Baseline Micronuclei Frequency Research Articles

Micronuclei frequency in peripheral blood lymphocytes of healthy subjects living in Turin (North-Italy): contribution of body mass index, age and sex

Background: Increased micronuclei (MNi) frequencies in human lymphocytes are an indicator of chromosome instability and could be influenced by different exogenous and endogenous factors. The increased exposure to environmental pollutants has led to the awareness of the necessity for constant monitoring of urban human populations.Aim: We evaluated the MNi frequency in a sample belonging to the non-occupationally exposed population of Turin (North-Western Italy). A possible effect of body mass index, age and sex on the genomic damage levels was also investigated.Subjects and Methods: The study included 150 subjects. MNi, nucleoplasmic bridges (NPBs) and nuclear buds (NBUDs) were scored in 1,000 lymphocytes per subject.Results: The MNi, NPBs and NBUDs average frequencies (‰ ± S.D.) were 7.19 ± 2.51, 1.65 ± 1.54 and 2.07 ± 1.76, respectively. Turin shows one of the highest MNi frequencies with respect to other Italian cities and European regions. A significant correlation was found between MNi, NPBs, NBUDs frequencies, age and body mass index.Conclusion: Baseline MNi frequency was established in a sample of a city, like Turin, exposed to high levels of environmental pollutants. We hope that the results of this study can be used as a stimulus for future biomonitoring programmes in other Italian and globally distributed cities.

Cytokinesis Block Micronucleus Cytome (CBMN Cyt) Assay Biomarkers and Their Association With Radiation Sensitivity Phenotype in Prostate Cancer Cases and DNA Repair Gene hOGG1 (C1245G) Polymorphism.

Prostate cancer (PC) is commonly diagnosed cancer in men but only a few risk factors, such as family history, ethnicity, and age have been established. Chromosomal instability is another possible risk factor but this has not been adequately explained previously. In this study, we tested the hypotheses that peripheral blood lymphocytes (PBL) of PC patients have (1) an abnormally high level of chromosomal instability; (2) that they are hypersensitive to ionizing radiation-induced DNA damage; and (3) that these phenotypes are affected by hOGG1 (C1245G) polymorphism. These experiments were performed using the cytokinesis-block micronucleus Cytome (CBMN cyt) assay in PC cases and controls. We found that spontaneous or radiation-induced (3G) micronucleus (MN) frequency is not significantly different between both groups. However, spontaneous frequency of nucleoplasmic bridges (NPBs) and radiation-induced nuclear buds (NBuds) were significantly higher in patients vs. controls (P < 0.0001; P = 0.0005, respectively). In addition, apoptosis and nuclear division index (NDI) was significantly higher in patients compared to controls after radiation treatment (P = 0.006; P = 0.0002, respectively). Furthermore carriage of at least one G allele of hOGG1 (C1245G) polymorphism was associated with a significantly increased odds ratio (OR) to have a base-line MN, NPB, or NBud frequency greater than medium level compared to homozygotes for C allele (OR:1.94, 1.77, 2.36, respectively, P = 0.02; 0.04, and 0.004, respectively). Our results support the hypotheses that those who develop PC have significantly higher level of genomic instability which is further increased in those who carry G allele of the hOGG1 (C1245G) polymorphism. Environ. Mol. Mutagen. 59:813-821, 2018. © 2018 Wiley Periodicals, Inc.

Baseline levels of environmental genotoxicity and potential confounding factors using common sole (Solea solea) as sentinel organism

Micronuclei (MN) and nuclear buds (NB) frequency was assessed monthly over a one-year period in erythrocytes of common soles (Solea solea) from the Basque continental shelf, a minor disturbed area, in order to determine baseline levels and potential biotic and abiotic confounding factors within biomonitoring purposes. Both genotoxic parameters presented seasonal variations, although only NB frequency was positively correlated with environmental variables (i.e. water temperature and salinity). On the contrary, MN and NB were not affected by age and gender. Therefore, samples of combined age and gender can be used for biomonitoring genotoxic effects, although sampling period together with water temperature and salinity should be thoroughly considered for NB. Overall, these findings are the first attempt to establish baseline MN (0.10–0.78‰) and NB (0.13–0.82‰) frequencies in common sole from Basque marine waters, which are useful for upcoming data comparisons and integration within genotoxicity evaluation procedures of similar marine environments under biomonitoring scopes.

