High Frequency Of Chromosomal Aberrations Research Articles

Radiation-induced changes in DNA methylation and their relationship to chromosome aberrations in nuclear power plant workers

Purpose: We investigated the association between occupational radiation exposure and DNA methylation changes in nuclear power plant workers. We also evaluated whether radiation- induced DNA methylation alterations are associated with chromosome aberrations.Materials and methods: The study population included 170 radiation-exposed workers and 30 controls. We measured global, long interspersed nuclear element-1 (LINE-1), and satellite 2 methylation levels in blood leukocyte DNA. The analysis of chromosome aberrations was performed on peripheral lymphocytes.Results: Global DNA methylation levels were lower in radiation-exposed workers than in controls. The methylation levels were negatively associated with the recent 1.5-year radiation dose in a multiple linear regression model (β = − 0.0088, p ≤ 0.001); the levels increased proportionally with the total cumulative dose in radiation-exposed workers. LINE-1 methylation levels were higher in radiation-exposed workers than in controls and were significantly associated with the total cumulative radiation dose in a multiple linear regression model (β = − 0.031, p = 0.035). Global DNA methylation levels were also correlated with chromosome aberrations among workers. Workers with low global methylation levels had a higher frequency of chromosome aberrations than did subjects with high global methylation levels.Conclusion: Occupational exposure to low-dose radiation could affect DNA methylation levels, and the radiation-induced DNA methylation alterations may be associated with chromosome aberrations.

Effects of royal jelly on genotoxicity and nephrotoxicity induced by valproic acid in albino mice

Epilepsy is one of the most common neurological diseases affecting at least 50 million people worldwide. Valproic acid (VPA) is a widely used antiepileptic medication for both generalized and partial seizures of epilepsy. The objective of the study was to investigate the anti-mutagenic and anti-histopathologic effects of royal jelly (RJ) on VPA-induced genotoxicity and nephrotoxicity in male albino mice (Mus musculus). 80 Mice were used for 21 days; they were divided into eight groups, (G1) served as normal control group, G2 received VPA (100 mg/kg) and (G3–G5) received RJ at doses 50, 100 and 200 mg/kg respectively. While (G6–G8) were administrated RJ simultaneously with VPA. In RJ treated mice at doses of 50 and 100 mg/kg, the kidney sections showed normal histological structure with non significant changes in chromosomal aberrations (CA) and mitotic index (MI), while RJ at dose of 200 mg/kg showed mild inflammatory cells infiltration and hyperemic glomeruli but not highly significant changes in CA and MI. The cortex of VPA treated mice revealed congested glomeruli with inflammatory cells infiltration, and marked degeneration of almost structures of the glomeruli including some vacuoles in mesangial cells with dark mesangial substances on the ultrastructure level. Some proximal tubules showed degeneration of microvilli on the apical parts of some cells. Cells of the distal tubules attained obliterated lumen and vacuolated lining epithelium. The results also revealed that valproic acid induced a high frequency of CA in bone marrow cells of mice and MI was significantly decreased indicating bone marrow cytotoxicity. The treatment of mice with RJ at doses 50, 100 and 200 mg/kg for 21 days simultaneously with VPA resulted in abating the histological alterations in renal tissues with significant reduction in chromosomal aberrations, for doses of 50 and 100 mg/kg, and elevation in mitotic index (P < 0.05). RJ at doses 50 and 100 mg/kg appeared more potent in exerting the ameliorative effect.

Genotoxic and histotoxic effects of air pollutants at a benzene station on albino rats

