Total Number Of Chromosomal Aberrations Research Articles

Mismatch repair, p53 and chromosomal aberrations in primary colorectal carcinomas

Colorectal carcinoma progresses via at least two genetic pathways. Microsatellite instability, due to defective mismatch repair genes, characterizes one pathway and gross chromosomal instability another. The involvement of p53 and mismatch repair gene abnormalities within these pathways has not been fully explored. We aimed to investigate the relationships of p53 and mismatch repair gene defects on gross chromosomal aberrations detected by comparative genomic hybridization in 49 colorectal carcinomas. Tumours demonstrating loss of expression for hMLH1 or hMSH2 proteins demonstrated a highly significant attenuation in the number of gross chromosomal aberrations (p = 0.007) and were less likely to show p53 overexpression (p = 0.02). Within the mismatch repair normal tumours, p53 status did not affect the total number of chromosomal aberrations but p53 overexpression was significantly associated with a higher frequency of amplifications at 8q22-ter and at 13q21-22. Colorectal cancer demonstrates distinct molecular phenotypes and should be sub-classified accordingly.

Effects of H2O2, Fe2+ and Fe3+ on curcumin-induced chromosomal aberrations in CHO cells

The effects of H2O2, Fe2+ and Fe3+ on curcumin-induced clastogenicity were evaluated in CHO cells. Curcumin combined with H2O2 did not increase the chromosomal aberrations more than expected based on a simple additive effect. In contrast, the combination of curcumin-Fe significantly decreased the total number of chromosomal aberrations and the number of abnormal metaphases. The clastogenicity of curcumin may be related to its pro-oxidant properties and its ability to generate free radicals.

Effects of vitamin A on doxorubicin-induced chromosomal aberrations in bone marrow cells of rats.

The present study was carried out to evaluate the role of vitamin A (VA) on the induction of chromosomal aberrations (CA) in rat bone marrow cells and to investigate its modulating effect on chromosomal damage induced by doxorubicin (DXR). Wistar rats were treated with VA (7.5, 15 and 30 microg/kg body wt) once a day for 2 days by gavage before injecting DXR (90 mg/kg body wt). Rats in the control group were treated with corresponding doses of water and olive oil. Animals treated with the medium dose of VA (15 microg/kg body wt) plus single dose of DXR presented a statistically significant reduction in total number of CA and in number of abnormal metaphases (P < 0.05). However, when compared with control and DXR groups, the low and high VA doses (7.5 and 30 microg/kg body wt) were found to be less efficient than the medium dose VA (15 microg/kg body wt) in terms of parameters analyzed. Furthermore, the high dose of VA group (30 microg/kg body wt) was found to be clastogenic (P < 0.05). This study concludes that the protective effect of VA against chromosome damage is dose dependent.

Chromosomal gains and losses detected by comparative genomic hybridization and proliferation activity in renal cell carcinoma.

The number of DNA losses found using comparative genomic hybridization (CGH) and the proliferation index MIB-1 have been shown to be prognostic factors in renal cell carcinoma (RCC). We evaluated the associations of these two factors with each other and with histopathology and clinical outcome. In this prospective study, specimens from 20 primary RCCs were investigated using CGH and MIB-1 assay. The associations of the commonest chromosomal aberrations with histopathology, stage and the clinical outcome of the disease were evaluated. CGH detected genetic aberrations in all tumours. Losses of genetic material (85%) were more common than gains (65%). Most common was loss in the short arm of chromosome 3, which was found in 70% of the tumours. Other frequent changes (20%) were losses of 4q, 13q, 18 and Xp, as well as gains of 5q, 7p, 7q (25%) and chromosome 12. The number of deleted chromosomal areas varied from none to six. The MIB-1 index varied from 0 to 39 (median 4.0). The total number of chromosomal aberrations or deletions showed no association with MIB-1 index or nuclear grade. Most grade 1 and 2 tumours showed a low MIB-1 index. All nuclear grade 4 tumours progressed and were associated with short survival. CGH gives an overview of DNA changes in RCC and helps to locate targets for more precise genetic evaluation. CGH findings are also helpful for classifying tumours. In this study, genetic aberrations in primary RCCs were not associated with histopathology, proliferation or clinical outcome, which suggests that CGH does not necessarily give any additional information on the prognosis of the disease. MIB-1 index and TNM stage were associated with survival.

