Chromatid-type aberrations following irradiation in G0 lymphocytes with heavy ions

We describe a low level of chromatid-type aberrations which included the relatively rare isochromatid/chromatid triradial in peripheral blood lymphocytes that were irradiated, ostensibly in GO, with accelerated heavy C-12 ions. These were produced only at the energies of 69 MeV/n (34.6 keV/ mu m), almost absent at the energy of either 58.6 McV/n (46.07 keV/mu m) or 19.3 MeV/n (97 keV/mu m), nor were they found after low-LET X-rays. Mechanisms potentially responsible for their formation are discussed.

Long-term genomic instability in human lymphocytes induced by single-particle irradiation

Recent evidence suggests that genomic instability, which is an important step in carcinogenesis, may be important in the effectiveness of radiation as a carcinogen, particularly for high-LET radiations. Understanding the biological effects underpinning the risks associated with low doses of densely ionizing radiations is complicated in experimental systems by the Poisson distribution of particles that ran be delivered, In this study, we report an approach to determine the effect of the lowest possible cellular radiation dose of densely ionizing at particles, that of a single particle traversal. Using microbeam technology and an approach for immobilizing human T-lymphocytes, we have measured the effects of single alpha -particle traversals on the surviving progeny of cells. A significant increase in the proportion of aberrant cells is observed 12-13 population doublings after exposure, with a high level of chromatid-type aberrations, indicative of an instability phenotype, These data suggest that instability may be important in situations where even a single particle traverses human cells. (C) 2001 by Radiation Research Society.

Distinct Roles of FANCO/RAD51C Protein in DNA Damage Signaling and Repair Implications for Fanconi Anemia and Breast Cancer Susceptibility

RAD51C, a RAD51 paralog, has been implicated in homologous recombination (HR), and germ line mutations in RAD51C are known to cause Fanconi anemia (FA)-like disorder and breast and ovarian cancers. The role of RAD51C in the FA pathway of DNA interstrand cross-link (ICL) repair and as a tumor suppressor is obscure. Here, we report that RAD51C deficiency leads to ICL sensitivity, chromatid-type errors, and G(2)/M accumulation, which are hallmarks of the FA phenotype. We find that RAD51C is dispensable for ICL unhooking and FANCD2 monoubiquitination but is essential for HR, confirming the downstream role of RAD51C in ICL repair. Furthermore, we demonstrate that RAD51C plays a vital role in the HR-mediated repair of DNA lesions associated with replication. Finally, we show that RAD51C participates in ICL and double strand break-induced DNA damage signaling and controls intra-S-phase checkpoint through CHK2 activation. Our analyses with pathological mutants of RAD51C that were identified in FA and breast and ovarian cancers reveal that RAD51C regulates HR and DNA damage signaling distinctly. Together, these results unravel the critical role of RAD51C in the FA pathway of ICL repair and as a tumor suppressor.

γ射线诱导人卵巢癌细胞G2-染色单体断裂与修复

应用早熟染色体凝集技术研究了γ-射线诱导人卵巢癌细胞G2-染色单体断裂畸变的剂量效应与畸变修复的时间效应。结果表明:G2-染色单体型断裂畸变(chromatid-type breaks)与辐射剂量呈线性关系;G2-等点染色单体型断裂畸变(iso-chromatid breaks)与辐射剂量呈线性平方关系。2Gyγ-射线诱导的G2染色单体断裂畸变随着孵育时间的延长发生了明显的连接即修复,对G2-染色单体型断裂畸变,有近65％的断裂在辐射后24h内得以修复;对G2-等点染色单体型断裂,在辐射后24h内只有20％左右得以修复,两类断裂畸变的修复主要发生在辐射后2h内,在辐射后12-24h内染色体断裂量趋于稳定,表明修复基本完成。

Radiosensitivity of hepatoma cell lines and human normal liver cell lines exposed in vitro to carbon ions and argon ions at the HIRFL

Human hepatoma (SMMC-7721) and normal liver (L02) cells were irradiated with c-rays, 12C6+ and 36Ar18+ ion beams at the Heavy Ion Research Facility in Lanzhou (HIRFL). By using the Calyculin-A induced premature chromosome condensation technique, chromatid-type breaks and isochromatid-type breaks were scored separately. Tumor cells irradiated with heavy ions produced a majority of isochromatid break, while chromatid breaks were dominant when cells were exposed to c-rays. The relative biological effectiveness (RBE) for irradiation-induced chromatid breaks were 3.6 for L02 and 3.5 for SMMC-7721 cell lines at the LET peak of 96 keVlm 1 12C6+ ions, and 2.9 for both of the two cell lines of 512 keVlm 1 36Ar18+ ions. It suggested that the RBE of isochromatid-type breaks was pretty high when high-LET radiations were induced. Thus we concluded that the high production of isochromatid-type breaks, induced by the densely ionizing track structure, could be regarded as a signature of high-LET radiation exposure.