The cytokinesis-blocked micronucleus assay: dose-response calibration curve, background frequency in the population and dose estimation.

An in vitro study of the dose responses of human peripheral blood lymphocytes was conducted with the aim of creating calibrated dose-response curves for biodosimetry measuring up to 4 Gy (0.25-4 Gy) of gamma radiation. The cytokinesis-blocked micronucleus (CBMN) assay was employed to obtain the frequencies of micronuclei (MN) per binucleated cell in blood samples from 16 healthy donors (eight males and eight females) in two age ranges of 20-34 and 35-50 years. The data were used to construct the calibration curves for men and women in two age groups, separately. An increase in micronuclei yield with the dose in a linear-quadratic way was observed in all groups. To verify the applicability of the constructed calibration curve, MN yields were measured in peripheral blood lymphocytes of two real overexposed subjects and three irradiated samples with unknown dose, and the results were compared with dose values obtained from measuring dicentric chromosomes. The comparison of the results obtained by the two techniques indicated a good agreement between dose estimates. The average baseline frequency of MN for the 130 healthy non-exposed donors (77 men and 55 women, 20-60 years old divided into four age groups) ranged from 6 to 21 micronuclei per 1000 binucleated cells. Baseline MN frequencies were higher for women and for the older age group. The results presented in this study point out that the CBMN assay is a reliable, easier and valuable alternative method for biological dosimetry.

Baseline micronuclei and nuclear abnormalities frequencies in native fishes from the Paraná River (Argentina).

This work aims to establish baseline frequencies of micronuclei (MN) and nuclear abnormalities (NA) in native fish species collected in situ from the Paraná River. For this purpose, the micronucleus test was applied in peripheral blood erythrocytes from specimens obtained from samplings collected at two localities (Posadas and Candelaria, Misiones, Argentina) during the period 2007-2010. The results were statistically analyzed using the Kruskal Wallis test. Data from nine fish species were obtained, among which Steindachnerina brevipinna (Characiformes) revealed the highest baseline frequency of MN and NA, showing statistically significant differences with regard to the other analyzed species. These results are the first report of baseline MN and NA frequencies for native fish species studied and could be useful for future comparisons with data of fishes belonging to other environments.

Genetic damage induced by water pollutants in the freshwater fish Hyphessobrycon luetkenii (Characidae) in a reservoir of the Canela National Forest, Brazil

Fish have been shown to act as sentinel organisms in genetic toxicology studies and the micronucleus (MN) test using fish erythrocytes has been successfully used to evaluate the genotoxic impact of environmental pollutants on aquatic environments. This study used the MN test of peripheral blood of specimens of a native fish species (Hyphessobrycon luetkenii) to evaluate the genotoxicity of the water of two unconnected reservoirs of the Canela National Forest in southern Brazil. Fish were caught in the reservoirs and MN frequencies in blood smears were determined. Baseline MN frequency of H. luetkenii was determined in the uncontaminated reservoir (reference site) and compared with the results obtained at two different sampling periods (winter and spring) in the reservoir which receives discharges of industrial and municipal wastes. In the spring season, MN frequency in the contaminated reservoir was about five times higher than in the reference site (0.51‰ and 0.10‰, respectively). The results of this study indicate that some fish populations are at risk of exposure to genotoxic pollutants in the Canela National Forest.

Influence of glutathione-s-transferase (GSTT1 and GSTM1) polymorphism on baseline micronuclei frequency in peripheral blood lymphocytes

We have analyzed impact of polymorphism in GSTT1 and GSTM1 genes on the micronuclei (MN) frequency in peripheral blood lymphocytes (PBLs). A total 134 women from central Serbia were enrolled in the study. Polymorphisms of GST genes were genotyped by performing a multiplex polymerase chain reaction (PCR) and cytokinesis block micronucleus (CBMN) test was used to assess MN frequency. GSTT1 null and GSTM1 null genotype carriers had higher MN frequencies as compared to positive counterparts but without statistical significance. Carriers of dual GSTT1/GSTM1 null genotypes had significantly higher MN frequency than positive/positive, positive/null and null/positive. Smokers and women &gt;45 years old with GSTT1 null genotype and GSTT1null/GSTM1null genotypes have statistically higher MN frequency than positive counterparts. Results suggest possible influence of dual null genotypes of GSTT1/GSTM1 on the baseline MN frequency, as well influence on the level of MN in smokers and in women age &gt;45 years. GSTT1 null genotype may have the potential to influence the baseline MN frequency in PBLs of smokers, as well as in women age &gt;45 years.