Background: This study was designed to explore the hazardous effects of occupational exposure to air pollutants arising from benzene stations. Methods: A total of 48 albino rats were divided into three groups each of sixteen animals. Groups-I and II were kept at a benzene station for 60 and 120 days, respectively; while group-III was kept as a control under normal laboratory conditions. At the end of the experiment, animals were sacrificed and bone marrow samples were taken to investigate the effect of air pollutants at a benzene station on chromosomal aberrations and micronuclei formation. Tissue samples were also picked out to evaluate histotoxic effects of these air pollutants. Results: Results indicated pronounced time-dependent effects because of the work place pollutants. Genetic examination revealed higher frequency of chromosomal aberrations and elevated mitotic index after exposure to air pollutants. Micronuclei formation also increased either in polychromatic or normochromatic erythrocyte due to air pollutants. Histopathological examination revealed congestion of the pulmonary blood vessels with pulmonary edema. Bronchial hyperplasia and metaplasia were also seen in late stage of exposure. The liver showed degenerative changes or even necrosis of hepatocytes, while the kidneys showed congestion of the renal blood vessels and glomerular tufts. Hyalinization of the glomeruli was also detected. The heart showed various mononuclear infiltration and the testes showed degenerative changes of seminiferous tubules. Spleen showed hemosiderosis while testes showed degenerative changes of seminiferous tubules. Conclusions: The findings of the present study indicated that benzene exposure may lead to toxic effects including, genotoxicities and histotoxicities. In order to minimize the predicted toxic effect of occupational exposure to benzene the strict protective measures should be put in consideration.

Lamin A/C Depletion Enhances DNA Damage-Induced Stalled Replication Fork Arrest

The human LMNA gene encodes the essential nuclear envelope proteins lamin A and C (lamin A/C). Mutations in LMNA result in altered nuclear morphology, but how this impacts the mechanisms that maintain genomic stability is unclear. Here, we report that lamin A/C-deficient cells have a normal response to ionizing radiation but are sensitive to agents that cause interstrand cross-links (ICLs) or replication stress. In response to treatment with ICL agents (cisplatin, camptothecin, and mitomycin), lamin A/C-deficient cells displayed normal γ-H2AX focus formation but a higher frequency of cells with delayed γ-H2AX removal, decreased recruitment of the FANCD2 repair factor, and a higher frequency of chromosome aberrations. Similarly, following hydroxyurea-induced replication stress, lamin A/C-deficient cells had an increased frequency of cells with delayed disappearance of γ-H2AX foci and defective repair factor recruitment (Mre11, CtIP, Rad51, RPA, and FANCD2). Replicative stress also resulted in a higher frequency of chromosomal aberrations as well as defective replication restart. Taken together, the data can be interpreted to suggest that lamin A/C has a role in the restart of stalled replication forks, a prerequisite for initiation of DNA damage repair by the homologous recombination pathway, which is intact in lamin A/C-deficient cells. We propose that lamin A/C is required for maintaining genomic stability following replication fork stalling, induced by either ICL damage or replicative stress, in order to facilitate fork regression prior to DNA damage repair.

Chromosome Imbalances and Alterations of AURKA and MYCN Genes in Children with Neuroblastoma

Neuroblastoma (NB), like most human cancers, is characterized by genomic instability, manifested at the chromosomal level as allelic gain, loss or rearrangement. Genetics methods, as well as conventional and molecular cytogenetics may provide valuable clues for the identification of target loci and successful search for major genes in neuroblastoma. We aimed to investigate AURKA and MYCN gene rearrangements and the chromosomal aberrations (CAs) to determine the prognosis of neuroblastoma. We performed cytogenetic analysis by G-banding in 25 cases [11 girls (44%) and 14 boys (66%)] and in 25 controls. Fluorescence in situ hybridization (FISH) with AURKA and MYCN gene probes was also used on interphase nuclei to screen for alterations. Some 18.4% of patient cells exhibited CAs., with a significant difference between patient and control groups in the frequencies (P<0.0001). Some 72% of the cells had structural aberrations, and only 28% had numerical chnages in patients. Structural aberrations consisted of deletions, translocations, breaks and fragility in various chromosomes, 84% and 52% of the patients having deletions and translocations, respectively. Among these expressed CAs, there was a higher frequency at 1q21, 1q32, 2q21, 2q31, 2p24, 4q31, 9q11, 9q22, 13q14, 14q11.2, 14q24, and 15q22 in patients. 32% of the patients had chromosome breaks, most frequently in chromosomes 1, 2, 3, 4, 5, 8, 9, 11, 12, 19 and X. The number of cells with breaks and the genomic damage frequencies were higher in patients (p<0.001). Aneuploidies in chromosomes X, 22, 3, 17 and 18 were most frequently observed. Numerical chromosome abnormalities were distinctive in 10.7% of sex chromosomes. Fragile sites were observed in 16% of our patients. Our data confirmed that there is a close correlation between amplification of the two genes, amplification of MYCN possibly contributing significantly to the oncogenic properties of AURKA. The high frequencies of chromosomal aberrations and amplifications of AURKA and MYCN genes indicate prognostic value in children with neuroblastomas and may point to contributing factors in their development.

