Spectrum Of Cytogenetic Abnormalities Research Articles

PB1801: CHROMOSOMAL ABNORMALITIES DURING THE CLINICAL COURSE OF ADULT ACUTE MYELOID LEUKEMIA

Background: Using conventional cytogenetics, an abnormal karyotype can be detected in 60-70% of adult acute myeloid leukemia (AML) patients. Taking into consideration the identified cytogenetic abnormalities AML patients are currently classified into three risk groups: favorable, intermediate and adverse. These genetic abnormalities are the most important factors in determining response to chemotherapy as well as outcome in AML. Aims: Aim of this study was to detect the diagnostic and prognostic significance of chromosomal abnormalities in leukemic cells at different phases of AML. Methods: Cytogenetic investigations of bone marrow and/or peripheral blood cells from 140 adult patients were performed during clinical evolution of AML: in newly diagnosed patients, in remission and at relapse. The methods of conventional cytogenetics (GTG) and fluorescence in situ hybridization (FISH) were used. Cytogenetic methods were performed using standard techniques and karyotypes were described according to the International System for Human Cytogenetic Nomenclature. Results: Cytogenetic investigations of 140 adult AML patients were performed in newly diagnosed patients, in remission and at relapse. Structural (del(5q), del(7q), rearrangements of 3q, 12p, 17p and 11q23, t(8;21)(q22;q22), t(9;22)(q34;q11), t(15;17)(q22;q21), t(16;16)(p13;q22), inv(16)(p13q22), marker and ring chromosomes, acentric structures and others) and numerical (-5, -7, -Y, +8, monosomal karyotype and others) chromosomal abnormalities in leukemic cells were found. Some genetic abnormalities (BCR/ABL1, PML/RARa, AML1/ETO, CBFβ/MYH11 fusion genes) were detected by molecular genetic methods (FISH). Spectrum of cytogenetic abnormalities had an important diagnostic and prognostic significance. Diagnosis of AML was possible due to the presence of specific genetic markers that can confirm some types of AML (AML with t(8;21)(q22;q22), t(9;22)(q34;q11), t(15;17)(q22;q21), t(16;16)(p13;q22)/inv(16)(p13q22), 3q21q26 rearrangements, BCR/ABL1, PML/RARa, AML1/ETO, CBFβ/MYH11 fusion genes). Taking into consideration the identified cytogenetic abnormalities AML patients were classified by risk groups: the group of patients with adverse cytogenetic markers (3q21q26 rearrangements, -5, -7, t(9;22)(q34;q11), BCR/ABL1 fusion gene, multiple changes (≥3), monosomal karyotype), the intermediate risk group without significant prognostic markers and the group with favorable prognostic factors (t(8;21)(q22;q22), t(15;17)(q22;q21), t(16;16)(p13;q22)/inv(16)(p13q22), AML1/ETO, PML/RARa, CBFβ/MYH11 fusion genes). In remission cytogenetic investigations showed a normal karyotype without cytogenetically visible changes in all patients. Cytogenetic investigations at relapse were performed in 5 of 140 AML cases. Additional/secondary chromosomal aberrations in leukemic cells or new cells clones with multiple structural and numerical changes at relapse was not detected. Summary/Conclusion: Cytogenetic investigations had an important significance for diagnosis, prognosis and selection the optimal treatment strategy of AML. Besides the analysis of chromosome banding patterns it is necessary for patients with AML to apply molecular genetic studies, namely FISH and polymerase chain reaction (PCR). Taking into consideration the identified cytogenetic abnormalities AML patients were classified by risk groups. Presence of the additional/secondary chromosomal aberrations in leukemic cells or new cells clones with multiple structural and numerical changes at AML relapse is the one sign of clonal evolution and progression of disease.

Cytogenetic effects in the needles intercalar meristem of Japanese red pine in the remote period after the Fukushima NPP accident

