Chromosome-type Aberrations Research Articles

Induction of mitotic and chromosomal abnormalities on Allium cepa cells by pesticides imidacloprid and sulfentrazone and the mixture of them.

To evaluate the cytotoxic and genotoxic effects of low concentrations of pesticides in non-target organisms, seeds of Allium cepa were exposed for 24 h to the imidacloprid insecticide, sulfentrazone herbicide and to the mixture of them, followed by recovery periods of 48 and 72 h. Imidacloprid results indicated an indirect genotoxic effect by inducing different types of chromosome aberration (CA), mainly bridges and chromosomal adherences. Cells with micronucleus (MN) were not significant in the analyzed meristems. Moreover, the 72-h recovery tests indicated that the two lower concentrations of the insecticide (0.036 and 0.36 g L(-1)) had their genotoxic effects minimized after discontinuation of treatment, differently to the observed for the field concentration (3.6 g L(-1)). Sulfentrazone herbicide at field concentration (6 g L(-1)) caused cytotoxic effects by inducing nuclear fragmentation and inhibition of cell division. The other concentrations (0.06, 0.6 and 1.2 g L(-1)) indicated genotoxic effects for this herbicide. The concentration of 0.06 g L(-1) induced persistent effects that could be visualized both by the induction of CA in the recovery times as by the presence of MN in meristematic and F1 cells. The induction of MN by this lowest concentration was associated with the great amount of breakage, losses and chromosomal bridges. The mixture of pesticides induced genotoxic and cytotoxic effects, by reducing the MI of the cells. The chromosomal damage induced by the mixture of pesticides was not persistent to the cells, since such damage was minimized 72 h after the interruption of the exposure.

Interactions of DNA repair gene variants modulate chromosomal aberrations in healthy subjects.

Human cancers are often associated with numerical and structural chromosomal instability. Structural chromosomal aberrations (CAs) in peripheral blood lymphocytes (PBL) arise as consequences of direct DNA damage or due to replication on a damaged DNA template. In both cases, DNA repair is critical and inter-individual differences in its capacity are probably due to corresponding genetic variations. We investigated functional variants in DNA repair genes (base and nucleotide excision repair, double-strand break repair) in relation to CAs, chromatid-type aberrations (CTAs) and chromosome-type aberrations (CSAs) in healthy individuals. Chromosomal damage was determined by conventional cytogenetic analysis. The genotyping was performed by both restriction fragment length polymorphism and TaqMan allelic discrimination assays. Multivariate logistic regression was applied for testing individual factors on CAs, CTAs and CSAs. Pair-wise genotype interactions of 11 genes were constructed for all possible pairs of single-nucleotide polymorphisms. Analysed individually, we observed significantly lower CTA frequencies in association with XPD Lys751Gln homozygous variant genotype [odds ratio (OR) 0.64, 95% confidence interval (CI) 0.48-0.85, P = 0.004; n = 1777]. A significant association of heterozygous variant genotype in RAD54L with increased CSA frequency (OR 1.96, 95% CI 1.01-4.02, P = 0.03) was determined in 282 subjects with available genotype. By addressing gene-gene interactions, we discovered 14 interactions significantly modulating CAs, 9 CTAs and 12 CSAs frequencies. Highly significant interactions included always pairs from two different pathways. Although individual variants in genes encoding DNA repair proteins modulate CAs only modestly, several gene-gene interactions in DNA repair genes evinced either enhanced or decreased CA frequencies suggesting that CAs accumulation requires complex interplay between different DNA repair pathways.

Uniparental disomy of the entire X chromosome in Turner syndrome patient-specific induced pluripotent stem cells.

