The micronucleus assay in human exfoliated cells of the nose and mouth: application to occupational exposures to chromic acid and ethylene oxide

We have applied the micronucleus (MN) assay to exfoliated cells of buccal and nasal cavities to monitor the genotoxic risk in a group of workers exposed to chromic acid and in another group exposed to ethylene oxide (EtO). The first group comprised 16 subjects working in a 'hard' type chrome-plating factory showing increased chromium absorption and chromium-induced rhinopathy. The second group comprised 9 subjects working in a sterilization unit, exposed to EtO concentrations lower than 0.38 ppm as timed weighted average (TWA) for a working shift; 3 of them were involved in a acute exposure too. The frequency of MN in buccal mucosa was within the norm for exposure both to chromium and to EtO. The MN frequency in nasal mucosa was not altered in chromium platers, whereas a significant increase (p less than 0.01) in MN was found in 2 out of 3 subjects involved in the accidental EtO leakage and a non-significant increase in MN was found in the group chronically exposed to EtO.     

The genotoxic potential of glutaraldehyde in mammalian cells in vitro in comparison with formaldehyde

Glutaraldehyde (GA) induces DNA-protein crosslinks (DPX), but conflicting results have been reported with regard to other genotoxic and mutagenic effects in mammalian cells in vitro. We, therefore, characterized the genotoxic and mutagenic potential of GA in V79 cells. Using the alkaline comet assay we demonstrated the induction of DPX by GA (reduction of gamma ray-induced DNA migration) at a concentration of 10 microM and above. The standard comet assay did not reveal a significant DNA strand-breaking activity of GA. Cross-linking concentrations of GA were also cytotoxic, i.e. inhibited cell growth of treated V79 cultures. Interestingly, a small but statistically significant increase in sister chromatid exchange (SCE) and micronuclei (MN) was already measured at lower concentrations (2 and 5 microM). FISH analysis revealed that the majority of GA-induced MN was due to chromosome breaks. We also compared the genotoxic activity of GA to that of formaldehyde (FA). Similar to GA, FA-induced DPX, SCE and MN, but distinct differences exist with regard to the sensitivity of the endpoints and the relationship between genotoxicity and cytotoxicity. However, the differences in genotoxicity cannot readily explain the different carcinogenic activities of the two compounds.     

Micronucleus induction and FISH analysis in buccal cells and lymphocytes of nurses administering antineoplastic drugs

A genotoxic effect for antineoplastic drugs, in particular micronucleus induction, has been shown in several studies. The aim of our study was to assess genotoxic effects in nurses administering different mixtures of antineoplastic drugs in an oncology hospital by evaluating the frequency of micronuclei in exfoliated buccal cells and blood lymphocytes by use of the standard micronucleus (MN) test and by identifying, by means of FISH analysis with centromeric probes, the mechanism of micronucleus induction (clastogenic or aneugenic). The study group comprised 23 nurses, 10 of whom worked in the day-care hospital and 13 in the ward. Twenty healthy subjects were selected as controls. Pan-centromeric FISH analysis was performed on lymphocytes from a selected group of nurses (12/23 subjects) characterized by higher MN frequencies as observed by standard Giemsa staining. A significant increase of micronucleus frequency compared with controls was found in exfoliated buccal cells of both groups of nurses: day-care hospital nurses 0.92 versus 0.45 (p=0.034) and ward nurses 0.94 versus 0.45 (p=0.051). An increase, although not statistically significant, of mean MN frequency was also found by the MN standard test on lymphocytes of the day-care hospital nurses (10.9 versus 7.5; p=0.056), while no differences were found in ward nurses (8.15 versus 7.5; p=0.56). We found that the administration of antineoplastic drugs by nurses in ward units induced a higher frequency of FISH MN+ (43% of subjects) than in the day-care hospital (20%). This was associated with the micronucleus size percentage. This finding could be correlated with the different compositions of administered mixtures of antineoplastic drugs: in ward units the mixtures contained drugs, such as vinorelbine, that were absent in the mixtures administered in the day-care hospital. Our results show genetic damage induced by administration of antineoplastic drugs, particularly in exfoliated buccal cells. This result suggests the useful application of this non-invasive sampling to evaluate genotoxic effects of occupational exposure to mixtures of inhalable chemicals at low doses.     

