Frequency Of Chromatid Breaks Research Articles

Expression level of miR-155, miR-15a and miR-19a in peripheral blood of ductal carcinoma breast cancer patients: Possible bioindicators for cellular inherent radiosensitivity

Examination of cellular radiosensitivity (RS) helps prevent the adverse side-effects of radiotherapy in radioresistant tumors. We aim to study whether miRNA-155 (miR-155), miR-19a and miR-15a can predict inherent RS according to cellular RS in breast cancer (BC) patients.This study was done on the blood samples of 40 invasive ductal carcinoma (IDC) BC patients and 15 healthy women. G2 assay was performed to evaluate cellular RS. To study the expression level of these miRNAs in blood, qRT-PCR was used. The sensitivity and specificity of the studied miRNAs were assessed by the receiver operating characteristic (ROC) curve.The yield of spontaneous (SY) and radiation-induced (RIY) chromatid breaks (CBs) was significantly different between control and patient groups (p < 0.0001). A cut-off value was specified to recognize the patients with cellular RS from those without. Expression of miR-15a was significantly downregulated (p < 0.0001) in BC patients. However, miR-19a showed upregulation in the blood of BC patients. It was also found the expression level of miR-155 and miR-19a were significantly associated with frequency of CBs (FCB) (p < 0.05). ROC curve analysis manifested that the miR-15a and miR-19a differentiate BC patients and healthy women with 0.91 and 0.68 yielding an area under the ROC curve, respectively. miR-155 and miR-19a discriminate between BC patients with and without cellular RS with area under the ROC curve 0.98 and 0.68.Our findings uncovered miR-155 and miR-19a could be applied as a bioindicator to predict cellular radiosensitivity of BC patients.

Smoking, chromosomal aberrations, and cancer incidence in healthy subjects

Chromosomal aberrations (CAs) in peripheral blood lymphocytes can be used as biomarkers of cancer risk. Cytogenetic tests were conducted on 2396 healthy Hungarian individuals and cancer incidence was followed up from 1989 to 2018. Venous blood samples were obtained from the subjects and metaphases from lymphocyte cultures were prepared. We compared the CA frequencies of the various smoking (1−5; 6−10; 11−19; or 20−40 cigarettes/day) and exposure (irradiation; chemical industry; chemical research laboratory) groups. Chromatid break (p = 0.0002), total aberration (p = 0.002), and aberrant cell (p = 0.001) frequencies were higher in smokers than in non-smokers. For very heavy smokers, total CAs were significantly higher than for non-smokers (<0.001) or less intensive smokers (p = 0.003−0.0006). Intensity of smoking was a predictor of chromosomal aberrations, while duration was not. During follow-up, 177 (7.3 %) cancer cases were found. A Cox-regression model showed that subjects with cell values ≥2 CAs developed cancer more frequently (hazard ratio = 1.39; 95 % CI, 1.02–1.90). The relative risks of cancer were 1.06 (95 % CI 0.53−2.06) for light smokers and 1.74 (95 % CI 1.08−2.77) for very heavy smokers. The distributions of cancer sites showed differences between smoker and non-smoker groups: in male smokers, lung cancer, in non-smokers, prostate, and in females (both groups) breast cancer were most common. Cancer incidence correlated with chromosome aberrations; smoking was not a confounder in this relationship.

Chromosomal instability in different species of agricultural animals (review)

