which identified unbalanced and cryptic translocations in 96% and 46% of the cases studied, respectively. Complementary FISH helped us identify involvement of TP53, MLL, and RUNX1/AML1 genes in 82% of cases, confirming their probable role in leukemogenesis.

Unbalanced translocation der(11)t(11;12)(q23;q13): a new recurrent cytogenetic aberration in myelodysplastic syndrome with a complex karyotype

Cytogenetic abnormalities are observed in approximately one half of cases of myelodysplastic syndrome (MDS). Partial or complete chromosome losses and chromosome gains are frequently found, but there is a relatively high incidence of unbalanced translocations in MDS. We describe here two cases of MDS with an unbalanced translocation, der(11)t(11;12)(q23;q13). Both patients were 69 years of age and diagnosed with refractory anemia with excess of blasts in transformation (RAEB-t) according to the high percentage of blasts in the peripheral blood. Cytoplasmic hypogranulation of neutrophils was evident as a dysplastic change. The blasts were positive for CD4 and CD41a as well as CD13, CD33, CD34 and HLA-DR in both cases. Chromosome analysis showed complex karyotypes including a der(11)t(1;11)(q11;p15)t(11;12)(q23;q13) in case 1 and der(11)t(11;12)(q23;q13) in case 2 plus several marker chromosomes. Spectral karyotyping confirmed the der(11)t(11; 12)(q23;q13) and clarified the origin of marker chromosomes, resulting in del(5q) and del(7q). Fluorescence in situ hybridization (FISH) analyses with a probe for the MLL gene demonstrated that the breakpoints at 11q23 were telomeric to the MLL gene in both cases. FISH also showed that the breakpoint at 11p15 of the case 1 was telomeric to the NUP98 gene. Considering another reported case, our results indicate that the der(11)t(11;12)(q23;q13) is a recurrent cytogenetic abnormality and may be involved in the pathogenesis of advanced-stage MDS.