The human induced pluripotent stem cell (iPSC) technique promises to provide an unlimited, reliable source of genetically matched pluripotent cells for personalized therapy and disease modeling. Recently, it is observed that cells with ring chromosomes 13 or 17 autonomously correct the defects via compensatory uniparental disomy during cellular reprogramming to iPSCs. This breakthrough finding suggests a potential therapeutic approach to repair large-scale chromosomal aberrations. However, due to the scarceness of ring chromosome samples, the reproducibility of this approach in different individuals is not carefully evaluated yet. Moreover, the underlying mechanism and the applicability to other types of chromosomal aberrations remain unknown. Here we generated iPSCs from four 45,X chorionic villous fibroblast lines and found that only one reprogrammed line acquired 46,XX karyotype via uniparental disomy of the entire X chromosome. The karyotype correction was reproducible in the same cell line by either retroviral or episomal reprogramming. The karyotype-corrected iPSCs were subject to X chromosome inactivation and obtained better colony morphology and higher proliferation rate than other uncorrected ones. Further transcriptomic comparison among the fibroblast lines identified a distinct expression pattern of cell cycle regulators in the uncorrectable ones. These findings demonstrate that the iPSC technique holds the potential to correct X monosomy, but the correction rate is very low, probably due to differential regulation of cell cycle genes between individuals. Our data strongly suggest that more systematic investigations are needed before defining the iPSC technique as a novel means of chromosome therapy.

Does the pattern of clonal evolution in the karyotype of patients with acute myeloid leukemia and myelodysplastic syndromes depend on the type of the primary chromosomal aberrations?

The aim of our study was to define if the type of primary chromosomal aberrations (CA) of the karyotype of patients with Acute myeloid leukemia (AML) and Myelodysplastic syndromes (MDS) determines the way and the rate of karyotype development. Conventional cytogenetic analysis was carried out on 248 AML and 105 MDS patients at diagnosis. Clonal evolution (CE) was found in 40% (51 of 128) of AML patients and in 47.5% (19 of 40) of MDS patients having CA in their karyotype. The first pattern we established was for the most frequent CA which initiate CE in 28 patients with a complex karyotype. These CA were non-balansed rearrangements in the following regions: 5q, 7q, 11q, 3q, monosomy 5, monosomy 7. The second pattern of CE was regarding the most frequent aneuploidias (+8, +11, +21, -Y, and the third pattern concerned balanced CA. We found significant difference in the distribution of karyotypes in different stages of progression between the first and the other two groups (p < 0.001). No statistical difference was found between the patterns in the second and the third group CA (p > 0.5).

Cytogenetic evidence that DNA topoisomerase II is not involved in radiation induced chromsome-type aberrations

ICRF-187 (Cardioxane™, Chiron) is a catalytic inhibitor of DNA topoisomerase II (Topo II), proposed to act by blocking Topo II-mediated DNA cleavage without stabilizing DNA-Topo II-“cleavable complexes”. In this study ICRF-187 was used to evaluate the potential involvement of DNA topoisomerase II in the formation of the radiation-induced chromosome-type aberrations in the G0 phase of the cell cycle in human lymphocytes from three healthy male donors. This is based on many evidences that DNA topoisomerases are involved in DNA recombination, mainly of illegitimate type (non-homologous) both in vitro and in vivo. The results obtained clearly indicated that ICRF-187 did not induce per se any chromosomal damage. When challenged with the non-catalytic Topo II poison VP-16 (etoposide), which acts by stabilizing the “cleavable complex” generating “protein concealed” DSB’s and thus chromosomal aberrations, it completely abolished the significant induction of chromosome-type aberrations and formation of dicentric chromosomes. This indicates that ICRF-187 acts effectively as catalytic inhibitor of Topo II. On the other hand, when X-ray treatments were challenged with ICRF-187 using experimental conditions as for VP-16 treatments, no modification of the incidence of chromosome-type aberrations and dicentric chromosomes was observed. On this basis, we conclude that Topo II is not involved in the formation of X-ray-induced chromosome-type aberrations and dicentric chromosomes in human lymphocytes in the G0 phase of the cell cycle.