The purpose of the work was to analyze the frequency of chromosomal instability in different species of agricultural animals in Western Siberia on the basis of literature data. The analysis of the literature on the topic of somatic chromosomal instability in agricultural animals has been carried out. Despite the stability of the chromosome set, deviations from it are quite common. It is noteworthy that chromosomal instability is characteristic of almost all individuals in the population and serves as an important indicator for assessing the natural mutability of chromosomes. It has been found if an aberration appeared in one tissue, it is very likely to occur in others. It has been noted that somatic chromosomal instability occurs in animals with reduced reproductive function, as well as those suffering from any pathology. For example, in calves with parakeratosis the increase in the frequency of chromatid and isochromatid breaks has been found. Analysis of the frequency of aberrations in sires, which differ in the level of perinatal mortality of offspring revealed the increased percentage of offspring mortality in fathers with the large number of chromosomal disorders. Therefore, low fertilization, spontaneous abortions and stillbirths may be indications for karyotypic analysis. It has been revealed that the lability of the karyotype is inherent in all animal species, regardless of the species, sex and age, as well as the morphofunctional state. The data on some types of somatic chromosomal instability in different types of farm animals in Western Siberia has been presented. Such indicators as the frequency of polyploidy, the number of cells with fragments of chromosomes, as well as single and paired fragments of chromosomes has been given. Different types of chromosomal instability varied depending on the animal species and climate zone. The presented data can be accepted as a physiological norm and used in veterinary medicine and animal science.

Association study of miR-22 and miR-335 expression levels and G2 assay related inherent radiosensitivity in peripheral blood of ductal carcinoma breast cancer patients.

Identifying patient's cellular radiosensitivity before radiotherapy (RT) in breast cancer (BC) patients allows proper alternations in routinely used treatment programs and reduces the adverse side effects in exposed patients. This study was conducted on blood samples taken from 60 women diagnosed with Invasive Ductal Carcinoma (IDC) BC (mean age: 47±9.93) and 30 healthy women (mean age: 44.43±6.7). The standard G2 assay was performed to predict cellular radiosensitivity. To investigate miR-22 and miR-335 expression levels in peripheral blood mononuclear cells (PBMCs), qPCR was performed. The sensitivity and specificity of the mentioned miRNAs were assessed by plotting the Receiver Operating Characteristic (ROC) curve. Binary logistic regression was performed to identify the miRNA involvement in BC and cellular radiosensitivity (CR) of BC patients. The frequency of spontaneous and radiation-induced chromatid breaks (CBs) was significantly different between control and patient groups (p<0.05). A cut-off value was determined to differentiate the patients with and without cellular radiosensitivity. miR-22 and miR-335 were significantly downregulated in BC patients. miRNAs expression levels were directly associated with CR. ROC curve assessment identified that both miRNAs had acceptable specificity and sensitivity in the prediction of BC and CR of BC patients. Binary logistic regression showed that both miRNAs could also predict BC successfully. Although only miR-22 was shown potent to predict CR of BC patients, both miR-22 and miR-335 might act as tumor suppressor miRNAs in BC. miR-22 and miR-335 may be promising potential biomarkers in BC prediction along with other important biomarkers. Moreover, mirR-22 might be a potential biomarker for the prediction of CR in BC patients.

Late Biochemical and Cytogenetic Changes in Plasma and Peripheral Blood Lymphocytes in People Exposed to Low-dose Radiation as a Result of the Accident at the Chernobyl Nuclear Power Plant

A study was conducted to evaluate the biochemical and cytogenetic parameters in peripheral blood lymphocytes in participants in the Chernobyl accident liquidation who were exposed to external and internal radiation in the dose range (0.1–70 cSv) and children living in territories with different levels of radionuclide contamination (1–20 Ci/km2) as a result of the Chernobyl accident. The effects of low-intensity radiation were studied in a comparative analysis of the relationship between the chromatid break index, the rate of mutagenesis in somatic cells (lymphocytes), and the level of reduced glutathione in blood plasma. The increased frequency of chromatid breaks in lymphocytes and an increased level of reduced glutathione in the blood plasma in children and liquidators exposed to low doses of radiation (0.1–20 cSv) were found to be statistically significant compared to the control. As the radiation dose increased (20–70 cSv), the increase in cytogenetic abnormalities in the peripheral blood lymphocytes of liquidators and children from Chechersk (Gomelsk oblast, Belarus) was accompanied by a decrease in the water-soluble antioxidant level in the plasma. The data on the relationship of the reduced glutathione level with the major indices of the cytogenetic status are important for identification of later pathological health-related conditions in people exposed to chronic ionizing radiation.