Background. The study of the long-term effects of chronic radiation exposure on plants and animals, which are still the subject of scientific discussion, is necessary to understand the consequences of radiation accidents. After the Fukushima nuclear power plant accident, some of the young pines and spruces showed an increased frequency of apical dominance cancelling. The most probable cause of the observed morphoses is associated with damage to the apical meristem of coniferous plants by radiation in the first year of the accident, when they received the highest absorbed doses. If this hypothesis is true, then even 8 years after the accident it will be possible with high degree of probability to detect an increased level of cytogenetic abnormalities in the intercalary meristem of needles of plants from these populations. The aim of this work was to verify this hypothesis. Materials and methods. Five populations of Japanese red pine from territories contaminated with radionuclides as a result of the accident at the Fukushima nuclear power plant were investigated. The frequency and spectrum of cytogenetic abnormalities in the intercalary meristem of needles were determined by the ana-telophase analysis. Results. The frequency of aberrant cells in the needles intercalary meristem of Japanese red pine from the contaminated with radionuclides territory statistically significantly exceeds the control level in all impact sites and increases along with the dose rate. Although there is no correlation between the frequency of cytogenetic abnormalities in needles and the presence of cancellation of apical dominance in plants, all pine populations from radioactively contaminated territories are characterized by an increased frequency of both cytogenetic abnormalities and morphoses associated with the cancellation of apical dominance. Conclusion. Radiation damage to the apical meristems of conifers in the first year of the accident, when they received the highest absorbed doses, is the most likely cause of the increased frequency of cancellation of apical dominance in the studied populations of Japanese red pine from the zone affected by the accident at the Fukushima nuclear power plant.

Types of cytogenetic abnormalities in apical root meristem of Elodea сanadensis from Yenisei River areas with different types of anthropogenic pollution

Background. The spectrum of cytogenetic abnormalities in the apical root meristem of Elodea сanadensis Michx. (elodea) from the Yenisei River was studied depending on the type of anthropogenic pollution. We compared elodea samples from areas with radiation-contaminated sediments (area affected by Rosatom Mining and Chemical Combine, MCC, Zheleznogorsk) and areas with chemical pollution (Krasnoyarsk). Materials and methods. The apical root meristem of elodea was fixed in acetic alcohol (96 % ethanol and glacial acetic acid, 3 : 1) and stained with 1 % aceto-orcein. The cytogenetic analysis of metaphase and ana-telophase elodea cells was carried out with temporal squashed preparations using an Olympus CX31 microscope. Results. At metaphase stage, the predominant types of abnormalities in elodea cells were disoriented chromosomes (up to 9 % of total metaphase cells) and chromosome agglutination (6 %). In the area affected by the MCC an increased content of ring chromosomes in elodea cells was detected, but in terms of frequency of their occurrence no significant differences were revealed between samples from areas with different types of pollution. Among abnormalities at ana-telophase stage, bridges (to 20% of dividing cells) and disoriented chromosomes (up to 8%) dominated. The following abnormalities were also detected: multipolar and asymmetrical mitoses, agglutination and cells with multiple chromosome abnormalities. It was shown that in areas with the highest content of 137Cs in bottom sediments the frequency of cells with bridges and multiple chromosome abnormalities significantly increased as compared to samples from other areas. Conclusion. In the radioactive contamination area of the Yenisei River the spectrum of abnormalities was dominated by chromosome aberrations (bridges, agglutination, chromosome fragmentation) and multiple abnormalities in one and the same cell. In areas with non-radioactive (chemical) contamination of sediments, mitotic spindle irregularities prevailed.

Оценка связи полиморфизмов генов с частотой и спектром цитогенетических аномалий у здоровых работников Сибирского химического комбината, подвергавшихся радиационному воздействию (microarray исследования)

The results from the research into the association between polymorphisms of genes-candidates for individual radiosensitivity and the frequency and spectrum of cytogenetic abnormalities are analyzed. The study was conducted among Siberian Group of Chemical Enterprises healthy employees exposed to professional irradiation in a dose range of 100-300 mSv. Genotyping of DNA samples from 96 employees was carried out by oligonucleotide microarray: "Cancer_SNP_Panel GT-17-211" ("Illumina") containing 1, 421 SNP-markers (Single Nucleotide Polymorphisms) of 406 genes. The standard cytogenetic analysis was performed in the entire examined group. We have also analyzed the association of these SNP with the frequencies of aberrant cells and following chromosomal aberrations: single chromatid fragments, chromatid exchanges, paired fragments, dicentric, ring and frequencies, translocations. We have found that 40 SNP (rs1800389, rs1051690, rs2392221, rs1041163, rs2114443, rs6083, rs1760904, rs4986894, rs488133, rs7462102, rs11249938, rs34206126, rs33945943, rs34324628, rs5742694, rs978458, rs5742667, rs2373721, rs2162679, rs889162, rs2233679, rs2010457, rs2873950, rs1574154, rs10934500, rs4688046, rs10934503, rs4624596, rs2288729, rs4227, rs1367696, rs751087, rs1269486, rs1149901, rs1800404, rs887477, rs696405, rs751087, rs81 92284, rs312016) are associated with the frequency of different types of chromosomal abnormalities (p-value with FDR of Benjamini-Hochberg--equal less than 0.05). 24 SNP (underlined) are associated with more than one type of chromosome abnormalities. In the future, we are going to confirm the results in further studies on the cohort of more than 600 persons.