Genetic susceptibility, cigarette smoking, and wood dust exposure in lung cancer: Case control analyses

This case control study was conducted to assess the association between lung cancer risk, mutagen sensitivity (a marker of cancer susceptibility), and a putative lung carcinogen, wood dust exposure. There were 165 cases (98 African-Americans, 67 Mexican-Americans) with newly diagnosed, previously untreated lung cancer, and 239 controls, frequency-matched on age, sex, and ethnicity.^ Mutagen sensitivity ($\ge$1 break/cell) was associated with a statistically significant elevated risk for lung cancer (odds ratio (OR) = 4.1, 95% confidence limits (CL) = 2.3,7.2). Wood dust exposure was also a significant predictor of risk (OR = 2.8, 95% CL = 1.2,6.6) after controlling for smoking and mutagen sensitivity. When stratified by ethnicity, wood dust exposure was a significant risk factor for African-Americans (OR = 4.0, 95% CL = 1.4,11.5), but not for Mexican-Americans (OR = 1.5, 95% CL = 0.3,7.1). Stratified analysis suggested a greater than multiplicative interaction between wood dust exposure and both mutagen sensitivity and smoking.^ The cases had significantly more breaks on chromosomes 4 and 5 than the controls did with ORs of 4.9 (95% CL = 2.0, 11.7) and 3.9 (95% CL = 1.6, 9.3), respectively. Breaks at 4p14, 4q27, 4q31, 5q21-22, 5q31, and 5q33 were significantly more common in lung cancer patients than in controls. Lung cancer risk had a dose-response relationship with breaks on chromosomes 4 and 5. Cigarette smoking had a strong interaction with breaks on chromosomes 2, 4, and 5.^ In a molecular cytogenetic study, using chromosome painting and G-banding, we showed that: (1) the proportion of chromosome 5 abnormalities surviving as chromosome-type aberrations remained significantly higher in cells of lung cancer cases (14%) than in controls (5%) (P $<$ 0.001). However, no significant differences were detected in chromosome 4 abnormalities between cases and controls; (2) the proportion of chromosome 5q13-22 abnormalities was 5.3% in the cases and 0.7% in the controls (P $<$ 0.001). 5q13-22 regions represented 40% of all abnormalities on chromosome 5 in the cases and only 14% in the controls.^ This study suggests that mutagen sensitivity, wood dust exposure, and cigarette smoking were independent risk factors for lung cancer, and the susceptibility of particular chromosome loci to mutagenic damage may be a genetic marker for specific types of lung cancer. ^

Straylight, lens yellowing and aberrations of eyes in type 1 diabetes

Straylight, lens yellowing and ocular aberrations were assessed in a group of people with type 1 diabetes and in an age matched control group. Most of the former had low levels of neuropathy. Relative to the control group, the type 1 diabetes group demonstrated greater straylight, greater lens yellowing, and differences in some higher-order aberration co-efficients without significant increase in root-mean-square higher-order aberrations. Differences between groups did not increase significantly with age. The results are similar to the findings for ocular biometry reported previously for this group of participants, and suggest that age-related changes in the optics of the eyes of people with well-controlled diabetes need not be accelerated.

Mechanism of anticlastogenicity of Agaricus blazei Murill mushroom organic extracts in wild type CHO (K-1) and repair deficient (xrs5) cells by chromosome aberration and sister chromatid exchange assays

Agaricus blazei Murill is a medicinal mushroom native to Brazil. The present work assessed the clastogenic and anticlastogenic potential of organic extracts (ethanol and chloroform/methanol) from the lineage AB97/11 in chinese hamster CHO-K-1 (wild type) and CHO-xrs5 (repair deficient) cells using the chromosome aberration (CA) and sister chromatid exchange (SCE) assays. In these experimental conditions were observed: (a) anticlastogenic effect at concentrations of 0.06 and 0.09% of the EtOH extract and at the 0.03 and 0.06% concentrations of the C/MetOH extract in CHO-K-1; (b) absence of protector effect on CHO-xrs5 cells; and (c) absence of protector effect in the SCE assay. These results indicate that organic extracts of A. blazei lineage AB97/11 present bio-antimutagenic type protective activity. (C) 2003 Elsevier B.V. B.V. All rights reserved.