Inter-individual variance in micronuclei frequency in lymphocytes of patients with cervical insufficiency

The aim of this work was to explain the inter-individual variance in baseline and induced micronuclei (MN) frequency in peripheral blood lymphocytes (PBLs) of females with uterine cervical insufficiency. The baseline and induced MN response of the PBLs in 32 patients were investigated using the cytokinesis-block micronucleus (CBMN) method. The obtained mean values of induced MN frequency (11.31 ? 4.44/1000 BN cells), were significantly higher (p &lt; 0.001) in comparison to their baseline MN frequencies (7.81 ? 3.33 MN/1000 BN cells). The analysis of variance (ANOVA) showed statistically significant difference between-group vs. within-group variance in baseline (p &lt; 0.05) and induced MN frequency (p &lt; 0.001), in professionally exposed patients when compared to the non-exposed. Multivariate logistic regression analysis confirmed that patients with high baseline MN frequency (cut-off 8.5 MN/1000 MN), had significantly increased (odds ratio OR = 5.875; CI = 1.28 - 26.795, p &lt; 0.05) induced MN frequency (&gt;12 MN/1000 BN cells). Our results suggest that the baseline MN frequency in PBLs directly influences the scope of the induced MN response.

Chromosomal instability in peripheral blood lymphocytes of patients with reproductive failure assessed by micronucleus assay

We investigated chromosomal instability in peripheral blood lymphocytes (PBL) of patients with reproductive failure in respect to age, smoking habits, gender, miscarriages, and semen parameters. The study involved 36 individual cases of reproductive failure (18 men and 18 women) attended at the Clinical Centre of Kragujevac, Serbia, and 30 healthy subjects (15 men and 15 women). Micronuclei (MN) frequency was estimated in PBL using the cytokinesis-block micronucleus (CBMN) assay. The baseline MN frequencies were significantly higher (p=0.031; p<0.001) in male [(9.22 ± 4.70) MN per 1000 BN cells] and female patients [(13.50 ± 2.5) MN per 1000 BN cells] than in male and female healthy controls [(6.27 ± 2.66) MN per 1000 BN cells; (6.80 ± 2.98) MN per 1000 BN cells]. The mean baseline MN frequency did not significantly differ between miscarriage groups and between patients with and without normal values of semen parameters. The correlations between poor sperm concentration (<20x106 mL-1), rapid progressive motility (<25 %), normal morphology (<30 %), and MN frequencies were negative, but not statistically significant. We found that only gender significantly influenced the MN rates in analysed patients. There were no significant differences between age groups and between smokers and non-smokers in patients and control samples. We conclude that the increase in baseline MN frequency in PBL of patients with reproductive failure corresponds to the increase in chromosomal damage, which occurs as a result of complex events that cause reproductive disorders.

Baseline values of Micronuclei and Comet Assay in the lizard Tupinambis merianae (Teiidae, Squamata)