Role of p53 codon 72 polymorphism in chromosomal aberrations and mitotic index in patients with chronic hepatitis B

Polymorphisms of the p53 gene, which participates in DNA repair, can affect the functioning of the p53 protein. The Arg and Pro variants in p53 codon 72 were shown to have different regulation properties of p53-dependent DNA repair target genes that can affect various levels of cytogenetic aberrations in chronic hepatitis B patients. The present study aimed to examine the frequency of chromosomal aberrations and the mitotic index in patients with chronic hepatitis B and their possible association with p53 gene exon 4 codon 72 Arg72Pro (Ex4+119 G>C; rs1042522) polymorphism. Fifty-eight patients with chronic hepatitis B and 30 healthy individuals were genotyped in terms of the p53 gene codon 72 Arg72Pro polymorphism by PCR-RFLP. A 72-h cell culture was performed on the same individuals and evaluated in terms of chromosomal aberrations and mitotic index. A high frequency of chromosomal aberrations and low mitotic index were detected in the patient group compared to the control group. A higher frequency of chromosomal aberrations was detected in both the patient and the control groups with a homozygous proline genotype (13 patients, 3 control subjects) compared to patients and controls with other genotypes [Arg/Pro (38 patients, 20 control subjects) and Arg/Arg (7 patients, 7 control subjects)]. We observed an increased frequency of cytogenetic aberrations in patients with chronic hepatitis B. In addition, a higher frequency of cytogenetic aberrations was observed in p53 variants having the homozygous proline genotype compared to variants having other genotypes both in patients and healthy individuals.

High frequency of chromosome aberrations observed in lymphocytes in postmenopausal obese women

Epidemiological studies indicate that obesity is associated with an increased risk of 20-25% with several types of cancer. The frequency of chromosome aberrations was evaluated in lymphocytes from postmenopausal obese and non-obese women. Twenty obese and 20 non-obese women, all post-menopause, were recruited. The groups were matched according to age (± 5 years) and place of origin. After signing the consent form, women were interviewed using a structured questionnaire, and a blood sample (5 ml) was drawn into vacutainer tubes. From each sample, lymphocyte cell cultures were established with and without mitomycin C (challenge assay). Afterwards, the frequency of chromosome aberrations were recorded for each group and treatment. Data were analyzed using the statistical program SPSS, v. 14.0. Obese women had a higher frequency of chromosome aberrations when compared with non-obese women. After exposing the cell cultures to mitomycin C, obese women presented an increase in the number of total chromosome aberrations in comparison to non-obese women (3.7± 0.6 vs. 2.70±0.6; p=0.001). The higher frequency of chromosome aberrations in lymphocytes from postmenopausal obese women compared to non-obese women suggested differences in the DNA repair capacity. This may indicate an association between genomic instability and the higher incidence of cancer in this population.

Allelic variants of polymorphic genes associated with a higher frequency of chromosome aberrations

Genotypic associations were studied for the frequency of chromosome aberrations in human peripheral blood lymphocytes. Cytogenetic analysis (1000 metaphase plate per individual) and genotyping at 19 sites of genes involved in detoxification and DNA repair were performed in a sample of 83 Chernobyl liquidators and a matched control sample of 96 volunteers. In either sample, the frequency of chromosome aberrations was higher in carriers of the minor alleles of the XPD gene (sites 2251T > G and 862G > A) and the positive genotypes of the GSTM1-GSTT1 genes. The highest frequency of chromosome aberrations was observed in carriers of a combined genotype including at least one minor allele of the XPD sites + at least one insertion in the GSTM1-GSTT1 genes. The high-risk genotype, which had a prevalence of 64%, was strongly associated with a higher frequency of chromosome aberrations in both volunteers (OR = 6.9, P = 0.008) and Chernobyl liquidators (OR = 5.6, P = 0.002).