The implausibility of systemic genotoxic effects measured by the comet assay in rats exposed to formaldehyde

A recent publication reported genotoxic effects in the alkaline comet assay in lymphocytes and liver cells of rats exposed to formaldehyde (FA) by inhalation (Im,H.; et al. J. Proteome Res. 2006, 5, 1354-1366). Rats were exposed to 5 and 10 ppm FA for 2 weeks in inhalation chambers. A similar dose-related increase in DNA migration was measured in both cell types. These results are inconsistent with published data concerning FA toxicity: (i) Systemic genotoxic effects are reported, whereas previous animal experiments indicated only local effects. (ii) Similar effects were observed in liver cells and lymphocytes despite administration by inhalation. (iii) Increased DNA migration was measured, whereas FA-induced DNA-protein cross-links (DPX) should reduce DNA migration. These three aspects are critically discussed, and the plausibility of the results published by Im and colleagues is questioned.     

Inhalation of formaldehyde does not induce genotoxic effects in broncho-alveolar lavage (BAL) cells of rats

Male Fischer-344 rats were exposed to formaldehyde (FA) by inhalation for 4 weeks (6 h/day, 5 days/week). Groups of six rats each were exposed to the target concentrations of 0, 0.5, 1, 2, 6, 10 and 15 ppm. Potential genotoxic effects in the lung were investigated as part of a comprehensive study on local and systemic toxic and genotoxic effects. Broncho-alveolar lavage (BAL) cells were obtained by lung lavage with physiological saline and counted. From one half of the cells, slides for the micronucleus test (MNT) were prepared by cytocentrifugation; with the other half, the comet assay was performed. DNA migration in the comet assay was measured both directly and after irradiation of the cells with 2 Gy gamma-radiation. The latter modification of the comet assay was included to increase its sensitivity for the detection of DNA-protein cross-links (DPX). For the comet assay, four slides were analysed from each cell sample, two without and two with irradiation. From each slide, 50 randomly selected cells were measured by image analysis and tail intensity (% tail DNA) and tail moment were evaluated. The frequency of micronucleated BAL cells was determined in acridine orange-stained slides by analysing 2000 cells per animal. FA did not induce any significant effect in any of the genotoxicity tests performed. It can be concluded that inhalation of FA in a 28 days study with FA concentrations up to 15 ppm does not lead to genotoxic effects in BAL cells of rats. Because detection of DPX by the comet assay is a very sensitive biomarker of FA exposure of cells, our results suggest that there is no genetically relevant exposure of the lung after FA inhalation. The results of our inhalation study, which was performed under GLP conditions, call into question the biological significance of previously reported genotoxic effects in the lung of rats after FA inhalation.     

Analysis of micronuclei, histopathological changes and cell proliferation in nasal epithelium cells of rats after exposure to formaldehyde by inhalation

The frequencies of micronuclei (MN), histopathological changes and cell proliferation were determined in the nasal epithelium of male Fischer-344 rats after exposure to formaldehyde (FA) by whole-body inhalation for four weeks (6h/day, 5 days/week). Groups of 12 rats each were exposed to the target concentrations of 0, 0.5, 1, 2, 6, 10 and 15ppm. The micronucleus test (MNT) was performed with nasal epithelial cells prepared from six animals per group. Two thousand cells per animal were analysed for the presence of MN. The other six rats per group were subcutaneously implanted with osmotic pumps containing 5-bromo-2'-deoxyuridine (BrdUrd), three days prior to necropsy. Paraffin sections were made from the nasal cavity (four levels) of these animals for histopathology and cell-proliferation measurements. The frequency of cells with MN was not increased in any of the groups. However, there was also no induction of MN in nasal cells of rats exposed to a single dose of cyclophosphamide (CP, 20mg/kg) by gavage and analysed 3, 7, 14 or 28 days after the treatment. In contrast, nasal epithelial cells from rats exposed to 10 or 15ppm FA vapour showed clear site-specific pathological changes (focal epithelial degeneration, inflammation and squamous metaplasia) in a decreasing gradient (anterior to posterior). Analysis of slides after anti-BrdUrd antibody staining clearly indicated increased cell proliferation (unit length labelling indices, ULLI) after exposure to 6ppm and higher. No treatment-related effects were measured after exposure to 0.5, 1 and 2ppm. When comparing the cell-proliferation rate of normal epithelium with that of directly adjacent metaplastic epithelium, no consistent pattern was found: depending on the location, cell proliferation of normal epithelia was either higher or lower. Our results support previous findings demonstrating local cytotoxic effects in the nose of rats after inhalation of FA. However, induction of MN in the nasal epithelium as an indicator of a mutagenic effect was not seen. Because only limited experience exists for the MNT with rat nasal epithelial cells, this result has to be interpreted with great care. The contribution of mutagenicity to FA's carcinogenicity in rat nasal epithelium remains unclear.     