The Micronucleus test (MN) and Comet assay (CA) are currently the most widely used methods that allow the characterization of DNA damage induced by physical and chemical agents in wild species. The continuous expansion of the cultivated areas in Argentina, since the introduction of transgenic crops, mainly soy, in association with the increased use of pesticides, transformed deeply the natural environments where the lizard Tupinambis merianae (tegu lizard) occurs. Despite the fact that reptiles have shown to be excellent bioindicators of environmental contaminants, there is no record of genotoxicity studies in T. merianae. The aim of the present study was to adjust the MN test and CA protocols to be applied in erythrocytes of T. merianae, and determine the baseline values of DNA damage in this species. We used 20 adult lizards (10 males: 10 females) from Estación Zoológica Experimental “Granja La Esmeralda” (Santa Fe, Argentina). Peripheral blood samples were collected from all animals and the MN test and CA applied according to the protocols established for other reptilian species. We test critical parameters of CA protocol (cell density, unwinding and electrophoresis times) using increasing concentrations of H2O2 (10, 25 and 50μM) as a known genotoxic agent to induce DNA damage. Based on this, we determined the most suitable conditions for the CA in this species: a cell density of 4×103 erythrocytes per slide, 10min of unwinding and 15min of electrophoresis at 0.90V/cm approximately. The baseline frequency of micronuclei (BFMN=MN/1000 erythrocytes counted) determined for this species was 0.95±0.27 and the basal damage index (BDI: calculated from 100 comet images classified in arbitrary units)=103.85±0.97. No differences were observed between sexes in the BFMN or BDI (p>0.05), and no relation was found between baseline values and length or weight of the analyzed animals (p>0.05).These results demonstrated the sensitivity of both biomarkers of genotoxicity to be applied in erythrocytes of this species, with baseline values comparable to those reported in other reptilian species. These results allow us to propose the tegu lizard for future in vivo studies to assess the genotoxicity of different agents, including those possibly affecting it in its natural geographic distribution.

Role of micronucleus test in predicting breast cancer susceptibility: a systematic review and meta-analysis

Background:The cytokinesis-block micronucleus test (MNT), as a marker of chromosomal mutagen sensitivity, was applied in a number of studies enrolling breast cancer (BC) patients and subjects with known or putative genetic predisposition to BC. The large majority of them involve the evaluation of induced micronuclei (MN) frequency in peripheral lymphocytes, after the in vitro challenge with ionising radiations.Methods:The aim of the present systematic review and meta-analysis is to investigate the role of MN assay in the identification of individuals at increased risk of BC and its potential use as prescreening test in women with a family history (FH) of BC.Results:Twelve studies were included in the meta-analysis, covering a time interval 1998–2007, and including 752 cases and 593 controls. Among the cases, 629 are cancer patients and 123 are cancer-free subjects, including 32 first-degree relatives of the susceptible subjects and 91 BRCA1/2 mutation carriers. Our meta-analysis reveals a significant increase of baseline MN frequency related to cancer status, but the association with FH of BC and specifically with BRCA mutations is not clear. A larger difference in MN frequency between cases and controls was observed after in vitro challenge, but response to radiation exposure doesn't appear to better discriminate cancer-susceptible subjects.Conclusion:Our study suggests the presence of some bias affecting many of these studies, reinforcing the suggestion that a more rigorous study design is needed in this area.

Micronuclei in neonates and children: effects of environmental, genetic, demographic and disease variables

Children may be more susceptible to the effects of the environmental exposure and medical treatments than adults; however, limited information is available about the differences in genotoxic effects in children by age, sex and health status. Micronucleus (MN) assay is a well established method of monitoring genotoxicity, and this approach is thoroughly validated for adult lymphocytes by the Human Micronucleus Biomonitoring project (HUMN.org). Similar international undertaking is in progress for exfoliated buccal cells. Most of the MN studies in children are focused on analyses of lymphocytes but in the recent years, more investigators are interested in using exfoliated cells from the oral cavity and other cell types that can be collected non-invasively, which is particularly important in paediatric cohorts. The baseline MN frequency is relatively low in newborns and its assessment requires large cohorts and cell sample counts. Available results are mostly consistent in conclusion that environmental pollutants and radiation exposures lead to the increase in the MN frequency in children. Effects of medical treatments are less clear, and more studies are needed to optimise the doses and minimise genotoxicity without compromising therapy outcomes. Despite the recent progress in MN assay in children, more studies are warranted to establish the relationship between MN in lymphocytes and exfoliated cells, to clarify sex, age and genotype differences in baseline MN levels and the changes in response to genotoxicants. One of the most important types of MN studies in children are prospective cohorts that will help to clarify the predictive value of MN and other cytome end points for cancer and other chronic diseases of childhood and adulthood. Emerging 'omic' and other novel molecular technologies may shed light on the molecular mechanisms and biological pathways associated with the MN levels in children.