Fluoride‐induced genotoxicity in mouse bone marrow cells: effect of buthionine sulfoximine and N‐acetyl‐ l‐cysteine

A significant level of reactive oxygen species generation was observed in sodium fluoride (NaF) treated mouse bone marrow cells (BMCs). Reduced glutathione (GSH) as a free radical scavenger could be an important determining factor in F-induced genotoxicity. We therefore attempted to monitor GSH to understand the mechanism of NaF-induced genotoxicity. NaF was injected intra-peritoneally in normal, buthionine sulfoximine (BSO) or N-acetyl-L-cysteine (NAC) treated mice (n = 5). After 13 h of NaF-treatment BMCs were collected to harvest them at the same divisional cycle and processed for analysis of cell cycle, induction of apoptosis and chromosomal aberrations (CAs). Level of GSH was also measured concomitantly. NaF induced significant CAs in all treatment groups except at 2.5 mg NaF kg(-1) body weight. BSO-treatment alone induced significantly high frequency of CAs. BSO treatment prior to injection of 2.5-7.5 mg NaF kg(-1) b.w. was found to increase the frequency of CAs, significantly when compared with the positive control group, but the level was not significant in case of higher doses of NaF treatment (15 and 30 mg kg(-1) b.w.). NaF-treated cells also showed a higher population of Annexin-V positive cells. NAC pre-treatment significantly reduced the extent of NaF-induced CAs, which clearly indicates the involvement of GSH in the NaF response. However, further study is warranted to evaluate the low synergistic effect of BSO on higher doses of NaF-induced CAs.

JC human polyomavirus is associated to chromosomal instability in peripheral blood lymphocytes of Hodgkin’s lymphoma patients and poor clinical outcome

BackgroundB cells are potential sites for latency and reactivation of the human neurotropic JC polyomavirus (JCV). We investigated JCV and Epstein–Barr virus (EBV) status in peripheral blood lymphocytes (PBL) from 74 Hodgkin’s lymphoma (HL) and 91 B-cell non-Hodgkin’s lymphoma (B-NHL) patients. Patients and methodsJCV and EBV DNA were assessed by PCR, and FISH technique was used to localize viral infection and to estimate chromosomal instability (rogue cells, ‘chromosomal aberrations’) throughout evolution. The influence of viral infection and chromosomal instability on freedom from progression (FFP) was investigated in HL patients. ResultsPCR product sequencing of PBL identified JCV in 42 (57%) circulating lymphocytes of HL patients. FISH analysis revealed that the presence of cells with a high JCV genome copy number—associated to the presence of rogue cells and ‘higher frequency of chromosomal aberrations’—increased from 15% before treatment to 52% (P < 10-5) after. The co-activation of JCV and EBV was independent of known prognostic parameters and associated with a shorter FFP (JCV and EBV co-activation P < 0.001, rogue cells P < 0.002). ConclusionIn HL, JCV activation and chromosomal instability have been identified in PBL and associated with a poorer prognosis, especially in EBV+.

Distribution of UVC-induced chromosome aberrations along the X chromosome of TCR deficient and proficient Chinese hamster cell lines

Cells with a transcription coupled repair (TCR) deficiency are characterized by a higher sensitivity to UVC irradiation and by an increase in apoptosis and chromosomal aberration frequencies. It has been claimed that the higher frequency of chromosomal aberrations results from the transcription blockage caused by UVC-lesions located in the transcribed strands of the genome. The distribution of chromosome breakpoints in euchromatic and heterochromatic regions of the X chromosome from TCR deficient and proficient Chinese hamster cell lines was studied. Most UVC-induced breakpoints occurred in euchromatic regions of the X chromosome in both cell lines. No increase of UVC-induced breakpoints in the euchromatic region of the UV61 X chromosome was observed, indicating that TCR failure alone cannot be responsible for the increased frequency of chromosomal aberrations. Differential chromatin remodeling in the TCR defective cell line is proposed as a possible mechanism involved in the distribution of UVC-induced breakpoints along the Chinese hamster X chromosome. A similar explanation for the increase of UVC-induced chromosomal aberrations in TCR defective cells is given.