Cytogenetics, Not Just Previous Therapy, Determines the Course of Therapy-Related Myeloid Neoplasms

Cytogenetics, Not Just Previous Therapy, Determines the Course of Therapy-Related Myeloid Neoplasms

PROGNOSIS AND THERAPY WHEN ACUTE PROMYELOCYTIC LEUKEMIA AND OTHER “GOOD RISK” ACUTE MYELOID LEUKEMIAS OCCUR AS A THERAPY-RELATED MYELOID NEOPLASM

Treatment for a pre-existing condition using chemotherapy, radiation therapy, immunosuppressive therapy, or a combination of these modalities may lead to the devastating complication of therapy-related myelodysplastic syndrome or acute myeloid leukemia (t-MDS/t-AML), collectively known as therapy-related myeloid neoplasm (t-MN). This disorder arises as a direct consequence of mutational events induced by the primary treatment. The outcomes for these patients have been historically poor compared to people who develop AML de novo. Currently comprising 10–20% of all cases of AML, t-MN is relatively resistant to conventional leukemia therapies, and is associated with s ort survival times. Median life expectancy from diagnosis is about 8–10 months in most series. Although the spectrum of cytogenetic abnormalities in t-AML is similar to AML de novo, the frequency of unfavorable cytogenetics, such as a complex karyotype or deletion or loss of chromosomes 5 and/or 7, is considerably higher in t-MN. Two distinct groups of patients with t-MN have been described. The more common subtype, seen in about 75% of patients, typically occurs 5–7 years after first exposure to alkylating agents or radiation, is often preceded by a myelodysplastic syndrome (MDS), and is frequently accompanied by clonal cytogenetic abnormalities such as the loss of all or part of chromosomes 5 or 7. Mutations of the P53 tumor suppressor gene are also common. The risk is related to total cumulative exposure over time to alkylating agents. In contrast, among individuals who develop t-AML after treatment with topoisomerase II inhibitors, the latency period to the development of t-AML is often only 1–3 years, antecedent MDS is rare, and gene rearrangements involving MLL at 11q23 or RUNX1/AML1 at 21q22 are common. It is now well recognized that APL and other subtypes of AML with balanced translocations sometimes occur as therapy-related myeloid neoplasms (t-MN) in patients who have previously received cytotoxic therapy or ionizing radiation therapy (RT). The most of this review will focus on these “good risk” leukemias, i.e. those with APL or inv(16)/t(16;16) or t(8;21).

Therapy-Related Myeloid Leukemia

Therapy-related myelodysplastic syndrome and acute myeloid leukemia (t-MDS/t-AML) are thought to be the direct consequence of mutational events induced by chemotherapy, radiation therapy, immunosuppressive therapy, or a combination of these modalities, given for a pre-existing condition. The outcomes for these patients have been poor historically compared to people who develop de novo AML. The spectrum of cytogenetic abnormalities in t-AML is similar to de novo AML, but the frequency of unfavorable cytogenetics, such as a complex karyotype or deletion or loss of chromosomes 5 and/or 7, is considerably higher in t-AML. Survival varies according to cytogenetic risk group in t-AML patients, with better outcomes being observed in those with favorable-risk karyotypes. Treatment recommendations should be based on performance status and karyotype. A deeper understanding of the factors that predispose patients to the development of therapy-related myeloid leukemia would help clinicians monitor patients more carefully after treatment for a primary condition. Ultimately, this knowledge could influence initial treatment strategies with the goal of decreasing the incidence of this serious complication.