Antioxidant action of bixin against cisplatin-induced chromosome aberrations and lipid peroxidation in rats

Cisplatin is one of the most active cytotoxic agents in the treatment of cancer, but has serious side effects, inducing nephrotoxicity and chromosome aberrations. In this study we evaluated the role of the carotenoid bixin on cisplatin-induced oxidative stress in Wistar rats through three markers of oxidative damage: chromosome aberrations, glutathione depletion and lipid peroxidation. The animals were divided into six treatment groups with six rats in each (n= 6). The dose of cisplatin (5.0 mg kg−1body wt.) was injected i.p. and bixin (2.5 or 5.0 mg kg−1body wt.) was given by gavage at 48, 24 h and 10 min before the cisplatin injection. The treatment with the highest dose of bixin resulted in a statistically significant reduction, by about 33%, in cisplatin-induced abnormal metaphases (P< 0.05). A single dose of cisplatin enhanced the formation of lipid peroxides in 29% and resulted in a 29% depletion in renal glutathione 24 h after cisplatin administration (P< 0.05). The pretreatment with bixin reduced the total number of chromosome aberrations, inhibited the increase in lipid peroxidation, and inhibited renal glutathione depletion induced by cisplatin. Since the pretreatment with bixin alone was safe, under the present experimental conditions, the results suggest that bixin may have future clinical application after further studies.

Comparison of chromosome aberrations in peripheral blood lymphocytes from people occupationally exposed to ionizing and radiofrequency radiation.

The genotoxic effects of occupational exposure to ionizing and non-ionizing radiation were investigated in 25 physicians and nurses working in hospitals and in 20 individuals working at radio-relay stations. Examination was conducted by chromosome aberration analysis of peripheral blood lymphocytes. The data showed that total number of chromosome aberrations in people exposed to ionizing and radio-frequency radiation (4.08 +/- 0.37 and 4.35 +/- 0.5 on 200 scored metaphases, respectively) were almost equally higher than those of non-irradiated subjects. The increase was in proportion to the number of individuals having more that 5-aberration/200 metaphases. Acentric fragments comprised the most frequently seen type of aberration. The average numbers in examined groups (11.8 x 10(-3) and 14.8 x 10(-3) per cell, respectively), were significantly higher than 4.2 x 10(-3), which was observed in controls, unexposed individuals. Dicentric fragments were also frequent (4.8 x 10(-3) and 6.25 x 10(-3), respectively, vs. 0.52 x 10(-3) in control). In contrast, the frequency of chromatid breaks increased only after ionizing radiation (3.8 x 10(-3) vs. 0.26 x 10(-3) in control). A positive correlation between the total number of chromosome aberrations and cumulative 6-years dosage was also found. The data emphasized the dangerous effects of prolonged exposure to both types of radiation and indicated that chromosomal aberration analysis should be obligatory for individuals working at radio-relay stations.

Long-Term Monitoring of Cytogenetic Aberrations in Adolescents of a Large Industrial Town

Long-term cytogenetic monitoring was carried out in adolescents of the town of Kemerovo. In total, aberrant metaphase frequency increased from 1.53% in 1992 to 4.40% in 1996 in Kemerovo adolescents, being significantly higher than a control frequency from 1993 to 1996. In all samples, chromosome aberrations mostly included acentric fragments, while exchanges were rare. The highest number of aberrations per aberrant metaphase was 2 in Kemerovo adolescents and 1 in the control sample. The observed increase in total number of chromosome aberrations suggests that the mutagenic effect of chemical environmental pollutants on Kemerovo adolescents increased over the five years.

Cytogenetic monitoring of cardiology unit hospital workers exposed to doppler ultrasound

We studied the effects of ultrasound on the peripheral blood lymphocytes of medical personnel from a cardiology unit working with colour Doppler ultrasonic equipment. Cytogenetic risks from ultrasound exposure were assessed by analysis of chromosome aberrations, sister chromatid exchanges (SCE), study of cell-cycle kinetics and micronucleus assay. We found significant increases (P < 0.001) in the total number of chromosome aberrations, mainly due to chromatid breaks and acentric fragments, increases in the total number of micronuclei and SCE and disturbances in cell-cycle kinetics in the exposed group compared to the control. In spite of their limitations, the results of the present investigation indicate that individuals occupationally exposed to ultrasound may experience an increased genotoxic risk and strongly emphasize the need for more research into the nature and extent of the biological consequences to medical personnel working with Doppler ultrasound. Copyright © 2000 John Wiley & Sons, Ltd.

Effects of selenium pretreatment on cisplatin-induced chromosome aberrations in wistar rats.

