Cytogenetic Damage In Lymphocytes Research Articles

Prognostic value of the micronucleus assay for clinical endpoints in neoadjuvant radiochemotherapy for rectal cancer

BackgroundThe question whether lymphocyte radiosensitivity is representative of patients’ response to radiotherapy (RT) remains unsolved. We analyzed lymphocyte cytogenetic damage in patients who were homogeneously treated with preoperative radiochemotherapy (RCT) for rectal cancer within clinical trials. We tested for interindividual variation and consistent radiosensitivity after in-vivo and in-vitro irradiation, analyzed the effect of patients’ and RCT characteristics on cytogenetic damage, and tested for correlations with patients’ outcome in terms of tumor response, survival and treatment-related toxicity.MethodsThe cytokinesis-block micronucleus cytome (CBMNcyt) assay was performed on the peripheral blood lymphocytes (PBLCs) of 134 patients obtained before, during, at the end of RCT, and during the 2-year follow-up. A subset of PBLCs obtained before RCT was irradiated in-vitro with 3 Gy. RCT included 50.4 Gy of pelvic RT with 5-fluorouracil (5-FU) alone (n = 78) or 5-FU plus oxaliplatin (n = 56). The analyzed variables included patients’ age, gender, RT characteristics (planning target volume size [PTV size], RT technique), and chemotherapy characteristics (5-FU plasma levels, addition of oxaliplatin). Outcome was analyzed as tumor regression, patient survival, and acute and late toxicity.ResultsCytogenetic damage increased significantly with the radiation dose and varied substantially between individuals. Women were more sensitive than men; no significant age-dependent differences were observed. There was a significant correlation between the cytogenetic damage after in-vitro irradiation and in-vivo RCT. We found a significant effect of the PTV size on the yields of cytogenetic damage after RCT, while the RT technique had no effect. Neither the addition of oxaliplatin nor the 5-FU levels influenced cytogenetic damage. We found no correlation between patient outcome and the cytogenetic damage.ConclusionsWe found consistent cytogenetic damage in lymphocytes after in-vivo RCT and in-vitro irradiation. Gender was confirmed as a well-known, and the PTV size was identified as a less well-known influencing variable on lymphocyte cytogenetic damage after partial-body irradiation. A consistent level of cytogenetic damage after in-vivo and in-vitro irradiation may indicate the importance of genetic factors for individual radiosensitivity. However, we found no evidence that in-vivo or in-vitro irradiation-induced cytogenetic damage is an adequate biomarker for the response to RCT in rectal cancer patients.

The Baseline Level of Cytogenetic Damage in Lymphocytes and Buccal Epitheliocytes of Lung Cancer Patients

The results of the study of chromosomal aberrations and micronuclei in blood lymphocytes, as well as micronuclei in buccal epithelium cells of 50 untreated men with lung cancer (LC) and 62 control donors, are presented. Using a variety of cytogenetic tests, a significant unidirectional increase in the base level of genetic instability in the cells of the patients was detected compared to the control. It was shown that, in LC patients, the elimination of damaged cells occurs predominantly by necrosis, whereas the frequencies of cells at the apoptosis stage do not differ in patients and control. The age of the patient, smoking status, type, and stage of LC do not have a significant impact on the performance of the baseline level of genetic damage. This fact suggests that the cytogenetic instability of the somatic cells of untreated LC patients is a constant sign that characterizes the genome response to the effect of the oxidative stress accompanying the neoplastic process.

Cytogenetic Abnormalities in Lymphocytes from Victims Exposed to Cobalt-60 Radiation

The present study investigates cytogenetic damage in lymphocytes, derived from three victims who were unfortunately exposed to cobalt-60 (60Co) radiation (the 1999 accident occurred in a village in China’s Henan province). Case A of the three victims was exposed to a higher dose of 60Co radiation than Cases B and C. The chromosomal aberrations, cytokinesis-block micronucleus (CBMN, the CBMN assay), and DNA double-strand breaks (DSBs, the comet assay) examined in this study are biomarkers for cytogenetic abnormalities. After the lymphocytes collected from the victims were cultured, the frequencies of dicentric chromosomes and rings (dic + r) and CBMN in the first mitotic division detected in the lymphocytes of Case A were found to be substantially higher than in Cases B and C. Similarly, the DNA-DSB level found in the peripheral blood collected from Case A was much higher than those of Cases B and C. These results suggest that an acutely enhanced induction of the 60Co-induced cytogenetic abnormality frequency in humans depends on the dose of 60Co radiation. This finding is supported by the data obtained using practical techniques to evaluate early lymphoid-tissue abnormalities induced after exposure to acute radiation.