Occupational genotoxicity risk evaluation through the comet assay and the micronucleus test

The micronucleus (MN) test and the alkaline single cell gel or comet assay were applied to exfoliated cells of the buccal mucous in order to evaluate the genotoxic risk associated with occupational exposure of 10 storage battery renovation workers, and 10 car painters, with age matched controls, in Pelotas, RS, in southern Brazil. In the MN test, 2000 exfoliated buccal cells were analyzed for each individual, while 100 cells were examined in the comet assay. In the comet test, both comet tail length and a damage index were calculated. Highly significant effects of occupational exposure were found with both the MN test and the comet assay (P<0.001). The comet assay was found to be rapid, of simple visualization, and it is a sensitive technique for measuring and analyzing DNA damage in human cells.     

EVALUATION OF FREQUENCY OF MICRONUCLEI IN EXFOLIATED CELLS FROM BLADDER OF MICE TREATED WITH BENZO(A)PYRENE, 2-ACETYLAMINOFLUORENE AND CYCLOPHOSPHAMIDE

The micronucleus test (MNT) was applied in the epithelial cells from the bladder of mice treated with benzo(a)pyrene (BaP), 2-acetylaminofluorene (2-AAF) and cyclophosphamide (CP). Micronuclei (MN) were scored at different time on Feulgen and fast green stained smear preparations of exfoliated cells. These cells were obtained by scraping the internal surface of the bladder. The tested compounds gave the maximal response at 7-10 days after treatment. The number of MN in epithelial cells was dose dependent. These results suggest that exfoliated bladder cells from mice can be used as indicators for genotoxic damage in proliferating cell populations.     

Nuclear anomalies in the buccal cells of calcite factory workers

The micronucleus (MN) assay on exfoliated buccal cells is a useful and minimally invasive method for monitoring genetic damage in humans. To determine the genotoxic effects of calcite dust that forms during processing, MN assay was carried out in exfoliated buccal cells of 50 (25 smokers and 25 non-smokers) calcite factory workers and 50 (25 smokers and 25 non-smokers) age- and sex-matched control subjects. Frequencies of nuclear abnormalities (NA) other than micronuclei, such as binucleates, karyorrhexis, karyolysis and 'broken eggs', were also evaluated. Micronuclei and the other aforementioned anomalies were analysed by two way analysis of covariance. The linear correlations between the types of micronucleus and nuclear abnormalities were determined by Spearman's Rho. There was a positive correlation between micronuclei and other types of nuclear abnormalities in accordance with the Spearman's Rho test. Results showed statistically significant difference between calcite fabric workers and control groups. MN and NA frequencies in calcite fabric workers were significantly higher than those in control groups (p < 0.05). The results of this study indicate that calcite fabric workers are under risk of significant cytogenetic damage.     