Replication Fork Progression during Re-replication Requires the DNA Damage Checkpoint and Double-Strand Break Repair

Replication origins are under tight regulation to ensure activation occurs only once per cell cycle [1, 2]. Origin re-firing in a single S phase leads to the generation of DNA double-strand breaks (DSBs) and activation of the DNA damage checkpoint [2-7]. If the checkpoint is blocked, cells enter mitosis with partially re-replicated DNA that generates chromosome breaks and fusions [5]. These types of chromosomal aberrations are common in numerous human cancers, suggesting that re-replication events contribute to cancer progression. It was proposed that fork instability and DSBs formed during re-replication are the result of head-to-tail collisions and collapse of adjacent replication forks [3]. However, previously studied systems lack the resolution to determine whether the observed DSBs are generated at sites of fork collisions. Here, weutilize the Drosophila ovarian follicle cells, which exhibit re-replication under precise developmental control [8-10], to model the consequences of re-replication at actively elongating forks. Re-replication occurs from specific replication origins at six genomic loci, termed Drosophila amplicons in follicle cells (DAFCs) [10-12]. Precise developmental timing of DAFC origin firing permits identification of forks at defined points after origin initiation [13, 14]. Here, we show that DAFC re-replication causes fork instability and generates DSBs at sites of potential fork collisions. Immunofluorescence and ChIP-seq demonstrate the DSB marker γH2Av is enriched at elongating forks. Fork progression is reduced in the absence of DNA damage checkpoint components and nonhomologous end-joining (NHEJ), but not homologous recombination. NHEJ appears to continually repair forks during re-replication to maintain elongation.

Cytogenetic effects of combination of tridecactide and met-enkephalin on lymphocytes of patients with multiple sclerosis

Introduction: The met-enkephalin (1-5 Adrenorphin) and tridecactide (alpha-corticotropin 1-13) combination is used in the multiple sclerosis (MS) immuno-modulatory treatment. A testing of cytogenetic effects of met-enkephalin resulted in reductions of lymphocytic aberrations in the in the lymphocytes of the peripheral blood (PBL) of patients with immune-mediated diseases. The aim of this research is to evaluate the in vitro effects of the combination of the met-enkephalin and tridecactide on the number and the type of chromosome aberrations in PBL of the MS patients. &#x0D; Methods: We used blood samples from seven female patients with the diagnosis multiple sclerosis based on a McDonald Diagnostic Criteria. The tested combination, met-enkephalin and alpha-ACTH 1-13 was added at three different concentrations and constant volume. &#x0D; Results: Results showed that the combination of tested substances did not reduce the number of structural aberrations, although the treatment did not result in severe aberrations such as ring, fragmented, and dicentric chromosomes. Furthermore, it elicited an increase in the number of numerical aberrations and aneuploidy after the treatment with the test combo. &#x0D; Conclusion: As the changes in ploidy significantly change the DNA as well as the biochemical cell phenotype, we concluded that more research in this field should be conducted, including both toxicological as well as the pharmacodynamic considerations.

Cytogenetic heterogeneity and their serial dynamic changes during acquisition of cytogenetic aberrations in cultured mesenchymal stem cells

To minimize the risk of tumorigenesis in mesenchymal stem cells (MSCs), G-banding analysis is widely used to detect chromosomal aberrations in MSCs. However, a critical limitation of G-banding is that it only reflects the status of metaphase cells, which can represent as few as 0.01% of tested cells. During routine cytogenetic testing in MSCs, we often detect chromosomal aberrations in minor cell populations. Therefore, we aimed to investigate whether such a minority of cells can expand over time or if they ultimately disappear during MSC passaging. We passaged MSCs serially while monitoring quantitative changes for each aberrant clone among heterogeneous MSCs. To investigate the cytogenetic status of interphase cells, which represent the main population, we also performed interphase FISH analysis, in combination with G-banding and telomere length determination. In human adipose tissue-derived MSCs, 4 types of chromosomal aberrations were found during culturing, and in umbilical cord MSCs, 2 types of chromosomal aberrations were observed. Sequential dynamic changes among heterogeneous aberrant clones during passaging were similar to the dynamic changes observed in cancer stem cells during disease progression. Throughout all passages, the quantitative G-banding results were inconsistent with those of the interphase FISH analysis. Interphase FISH revealed hidden aberrations in stem cell populations with normal karyotypes by G-banding analysis. We found that telomere length gradually decreased during passaging until the point at which cytogenetic aberrations appeared. The present study demonstrates that rare aberrant clones at earlier passages can become predominant clones during later passages. Considering the risk of tumorigenesis due to aberrant MSCs, we believe that our results will help to establish proper safety guidelines for MSC use. In particular, we believe it is critical to test for chromosomal aberrations using both G-banding and FISH to ensure the safety of human stem cells that are manufactured in vitro for clinical applications.

