Evaluation of micronucleated lymphocytes, constitutional karyotypes and anti-p53 antibodies in 21 children with various malignancies

Absence of cytogenetic effects in children and adults with attention-deficit/hyperactivity disorder treated with methylphenidate

Attention-deficit/hyperactivity disorder (ADHD) is the most common psychiatric condition with onset in childhood, and in more than 50% of cases it persists into adulthood as a chronic disorder. Over five million methylphenidate (MPH) prescriptions were issued in the USA in 2003, mostly for children. A previous report [R.A. El-Zein, S.Z. Abdel-Rahman, M.J. Hay, M.S. Lopez, M.L. Bondy, D.L. Morris and M.S. Legator Cytogenetic effects in children treated with methylphenidate, Cancer Lett. 230 (2005) 284-291.] described the induction of chromosome abnormalities by MPH in children treated for three months, contrary to most of the in vitro and in vivo studies reported since then. We present new relevant information concerning the cytogenetic effects of MPH in children and adults. We include a prospective sample of 12 children and 7 adults with a new diagnosis of ADHD and naive to MPH. We analyzed the cytogenetic effects on peripheral lymphocytes before and three months after starting MPH therapy. The cytogenetic analyses included a cytokinesis-block micronucleus (CBMN) assay, a sister chromatid exchange (SCE) analysis and the determination of chromosome aberrations (CA). Following the same strategy and analyzing the same cytogenetic endpoints that were investigated in the original report [R.A. El-Zein, S.Z. Abdel-Rahman, M.J. Hay, M.S. Lopez, M.L. Bondy, D.L. Morris and M.S. Legator Cytogenetic effects in children treated with methylphenidate, Cancer Lett. 230 (2005) 284-291.], we found no evidence of increased frequency of micronuclei, sister chromatid exchanges or chromosome aberrations induced by MPH in children and adult populations. MPH treatment of children and adults with ADHD resulted in no significant genomic damage (as suggested by the three endpoints studied), results that do not support a potential increased risk of cancer after exposure to MPH.

Frequency of sister chromatid exchanges and micronuclei monitored over time in patients with early-stage breast cancer: results of an observational study

Spontaneous chromosomal instability correlates with a high risk of cancer. The frequency of spontaneous sister chromatid exchanges (SCE) and micronuclei (MN) in peripheral blood lymphocytes was used for evaluation of spontaneous chromosomal instability in early-stage breast cancer patients to determine whether SCE and MN frequencies are biomarkers of damage from chemotherapy and radiotherapy. In 20 stage I-II breast cancer patients, SCE and MN were measured before surgery and at 4 weeks after. In patients who received adjuvant chemotherapy (CTx), they were also determined before starting radiotherapy (RTx). Other assessments were done 2, 6, and 12 months after RTx in almost all patients and at 18 months in 4 patients. Generalized estimating equations (GEE) were used to estimate population averaged effects at the different treatment and follow-up time points. Moreover, SCE and MN baseline values in patients were compared with those of a control group of 12 healthy women. A significant difference emerged between patients and healthy controls (P<0.0001 for SCE and P<0.0003 for MN; Mann-Whitney test); SCE increased significantly after CTx and MN increased significantly after RTx. In the GEE model, the smoking habit was associated with increased SCE in patients treated with CTx; age significantly affected MN frequencies. Both MN and SCE frequencies are increased in breast cancer patients and are indicators of CTx and RTx damage, respectively. The increased SCE levels in patients treated with CTx may be due to a synergic effect of smoking and chemotherapy.

DNA damage in lymphocytes and buccal mucosa cells of children with malignant tumours undergoing chemotherapy

The aim of the present study was to evaluate DNA damage (micronucleus) in cytokinesis-blocked lymphocytes and exfoliated buccal mucosa cells from children with malignant tumours and under chemotherapy. Micronucleated cells (MNCs) were assessed from children before and during chemotherapy. A total of 21 healthy children (controls), matched for gender and age, were used as control. The results pointed out higher frequencies of micronucleated lymphocytes in children with malignant tumour before any therapy when compared to healthy probands. Furthermore an increase of micronucleated lymphocytes during chemotherapy was detected when compared to the data obtained before chemotherapy. No statistically significant increases of MNCs were noticed in buccal mucosa cells at any of the timepoints evaluated. Taken together, these data indicate that the presence of malignant tumours may increase the frequency of DNA damage in circulating lymphocytes, these cells being more sensitive for detecting chromosome aberrations caused by anti-cancer drugs.

Baseline micronuclei frequency in children: estimates from meta- and pooled analyses

The number of studies evaluating the effect of environmental exposure to genotoxic agents in children has rapidly increased in the last few years. The frequency of micronuclei (MN) in peripheral blood lymphocytes determined with the cytokinesis block assay is among the most popular biomarkers used for this purpose, although large inter- and intralaboratory variability of this end point has been observed in population studies. The availability of reference measures is therefore necessary for laboratories to validate protocols and analytical procedures, and for molecular epidemiologists, as well, to estimate the statistical power of studies and to assess the quality of data. In this article, we provide estimates of the baseline frequency of MN in children, conducting a meta-analysis of MN frequency reported by field studies in children and a pooled analysis of individual data [available from published studies and from the Human Micronucleus International Collaborative Study (HUMN) database]. Thirteen articles were selected for meta-analysis, and individual data included in the pooled analysis were retrieved from the databases of 12 laboratories. Overall means of 4.48 [95% confidence interval (CI), 3.35-5.98] and 5.70 (95% CI, 4.29-7.56) MN per 1,000 binucleated cells were estimated by the meta- and pooled analysis, respectively. A clear effect of age was detected, even within the restricted range of pediatric age considered, with significantly lower frequency values in newborns. No influence of sex was found. The study showed the advantage of using data from large collaborative studies and suggested a synergistic use of meta- and pooled analysis.