Heritability of baseline and induced micronucleus frequencies

The scoring of micronuclei (MN) is widely used in biomonitoring and mutagenicity testing as a surrogate marker of chromosomal damage inflicted by clastogenic agents or by aneugens. Individual differences in the response to a mutagenic challenge are known from studies on cancer patients and carriers of mutations in DNA repair genes. However, it has not been studied to which extent genetic factors contribute to the observed variability of individual MN frequencies. Our aim was to quantify this heritable genetic component of both baseline and radiation-induced MN frequencies. We performed a twin study comprising 39 monozygotic (MZ) and 10 dizygotic (DZ) twin pairs. Due to the small number of DZ pairs, we had to recruit controls from which 38 age- and gender-matched random control pairs (CPs) were generated. For heritability estimates, we used biometrical modelling of additive genetic, common environmental, and unique environmental components (ACE model) of variance and direct comparison of variance between the sample groups. While heritability estimates from MZ to DZ comparisons produced inconclusive results, both estimation methods revealed a high degree of heritability (h(2)) for baseline MN frequency (h(2) = 0.68 and h(2) = 0.72) as well as for the induced frequency (h(2) = 0.68 and h(2) = 0.57) when MZ were compared to CP. The result was supported by the different intraclass correlation coefficients of MZ, DZ and CP for baseline (r = 0.63, r = 0.31 and r = 0.0, respectively) as well as for induced MN frequencies (r = 0.79, r = 0.74 and r = 0.0, respectively). This study clearly demonstrates that MN frequencies are determined by genetic factors to a major part. The strong reflection of the genetic background supports the idea that MN frequencies represent an intermediate phenotype between molecular DNA repair mechanisms and the cancer phenotype and affirms the approaches that are made to utilise them as predictors of, for example, cancer risk.

High Micronucleus Frequency in Peripheral Blood Lymphocytes of Untreated Cancer Patients Irrespective of Gender, Smoking and Cancer Sites

Chromosomal instability could be one of primary causes for malignant cell transformation. The objective of the present study was to evaluate the spontaneous genetic damages in circulated lymphocytes of newly diagnosed cancer patients by using cytokinesis-block micronucleus (CBMN) assay, with respect to the factors that might affect micronucleus frequency (i.e. age, gender, smoking habits and cancer sites). Micronuclei (MN) are small nuclei that are originated from chromosome fragments or whole chromosomes. The analyzed samples included 44 untreated cancer patients (19 females and 25 males with mean age of 60.89 years) with different cancer sites (12 patients with breast cancer, 5 with uterine cancer and 27 with cancer of pharynx). Control group included 40 healthy donors (28 females and 12 males with mean age of 43.95 years). The mean baseline MN frequency was significantly higher (p < 0.001) in cancer patients (15.18 +/- 5.05 MN/1000 BN cells ranging from 4 to 27) than the baseline frequency in healthy controls (6.45 +/- 2.75 MN/1000 BN cells, ranging from 1 to 11). There was no gender difference in baseline MN frequency in cancer patients and healthy controls. Moreover, the MN frequency did not significantly differ among cancer sites, and between smokers and non-smokers in both patient and control samples. In conclusion, untreated cancer patients may be associated with an increase of chromosomal instability in peripheral blood lymphocytes, irrespective of gender, cigarette smoking and cancer sites.

Human population studies with the exfoliated buccal micronucleus assay: Statistical and epidemiological issues

Micronucleus (MN) assay in buccal exfoliated cells is a minimally invasive method for monitoring genetic damage in human populations. Statistical and epidemiological issues related to the design and analysis of studies based on this biomarker are addressed. A systematic review of recent literature on the buccal MN assay has been carried out to provide a state-of-the-art evaluation of how critical topics such as control for confounding, sample size and statistical power, number of cells scored, endpoint selection, and statistical modelling, are considered. In addition, a meta-analysis has been performed to estimate the impact of most common confounders on MN frequency, and to provide a baseline value of MN frequency in the control population. A total number of 63 eligible studies were included in the analysis. Age (98.4%), gender (85.7%), and smoking habit (90.5%) were the most commonly studied confounders. Univariate statistics were estimated in most studies while multivariate analysis was applied only in the 47.6%. Baseline MN frequency in controls was 1.10/1000 cells (95% confidence interval 0.70-1.72), and the relative increment in subjects exposed to genotoxic agents or affected by disease correlated with similar observations in lymphocytes (R(2)=0.74). A minimum number of 4000 cells is recommended to reduce the variability of the MN mean estimates, in contrast with the current practice of scoring only 2000 cells (81% of studies). Poisson or Negative Binomial are the preferred statistical models when more than 2000 cells are scored. Studies scoring smaller numbers of cells should consider the use of statistical models taking into account the excess of zeros, e.g., the Zero Inflated Poisson (ZIP) models. The quality of papers published on the buccal MN assay can be substantially improved, with better consideration of basic issues such as power analysis, control for confounding, choice of the statistical model, and the number of cells to be scored.