Chromosome aberration model combining radiation tracks, chromatin structure, DSB repair and chromatin mobility.

The module that simulates the kinetics and yields of radiation-induced chromosome aberrations within the biophysical code PARTRAC is described. Radiation track structures simulated by Monte Carlo methods are overlapped with multi-scale models of DNA and chromatin to assess the resulting DNA damage. Spatial mobility of individual DNA ends from double-strand breaks is modelled simultaneously with their processing by the non-homologous end-joining enzymes. To score diverse types of chromosome aberrations, the joined ends are classified regarding their original chromosomal location, orientation and the involvement of centromeres. A comparison with experimental data on dicentrics induced by gamma and alpha particles shows that their relative dose dependence is predicted correctly, although the absolute yields are overestimated. The critical model assumptions on chromatin mobility and on the initial damage recognition and chromatin remodelling steps and their future refinements to solve this issue are discussed.

Structural chromosomal aberrations as potential risk markers in incident cancer patients.

Epidemiological prospective studies have shown that increased chromosomal aberrations (CAs) in peripheral blood lymphocytes may predict cancer risk. Here, we report CAs in newly diagnosed 101 colorectal, 87 lung and 158 breast cancer patients and corresponding healthy controls. Strong differences in distributions of aberrant cells (ACs), CAs, chromatid-type aberrations (CTAs) and chromosome-type aberrations (CSAs) were observed in lung and breast cancer patients as compared to healthy controls. In colorectal cancer (CRC) patients, only CTAs were significantly elevated. Binary logistic regression, adjusted for main confounders, indicates that all the analysed cytogenetic parameters along with smoking were significantly associated with breast and lung cancer risks. Significant differences in terminal deletions between breast cancer patients and corresponding female controls were recorded (0.39 vs. 0.18; P ≤ 0.05). We did not find any association of CAs with TNM (tumor nodus metastasis) stages or histopathological grade in either cancer type. CAs were neither associated with additional tumor characteristics-invasivity, ductal and lobular character, estrogene/progesterone receptors in breast tumors nor with non-small/small cell and bronchogenic/pulmonary types of lung tumors. Our study demonstrates that CAs serve as a predictive marker for breast and lung cancer, whereas only CTAs were elevated in incident CRC patients.

Computer assisted human karyotyping – an analysis of 131 cases

Introduction: Karyotyping is the process of pairing and ordering all the chromosomes of an organism, thus providing a genome-wide snapshot of an individual’s chromosome. G-banded karyograms are routinely used to diagnose a wide range of chromosomal abnormalities in individuals. Although the resolution of chromosomal changes detectable by G-banded karyotyping is typically a few megabases, this can be sufficient to diagnose certain categories of abnormalities. Objectives: The primary aim of this study was to investigate the different types of chromosomal aberrations and their relative frequencies in a group of referred patients with suspected genetic disorders. Methods: This observational study was carried out at Armed Forces Institute of Pathology (AFIP) for a period of two years from January 2011 to December 2012. A total of 131 patients were included in this study. These patients were referred to AFIP from different Combined Military Hospitals (CMH) of Bangladesh Army and also from civil medical installations. All the patients were subjected to full genetic study; complete genetic examination and pedigree construction was done to exclude nonchromosomal causes of anomaly. Detailed history and physical findings were also noted in a prescribed format. The study included peripheral lymphocyte culture by a standard method using the G–banding technique. 32 JAFMC Bangladesh. Vol 9, No 2 (December) 2013 Results: Out of 131 patients, 54 (42.2%) were male and 77 (57.8%) were female with male to female ratio 0.7:1. The age limit of the patient ranges from 04 days to 70 years. Most of the patients (32.1%) were in the age group of 0–10 years followed by 21–30 year age group (30.5%). Consanguineous marriage was found in 15 (11.5%) cases in which 3 (2.3%) cases had chromosomal aberrations. Recurrent abortion was the main clinical indication (18.3%) followed by infertility (15.3%). Chromosomal aberrations were detected in 26 patients (19.8%); of these, 20 (15.2%) involved autosomes, while only 6 (4.6%) involved gonosomes. Trisomy 21 was detected in 12 (9.1%) patients and Philadelphia chromosome was found in 8 (6.1%) patients. Turner syndrome was detected in 5 (3.8%) patients and Klinefelter syndrome was found in 1 (0.8%) patient. Conclusion: The precise delineation of different types of chromosomal aberrations is only possible using clinical examination and advanced cytogenetic tools by experienced cytogeneticists. DOI: http://dx.doi.org/10.3329/jafmc.v9i2.21823 Journal of Armed Forces Medical College Bangladesh Vol.9(2) 2013