A Molecular Epidemiology Case Control Study on Pleural Malignant Mesothelioma

Pleural malignant mesothelioma is an uncommon neoplasm usually associated with asbestos exposure. The increasing incidence of malignant mesothelioma cases involving individuals with low levels of asbestos exposure suggests a complex carcinogenetic process with the involvement of other cofactors. Cytogenetic studies revealed the complexity of the genetic changes involved in this neoplasm reflecting the accumulation of genomic damage. One of the most used methodologies for assessing genomic damage is the cytokinesis-blocked micronucleus test applied in peripheral blood lymphocytes (PBL). This approach allows the detection of chromosomal alterations expressed in binucleated cells after nuclear division in vitro. This marker could provide a tool for assessing genetically determined constitutional differences in chromosomal instability. A biomonitoring study was carried out to evaluate the micronuclei frequency in PBLs of patients with pleural malignant mesothelioma with respect to lung cancer, healthy, and risk controls as a marker of cancer susceptibility in correlation with the presence of SV40. A significant increased micronuclei frequency was observed in patients with malignant mesothelioma in comparison with all the other groups, the mean micronuclei frequency was double in patients with malignant mesothelioma compared with healthy controls, risk controls, and patients with lung adenocarcinoma (median 11.4 binucleated cells with micronuclei/1,000 binucleated cells versus 6.2, 6.1, and 5.1, respectively). Our data indicate that human T lymphocyte samples carry DNA sequences coding for SV40 large T antigen at low prevalence, both in cancer cases and controls. Evidence of cytogenetic damage revealed as micronuclei frequency in mesothelioma cancer patients could be related to exogenous and endogenous cofactors besides asbestos exposure.

Micronuclei frequency in children exposed to environmental mutagens: a review

Cytogenetic monitoring has been traditionally used for the surveillance of populations exposed to genotoxic agents. In recent years sensitivity problems emerged in surveys of populations exposed to low levels of mutagens, and therefore alternative approaches have been explored. Biomonitoring studies in children are a promising field, since because of evident differences in the uptake, metabolism, distribution and excretion of mutagens this population seems to be more susceptible than adults. Further, the effect of major confounders such as cigarettes smoking, occupation, life-style, and dietary factors plays a minor role. Among cytogenetic assays, the micronucleus assay (MN) has several advantages and is increasingly used. A review was then carried out to synthesize the published data on the occurrence of MN in children and adolescents (age range 0-18 years), and to assess the impact of genotoxic exposure on MN frequency. Overall, 20 papers from international literature and 8 Russian papers were included. An effect of age was found within this age range, while the influence of gender on MN frequency was irrelevant. These results were confirmed by the re-analysis of data for 448 children selected from the HUMN database. An effect of chronic and infectious diseases on MN levels has been reported by various authors. Most studies describing the effect of exposure to genotoxic agents (ionizing radiation, chemicals, drugs, environmental tobacco smoke) found an increase of MN in exposed children. The limited number of published papers indicates that the conduct of properly designed studies on the effect of environmental pollutants in children may be difficult. This review confirmed the usefulness of MN assay in biomonitoring studies conducted in children, revealing that in many circumstances investigating children increases the sensitivity of the study, even with low dose exposures.

Acentromeric micronuclei are increased in peripheral blood lymphocytes of untreated cancer patients

Increased micronucleated cell rates, dicentric chromosomes, and other chromosomal damages have been reported in lymphocytes of cancer patients prior to the initiation of chemotherapy, and/or radiotherapy. The cause of these chromosomal damages in these lymphocytes remains unclear. In the present work, we investigated whether these micronuclei mainly reflect structural or numerical chromosomal aberrations by applying the cytokinesis-blocked micronucleus (CBMN) assay in combination with fluorescent in situ hybridization (FISH) of a DNA centromeric probe on blood samples of 10 untreated cancer patients (UCPs), and 10 healthy subjects (HSs). Micronucleated binucleated lymphocyte rate was significantly increased in patients (mean+/-S.D.: 19.0 per thousand +/-14.1 versus 9.2 per thousand +/-4.6 in controls). Trinucleated cytokinesis-blocked cells were not significantly higher in patients than in controls. Acentromeric, centromeric, and multicentromeric micronucleus levels were two-fold higher in patients than in controls, but the difference was significant only with acentromeric micronuclei. The percentage of micronuclei containing one or more centromeres averaged 69.2, and 71.5% in patients, and controls, respectively. The percentage of micronuclei containing several centromeres was 44.7% in patients, and 54.6% in controls. Among centromere-positive micronuclei, the percentage of micronuclei containing several centromeres averaged 59.7% in patients, and 75.4% in controls. These results indicate that genetic instability in peripheral blood lymphocytes of UCPs occurs because of enhanced chromosome breakage. However, a substantial proportion of this genetic instability occurs because of defects in chromosome segregation.