Parp1–XRCC1 and the repair of DNA double strand breaks in mouse round spermatids

The repair of DNA double strand breaks (DSBs) in male germ cells is slower and differently regulated compared to that in somatic cells. Round spermatids show DSB repair and are radioresistant to apoptosis induction. Mutation induction studies using ionizing irradiation, indicated a high frequency of chromosome aberrations (CA) in the next generation. Since they are in a G1 comparable stage of the cell cycle, haploid spermatids are expected to repair DSBs by the non-homologous end-joining pathway (NHEJ). However, immunohistochemical evidence indicates that not all components of the classical NHEJ pathway are available since the presence of DNA-PKcs cannot be shown. Here, we demonstrate that round spermatids, as well as most other types of male germ cells express both Parp1 and XRCC1. Therefore, we have determined whether the alternative Parp1/XRCC1 dependent NHEJ pathway is active in these nuclei and also have tested for classical NHEJ activity by a genetic method. To evaluate DSB repair in SCID mice, deficient for DNA-PKcs, and to study the involvement of the Parp1/XRCC1 dependent NHEJ pathway in round spermatids, the loss of γ-H2AX foci after irradiation has been determined in nucleus spreads of round spermatids of SCID mice and in nucleus spreads and histological sections of Parp1-inhibited mice and their respective controls. Results show that around half of the breaks in randomly selected round spermatids are repaired between 1 and 8 h after irradiation. The repair of 16% of the induced DSBs requires DNA-PKcs and 21% Parp1. Foci numbers in the Parp1-inhibited testes tend to be higher in spermatids of all epithelial stages reaching significance in stages I–III which indicates an active Parp1/XRCC1 pathway in round spermatids and a decreased repair capacity in later round spermatid stages. In Parp1-inhibited SCID mice only 14.5% of the breaks were repaired 8 h after irradiation indicating additivity of the two NHEJ pathways in round spermatids.

Genetic Instability in Migrant and Seasonal Farmworker (MSF) Children of Mexican Origin From Texas

ISEE-243 Objective: To evaluate the frequency of chromosomal aberrations (CA) in the lymphocytes of migrant/seasonal farmworker (MSF) children from urban (Baytown) and agricultural (La Joya) regions of Texas. Material and Methods: It is well-documented from prospective population studies that higher frequency of CA in circulating lymphocytes indicates an increased risk for cancer. We used the fluorescence in situ hybridization (FISH) cytogenetic technique, an employed biomarker of genotoxic effects in populations exposed to environmental contaminants, to evaluate the frequency of CA in 73 MSF children aged 5 to 18 enrolled in our ongoing study Biomarkers of Genetic Susceptibility in Environmentally Exposed MSF Children. Chi-square and 2-sample t tests were used to describe the sociodemographic and exposure characteristics of study participants; 2-sample t test was used to calculate differences in mean CA between groups and linear regression analyses to determine the relationship between CA and epidemiologic data (the children's gender, age, birthplace, city of residence, and home pesticide use). Results: Most of the children were born in the United States (79.5%), girls (57.5%), with a mean age of 11.9 years, from La Joya (56.2%), with reported home pesticide use (91.8%). Overall, we observed a mean of 4.0 ± 1.8 (SD) CAs per 1,000 cells in the children. Interestingly, our data indicate that children residing in La Joya (agricultural area) had statistically higher levels of CAs (4.4 ± 2.2) compared with children residing in Baytown (urban area: 3.3 ± 1.0; P =0.042), even after adjusting for age, gender, country of birth and home pesticide use (P = 0.001). Conclusions: Preliminary data from our study suggest that MSF children residing in an agricultural region may be at a higher risk for genetic instability than MSF children residing in urban areas. Due to the small sample, we cannot generalize our findings to the general population of MSF children of Mexican origin residing in Texas. Larger studies among similar populations are needed to corroborate our findings (Supported by NCMHD P60MD000503).