Cytogenetic effects of hexavalent chromium in Bulgarian chromium platers

The aim of the present study was to evaluate the genotoxic effects of hexavalent chromium (Cr(VI)) in vivo in exposed Bulgarian chromium platers by using classical cytogenetic and molecular cytogenetic analyses of peripheral lymphocytes and exfoliated buccal cells. No significant difference was observed between the exposed workers and the controls with regard to the frequency of cells with chromosome aberrations (CAs) using conventional Giemsa staining and in the frequency of sister chromatid exchanges (SCEs). However, there was a significant increase in the number of cells with micronuclei (MN) in peripheral lymphocytes from chromium exposed workers as compared to the controls. In the buccal cells from these workers, this increase was even more pronounced. Cytosine arabinoside (AraC), an inhibitor of DNA synthesis and repair, was found to significantly increase the levels of MN in vitro in the lymphocytes of both groups. The increase was more expressed in the lymphocytes of chromium exposed workers. Both centromere positive (C(+)) as well as centromere negative (C(-)) MN were observed by the fluorescence in situ hybridization (FISH) technique in both of the cell types studied. No difference between C(+) and C(-) MN frequencies was found in the lymphocytes as well as in the buccal cells. Thus, Cr(VI) appears to have both clastogenic as well as aneugenic effects in humans.     

Is individual nasal sensitivity related to cellular metabolism of formaldehyde and susceptibility towards formaldehyde-induced genotoxicity?

Forty-one volunteers (male non-smokers, aged 32 ± 9.6yrs) were tested for susceptibility towards unspecific nasal irritation (sensitivity towards CO(2)) in order to define subgroups of hypersensitive and hyposensitive subjects. Blood samples were taken and the expression (mRNA level) of the GSH-dependent formaldehyde dehydrogenase gene (FDH, identical to alcohol dehydrogenase 5, ADH5; EC 1.2.1.46) was measured in leukocytes by quantitative real-time RT-PCR with TaqMan probes. FDH is the most important enzyme for the metabolic inactivation of FA. Blood samples were exposed to 150μM formaldehyde (FA) for 2h and the induction of DNA-protein crosslinks (DPX) in leukocytes was measured by means of a modification of the alkaline comet assay (i.e., by assessing the reduction of DNA migration induced by γ-radiation). Removal of DPX was determined by the abolition of FA-induced reduction in DNA migration within 4h after the end of the exposure. Furthermore, the induction of sister chromatid exchange (SCE) in cultured lymphocytes was studied after treatment of whole blood cultures with FA (150μM). A correlation analysis was performed for all parameters tested for the whole study group and for hypersensitive and hyposensitive subgroups. The results indicate that despite large differences in CO(2)-sensitivity, the susceptibility towards nasal irritation was not related to the induction of genotoxic effects (DPX, SCE) in peripheral blood or to the protection of blood cells against FA-induced effects (expression of FDH, repair capacity for FA-induced DPX). There was no correlation between CO(2)-sensitivity and the expression of FDH. There was also no close correlation between the various indicators of cellular sensitivity towards FA-induced genotoxic effects and no subgroups were identified with particular mutagen sensitivity towards FA.     

Cytogenetic analysis of nasal mucosa cells and lymphocytes from high-level long-term formaldehyde exposed workers and low-level short-term exposed waiters

The evidence for genotoxic potential of formaldehyde (FA) in humans is insufficient and conflicting. We previously reported a higher frequency of micronuclei in nasal and oral exfoliative cells from students exposed to formaldehyde vapor for short-term. To further evaluate the genetic effects of long-term occupational exposure to FA and short-term exposure to FA of indoor sources, the frequencies of micronuclei (MN) in nasal mucosa cells, sister chromatid exchanges (SCEs) of peripheral lymphocytes, and the lymphocyte subsets were evaluated in 18 non-smoking workers (mean exposure duration was 8.6 years) in an FA factory and 16 non-smoking waiters exposed to FA for 12 weeks in a ballroom. A non-smoking student group without occupational exposure (n=23) to FA was used as control. The 8h time-weighted average (TWA) concentrations of formaldehyde was 0.985+/-0.286 mg/m3 with the ceiling exposure concentration of 1.694 mg/m3 in the workshop, and 0.107+/-0.067 mg/m3 in the ballroom (5 h TWA). Higher frequencies of micronuclei per thousand cells in nasal mucosa cells of workers versus control (2.70+/-1.50 versus 1.25+/-0.65, p<0.05) and higher frequency of SCEs in peripheral lymphocytes of workers group (8.24+/-0.89 versus 6.38+/-0.41, p<0.05) were observed. Increased frequency of micronuclei in nasal mucosa cells or SCE in peripheral lymphocytes was not found among waiters group. The results suggest that the genotoxic potential of high level FA exposure may have occupational risks in long-term exposure groups.     