Determination of spontaneous dicentric frequencies and establishment of dose-response curves after expose of human peripheral blood lymphocytes to low- and high-dose rate 60Co gamma rays – the basis for cytogenetic biodosimetry in Vietnam

Purpose: The purposes of this study are to investigate spontaneous dicentric frequencies and dose–response curves of dicentrics induced by gamma 60Co for replenishing the data sets used for biodosimetry in Vietnam.Materials and methods: One hundred and four healthy donor blood samples were collected for chromosome aberrations background study, 03 healthy donor blood samples were used for generating the dose–response curves at 1.96 mGy/min and 275 mGy/min. Blood collection, in vitro irradiation, cell culture and harvest, slide preparation and metaphase scoring were performed according to IAEA standard protocol (2011). Blind exposed samples were scored for verifying each curve.Results: The dicentric, fragment and chromatid break frequencies in 106,310 metaphases of 104 donors were 0.023% ± 0.005%, 0.045% ± 0.007% and 0.101% ± 0.011%, respectively. The dose–response curve for low-dose rate was y = C + (0.0137 ± 0.0055)D + (0.0912 ± 0.0142)D2 and for high-dose rate was y = C + (0.0337 ± 0.0046)D + (0.0539 ± 0.0031)D2, where both of them were verified.Conclusion: The data of this study were established for biological dose assessment in cases with low LET of accidental or occupational radiation exposures in the dose range of 0.1–5.0 Gy.

Genotoxicity of recycled electronic waste in Idhna, Hebron District, occupied Palestinian territory: a case-controlled study

BackgroundElectronics waste is solid waste that accumulates because of the short lifespan of many types of electronic equipment. Most electronics waste ends up in landfills, whereas some is recycled. In the occupied Palestinian territory, the village of Idhna in the Hebron District is a large site for recycling electronics waste (much of this waste originates from Israel). The aim of this study was to evaluate the effects of electronics waste on human DNA damage and chromosome breaks. MethodsIn this cross-sectional study, we recruited non-smoker individuals with direct exposure to electronics waste either because they were employed in the workshops or resident in Idhna. Control participants were selected to match the test sample in age and sex distribution, were recruited from Bethlehem and Al-Aizariya (Bethany). Blood samples in sodium heparin were evaluated for DNA damage using the COMET assay, whereas chromosome aberrations were tested by using conventional cytogenetic techniques. Findings46 participants were included in the test sample, and 16 participants were included in the control sample. Participants in the test sample had an average of 3·77 chromosomes with aberrations (SD 2·5), whereas participants in the control group had an average of 0·75 chromosomes with aberrations (SD 0·61). The frequency of chromatid and chromosome breaks, formation of rings, and total chromosome aberrations was statistically different between exposed and control samples, but no difference was observed between exposed and controls for the incidence of dicenterics and tetraploidy. Results of the Comet assay showed a significant difference in DNA damage between exposed and control participants (p<0·05). No difference between the workers and the residents living in the area was noted (p<0·05). InterpretationExposure to recycled electronics waste in Idhna has potentially adverse health consequences. This is the second study of this kind in the occupied Palestinian territories. Hammad and Qumsiyeh (2013) have previously shown substantial genotoxic effects of Israeli industrial settlement discharge on human populations in Salfit (northern West Bank). Considering increased incidence of cancer and congenital birth defects in the southern part of the West Bank, these findings were important in promoting the case for mitigation measures, which are now under way. FundingNone.