Selenium is an essential trace element and a potent anticancer agent. Extensive laboratory studies demonstrate that selenium is an effective chemopreventive agent in various sites in animals. The administration of selenium as a chemopreventive agent raises the question whether the antioxidant selenium, alone or in combination with other dietary antioxidants, could protect non-tumor cells from the clastogenic effect of cisplatin. Therefore, the present study was undertaken to investigate the modulatory effects of selenium, combined or not with vitamin C, on cisplatin-induced chromosomal aberrations in Wistar rat bone marrow cells. The animals were sacrificed 18, 24, or 72 h after cisplatin injection. The results obtained in Wistar rat bone marrow cells showed a slight nonsignificant reduction in the total number of chromosomal aberrations induced by cisplatin (5 mg/kg b.w.) observed in the animals that received a pretreatment with a single dose of selenium (2 mg/kg b.w.). The administration of two doses of selenium (1 mg/kg b.w.) also did not inhibit the chromosomal damage induced by cisplatin. In the present study, no protective response was obtained with either a single or double dose of selenium in rats treated with cisplatin. Furthermore, the combination between selenium+vitamin C was no more effective than vitamin C alone in the protection against damage caused by this antitumor drug. Further investigations, with other forms of selenium, are necessary to elucidate a possible protective role of selenium in clastogenicity induced by free radicals generated by antitumor drugs.

Cytogenetic monitoring of cardiology unit hospital workers exposed to Doppler ultrasound.

We studied the effects of ultrasound on the peripheral blood lymphocytes of medical personnel from a cardiology unit working with colour Doppler ultrasonic equipment. Cytogenetic risks from ultrasound exposure were assessed by analysis of chromosome aberrations, sister chromatid exchanges (SCE), study of cell-cycle kinetics and micronucleus assay. We found significant increases (P < 0.001) in the total number of chromosome aberrations, mainly due to chromatid breaks and acentric fragments, increases in the total number of micronuclei and SCE and disturbances in cell-cycle kinetics in the exposed group compared to the control. In spite of their limitations, the results of the present investigation indicate that individuals occupationally exposed to ultrasound may experience an increased genotoxic risk and strongly emphasize the need for more research into the nature and extent of the biological consequences to medical personnel working with Doppler ultrasound.

Effects of high doses of vitamins C and E against doxorubicin-induced chromosomal damage in Wistar rat bone marrow cells

Doxorubicin (DXR) is one of the major antitumoral agents available for clinical use. In addition to intercalating into the DNA molecule, this drug generates free radicals. Vitamins C (VC) and E (VE) can protect normal cells from the damage caused by radicals without interfering with the cytotoxicity of DXR against tumors. The objective of the present study was to investigate the possible protective effect of VC and/or VE on mammalian cells treated with DXR in vivo. Animals treated with the lowest doses of VC and/or VE, alone or in combination, plus a single dose of DXR presented a statistically significant reduction in total number of chromosome aberrations and in number of abnormal metaphases. The highest vitamin doses tested caused no changes in the parameters analyzed when compared with control. Under the present experimental conditions, the efficiency of VC and/or VE in protecting against chromosome damage was dependent on the dose used.

Homologous recombination and non-homologous end-joining pathways of DNA double-strand break repair have overlapping roles in the maintenance of chromosomal integrity in vertebrate cells.

Eukaryotic cells repair DNA double-strand breaks (DSBs) by at least two pathways, homologous recombination (HR) and non-homologous end-joining (NHEJ). Rad54 participates in the first recombinational repair pathway while Ku proteins are involved in NHEJ. To investigate the distinctive as well as redundant roles of these two repair pathways, we analyzed the mutants RAD54(-/-), KU70(-/-) and RAD54(-/-)/KU70(-/-), generated from the chicken B-cell line DT40. We found that the NHEJ pathway plays a dominant role in repairing gamma-radiation-induced DSBs during G1-early S phase while recombinational repair is preferentially used in late S-G2 phase. RAD54(-/-)/KU70(-/-) cells were profoundly more sensitive to gamma-rays than either single mutant, indicating that the two repair pathways are complementary. Spontaneous chromosomal aberrations and cell death were observed in both RAD54(-/-) and RAD54(-/-)/KU70(-/-) cells, with RAD54(-/-)/KU70(-/-) cells exhibiting significantly higher levels of chromosomal aberrations than RAD54(-/-) cells. These observations provide the first genetic evidence that both repair pathways play a role in maintaining chromosomal DNA during the cell cycle.