No Chromosomal Damage Seen From ADHD Medications

Back to table of contents Previous article Next article Clinical & Research NewsFull AccessNo Chromosomal Damage Seen From ADHD MedicationsJun YanJun YanSearch for more papers by this authorPublished Online:2 Jan 2009https://doi.org/10.1176/pn.44.1.0018aStimulants commonly used to treat attention-deficit/hyperactivity disorder (ADHD), specifically methylphenidate and amphetamine, do not cause chromosomal damages in circulating white blood cells, a study in the December 2008 Journal of the American Academy of Child and Adolescent Psychiatry finds.A study published in the December 18, 2005, Cancer Letters presented evidence of an increased frequency of three types of chromosomal damage in peripheral lymphocytes in 12 children after they had taken methylphenidate for three months. These types of chromosomal damage indicate DNA damage and structural changes to chromosomes and are associated with an increased risk of cancer.Since this alarming finding, several smaller human, in vitro, and animal studies were published that failed to replicate the stimulant-associated chromosomal damage seen in the original study.The new study was conducted with a methodology similar to the original study, but expanded the number of subjects and included mixed amphetamine salts (MAS) in addition to methylphenidate. Sixty-three children aged 6 to 12 with a DSM-IV diagnosis of ADHD were randomly assigned to open-label treatment with either methylphenidate or MAS for three months. None of them had taken stimulants before.The researchers found no significant increase from baseline to the end of the three-month treatment in any of the types of chromosomal damage reported in the previous study in either patients who took methylphenidate (n=25) or those who took MAS (n=22). In addition to these 47 subjects, 14 discontinued study participation prematurely for various reasons, and two were switched to different medications by their physicians and completed three months of treatment. No significant association between treatment and chromosomal damage was found in these individuals.The researchers examined the participants' blood samples, taken before and after the three months of stimulant treatment, for any chromosomal damage in lymphocytes. The percentages of cells with the damage at both time points as well as between the methylphenidate and the MAS groups were compared. No significant difference was seen between the two groups.The study was conducted at the Duke University Medical Center by Kristine Witt, M.S., and colleagues affiliated with the National Institute of Child Health and Human Development (NICHD) and the National Toxicology Program of the National Institute of Environmental Health Sciences (NIEHS). NICHD and NIEHS, both divisions of the National Institutes of Health, provided funding for the study.“These results add to the accumulating evidence that therapeutic levels of methylphenidate do not induce cytogenetic damage in humans,... and amphetamine-based products do not pose a risk for cytogenetic damage in children,” the authors concluded.An abstract of “Methylphenidate and Amphetamine Do Not Induce Cytogenetic Damage in Lymphocytes of Children With ADHD” is posted at<www.jaacap.com/pt/re/jaacap/abstract.00004583-200812000-00006.htm>.▪ ISSUES NewArchived

Methylphenidate and Amphetamine Do Not Induce Cytogenetic Damage in Lymphocytes of Children With ADHD

ObjectiveIn response to previously published findings of methylphenidate-induced chromosomal changes in children, this study was designed to determine whether methylphenidate- or amphetamine-based drugs induce chromosomal damage (structural aberrations, micronuclei, and sister chromatid exchanges) in peripheral blood lymphocytes of children with attention-deficit/hyperactivity disorder after 3 months of continuous treatment. MethodStimulant drug-naïve subjects, 6 to 12 years of age, in good overall health, and judged to be appropriate candidates for stimulant therapy based on rigorously diagnosed ADHD using DSM-IV criteria, were randomized into two open-label treatment groups (methylphenidate or mixed amphetamine salts). Each subject provided a blood sample before initiation of treatment and after 3 months of treatment. Pretreatment and posttreatment frequencies of chromosomal aberrations, micronuclei, and sister chromatid exchanges were determined for each subject. ResultsSixty-three subjects enrolled in the study; 47 subjects completed the full 3 months of treatment, 25 in the methylphenidate group and 22 in the amphetamine group. No significant treatment-related increases were observed in any of the three measures of cytogenetic damage in the 47 subjects who completed treatment or the 16 subjects who did not. ConclusionsEarlier findings of methylphenidate-induced chromosomal changes in children were not replicated in this study. These results add to the accumulating evidence that therapeutic levels of methylphenidate do not induce cytogenetic damage in humans. Furthermore, our results indicate that amphetamine-based products do not pose a risk for cytogenetic damage in children.