Micronuclei And G2 Assays For Assessment Of Chromosomal Radiosensitivity As Assistant Tool In Radiotherapy: Method-Comparison Study

Radiation therapy is widely used for cancer treatment. Medical application of ionizing radiation can cause different responses in human depending on individual radiosensitivity. Therefore, assessment of individual radiosensitivity could be proposed as assistant tool in optimizing radiotherapy. The cytokinesis- block micronucleus and G2 chromosomal radiosensitivity assays were proposed as appropriate methods for assessment of individual radiosensitivity. In current study we carried out a pilot cytokinesis-block micronucleus and G2 chromosomal radiosensitivity assays comparison by evaluating specificity of chromatid breaks yield and micronuclei frequency in peripheral blood lymphocytes as biomarkers of individual radiosensitivity in three cancer patients treated with radiotherapy. Our study revealed positive correlation between higher increase in frequency of micronuclei and chromatid breaks after in vitro irradiation in radiotherapy patients peripheral blood lymphocytes with occurrence of adverse radiation effects in tissue which are not being targeted. G2 assay appeared to be more sensitive than micronuclei assay for assessment of irradiation-induced alterations in individual radiosensitivity during the radiotherapy that could affect development of treatment side effects. Therefore, further investigations involving more radiotherapy patients as well as healthy donors are required to select the most sensitive method and reveal the possible correlation between individual radiosensitivity and adverse effect of radiotherapy.

4-nitroquinoline-1-oxide-induced mutagen sensitivity and risk of cutaneous melanoma: a case-control analysis.

Mutagen sensitivity assay, which measures the enhanced cellular response to DNA damage induced in vitro by mutagens/carcinogens, has been used in the study of cancer susceptibility. 4-Nitroquinoline-1-oxide (4-NQO), an ultraviolet (UV) radiation-mimetic chemical, can produce chromosomal breaks in mammalian cells and induce cancer. Given the potential role of 4-NQO as the experimental mutagen substituting for UV as the etiological carcinogen of cutaneous melanoma (CM), we tested the hypothesis that cellular sensitivity to 4-NQO is associated with the risk of developing CM in a case-control study of 133 patients with primary CM and 176 cancer-free controls. Short-term blood cultures were treated with 4-NQO at a final concentration of 10 μmol/l for 24 h and scored chromatid breaks in 50 well-spread metaphases. Multivariate logistic regression was used to calculate odds ratios and 95% confidence intervals. We found that the log-transformed frequency of chromatid breaks was significantly higher in 133 patients than in 176 controls (P=0.004) and was associated with an increased risk for CM (adjusted odds ratio=1.78, 95% confidence interval: 1.12-2.84) after adjustment for age and sex. Moreover, as the chromatid break values increased, the risk for CM increased in a dose-dependent manner (P(trend)=0.003). Further analysis explored a multiplicative interaction between the sensitivity to 4-NQO and a family history of skin cancer (P(interaction)=0.004) on the risk of CM. Therefore, our findings suggest that sensitivity to 4-NQO may be a risk factor for the risk of CM, which is more sensitive than UV-induced chromotid breaks.

Evaluation of chromosomal aberrations induced by hydralazine in Chinese hamster ovary cells

Background and purposeHydralazine (HDZ) is a cardiovascular drug that is widely used to treat hypertension. The present study was done to assess the cytogenetic effects of HDZ on Chinese hamster ovary (CHO) cells. Materials and methodsMethylthiazol tetrazolium (MTT) assay was carried out to determine the half maximal inhibitory concentration (IC50) of the drug. The IC50 value for HDZ was 243.3±16.9μg/ml. To investigate the clastogenic effects of the drug, chromatid breaks and polyploidy in metaphases were analyzed. CHO cells were exposed to different concentrations of HDZ (20 and 40μg/ml) for 24h. The experiments were carried out in the presence and absence of metabolic activation system (S9 mix; 1ml S9 mix contained: 0.3ml phosphate solutions, 0.2ml KCl, 0.2ml MgCl2, 0.1ml S9 fraction, 0.1ml G-6-P and 0.1ml NADP), because HDZ is metabolized in the liver. Mitomycin-C and sodium arsenite were used as positive controls. ResultsIn the absence of S9 fraction, the level of chromatid breaks statistically increased (P=0.011) and mitotic index significantly decreased (P<0.001) in CHO cells treated with HDZ. There was no significant difference between treated and untreated CHO cells with HDZ for the level of polyploidy (F=0.05; df=2, 6; P=0.945). In the presence of S9 fraction, although the mitotic index elevated, still there was a significant difference between control and treated cells (F=50.53; df=2, 6; P<0.001). There was no significant difference between 20μg/ml of HDZ (+S9) and untreated cells for frequency of chromatid breaks. However, at the 40μg/ml concentration of HDZ (+S9), there was a significant difference between treated and untreated cells. ConclusionHDZ have genotoxic effects on CHO cells in their non-toxic dose, but S9 mix addition decreased these effects.