Metabolic gene variants associated with chromosomal aberrations in healthy humans.

Nonspecific chromosomal aberrations (CAs) are found in about 1% of lymphocytes drawn from healthy individuals. They include chromosome-type aberrations (CSAs), which are increased in exposure to ionizing radiation, and chromatid-type aberrations (CTAs) which in experimental systems are formed by DNA binding carcinogens and mutagens. The frequency of CAs is associated with the risk of cancer, but the causes of CAs in general population are unknown. Here, we want to test whether variants in metabolic genes associate with CAs in healthy volunteers. Cases were considered those whose total CA (CAtot) frequency was >2% and for CSA and CTA the limit was >1%. Controls had lower frequencies of CAs. Functional polymorphisms in seven genes were selected for analysis: cytochrome P450 1B1 (CYP1B1), epoxide hydrolase 1 (EPHX1), NAD(P)H:quinone oxidoreductase 1 (NQO1), each coding for phase 1 enzymes, and glutathione S-transferase P1 (GSTP1), glutathione S-transferases M1 (GSTM1) and T1 (GSTT1), coding for enzymes which conjugate reactive metabolites, that is, phase 2 enzymes. The number of volunteers genotyped for each gene varied from 550 to 1,500. Only EPHX1 was individually associated with CAtot; high activity genotypes decreased CAtot. A total of six significant (P < 0.01) pair-wise interactions were observed, most including a GST variant as one of the pair. In all genotype combinations with significant odds ratios for CAs a GST variant was involved. The present data provide evidence that variants in genes coding for metabolic enzymes, which individually have small effects, interact and are associated with CA frequencies in peripheral lymphocytes of healthy volunteers.

Chromosomal Abnormalities among Petrol Station Workers Occupationally Exposed to Benzene

It is known that the vast majority of malignancies are the result of genetic and environmental interactions. Fuel (diesel and petrol) constitutes a complex mixture of benzene, toluene and xylene and other monocyclic, aromatic, aliphatic and polycyclic aromatic hydrocarbons; benzene being the most hazardous because of its carcinogenic potency. This study aims to evaluate the genotoxic effects of occupational exposure to benzene through cytogenetic analysis at low levels of exposure also to investigate the possibility of liver and kidney affections. The studied group comprised 40 workers from 3 different petrol stations occupationally exposed to benzene and 20 control subjects. The two studied groups were matched regarding age and sex. Results show significant difference between exposed workers and control group in chromosomal abnormalities regarding mitotic index, gap, isogap and break. Regarding period of exposure, the frequency of different types of chromosomal aberrations was relatively high during first few years of exposure and decrease with Original Research Article El Mahdy et al.; BJAST, 7(5): 502-513, 2015; Article no.BJAST.2015.168 503 increasing duration. Regarding liver function tests, levels were within normal ranges but higher in workers with statistically significant difference between exposed workers and control group and they were significantly correlated with the duration of exposure (p value= .05). Occupational exposure to mutagenic and carcinogenic agents creates a significant impact on the health status of gasoline station attendants. Identification and prevention of possible health problems related to such exposure would help in maintaining good health of workers; prevent reduction in working capacity and loss of working hours besides reducing the cost of medical care for affected workers. Further studies are needed to assess DNA status in the lymphocytes that might be a predictor of future cancer risks and might help to prevent further deterioration in the health of these workers.