Assessment of genome damage in occupational exposure to ionising radiation and ultrasound

The mutagenic effects of low doses of radiation on occupationally exposed subjects were studied on lymphocyte culture using two methods: analysis of structural chromosome aberrations and micronucleus assay. The results obtained in subjects exposed to ionising radiation alone were compared to those exposed to both ionising radiation and ultrasound. A correlation between the total number of chromosome aberrations and distribution of micronuclei in the genome of somatic cells show higher deviation in the group exposed to X-ray and ultrasound than in the group exposed to X-rays alone. The degree of genome damage in occupational exposure to X-rays and ultrasound were discussed.

CHROMOSOME ABERRATIONS IN PATIENTS WITH COELIAC DISEASE (CD)

According to one study performed so far, there is an increased chromosome instability in adult coeliac patients compared to healthy controls, which may be related to higher frequency of malignancies, known to occur in those patients (1). No similar work has been done in children. We have, therefore conducted a prospective study with the aim to assess the frequency of chromosome aberrations in peripheral blood lymphocytes in children with untreated CD and to compare it to healthy controls and to infants with other chronic enteropathies. Chromosomal studies were performed in: a) 18 children with untreated coeliac disease confirmed by a typical jejunal biopsy and a good recovery on a gluten-free diet; b) 13 healthy controls, and c) 10 infants with chronic diarrhoea of non-coeliac origin. Chromosomes were analysed in peripheral blood lymphocytes. 100 Giemsa-stained metaphases were studied for each individual by a single cytogenetist who was blinded to the source of the cells, and was not involved in the treatment of the patients. The three groups were compared according to number of aberrant cells and the total number of aberrations (gaps and breaks). Results, A. The total number of chromosome aberrations was: i) significantly higher in CD patients compared to healthy controls (p<0.001); ii) significantly higher in infants with other chronic enteropathies compared to healthy controls (p < 0.01); iii) not different in patients with CD compared to patients with other chronic diarrhoea (p > 0.05). B. The number of aberrant lymphocytes was: i) increased in patients with CD compared to healthy controls (p < 0.01); ii) not significantly different between patients with CD and other enteropathies (p > 0.05); iii) significantly increased in infants with chronic non-coeliac diarrhoea compared to healthy controls (p < 0.05). In conclusion, according to the results obtained it may be possible that chronic intestinal inflammation, and not exclusively CD is related to the increased level of chromosome aberrations, and is inducing genomic instability.

Radiation-Induced Damage, Repair and Exchange Formation in Different Chromosomes of Human Fibroblasts Determined by Fluorescence In Situ Hybridization

We have used fluorescence in situ hybridization with whole-chromosome probes for human chromosomes 1, 4, 8 and 13 to investigate the extent to which the induction of damage and its repair after exposure to ionizing radiation is distributed randomly among these chromosomes. All the studies were performed with AG1522 human fibroblasts irradiated with 6 Gy and maintained in a nondividing state for at least 6 h after irradiation except for the measurements of initial damage. The extent of initial damage was determined by fusion of the cells immediately after irradiation with metaphase HeLa cells to obtain premature chromosome condensation (PCC). Breaks and exchanges were also scored by PCC 24 h after irradiation and in metaphase spreads at the first division after irradiation. The data obtained were consistent with random breakage and repair in these chromosomes. Comparing PCC 24 h after irradiation with first metaphase, there was a deficit in aberrations at metaphase, particularly in unrejoined breaks, implying loss or slowing of cells containing aberrations prior to the first division. An analysis of dicentrics and translocations in chromosome 4 at first and in subsequent divisions showed that there was an equal number of dicentrics and translocations at first metaphase with loss of dicentrics, but no loss of translocations in subsequent divisions. These data are supportive of the hypothesis tht the total number of chromosome aberrations in cells can be estimated from a single chromosome pair.

The rate of elimination of chromosomal aberrations after accidental exposure to microwave radiation

Analysis of structural chromosome aberrations was performed in a group of radar station personnel who were engaged in repairing radar devices a couple of days earlier. Test results showed a major decline from the values recorded by regular mutagenic monitoring in terms of a significantly increased number of chromosome breaks, acentric fragments, dicentric and polycentric chromosomes with accompanying fragments, ring chromosomes and chromatid interchange. Multiply repeated mutagenic testing demonstrated for all subjects a fall in the total number of chromosome aberrations as a function of time. During a 30-week-long follow-up study a decrease in the total number of chromosome aberrations was observed. In the same period the presence of unstable aberrations such as dicentrics and ring chromosomes persisted, together with a relatively unchanged incidence of stable aberrations.

Beta-carotene as a modulator of chromosomal aberrations induced in mouse bone marrow cells.