PROPRANOLOL INDUCED CHROMOSOMAL ABERRATIONS IN CHINESE HAMSTER OVARY CELL LINE

Propranolol (PL), a non-selective beta-blocker, is a cardiovascular drug widely used to treat hypertension. The present study was concerned with assessing the cytogenetic effects of this drug on Chinese hamster ovary (CHO) cell line. MTT assay was then carried out to determine the cytotoxicity index (IC50) of the drug. The IC50 value of PL was 0.43±0.02 mM. To investigate the clastogenic effects of the drug, chromatid and chromosome breaks and polyploidy in metaphases were analyzed. CHO cells were exposed to different concentrations of the drug (0.1, 0.2, 0.3, 0.4 mM) for 24 hours. Considering that PL has liver metabolism, experiments were carried out in the presence and absence of the metabolic activation system (S9 mix). Mitomycin-C and sodium arsenite were used as positive controls. It was observed that in cells treated with different PL concentrations as 0.1, 0.2 and 0.3 mM, the frequency of chromatid and chromosome breaks as well as polyploidy increased when compared with untreated CHO cells. The addition of S9 mix significantly decreased the chromatid breaks, chromosome breaks and polyploidy compared to the treatment of PL alone. It is concluded that, PL causes chromatid and chromosome aberrations in CHO cell line and the metabolic activation system (S9 mix), playing an important role in drug cytotoxicity reduction.

Topoisomerase II levels and G2 radiosensitivity in T-lymphocytes of women presenting with breast cancer

Previous studies from our laboratory have identified a link between intracellular topoisomerase IIα (topo IIα) levels and chromosomal radiosensitivity, as measured by the frequencies of chromatid breaks in the so-called G2-assay. Lower topo IIα levels were associated with reduced chromosomal radiosensitivity in cultured human cells. These findings supported a model, in which it is proposed that such chromatid breaks are the result of radiation-induced errors made by topoisomerase IIα during decatenation of chromatids. Studies from our and other laboratories, using the G2-assay, have shown that phytohaemagglutinin (PHA)-stimulated peripheral blood T-lymphocytes from 40% of female breast cancer cases show elevated chromatid break frequencies when exposed to a small standard dose of ionizing radiation, i.e. elevated above the 90th percentile of a group of female control samples. In the present study we have used a modified G2-assay to test whether elevated frequency of chromatid breaks in breast cancer cases is linked with elevated intracellular topo IIα level in PHA-stimulated T-lymphocytes, and also whether there is a general correlation between chromosomal radiosensitivity and topo IIα level. Our results confirm previous studies that 40% of breast cancer cases show elevated radiosensitivity as compared with controls. Also, the mean chromatid break frequency in breast cancer cases was significantly higher than in controls (P = 0.0001). We found that the mean topo IIα level in the cohort of breast cancer cases studied was significantly raised, as compared with controls (P = 0.0016), which could indicate a genetic propensity towards a raised intracellular production of topo IIα in these individuals. There was no direct correlation between chromosomal radiosensitivity and topo IIα level for individual samples either in the breast cancer cohort or in controls. However, a comparison between control and breast cancer samples shows a higher mean topo IIα level in breast cancer samples that correlates with the elevated mean chromatid break frequency seen in these patient samples. We found no meaningful correlations between either chromatid break frequency or topo IIα level and either tumour grade or hormone status. We conclude that elevated intracellular topo IIα level is likely to be a significant factor in determining the chromosomal response of stimulated T-lymphocytes from certain breast cancer cases.