Effects of some popular medicinal plants on Mus musculus

AbstractMimosa pudica, Vitex trifolia, Centella asiatica, Leucas aspera and Plantago major are widely used in traditional medicine. In an attempt to determine whether aqueous extracts of the plants interact with genetic material, mammalian cytogenetic assay was used. Mice which received intraperitonial injections of different doses of the extract of Mimosa pudica showed dose dependent increase in chromosomal aberrations, SC damages and micronucleus frequency, while the other plant extracts did not induce significantly higher frequency of chromosome aberrations.

IMMUNE, REPRODUCTIVE, AND CYTOGENETIC CHANGES AMONG WASTE INCINERATION WORKERS AT THE COMPOST FERTILIZER PLANT IN ZAGAZIG CITY

Background: The adverse health effects associated with mass burn incineration are of great concern as large population groups and workers may be exposed to derived toxic substances. Objectives: 1) determining some of the immunological, reproductive,and cytogenetic changes among workers exposed to waste incineration emissions at the waste incineration area of the compost fertilizer plant in Zagazig City, 2)determining the blood lead levels of the studied workers, and 3) assessing airborne particulate matter concentrations at the open dump and waste incineration area. Subjects and methods: This comparative cross-sectional study was conducted on 42 waste incineration workers, who were exposed to waste incineration emissions at the compost fertilizer plant in Zagazig City and a non-exposed control group (51 workersfrom 2 sweet factories). All workers were subjected to questionnaires, clinical examinations,and laboratory investigations, that included blood lead levels estimation, immunoglobulins estimation, flow cytometric analysis, and conventional cytogenetic analysis; While, only 12 workers from both groups agreed to perform semen analysis. Also, sampling of respirable airborne particulates, at the open dump and waste incineration area, was done. Results: Significantly higher percent of waste incineration workers had past history of recurrent infections suggesting depressed immune responsecompared to the controls. Also, married waste incineration workers had significantly higher complaints from secondary infertility, decreased libido, and congenital anomalies in their children compared to the married controls. mmunoglobulins and flow cytometric results demonstrated a significant increase in both CD8 and CD 25+cells (P<0.05) and a significantdecrease in CD4/CD8 ratio (P<0.05) among waste incineration workers compared to the control group; while there were no significant differences detected regarding immunoglobulins profile, CD3, and CD4. The results of semen analysis illustrated that, waste incineration workers had a significant decrease in the total sperm count and sperm motility and a significant increase in the percentage of abnormal forms of sperms than did the controls. The conventional cytogenetic analysis of this study revealed significantly higher frequency of chromosomal aberrations (dicentric chromosomes and accentric fragment) among waste incineration workers compared to the controls (P<0.001). Moreover, waste incineration workers with chromosomal aberrations had significantly longer duration of employment thanthose without chromosomal aberrations (P<0.05); while, smoking had no significant effect on the results of their cytogenetic analysis. Waste incineration workers were found to have significantly higher blood lead levels (11.8 + 3.4 μg/dl) when compared to the controls (7.8 ± 1.85 μg/dl) (P<0.001). Finally, the average concentrationof the respirable particulate matter in the open dump and waste incineration area was 0.47 mg/m3, which exceeds its threshold limit value (TLV). Conclusion and recommendations:unprotected occupational exposure to waste incineration emissions can cause serious immunological, reproductive, and cytogentic changes. So, a well designed control program is recommended, which should include; avoiding open burning of waste products and promote the use of non- incineration treatment technologies,using incinerators equipped with proper emission control system, continuous environmental and biological monitoring for lead, particulate matter, and other hazardous materials, using immune system parameters, semen quality, and chromosomal aberrations as biomarkers of effect in such workers, and using suitable protectiveequipment during work.