The inhibitory effects of beta-carotene on cyclophosphamide (CPA)-induced chromosomal aberrations in mouse bone marrow cells were investigated. Male Balb C mice, 8-10 weeks old, were treated with beta-carotene (0.5, 1.0, 2.0, 5.0, 10, 25, 50, 100, and 200 mg/kg) or with corn oil (0.05 ml/10 g b.w.) by gavage for 5 consecutive days. Four hours after the last treatment with or without beta-carotene, the animals were intraperitoneally injected with CPA and killed 24 hr later for cytological preparations and analysis. The results obtained show that beta-carotene provides significant protection against the clastogenicity of CPA. The maximum reduction in the frequency of aberrant metaphases (26.9%) and in total number of chromosomal aberrations were observed when beta-carotene was used at 50 mg/kg. Nevertheless, no direct dose-response relationship was detected, suggesting that beta-carotene might act through different mechanisms at different doses. The results obtained in animals studies have served as part of the basis for the human intervention studies now underway to determine if beta-carotene does indeed function as a chemopreventive agent in human nutrition.

Chromosome instability in bladder carcinoma patients

The relationship between the presence of a high frequency of chromosome aberrations and a predisposition to cancer has been well established in the so-called chromosome instability syndromes. Chromosome instability is also present in a variety of patients affected by cancer, and sometimes in their healthy relatives. We present a cytogenetic study carried out in lymphocytes from 13 untreated bladder carcinoma patients (only four of them had a history of occupational exposure to mutagens). Percentages of aberrant metaphases were significantly higher in cancer patients than in controls. Of the total number of chromosome aberrations in cancer patients, 67.16% corresponded to major structural chromosome abnormalities, while 25.37% were gaps or breaks. Numerical abnormalities represented 7.46% of the total. The bands more frequently involved in chromosome rearrangements were 5q31 and 1q32. Our results tentatively indicate that a significant proportion of patients with bladder carcinoma may have an underlying inherent chromosome instability. An age effect cannot be excluded, but we did not find significant differences between patients over 50 years of age and patients under 50 years of age.

A Model Relating Cell Survival to DNA Fragment Loss and Unrepaired Double-Strand Breaks

The model of radiation action that is presented relates the surviving fraction of irradiated cells to unrepaired DNA double-strand breaks (DSBs). The following assumptions are made in the model: (i) A DNA fragment created by the induced DSBs may move out of its chromosome (become lost), and the probability of that process depends on the fragment size. (ii) An irradiated cell will lose its proliferative capacity if it has an unrepaired DSB (including DNA fragments) at certain points in the cell cycle. Mathematical expressions of the model yield the dose and time dependencies of the surviving fraction, the number of unrepaired DSBs, and the number of prematurely condensed chromosome fragments. Radiobiological phenomena described include effects of low dose rate, delayed plating, hypertonic solution, araA, and high-LET radiation. The calculated dose dependence of the residual number of unrepaired DSBs for ataxia telangiectasia and normal fibroblast cells is very close to the experimentally obtained [M. N. Cornforth and J. S. Bedford, Radiat. Res. 111, 385-405 (1987)] total number of chromosomal aberrations. This leads to the conclusion that each unrepaired DSB becomes a chromosomal aberration. Analysis in terms of the model shows that the radiosensitivity of various cell lines is predominantly due to the different amounts of time available for DSB repair in these cells.

A comparison of aberration distribution and cell-cycle progression in cells treated with bleomycin with those exposed to X-rays

The extent of cell-cycle delay and the frequency of aberrant metaphases induced by bleomycin (BLM) and X-rays have been compared at doses which produce similar frequencies of chromosome aberrations by the 2 clastogenic agents (BLM, 40 ωg/ml and X-rays, 2 Gy) in muntjac lymphocytes. The frequency of aberrant metaphases was low in BLM-treated cells; however, the number of aberrations per metaphase was higher than in cells exposed to X-rays. Thus in contrast to their uniform sensitivity to X-rays, the lymphocytes showed differential sensitivity to BLM. This might be due to differences among the cells in their uptake of BLM and/or its action on the nuclear membrane-DNA complex. In spite of the total number of chromosome aberrations being similar to that induced by X-rays, BLM did not induce a significant delay in cell-cycle progression as observed in the case of X-rays. A possible explanation could be that the DNA damages being limited to fewer cells than in the case of X-irradiation, the BLM-treated cultures had more normal cells allowing faster progression and/or unlike X-rays BLM may not be causing other cellular damages in addition to DNA breaks.