Gamma-ray-induced mutagen sensitivity and risk of sporadic breast cancer in young women: a case–control study

Hypersensitivity to radiation exposure has been suggested to be a risk factor for the development of breast cancer. In this case-control study of 515 young women (≤ 55 years) with newly diagnosed sporadic breast cancer and 402 cancer-free controls, we examined the radiosensitivity as measured by the frequency of chromatid breaks induced by gamma-radiation exposure in the G2 phase of phytohemagglutinin-stimulated and short-term cultured fresh lymphocytes. We found that the average chromatid breaks per cell from 50 well-spread metaphases were statistically significantly higher in 403 non-Hispanic White breast cancer patients (0.52 ± 0.22) than that in 281 non-Hispanic White controls (0.44 ± 0.16) (P value < 0.001), and in 60 Mexican American breast cancer patients (0.52 ± 0.19) than that in 65 Mexican American controls (0.44 ± 0.16) (P value = 0.021), but the difference was not significant in African Americans (52 cases [0.45 ± 0.16] versus 56 controls [0.47 ± 0.16], P = 0.651). The frequency of chromatid breaks per cell above the median of control subjects was associated with two-fold increased risk for breast cancer in non-Hispanic Whites and Mexican Americans. A dose-response relationship was evident between radiosensitivity and risk for breast cancer (P (trend) < 0.001) in these two ethnic groups. We concluded that gamma-ray-induced mutagen sensitivity may play a role in susceptibility to breast cancer in young non-Hispanic White and Mexican American women.

Impact of heterozygous c.657-661del, p.I171V and p.R215W mutations in NBN on nibrin functions

Nibrin, product of the NBN gene, together with MRE11 and RAD50 is involved in DNA double-strand breaks (DSBs) sensing and repair, induction of apoptosis and cell cycle control. Biallelic NBN mutations cause the Nijmegen breakage syndrome, a chromosomal instability disorder characterised by, among other things, radiosensitivity, immunodeficiency and an increased cancer risk. Several studies have shown an association of heterozygous c.657-661del, p.I171V and p.R215W mutations in the NBN gene with a variety of malignancies but the data are controversial. Little is known, however, whether and to what extent do these mutations in heterozygous state affect nibrin functions. We examined frequency of chromatid breaks, DSB repair, defects in S-phase checkpoint and radiosensitivity in X-ray-irradiated cells from control individuals, NBS patients and heterozygous carriers of the c.657-661del, p.I171V and p.R215W mutations. While cells homozygous for c.657-661del displayed a significantly increased number of chromatid breaks and residual γ-H2AX foci, as well as abrogation of the intra-S-phase checkpoint following irradiation, which resulted in increased radiosensitivity, cells with heterozygous c.657-661del, p.I171V and p.R215W mutations behaved similarly to control cells. Significant differences in the frequency of spontaneous and ionising radiation-induced chromatid breaks and the level of persistent γ-H2AX foci were observed when comparing control and mutant cells heterozygous for c.657-661del. However, it is still possible that heterozygous NBN mutations may contribute to cancer development.

Error-prone nonhomologous end joining repair operates in human pluripotent stem cells during late G2

Genome stability of human embryonic stem cells (hESC) is an important issue because even minor genetic alterations can negatively impact cell functionality and safety. The incorrect repair of DNA double-stranded breaks (DSBs) is the ultimate cause of the formation of chromosomal aberrations. Using G2 radiosensitivity assay, we analyzed chromosomal aberrations in pluripotent stem cells and somatic cells. The chromatid exchange aberration rates in hESCs increased manifold 2 hours after irradiation as compared with their differentiated derivatives, but the frequency of radiation-induced chromatid breaks was similar. The rate of radiation-induced chromatid exchanges in hESCs and differentiated cells exhibited a quadratic dose response, revealing two-hit mechanism of exchange formation suggesting that a non-homologous end joining (NHEJ) repair may contribute to their formation. Inhibition of DNA-PK, a key NHEJ component, by NU7026 resulted in a significant decrease in radiation-induced chromatid exchanges in hESCs but not in somatic cells. In contrast, NU7026 treatment increased the frequency of radiation-induced breaks to a similar extent in pluripotent and somatic cells. Thus, DNA-PK dependent NHEJ efficiently participates in the elimination of radiation-induced chromatid breaks during the late G2 in both cell types and DNA-PK activity leads to a high level of misrejoining specifically in pluripotent cells.