Sister chromatid exchanges and chromosome aberrations in lymphocytes of nurses handling antineoplastic drugs

Chromosomal aberrations (CA) and sister-chromatid exchanges (SCE) were investigated in peripheral lymphocytes of 15 nurses and nurse's aides handling cytostatic agents in hospital oncology units. Significantly increased frequencies were noted for both CA and SCE rates when the exposed individuals were compared with 15 nurses working in other hospital units and to a control sample matched by sex and age. This points to the need for emphasizing protective measures in the handling of anti-neoplastic agents.

Monocular amblyopia and higher order aberrations

This study compared the corneal and total higher order aberrations between the fellow eyes in monocular amblyopia. Nineteen amblyopic subjects (8 refractive and 11 strabismic) (mean age 30 ± 11 years) were recruited. A range of biometric and optical measurements were collected from the amblyopic and non-amblyopic eye including; axial length, corneal topography and total higher order aberrations. For a sub-group of eleven non-presbyopic subjects (6 refractive and 5 strabismic amblyopes, mean age 29 ± 10 years) total higher order aberrations were also measured during accommodation (2.5 D stimuli). Amblyopic eyes were significantly shorter and more hyperopic compared to non-amblyopic eyes and the interocular difference in axial length correlated with both the magnitude of anisometropia and amblyopia (both p < 0.01). Significant differences in higher order aberrations were observed between fellow eyes, which varied with the type of amblyopia. Refractive amblyopes displayed higher levels of 4th order corneal aberrations C(4, 0)(spherical aberration), C(4, 2)(secondary astigmatism 90°) and C(4, −2)(secondary astigmatism along 45°) in the amblyopic eye compared to the non-amblyopic eye. Strabismic amblyopes exhibited significantly higher levels of C(3, 3)(trefoil) in the amblyopic eye for both corneal and total higher order aberrations. During accommodation, the amblyopic eye displayed a significantly greater lag of accommodation compared to the non-amblyopic eye, while the changes in higher order aberrations were similar in magnitude between fellow eyes. Asymmetric visual experience during development appears to be associated with asymmetries in higher order aberrations, in some cases proportional to the magnitude of anisometropia and dependent upon the amblyogenic factor.

Chromosomal aberrations in squamous cell carcinoma and solar keratoses revealed by comparative genomic hybridization

OBJECTIVE: To identify chromosomal copy numbers of frequent genetic aberrations within squamous cell carcinomas (SCCs) and solar keratoses (SKs), and provide further evidence to support or challenge current dogma concerning the relationship between these lesions. DESIGN: Retrospective analysis of genetic aberrations in DNA from SK and SCC biopsy specimens by comparative genomic hybridization. SETTING: University-based research laboratory in Queensland, Australia. PATIENTS: Twenty-two biopsy specimens from patients with diagnosed SKs (n = 7), cutaneous SCCs (n = 10), or adjoining lesions (n = 5). MAIN OUTCOME MEASURES: Identification of frequent genetic aberrations both specific to SK and SCC and shared by these lesions to investigate their clonal relationship. RESULTS: Shared genomic imbalances were identified in SK and SCC. Frequent gains were located at chromosome arms 3q, 17q, 4p, 14q, Xq, 5p, 9q, 8q, 17p, and 20q, whereas shared regional losses were observed at 9p, 3p, 13q, 17p, 11p, 8q, and 18p. Significant loss of 18q was observed only in SCC lesions. CONCLUSIONS: Our results demonstrate that numerous chromosomal aberrations are shared by the 2 lesions, suggesting a clonal relationship between SK and SCC. Additionally, the genomic loss of 18q may be a significant event in SK progression to SCC. Finally, the type and frequency of aberrations suggests a common mode of tumorigenesis in SCC-derived tumors.