Cytogenetic damage in lymphocytes of patients undergoing therapy for small cell lung cancer and ovarian carcinoma

The level of cytogenetic damage in peripheral blood lymphocytes of patients undergoing chemotherapy has been analyzed incisively 20 years ago. The results showed that the highest level of cytogenetic damage was observed at the end of therapy. In recent years, the doses of anticancer drugs were intensified thanks to the discovery of colony stimulating factors. Therefore, it was interesting to analyze the kinetics of micronuclei formation in lymphocytes of patients undergoing modern chemotherapy. The frequencies of micronuclei were measured in lymphocytes of 6 patients with small cell lung cancer treated with a combination of cisplatin and etoposide and 7 patients with ovarian carcinoma treated with a combination of taxol and cisplatin. 3 patients with lung cancer received radiotherapy in addition to chemotherapy. Micronuclei were analyzed in lymphocytes collected before the start of therapy and 1 day before each following cycle of chemotherapy. The micronucleus frequencies were compared with the kinetics of leukocyte counts. The micronucleus frequencies showed an interindividual variability. On average, the frequencies of micronuclei increased during the first half of therapy and declined thereafter, reaching, in some patients with ovarian carcinoma, values below the pre-treatment level. Leukocyte counts decreased strongly at the beginning of therapy with an upward trend at the end. We suggest that the decline of micronuclei was due to repopulation of lymphocytes and acquired drug resistance.

Cytogenetic damage in lymphocytes for the purpose of dose reconstruction: a review of three recent radiation accidents

The analysis of chromosomal aberrations in peripheral blood of radiation accident victims is an established method of biological dosimetry. The dose estimate on the basis of an in vitro calibration curve is straightforward when the radiation exposure is homogeneous and the analysis not delayed. In recent years three radiation accidents occurred, where the irradiation or sampling conditions precluded a simple estimation of the dose. During the Georgian accident soldiers carried in their pockets small sources of ¹³⁷Cs leading to partial and protracted body exposures. During the Tokai-mura accident, three employees involved in the process of ²³⁵U enrichment were exposed to very high doses of gamma rays and neutrons. During the Bialystok accident, five patients with breast cancer undergoing radiotherapy were exposed to a single dose of electrons which reached about 100 Gy. In the present paper the approaches chosen to estimate, by cytogenetic methods, the doses absorbed by the people involved in the accidents are described.

Chromosomal aberrations and micronuclei in lymphocytes of breast cancer patients after an accident during radiotherapy with 8 MeV electrons.

In February 2001 a radiation accident occurred in a radiotherapy unit of an oncology hospital in Poland. Five breast cancer patients undergoing radiotherapy received a single high dose of 8 MeV electrons. The exact doses are not known, but they were heterogeneous and may have reached about 100 Gy. To assess whether such exposure would be detectable in peripheral blood lymphocytes, chromosomal aberrations and micronuclei were analyzed in lymphocytes from the accident patients and compared to values for lymphocytes from 10 control patients who were not involved in the accident but who received similar radiotherapy treatments. Lymphocytes were harvested for analysis of chromosomal aberrations at three different culture times to determine whether heavily damaged cells reached mitosis with a delay. There was no effect of harvest time on the frequencies of chromosomal aberrations, indicating that there was no delay of heavily damaged cells in entering mitosis. A good correlation was observed between micronuclei and chromosomal aberrations. In lymphocytes from three of the accident patients, significantly enhanced frequencies of both aberrations and micronuclei were found. The great individual variability observed in the frequency of cytogenetic damage in lymphocytes from both control and accident patients precluded the unambiguous identification of all accident patients.