Analysis of genomic instability in the offspring of fathers exposed to low doses of ionizing radiation

Transgenerational genomic instability was studied in nonirradiated children born from fathers who were irradiated with low doses of ionizing radiation while working as clean-up workers at the Chernobyl Nuclear Power Plant (liquidators) and nonirradiated mothers from nuclear families. Aberrant cell frequencies (ACFs), chromosomal type aberration frequencies, and chromatid break frequencies (CBFs) in the lymphocytes of fathers-liquidators, and their children were significantly higher when compared with the control group (P < 0.05). Individual ACFs, aberration frequencies, and CBFs were independent of the time between irradiation of the father and conception of the child (1 month to 18 years). Chromosomes were categorized into seven groups (A through G). Analysis of aberrant chromosomes within these groups showed no differences in the average frequency of aberrant chromosomes between children and fathers-liquidators. However, significant differences were observed in the average frequency of aberrant chromosomes in groups A, B, and C between children and mothers in the families of liquidators. These results suggest that low doses of radiation induce genomic instability in fathers. Moreover, low radiation doses might be responsible for individual peculiarities in transgenerational genomic instability in children (as a consequence of response to primary DNA damage). Thus, genomic instability may contribute to increased morbidity over the lifetime of these children.

Cholestasis in patients with Cockayne syndrome and suggested modified criteria for clinical diagnosis

BackgroundCockayne syndrome is a rare autosomal recessive neurodegenerative disease characterized by low-to-normal birth weight; growth failure; brain dysmyelination with calcium deposits, cutaneous photosensitivity; pigmentary retinopathy, cataract, and sensorineural hearing loss. To the best of our knowledge, cholestatic liver disease was not previously reported in these patients.AimTo highlight the presence of cholestasis and liver dysfunction in this group of patients and to suggest modified criteria for clinical diagnosis.MethodsThe study included nine patients with Cockayne from four different families (five males and four females) in which Cockayne was suspected clinically. In all patients chromosomal breakage studies revealed mild (45%) to moderate (60%) increase in frequency of chromatid and chromosome gaps and breaks versus 25% in normal controls. Diagnosis was confirmed by DNA repair assay.ResultsDuring routine follow up of these patients, seven of them had evident liver affection ranging from mild elevation in liver enzymes to cholestatic liver disease and liver cell failure. The attacks were recurrent in two patients and were sometimes preceded by infection. The attack may lead to deterioration of neurological and/or liver condition. It may end in liver cell failure that either recovers completely or may lead to death.Conclusionsliver disease could be considered common in Egyptian patients with Cockayne with the cholestatic form being the most evident. The syndrome should be included in the list of causes of cholestatic liver disease. Chromosomal breakage study and positive family history should be included as major criteria for clinical diagnosis of Cockayne especially in a population like ours where consanguineous marriage is very high and molecular testing and UV sensitivity tests are considered unaffordable.

Effect of Mycoplasma salivarium with and without L-arginine on karyotypic variability in cell line of Indian muntjac skin fibroblasts at long-term cultivation