Higher frequency of chromosomal aberrations in ovarian endometriosis compared to extragonadal endometriosis: a possible link to endometrioid adenocarcinoma

Endometriosis may progress to invasive endometrioid adenocarcinoma, particularly in the ovary. Up to now, little is known of the molecular mechanisms possibly involved in the malignant transformation of endometriosis. Therefore, in this study, extragonadal endometriosis (n=10), ovarian endometriosis without malignancy (n=10), ovarian endometriosis with direct transition into endometrioid adenocarcinoma (n=8), and normal endometrium (n=12) were investigated for numerical chromosomal aberrations by fluorescence in situ hybridization using centromere enumeration probes. The proportions of cells with aneusomies were semiquantitatively assessed. Trisomies 1 and 7, and monosomies 9 and 17 were found in endometriosis, ovarian endometrioid adenocarcinoma, and normal endometrium. The proportions of aneusomic cells were significantly higher in ovarian endometrioid carcinoma compared with ovarian endometriosis (P<0.001), and in ovarian endometriosis compared with extragonadal endometriosis and normal endometrium (P<0.001). The data provide new evidence of a common lineage of endometriosis and ovarian endometrioid carcinoma. The higher frequency of chromosomal aberrations in endometrioid carcinoma than in endometriosis may reflect an expansion of aberrant cell clones already present in endometriosis during the progression to cancer. The higher frequency of chromosomal aberrations in ovarian endometriosis than in extragonadal endometriosis suggests a role of the ovarian stromal milieu in the induction of genetic changes, which may eventually lead to invasive cancer.

A multi‐biomarker analysis of DNA damage in automobile painters

The genotoxic effects associated with automobile painting were analyzed using a panel of biomarkers. Chromosomal aberrations (CAs), sister chromatid exchange (SCE), and micronuclei were evaluated in 25 car painters (12 smokers, 13 nonsmokers) working in different automobile paint-shops in Italy and in 37 control subjects. The controls were healthy blood donors (14 smokers, 23 non-smokers) that were matched with the experimental population for gender and age. Air samples were analyzed regularly at the work places, and elevated concentrations of benzene and toluene were detected consistently. The exposed group had higher frequencies of CAs (both chromosome- and chromatid-type), micronuclei, and SCE (P < 0.5 - P < 0.001). Furthermore, exposed and control subjects were also genotyped for GSTM1 and GSTT1 polymorphism. No significant associations were detected between the biomarker responses and either the GSTM1 or GSTT1 genotype of the subjects, but the small sample size does not allow definite conclusions on the relationship between the genetic polymorphism and the biomarkers. The results indicate that automobile painters have increased levels of clastogenic and possible aneugenic damage and that smoking may be a confounding factor for the responses.

Defective sister-chromatid cohesion, aneuploidy and cancer predisposition in a mouse model of type II Rothmund-Thomson syndrome

Type II Rothmund-Thomson syndrome (Type II RTS) is a rare autosomal recessive genetic disorder characterized by a congenital skin rash, birth defects of the skeleton, genomic instability and cancer predisposition. It is caused by mutations in the RECQL4 gene and thus represents one of the three cancer-prone genetic diseases that are caused by mutations in a RecQ helicase-encoding gene. Genomic instability has been suspected as a major underlying cause of this disease, and analyses of Type II RTS patient-derived cells demonstrate unusually high frequencies of chromosomal aberrations, suggesting the involvement of chromosomal instability. However, the nature of the instability induced by RECQL4 mutations has not been clearly defined. We created a viable Recql4 mutant mouse model. These mice exhibit a distinctive skin abnormality, birth defects of the skeletal system, genomic instability and increased cancer susceptibility in a sensitized genetic background. Thus, they provide a useful model for studying Type II RTS. In addition, we demonstrate that cells from these mutant mice have high frequencies of premature centromere separation and aneuploidy. Thus, our observations provide evidence for a previously unsuspected role for Recql4 in sister-chromatid cohesion, and suggest that the chromosomal instability may be the underlying cause of cancer predisposition and birth defects in these mutant mice.

The contribution of genetic and epigenetic changes in granulosa cell tumors of ovarian origin.