Assessment of cytogenetic damage in lymphocytes and in exfoliated nasal cells of dental laboratory technicians exposed to chromium, cobalt, and nickel

Dental laboratory technicians may be exposed to metal alloys that are used in the production of crowns, bridges and removable partial dentures. These alloys consist of 35–65% cobalt, 20–30% chromium, 0–30% nickel, and small amounts of molybdenum, silica, beryllium, boron and carbon. The aim of this study was to assess whether dental technicians are occupationally exposed to chromium, cobalt and nickel, by analyzing urinary excretion levels of these metals and to investigate the genotoxic effects of occupational exposure associated with dental prostheses production operations by analyzing cytokinesis-blocked micronucleus (CB-MN) frequencies in peripheral lymphocytes and micronucleus (MN) frequencies in exfoliated nasal cells from 27 dental laboratory technicians and 15 control subjects. The differences in the urinary excretion of metals between technicians and controls were statistically significant. The mean (±S.D.) CB-MN frequencies (‰) in peripheral lymphocytes were 4.00 (±2.98) among the dental technicians and 1.40 (±1.30) among the controls, a statistically significant difference ( P<0.005). The mean (±S.D.) MN frequencies (‰) in nasal cells were 3.50 (±1.80) among the dental technicians and 1.19 (±0.53) among the controls, which was also a statistically significant difference ( P<0.005). There was a significant correlation between duration of exposure and MN frequencies in lymphocytes ( r=0.642, P<0.01), but not in nasal cells of technicians. Our data reveal that in vivo exposure to chromium, nickel and cobalt metals is evident and that this occupational exposure may contribute to the observed genotoxic damage in two types of cells, e.g. lymphocytes and exfoliated nasal cells. However, it cannot be determined which compound(s) are responsible for the genotoxic damage observed in this study.

Cytogenetic damage related to low levels of methyl mercury contamination in the Brazilian Amazon.

The mercury rejected in the water system, from mining operations and lixiviation of soils after deforestation, is considered to be the main contributors to the contamination of the ecosystem in the Amazon Basin. The objectives of the present study were to examine cytogenetic functions in peripheral lymphocytes within a population living on the banks of the Tapajós River with respect to methylmercury (MeHg) contamination, using hair mercury as a biological indicator of exposure. Our investigation shows a clear relation between methylmercury contamination and cytogenetic damage in lymphocytes at levels well below 50 micrograms/gram, the level at which initial clinical signs and symptoms of mercury poisoning occur. The first apparent biological effect with increasing MeHg hair level was the impairment of lymphocyte proliferation measured as mitotic index (MI). The relation between mercury concentration in hair and MI suggests that this parameter, an indicator of changes in lymphocytes and their ability to respond to culture conditions, may be an early marker of cytotoxicity and genotoxicity in humans and should be taken into account in the preliminary evaluation of the risks to populations exposed in vivo. This is the first report showing clear cytotoxic effects of long-term exposure to MeHg. Although the results strongly suggest that, under the conditions examined here, MeHg is both a spindle poison and a clastogen, the biological significance of these observations are as yet unknown. A long-term follow-up of these subjects should be undertaken.

X-rays vs. carbon-ion tumor therapy: cytogenetic damage in lymphocytes

Purpose: To measure chromosomal aberrations in peripheral blood lymphocytes from cancer patients treated with X-rays or carbon ions (C-ions). Methods and Materials: Blood samples from patients diagnosed for esophageal or uterine cervical cancer were obtained before, during, and at the end of the radiation treatment. The novel technique of interphase chromosome painting was used to detect aberrations in prematurely condensed chromosomes 2 and 4. The fraction of aberrant lymphocytes was measured as a function of the dose to the tumor volume. For comparison, blood samples were also exposed in vitro to X-rays or to carbon ions accelerated at the HIMAC. Results: C-ions were more efficient than X-rays in the induction of chromosomal aberrations in vitro. In patients with similar pathologies, tumor positions, and radiation field sizes, however, C-ions induced a lower fraction of aberrant lymphocytes than X-rays during the treatment. The initial slope of the dose–response curve for the induction of chromosomal aberrations during the treatment was correlated to the relative decrease in the number of white blood cells and lymphocytes during the treatment. Conclusion: C-ions induce a lower level of cytogenetic damage in lymphocytes than X-rays, reducing the risk of bone marrow morbidity.