Etiology and Management of Therapy-Related Myeloid Leukemia

The diagnosis of therapy-related myeloid leukemia (t-MDS/t-AML) identifies a group of high-risk patients with multiple and varied poor prognostic features. These neoplasms are thought to be the direct consequence of mutational events induced by cytotoxic therapy. Their outcomes have historically been poor compared with those of people who develop acute myeloid leukemia (AML) de novo. The question arises whether a diagnosis of t-AML per se indicates a poor prognosis, or whether their bad outcomes result from other clinical and biologic characteristics. Because of lingering damage from prior cytotoxic therapy and, in some cases, the persistence of their primary disorder, patients with t-AML are often poor candidates for intensive AML therapy. The spectrum of cytogenetic abnormalities in t-AML is similar to de novo AML, but the frequency of unfavorable cytogenetics, such as a complex karyotype or deletion or loss of chromosomes 5 and/or 7, is higher in t-AML. Survival varies according to cytogenetic risk group, with better outcomes observed in patients with t-AML with favorable-risk karyotypes. Treatment recommendations should be based on performance status and karyotype. Patients with t-AML should be enrolled on front-line chemotherapy trials, appropriate for de novo AML patients with similar disease characteristics. Allogeneic hematopoietic cell transplantation can cure some patients with t-AML. Most important , the molecular and genetic differences that appear to determine the phenotype and the outcome of these patients need to be investigated further.

Aberrant DNA Methylation Patterns in Chronic Idiopathic Myelofibrosis.

Chronic idiopathic myelofibrosis (CIMF) is a clonal myeloproliferative disorder characterized by bone marrow fibrosis, angiogenesis and extramedullary hematopoiesis. No specific genetic defect underlying the disease has been identified so far. The spectrum of cytogenetic abnormalities in CIMF includes del (13q), del (20q) and partial trisomy 1q as well as abnormalities of chromosomes 1, 7 and 9. Hypermethylation of CpG islands within gene promoter regions is associated with transcriptional inactivation and represents an important mechanism of gene silencing in the pathogenesis of hematopoietic malignancies. This epigenetic phenomenon acts as an alternative to mutations and deletions to disrupt tumor suppressor gene function in cancerogenesis. In order to investigate the role of DNA methylation changes in the pathogenesis of CIMF, we have analyzed the methylation status of the promoter-associated CpG islands of 13 well-characterized tumor suppressor genes by methylation-specific polymerase chain reaction in peripheral blood cells from 20 adult patients with CIMF. The frequency of aberrant methylation among the patient samples was 25.0 % (5/20) for SOCS-1 and 5.0 % (1/20) for E-cadherin, MGMT, p73 as well as TIMP-2. There was no hypermethylation of p15, p16, RARbeta, DAP kinase 1, SOCS-3, hMLH1, TIMP-3 and RASSF1A. We detected at least one hypermethylated gene promoter region in 35.0 % (7/20) of the primary patient samples. Our data indicate that hypermethylation of tumor suppressor genes is a common event in CIMF. Epigenetic modification of genes regulating growth factor signaling, cell adhesion and DNA repair may, in addition to genetic aberrations, contribute to the malignant phenotype in CIMF. The exploration of our growing knowledge about epigenetic aberrations in tumorigenesis may help develop novel strategies in diagnosis and treatment of CIMF for the future.

Isolated 13q14 abnormalities and normal karyotypes are associated with typical lymphocyte morphology in B-cell chronic lymphocytic leukemia.

Peripheral blood lymphocyte morphology and karyotype were correlated across the spectrum of cytogenetic abnormalities in 78 previously karyotyped cases of B-cell chronic lymphocytic leukemia (CLL). Cases were classified according to French-American-British morphologic criteria as typical CLL or CLL, mixed-cell type; the latter category was divided into CLL with a mixture of small and large cells and CLL with increased prolymphocytes (CLL/PL). Other leukemic lymphoproliferative disorders were excluded from this analysis. CLL cases with normal karyotypes were more likely to demonstrate typical morphology than those with clonal abnormalities (P = .042). In addition, all six cases containing isolated 13q14 abnormalities had typical morphology, compared with six of 16 other isolated abnormalities (P = .009), including one of seven cases of isolated trisomy 12. In contrast with the cases of isolated 13q14 changes, only seven of 17 cases with 13q14 as part of complex abnormalities had typical morphology (P = .012). Trisomy 12 was associated with mixed-cell morphology, particularly CLL/PL, consistent with previous reports. We conclude that isolated 13q14 abnormalities and normal karyotype are associated with typical CLL morphology, while other clonal abnormalities, including trisomy 12, are associated with mixed-cell morphology. These results further support the concept of distinct CLL subgroups based on karyotype. Furthermore, the association of trisomy 12 and complex abnormalities with mixed-cell morphology may have implications for clonal evolution in CLL.