Granulosa cell tumors (GCTs) are relatively rare and are subtypes of the sex-cord stromal neoplasms. A better understanding of the molecular genetics underlying various steps in malignant transformation is critical to success in the battle against this disease. Changes in the status of methylation, known as epigenetic alterations, are one of the most common molecular alterations in human cancers, including GCTs. Chromosomal instability and microsatellite instability (MSI) are common in these GCTs. We tested the hypothesis that C-->T transition polymorphism in the promoter region of cytosine DNA-methyltransferase-3B (DNMT3B) and its altered expression are also associated with hypermethylation of the genes. We also attempted to determine the relationship between MSI of ovarian carcinoma and hMLH1 hypermethylation in these tumors. We studied chromosome instability in 25 GCTs by detecting gross chromosome rearrangements in cultured peripheral blood lymphocytes. MSI was assessed using six microsatellite markers (BAT25, BAT26, D2S123, D5S346, D11S1318, and D17S250). Using sensitive methylation-specific PCR, we searched for aberrant promoter hypermethylation in a panel of genes including p16, BRCA1, RASSF1A, ER-alpha, TMS1, TIMP3, Twist, GSTP1, AR, and hMLH1. Polymorphism in the DNMT3B gene was assessed by the PCR-RFLP method, and DNMT3B expression was studied by reverse transcription-PCR assay. Chromosome instability was indicated by significantly higher frequencies of chromosome aberrations (6.24%; P < 0.001) compared with controls (2.12%). The most frequently observed changes include trisomy 14 and monosomy 22. MSI has been found in 19 of 25 tumors, and loss of heterozygosity has been found in 9 of 25 tumors. Frequencies of methylation in GCTs were 40% for p16 and ER-alpha; 36% for BRCA1 and RASSF1A; 28% for hMLH1; 24% for TIMP3, Twist, and GSTP1; and 20% in TMS1 and AR. TT genotype was found only in two cases; the remainder were either CC or CT type. There was no significant alteration in the expression of DNMT3B in these patients. Coexistence of chromosome instability, MSI, and hypermethylation suggests that both genetic and epigenetic mechanisms may act in concert to inactivate the above-mentioned genes in these GCTs. These mechanisms can be an early event in the pathogenesis of these tumors, and it can be a critical step in the tumorigenic process. All these events might play an important role in early clinical diagnosis and in chemotherapeutic management and treatment of the disease. Larger studies may lend further understanding to the etiology and clinical behavior of these tumors.

Chromosomal aberrations and risk of cancer in humans: an epidemiologic perspective

The pioneering papers published more than one century ago by Theodor Boveri opened the way to extensive research on the mechanism linking chromosomal abnormalities to the pathogenesis of cancer. As a result of this effort, robust theoretical and empirical evidence correlating cytogenetic damage to early stages of cancer in humans was consolidated, and an increased cancer risk was postulated in healthy subjects with high levels of chromosomal aberrations (CA). The first epidemiological investigation aimed at validating CA as predictor of cancer risk was carried out in the early 1990s. In that report the Nordic Study Group described an 80% increased risk of cancer in healthy subjects with high frequencies of CA. The results of this first study were replicated a few years later in a parallel research initiative carried out in Italy, and the subsequent pooled analysis of these two cohorts published in 1998 contributed to refine the quantitative estimate of the CA/cancer association. A small case-control study nested in a cohort of subjects screened for CA in Taiwan found an increased risk in subjects with high frequency of chromosome-type CA, while in 2001 a significant increase of cancer incidence associated with high levels of CA was described in a new independent cohort of radon exposed workers from the Czech Republic. Despite some common limitations affecting study design, the studies cited above have provided results of great interest both for the understanding of mechanisms of early stages of carcinogenesis, and for their potential implication for cancer prevention. The recent evolution of molecular techniques and the refinement of high throughput techniques have the potential to improve the knowledge about the role of specific sub-types of CA and to provide further insight into the mechanisms. Finally, the most challenging perspective in the field is the passage from research to regulation, with the implementation of preventive policies based on the accumulated knowledge.