A variant of the breast cancer type 2 susceptibility protein (BRC) repeat is essential for the RECQL5 Helicase to interact with RAD51 Recombinase for genome stabilization

The BRC repeat is a structural motif in the tumor suppressor BRCA2 (breast cancer type 2 susceptibility protein), which promotes homologous recombination (HR) by regulating RAD51 recombinase activity. To date, the BRC repeat has not been observed in other proteins, so that its role in HR is inferred only in the context of BRCA2. Here, we identified a BRC repeat variant, named BRCv, in the RECQL5 helicase, which possesses anti-recombinase activity in vitro and suppresses HR and promotes cellular resistance to camptothecin-induced replication stress in vivo. RECQL5-BRCv interacted with RAD51 through two conserved motifs similar to those in the BRCA2-BRC repeat. Mutations of either motif compromised functions of RECQL5, including association with RAD51, inhibition of RAD51-mediated D-loop formation, suppression of sister chromatid exchange, and resistance to camptothecin-induced replication stress. Potential BRCvs were also found in other HR regulatory proteins, including Srs2 and Sgs1, which possess anti-recombinase activities similar to that of RECQL5. A point mutation in the predicted Srs2-BRCv disrupted the ability of the protein to bind RAD51 and to inhibit D-loop formation. Thus, BRC is a common RAD51 interaction module that can be utilized by different proteins to either promote HR, as in the case of BRCA2, or to suppress HR, as in RECQL5.

Évaluation de la cytogénotoxicité humaine induite par l’exposition à de faibles doses de benzo-a-pyrène, à l’aide de biomarqueurs précoces

Le benzo-a-pyrène (BaP) est un hydrocarbure aromatique polycyclique (HAP) cancérogène pour l’homme, qui contamine toutes les sphères de notre environnement. Son métabolite, le BaP-7,8-diol-9,10-époxyde (BPDE) est considéré comme son cancérogène ultime. Le BPDE se lie à l’ADN, formant des adduits qui doivent être réparés et qui seraient responsables des dommages à l’ADN et de la cancérogenèse induite par le BaP. Les adduits BPDE-ADN et les dommages à l’ADN (bris simple-brin [BSB] à l’ADN, aberrations chromosomiques [AC], échanges entre chromatides-sœurs [ÉCS] et micronoyaux [MN]) ont été mesurés dans les lymphocytes humains exposés à de faibles concentrations de BaP, provenant de jeunes volontaires non-fumeurs et en santé. Suite à l’exposition au BaP, le niveau d’adduits BPDE-ADN et la fréquence des AC et des MN augmentent significativement, puis diminuent aux concentrations les plus élevées de BaP testées, suggérant une induction du métabolisme de phase II du BaP. Lors de la mesure des ÉCS, nous obtenons une courbe dose-réponse linéaire, indiquant la production d’un autre type de lésions devant être réparées par le système de réparation par recombinaison homologue. Ces lésions pourraient être des bris à l’ADN ou des bases oxydées (8-OH-dG), ce qui est suggéré par l’analyse des corrélations existant entre nos biomarqueurs. Par ailleurs, la comparaison de la courbe dose-réponse des hommes et des femmes montre que des différences existent entre les sexes. Ainsi, les ÉCS, les AC et les MN sont significativement augmentés chez les hommes à la plus faible concentration de BaP, alors que chez les femmes cette augmentation, quoique présente, est non significative. Des différences interindividuelles sont également observées et sont plus importantes pour les adduits BPDE-ADN, les MN et les AC, alors que pour les ÉCS elles sont minimes. Les analyses statistiques effectuées ont permis d’établir que quatre facteurs (niveau d’exposition au BaP, adduits BPDE-ADN, fréquence des AC et nombre de MN par cellule micronucléée) expliquent jusqu’à 59 % de la variabilité observée dans le test des ÉCS, alors qu’aucun facteur significatif n’a pu être identifié dans le test des AC et des MN. L’analyse du mécanisme de formation de nos biomarqueurs précoces permet de suggérer que les bris à l’ADN et les bases oxydées devraient être classées comme biomarqueurs de dose biologique efficace, au sein des biomarqueurs d’exposition, dans le continuum exposition-maladie du BaP, étant donné qu’ils causent la formation des biomarqueurs de génotoxicité (ÉCS, AC et MN). Par ailleurs, le test des AC et des MN ont permis de confirmer l’action clastogénique du BaP en plus de mettre en évidence des effets aneugènes affectant surtout la ségrégation des chromosomes lors de la division cellulaire. Ces effets aneugènes, reliés à l’étape de progression dans la cancérogenèse, pourraient être particulièrement importants puisque l’exposition au BaP et aux HAP est chronique et dure plusieurs années, voire des décennies. La compréhension des mécanismes régissant la formation des biomarqueurs étudiés dans cette étude, ainsi que des relations existant entre eux, peut être appliquée à de nombreux contaminants connus et émergents de notre environnement et contribuer à en évaluer le mode d’action.