The effect of selenium, as selenomethionine, on genome stability and cytotoxicity in human lymphocytes measured using the cytokinesis-block micronucleus cytome assay

A supranutritional intake of selenium (Se) may be required for cancer prevention, but an excessively high dose could be toxic. Therefore, the effect on genome stability of seleno-L-methionine (Se-met), the most important dietary form of Se, was measured to determine its bioefficacy and safety limit. Peripheral blood lymphocytes were isolated from six volunteers and cultured with medium supplemented with Se-met in a series of Se concentrations (3, 31, 125, 430, 1880 and 3850 microg Se/litre) while keeping the total methionine (i.e. Se-met + L-methionine) concentration constant at 50 microM. Baseline genome stability of lymphocytes and the extent of DNA damage induced by 1.5-Gy gamma-ray were investigated using the cytokinesis-block micronucleus cytome assay after 9 days of culture in 96-microwell plates. High Se concentrations (>or=1880 microg Se/litre) caused strong inhibition of cell division and increased cell death (P < 0.0001). Baseline frequency of nucleoplasmic bridges and nuclear buds, however, declined significantly (P trend < 0.05) as Se concentration increased from 3 to 430 microg Se/litre. Se concentration (<or=430 microg Se/litre) had no significant effect on baseline frequency of micronuclei and had no protective effect against genome damage induced by exposure to 1.5-Gy gamma-ray irradiation. In conclusion, Se, as Se-met, may improve genome stability at concentrations up to 430 microg Se/litre, but higher doses may be cytotoxic. Therefore, a cautious approach to supplementation with Se-met is required to ensure that optimal genome health is achieved without cytotoxic effects.

Spontaneous frequency of micronuclei among the newborns from high level natural radiation areas of Kerala in the southwest coast of India

Purpose: The present study was an attempt to determine the spontaneous frequency of micronuclei (MN) in newborns from High Level Natural Radiation Areas (HLNRA) and the adjoining Normal Level Radiation Areas (NLNRA) of the monazite-bearing Kerala Coast in Southern West India using Cytochalasin Blocked Micronuclei (CBMN) assay.Materials and methods: Human umbilical cord blood samples were collected from a total number of 271 newborns (61 from NLNRA and 210 from HLNRA), born to mothers aged between 17 and 37 years (mean maternal age: 24.08 ± 4.23 years). Lymphocyte cultures were set up following microculture techniques and cultures were terminated at 72 hours. Cytochalasin B at a concentration of 4.0 μg/ml was added to the lymphocyte cultures at 44 h. Enumeration of micronuclei was restricted to Cytochalasin Blocked binucleated (BN) cells only.Results: The frequency of MN among the newborns from NLNRA (1.40 ± 0.12) per 1000 BN cells was not statistically significant as compared to HLNRA newborns (1.33 ± 0.04) per 1000 BN cells. Our data did not show any radiation dose response. Odds ratios (OR) and confidence intervals (CI) have been calculated to see statistical significance in the mean MN frequency among the newborns from various dose groups with respect to control and it did not reveal any significant difference (p > 0.05). A marginal increase in the frequency of micronuclei was observed among the female newborns as compared to males with increasing mothers' age groups except for the mothers aged > 30 years, though not statistically significant.Conclusion: The baseline frequency of micronuclei in HLNRA newborns is not statistically different from NLNRA newborns suggesting that elevated level of naturally occurring radiation has no significant effect on the induction of micronuclei frequency among the newborns.