The monosomy 18p detected by the amniocentesis: de Grouchy syndrome 1

Monosomy 18p (de Grouchy syndrome 1) is a structural chromosome aberration provoked by the deletion of a part of or the entire 18 chromosome's short arm. In 2/3 of cases it is provoked because of the de novo terminal deletion of 18 chromosome's short arm, while in the rest of the cases there is a transmission from parents. The clinical manifestations of this syndrome are moderate and nonspecific. In the clinical research they could be neglected. Its usual manifestations include: mental retardation in various degree, postnatal growth restriction, short stature, delayed speech development, as well as craniofacial malformations. At birth, the phenotypic manifestations of the syndrome are minimal and the abnormalities become visible after the age of three. The final diagnosis requires karyotyping and an analysis of fetal chromosomes or an analysis of an afflicted person. Previous research have shown that the critical point for the breakage located near the centromere in the region 18 p11.1 (it is present in 44% - 72% of examinees). The breakage in the region between p11.1 and p1.21 is linked to a higher degree of mental retardation compared to the breakages distally from these points at the p chromosome's arm. The examples of prenatally detected monosomy 18p are sporadic and they are usually found after abnormal ultrasound findings in the first trimester or accidentally by invasive prenatal diagnostics. In the cases of monosomy 18 p detected prenatally or in the cases of giving a birth to a child with this type of chromosomal aberration, a parents' karyotypes should be defined with the purpose to provide genetic advice to the parents.

Neurotoxic and Genotoxic Potentials of Short Term Copper Exposure in Adult Male Albino Rats (Biochemical, Histopathological, Immunohistochemical and Genotoxic Study)

Objective: Although copper is an essential micronutrient involved in a variety of biological processes indispensable for sustaining life yet it can be toxic when administered in excess. Material and Methods: Thirty six adult male albino rats were equally divided into three groups; the first group was used as a negative control, the second group received normal saline intraperitoneal (positive control group) and the third group received copper chloride 7mg/kg twice weekly intraperitoneal for 8 weeks (treated group). At the end of the experimental period, blood was withdrawn for measuring serum malondialdhyde (MDA) and catalase (CAT), then the rats were sacrificed and the brain was examined by light microscope for detecting histopathological changes. Brain sections were examined immunohistochemically for the detection of the apoptotic BaX protein and finally, the bone marrow was examined for detection of chromosomal aberrations. Results: In Cu chloride treated group (group III), there was a significant elevation in serum malondialdehyde & a significant decrease in serum catalase. Histopathological changes were in the form of increased cellularity of astrocytes, swelling of astrocytes that showed dense eosinophilic cytoplasm, with pyknotic nuclei and multiple apoptotic bodies. Also, there were degenerated neurons with deep eosinophilc cytoplasm using light microscope and BaX showed strong immunoreactions in the brain. Bone marrow showed significant increase in all types of chromosomal aberrations after 8 weeks of Cu chloride treatment. Conclusion: From the previous results, it can be concluded that Cu chloride exposure can induce oxidative stress changes in the form of a significant increase in MDA and significant decrease in CAT enzyme as well as histopathological changes in the brain and genotoxicity in adult male albino rats after short term exposure.