Monitoring of Molecular and Cytogenetic Damage in Lymphocytes from Three Persons with Polycystic Kidney Disease

Background Much interest has been generated in the studies that would help to understand whether there is a causal association between disease and various types of molecular or cytogenetic damage detected in human cells. Materials and Methods The aims of this study were to elicit the possible association between DNA and cytogenetic damage induced in lymphocytes of three members of a family with autosomal dominant polycystic kidney disease (ADPKD). The predictability to develop cancer or to sensitive response to environmental exposure of the young girl at the age of 19, her brother (9 years old) and a maternal aunt at the age of 41 were sought. Cytogenetic studies, analysis of DNA damage by single cell gel electrophoresis assay (SCGE known as a Comet assay), and analysis of p21ras protein level in blood plasma were carried out on their lymphocytes. Results The analysis for presence of chromosome aberrations in the first mitosis and sister chromatid exchanges in the second mitosis revealed elevated levels of cytogenetic biomarkers when compared to the mean values observed in the reference group in environmental biological monitoring studies. Results of sister chromatid exchanges (SCE) and percent of cells with elevated number of exchanges (high frequency cells) that were significantly higher in two probands had demonstrated susceptibility to or possibility of environmental exposure (pesticides, smoking). The results of this study show that the lymphocytes of two persons revealed increased sensitivity to 0.5 Gy dose of gamma radiation expressed in the increased, although statistically insignificant, damage detected on the molecular level after cell irradiation. Conclusions The latter might be associated with a specific aberration present in the cells of these persons. But final conclusions can be arrived at when an application of FISH technique is completed.

Cytogenetic damage in lymphocytes of healthy and thyroid tumor-affected children from the Gomel region (Belarus)

During 1994, 19 thyroid tumor-affected children and 17 healthy children from the Gomel region, one of the areas most polluted by the Chernobyl fallout, were analysed for (i) the presence of 137Cs in their urine and (ii) chromosome aberrations (CA) in circulating lymphocytes. They were compared with 35 healthy children from Pisa, Italy. Tumor-affected children showed significantly ( p < 0.05) higher 137Cs levels in their urine as compared to healthy controls from the Gomel region. No radioactivity was found in urine from the Pisa controls. CA frequency was significantly higher in tumor-affected children compared to the Gomel controls, but was not significantly different between Gomel and Pisa controls. However, dicentric chromosomes were found in a significantly ( p < 0.01) greater proportion in both affected and healthy Gomel children (3.4 and 1.3 1000 cells, respectively) as compared to the Pisa controls ( r 0.4 1000 cells). Multiple regression analysis showed that the proportion of cells with acentric fragments, dicentric and ring chromosomes was significantly correlated ( p < 0.05) with the amount of 137Cs excreted in their urine. These findings suggest that children from the Gomel region were still being exposed to radionuclides, which makes it possible to study a dose-effect relationship.

Assessment of genotoxic exposure in Swedish coke-oven work by different methods of biological monitoring.

This study evaluated the results of several biological methods used simultaneously to monitor coke-oven work. Blood samples from 44 male coke-oven workers and 48 male referents, matched for age and smoking/snuff consumption, were examined for cytogenetic damage in lymphocytes. Urinary thioether excretion was determined for 62, and urine mutagenicity for 31, of the subjects, who followed a standardized diet during the urine sampling. Exposure to polycyclic aromatic hydrocarbons varied with work task, the ambient air levels of benzo[a]pyrene sometimes exceeding 5 micrograms/m3. Cytogenetic damage, urine mutagenicity, and thioether excretion did not differ between the groups. The smokers, however, had significantly higher sister chromatid exchange frequencies, urine mutagenicity, and thioether excretion than the nonsmokers. The absence of biological indications of genotoxic exposure was unexpected and indicates that the studied methods are not adequate to assess the carcinogenic risks of Swedish coke-oven workers.

Cytogenetic damage in lymphocytes of rubber industry workers

Cytogenetic investigations were conducted in workers who are occupationally exposed to rubber chemicals such as tetramethylthiuram disulfide, zinc dimethyldithiocarbamate, and tetraethylthiuram disulfide using lymphocytes of peripheral blood. A significant increase in the frequency of chromosomal breaks and gaps was recorded regardless of the duration of exposure to these chemicals.