The effect of Mycoplasma salivarium on the numerical and structural karyotypic variability was studied in the markerless cell line of Indian muntjac skin fibroblasts (line M) during long-term cultivation with and without L-arginine. The cultivation of mycoplasma-contaminated cells for 15 and 30 days did not change the character of cell distribution for the number of chromosomes. In contaminated cells cultivated for 60 and 75 days, the character of cell distribution for the chromosome number changed. These changes involve bimodal distribution for the chromosome number due to a significant decrease in frequency of the cells with the modal number of chromosomes with the main structural variant of karyotype (SVK) 2 + 2 + 1 + 1 + 1 and an increase in the frequency of cells with the submodal number of chromosomes with a main SVK of 2 + 2 + 1 + 1. Furthermore, a significant increase in the frequency of cells with lower numbers of chromosomes was observed after 60 days compared to that after 75 days of cultivation. After the cultivation of the contaminated and control cells in the medium with an elevated concentration of L-arginine for 60 days, the numerical parameters were unchanged relative to the control. The cultivation of contaminated cells for 60 days followed by the addition of L-arginine for 15 days restored the numerical parameters to the control level. In the contaminated cells, the frequency of chromosomal aberrations for 30, 60, and 75 days increased significantly compared to the control variant. After 30 days of cultivation, a small but statistically significant increase took place due to a uniform slight increase in the frequency of chromosomal aberrations of all types. After 60 and 75 days, a greater increase occurred due to a statistically significant increase in the frequency of chromosomal and chromatid breaks. Moreover, after 60 days, the level of dicentrics (telomeric associations) mainly produced by chromosomes 1 and 2 increased significantly. The role of dicentrics as for a means of adaptation for markerless cell lines to the condition of cultivation and the role of L-arginine in the restoration of the normal karyotypic structure of the line M cell population at mycoplasmal contamination are discussed.

The mTOR Inhibitor Rapamycin Suppresses DNA Double-Strand Break Repair

mTOR (mammalian target of rapamycin) signaling plays a key role in the development of many tumor types. Therefore, mTOR is an attractive target for cancer therapeutics. Although mTOR inhibitors are thought to have radiosensitization activity, the molecular bases remain largely unknown. Here we show that treating MCF7 breast cancer cells with rapamycin (an mTOR inhibitor) results in significant suppression of homologous recombination (HR) and nonhomologous end joining (NHEJ), two major mechanisms required for repairing ionizing radiation-induced DNA DSBs. We observed that rapamycin impaired recruitment of BRCA1 and Rad51 to DNA repair foci, both essential for HR. Moreover, consistent with the suppressive role of rapamycin on both HR and NHEJ, persistent radiation-induced DSBs were detected in cells pretreated with rapamycin. Furthermore, the frequency of chromosome and chromatid breaks was increased in cells treated with rapamycin before and after irradiation. Thus our results show that radiosensitization by mTOR inhibitors occurs via disruption of the major two DNA DSB repair pathways.

Association between TP53 gene ARG72PRO polymorphism and chromosome aberrations in human cancers

It is well known that the TP53 gene considerably influences on DNA repair processes. Polymorphisms in the TP53 gene, particularly the well-known Arg72Pro in codon 72 of exon 4 (Ex4+119 G>C; rs1042522), can modify the functionality of the p53 protein and activation of DNA repair. Actually, polymorphic variants Arg and Pro were found to have different properties of regulation of TP53-dependent DNA repair target genes, that can effect various levels of chromosome aberrations in cancer patients with these genotypes. Here, we studied frequency of chromatid breaks (CB), chromosome-type aberrations (CTA) and aberrant cells (AC) in cancer patients (n = 102) with various Arg72Pro genotypes. It was shown that the Arg variant of TP53 gene is associated with high frequency of AC and chromatid breaks. That is Arg/Arg carriers have more different chromosome aberrations in comparison to individuals with Arg/Pro and Pro/Pro genotypes (P < 0.05). Conversely, the lowest level of AC and chromatid breaks were detected in cancer patients with the Pro/Pro genotype. A completely unexpected result was that women with Arg/Arg genotype had the most high frequency of CB and AC in comparison to Arg/Pro and Pro/Pro women carriers (P < 0.001). In the group of male patients we did not show any differences in chromosome aberrations between carriers of Arg72Pro genotypes. In conclusion, the TP53 gene Arg72Pro polymorphism appreciably influence on occurrence of chromosome aberrations in cancer.