The Frequency and Types of Chromosomal Aberrations in the Patients with Hypogonadism

Objectives: Hypogonadism is the clinical manifestation of the impaired function of the testes and the ovaries, and is either due to endocrinological problems or chromosomal abnornlalities (CA). Chromosomal analysis is one important piece in the hypogonadism individuals, and becomes essential from the clinical point of view. Design: To determine the frequency, types of CAs in a hypogonadism population. Materials and method: The current study was a retrospective analysis to examine the CAs and prevalence in 64 cases with unexplained hypogonadism problem. The samples were cultured routinely for the karyotype analysis using G banding. Results: A total of 64 individuals with infertility was analysed. The karyotype results were normal in 52 (81.2%) of 64 individuals. However, CAs were detected in 12 (18.8%) of all individuals. The 15.6% of these CAs was numerical aberrations, and also structural CA was 3.1%. Specifically, Klinefelter syndrome (KS) was the most common karyotype (14.1%,9 cases) among the all cases, followed by 46,XX,anoploidy; 46,Xi(Xq) and 46,XY,robt(14;15). Conclusion: We found a high rate CAs (18.8%) in patients with hypogonadism. Therefore, cytogenetic analysis can be strongly recommended in hypogonadism individuals, and should be performed routinely in both the male and female with hypogonadism.

APOBEC3B: pathological consequences of an innate immune DNA mutator.

Cancer is a disease that results from alterations in the cellular genome. Several recent studies have identified mutational signatures that implicate a variety of mutagenic processes in cancer, a major one of which is explained by the enzymatic activity of the DNA cytosine deaminase, APOBEC3B. As a deaminase, APOBEC3B converts cytosines to uracils in single-stranded DNA. Failure to properly repair these uracil lesions can result in a diverse array of mutations. For instance, DNA uracils can template the insertion of complementary adenines leading to C-to-T transition mutations. DNA uracils can also be converted into abasic sites that, depending upon the DNA polymerase recruited to bypass this lesion in the template strand, can lead to adenine insertion and C-to-T mutations as well as cytosine insertion and C-to-G transversion mutations. Finally, DNA uracils can also be converted into DNA breaks that may precipitate some types of larger chromosomal aberrations observed in cancer. These studies cumulatively demonstrate that APOBEC3B is a major source of genetic heterogeneity in several human cancers and, as such, this enzyme may prove to be a critical diagnostic and therapeutic target.

Abstract 4157: Autosome instability and loss of chromosome Y in blood lymphocytes predict lung cancer risk

Abstract Background: Cancer cells are characterized by frequent chromosome aberrations (CA), which reflect defects of the underlying mechanisms that maintain genomic stability. Chromosome aberrations in peripheral blood lymphocytes has been shown to be associated with overall cancer risk in previous small studies. However, the relationship between types of chromosome aberrations in blood lymphocytes and lung cancer risk has not been well defined. In a case-control study of non-small cell lung cancer, we evaluated if CA in autosomes and sex chromosomes were predictive of lung cancer risk. Method: Chromosome aberrations were determined by G-banding analysis of metaphase chromosomes from short-term cultured blood lymphocytes. Logistic regression was used to estimate the strength of association between CAs and lung cancer risk. Results: Autosome instability (defined as CA in any of the 22 pairs of autosomes in &amp;gt; 5% of the cells) was significantly associated with lung cancer risk among individuals who were &amp;lt;= 67 years of age; adjusted odds ratio (OR) of 5.0 [95% confidence interval (CI) = 1.6 - 15.3]. There was no significant association between autosome instability and lung cancer risk in individuals who were older than 67 years of age. Loss of chromosome Y was significantly associated with an elevated risk of lung cancer among males; adjusted OR of 3.2 (95% CI = 1.2 - 8.8). This association appeared to be stronger in older males (&amp;gt; 67 years of age) and in African American males. We observed no significant association between loss of chromosome X and lung cancer risk in both males and females. Conclusion: Autosome instability and loss of chromosome Y in blood lymphocytes were significantly associated with lung cancer risk. Analysis of chromosome aberrations in blood lymphocytes may be a promising tool for the identification of sub-population who are at high risk of developing lung cancer. Citation Format: Bing Sun, Ying Wang, Krishna Kota, Yaru Shi, Kepher H. Makambi, Christopher A. Loffredo, Peter G. Shields, Curtis C. Harris, Yun-Ling Zheng. Autosome instability and loss of chromosome Y in blood lymphocytes predict lung cancer risk. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 4157. doi:10.1158/1538-7445.AM2014-4157