Structural Chromosomal Alterations Induced by Dietary Bioflavonoids in Fanconi Anemia Lymphocytes

Introduction Fanconi anemia is an autosomal recessive disease characterized by a variety of congenital abnormalities, progressive bone marrow failure, increased chromosomal instability and higher risk to acute myeloid leukemia, solid tumors. This entity can be considered an appropriate biological model to analyze natural substances with possible genotoxic effect. The aims of this study were to describe and quantify structural chromosomal aberrations induced by 5 flavones, 2 isoflavones and a topoisomerase II chemotherapeutic inhibitor in Fanconi anemia lymphocytes in order to determine chromosomal numbers changes and/ or type of chromosomal damage. Materials and methods Chromosomes stimulated by phytohaemagglutinin M, from Fanconi anemia lymphocytes, were analysed by conventional cytogenetic culture. For each chemical substance and controls, one hundred metaphases were evaluated. Chromosomal alterations were documented by photography and imaging analyzer. To statistical analysis was used chi square test to identify significant differences between frequencies of chromosomal damage of basal and exposed cell cultured a P value less than 0.05. Results There were 431 chromosomal alterations in 1000 metaphases analysed; genistein was the more genotoxic bioflavonoid, followed in descendent order by genistin, fisetin, kaempferol, quercetin, baicalein and miricetin. Chromosomal aberrations observed were: chromatid breaks, chromosomal breaks, cromatid and chromosomal gaps, quadriratials exchanges, dicentrics chromosome and complex rearrangements. Conclusion Bioflavonoids as genistein, genistin and fisetin, which are commonly present in the human diet, showed statistical significance in the number of chromosomal aberrations in Fanconi anemia lymphocytes, regarding the basal damage.

Reduced Skeletal Muscle Uncoupling Protein-3 Content in Prediabetic Subjects and Type 2 Diabetic Patients: Restoration by Rosiglitazone Treatment

Context: The mitochondrial uncoupling protein-3 (UCP3) has been implicated in the protection of the mitochondrial matrix against lipid-induced mitochondrial damage. Recent evidence points toward mitochondrial aberrations as a major contributor to the development of insulin resistance and diabetes, and UCP3 is reduced in diabetes.
Objective: We compared skeletal muscle UCP3 protein levels in prediabetic subjects [i.e. impaired glucose tolerance (IGT)], diabetic patients, and healthy controls and examined whether rosiglitazone treatment was able to restore UCP3.
Patients, Design, Intervention: Ten middle-aged obese men with type 2 diabetes mellitus [age, 61.4 ± 3.1 yr; body mass index (BMI), 29.8 ± 2.9 kg/m2], nine IGT subjects (age, 59.0 ± 6.6 yr; BMI, 29.7 ± 3.0 kg/m2), and 10 age- and BMI-matched healthy controls (age, 57.3 ± 7.4 yr; BMI, 30.1 ± 3.9 kg/m2) participated in this study. After baseline comparisons, diabetic patients received rosiglitazone (2 x 4 mg/d) for 8 wk.
Main Outcome Measures: Muscle biopsies were sampled to determine UCP3 and mitochondrial protein (complex I–V) content.
Results: UCP3 protein content was significantly lower in prediabetic IGT subjects and in diabetic patients compared with healthy controls (39.0 ± 28.5, 47.2 ± 24.7, and 72.0 ± 23.7 arbitrary units, respectively; P < 0.05), whereas the levels of the mitochondrial protein complex I–V were similar between groups. Rosiglitazone treatment for 8 wk significantly increased insulin sensitivity and muscle UCP3 content (from 53.2 ± 29.9 to 66.3 ± 30.9 arbitrary units; P < 0.05).
Conclusion: We show that UCP3 protein content is reduced in prediabetic subjects and type 2 diabetic patients. Eight weeks of rosiglitazone treatment restores skeletal muscle UCP3 protein in diabetic patients.