Micronuclei frequency in peripheral blood lymphocytes of cancer patients: A meta-analysis

Micronuclei (MN) frequency is a biomarker of chromosomal damage, genome instability, and cancer risk that integrates acquired mutations and genetic susceptibility. To evaluate and summarize the evidence reporting association between cancer and MN formation, we performed a meta-analysis assessing the frequency of this biomarker in cancer patients. Findings from 37 publications were retrieved through an extensive search of the MedLine/PubMed database. Given the heterogeneity of the study design, all studies were re-classified into three groups: (i) baseline MN frequency of untreated cancer patients (25 studies), (ii) induced MN frequency in thyroid cancer patients undergoing radioiodine treatment (9 studies), and (iii) radiosensitivity of lymphocytes (12 studies) in untreated cancer patients. A meta-estimate of the frequency ratio (meta-FR) was computed in each group. A significant increase of MN frequency was found in untreated cancer patients (meta-FR=1.45; 95% Confidence Interval (95% CI): 1.28-1.64) and in thyroid cancer patients after radioiodine treatment (meta-FR=2.26; 95% CI: 1.90-2.68). The third meta-analysis showed a negative trend of meta-FR's when plotted vs. the dose used to study patients' radiosensitivity, possibly associated to a high rate of apoptosis. The results of this review substantiate the existing evidence about a role of MN in various steps of carcinogenesis. The relatively small numbers of papers suitable for the meta-analysis call for new and larger studies, possibly based on high-throughput techniques, to further understand the role of MN formation in the occurrence of genetic instability and cancer.

Basal level micronucleus frequency in stimulated lymphocytes of untreated patients with leukemia

Structural chromosomal aberrations have been described in various types of human leukemia. The micronucleus technique provides a measure of both chromosome breakage and chromosome loss. The present study investigated micronucleus (MN) frequency in mitogen-stimulated peripheral blood lymphocytes from 20 newly diagnosed and untreated leukemia patients: 4 with acute lymphoblastic leukemia (ALL), 10 with acute myeloid leukemia (AML), and 6 with chronic lymphocytic leukemia (CLL).The mean MN frequency for untreated patients was 3.65 ± 1.47 in ALL, 3.55 ± 1.24 in AML, 3.03 ± 1.05 in CLL. No differences in MN frequency were seen between leukemia types ALL, AML, and CLL ( P = 0.503). The mean basal MN frequency for all patients, regardless of leukemia type, was 3.41 ± 1.19, which was significantly higher ( P = 0.001) than that of 20 age-matched control subjects, 1.87 ± 0.75. Although no significant relationship was found between age and MN frequency in patients with leukemia ( r = 0.050; P = 0.835), the MN frequency in the lymphocytes of healthy control increased regularly and significantly with age ( r = 0.531; P = 0.016). These data indicate that the increased baseline MN frequency in lymphocytes of untreated patients with leukemia may reflect genomic instability or deficiency of DNA repair capacity. MN enhancement in this disease may thus be a consequence of the disease process.

Radiosensitivity of Peripheral Blood Lymphocytes in Patients with Genital Cancer

Purpose: To evaluate the in vitro radiation sensitivity of the peripheral blood lymphocytes obtained from genital cancer patients (n = 20) in comparison to healthy individuals (n=15). Materials and Methods: Chromosomal radiosensitivity was measured by the cytokinesis-blocked micronucleus (MN) assay. Unstimulated whole blood cultures were exposed in vitro to 2,5 Gy 60Co gamma rays delivered at a high dose-rate (HDR: 25 cGy / min) or low dose-rate (LDR: 0,25 cGy / min). Results: Spontaneous micronucleus frequencies (MNSP) in blood lymphocytes from patients and controls are not statistically different. Cancer patients group had a significantly higher mean baseline micronucleus frequency (p < 0,05) than normal healthy controls at LDR irradiation. After HDR irradiation, we observed no difference in radioinduced micronucleus frequency between the two studied groups of individuals. Conclusion: The results indicate that cancer patients were more radiosensitive than normal subjects at LDR irradiation. Enhanced radiosensitivity could be due to defects in DNA repair genes involved in genital cancer formation.