Cytogenetic analysis of the residents of North Ossetia living in ecologically different regions

Background. Cytogenetic biomarkers are the most frequently used end point in human biomonitoring studies and are used extensively to assess the impact of environmental, occupational and medical factors on genomic stability.Materials and methods. The study was conducted on blood samples from 55 residents living in ecologically different areas of North Ossetia: 47 adults with the mean age of 34 ± 3.2 and 8 children with the mean age of 14 ± 1.0. Chromosome aberration analysis was performed on peripheral blood lymphocytes, cultures were incubated for 48h.Results. The results of the study showed a statistically significant difference between the frequencies of cells with chromosome aberrations among the residents living in ecologically different areas of North Ossetia. During the cytogenetic studies, three groups of residents living at different distances from the pollution source (a metallurgical enterprise) were examined, and significant variations of chromosomal aberrations frequencies have been found. In residents living up to 3 km from the enterprise the average frequency of chromosome aberrations was maximal (4.3 ± 0.5), while in residents from remote areas (more than 5 km) the frequency was 2.8 ± 0.3, р ≤ 0.003. Among the examined children frequencies of chromosomal aberrations were 4.1 ± 0.7 and 1.3 ± 0.5, respectively (р ≤ 0.04). Conclusion. A high average frequency of metaphases with aberrations is an indication of adverse environmental conditions which have developed after the accident. Increase of the proportion of chromosome type aberrations in the spectrum of cytogenetic damage among residents of North Ossetia allows to assume the presence of mutagenic effects of chemical as well as radiation nature. "Afobazol" has shown protective properties in donors blood of residents of the region affected by anthropogenic press.

6IN - The Interface Between Cancer Numerical and Structural Chromosomal Instability: Mechanisms Accelerating Cancer Diversity

ABSTRACT Various types of chromosomal aberrations, including numerical (aneuploidy) and structural (e.g. translocations, deletions), are commonly found in human tumors. Aneuploidy is a direct consequence of chromosome segregation errors in mitosis, but recent reports have shown that chromosome segregation errors can also result in structural chromosome aberrations. We found that chromosomes that missegregate are frequently damaged during cytokinesis. Importantly, we found that these double strand breaks can lead to unbalanced translocations in the daughter cells. These and other data shed light on the mechanisms that can facilitate rapid cancer diversification. To prevent chromosome segreation errors, cells depend on the Spindle Assembly Checkpoint (SAC), a complex signaling network that allows time for proper chromosome bi-orientation. We are testing a specific small molecule kinase inhibitor of Mps1, an important SAC component that sustains SAC function, but also contributes to chromosome alignment. In cultured mammalian cells Mps1 inhibition accelerates mitosis, and prevents full chromosome alignment, resulting in chromosome segregation errors. Proliferation assays indicate that tumor cell lines are more sensitive to Mps1 inhibition than normal non-transformed cell lines. This observation lead us to explore Mps1 inhibition as a tool to specifically target cancer cells, without compromising normal stable cells. We used FVB mouse models to characterize the effects of Mps1 inhibition in vivo. Cell lines derived from BRCA1- and p53-deficient breast tumors display impaired cell proliferation upon Mps1 inhibition and we observe a synergistic increase when combined with docetaxel treatment. In a model for hereditary triple-negative breast cancer (BRCA1f/f; p53f/f model), treatment of a combination of Mps1 inhibitor and docetaxel resulted in tumor regression and an increase in mouse survival. A higher percentage of anaphase figures with lagging chromosomes was observed in tumors and in the gut. These data support Mps1 inhibition in combination with anti-mitotic agents as a novel therapeutic approach for triple negative breast cancer. Disclosure: R.C. Buijsman: Rogier C. Buijsman is founder and shareholder of NTRC G.J.R. Zaman: Guido J.R. Zaman is founder and shareholder of NTRC All other authors have declared no conflicts of interest.