Micronuclei level in exfoliated buccal mucosa cells of patients with benign and malignant tumors of female reproductive organs and breast

Micronucleus (MN) levels in exfoliated buccal mucosa cells of primary breast, cervix and corpus uteri cancer patients, and patients with benign tumors of uterus (myoma) and breast (fibroadenoma) were studied. Significantly increased number of MN in cells of cancer patients was observed compared to both healthy persons and patients with benign tumors. In patients with benign tumors no increase in MN quantity was observed. The evaluation of MN number in buccal mucosa cells shows genomic instability caused by malignant tumor in somatic cells of humans.     

Measurement and characterization of micronuclei in exfoliated human cells by fluorescence in situ hybridization with a centromeric probe

The micronucleus (MN) assay in human exfoliated cells has been widely used to detect the genotoxic effects of environmental mutagens, infectious agents and heriditary diseases. Substantial variability characterizes the MN frequencies reported by different research groups. One reason for this may be the restricted resolution power of the Feulgen-Fast-Green staining that is routinely used. Here we describe a new version of the MN assay that employs fluorescent propidium iodide staining along with fluorescence in situ hybridization (FISH) with a centromeric probe. Buccal and urothelial cells were collected from 5 healthy unexposed female volunteers and 55 000 cells analyzed for MN frequency and abnormal nuclear events. The Feulgen-Fast-Green and the new fluorescent staining produced very similar results. The frequency of MN in buccal cells was 0.145±0.118% and in urothelial cells 0.083±0.074%. No correlation was found between the frequencies of MN in the two types of exfoliated cells. FISH with a centrometric probe allowed MN containing whole chromosomes with a centromere to be differentiated from those containing only acentric fragments. The former appear as a result of chromosome lagging in mitosis, while those without a centromere are due to chromosome breakage. In urothelial cells 43% of MN were centromere-negative and in buccal cells — 44%. Fluorescent staining provided more accurate scoring of degenerative cells than standard Feulgen-Fast-Green staining. The combined frequency of pycnotic cells, “broken eggs” and cells with fragmented nuclei did not exceed 2%, while that of karyorrhexis and karyolysis together was as high as 21%. Significant interindividual variability was found in the frequency of cells with karyolysis and karyorrhexis. Thus, the new version of micronucleus assay allows for MN to be scored more precisely, the mechanism of MN formation to be determined and abnormal nuclear events to be readily identified in exfoliated human cells. It is therefore ideal for studying genotoxicity in human populations using exfoliated cells from the mouth, bladder and nose.     

Low sensitivity of the comet assay to detect acetaldehyde-induced genotoxicity

Acetaldehyde (AA) is known to induce DNA-protein cross-links (DPX) and other genotoxic and mutagenic effects in cultured mammalian cells. Compared to formaldehyde (FA), AA is a very weak inducer of DPX and increased DPX levels are only measured at high, cytotoxic concentrations by different methods. Besides DPX, AA also induces DNA-DNA cross-links. Because the comet assay is increasingly used for the detection of cross-linking agents, we characterized the effects of AA in the comet assay in relation to cytotoxicity and other genetic endpoints such as the induction of sister chromatid exchange (SCE) and micronuclei (MN). The standard alkaline comet assay did not indicate induction of DNA strand-breaks by AA in a range of concentrations from 0.2 to 20 mM. AA at a concentration of 20 mM was clearly cytotoxic and reduced cell growth and population doubling to less than 50% of the control. Using the comet assay modification with proteinase K, slightly enhanced DNA migration was measured in comparison to treatment with AA only. No significant induction of cross-links by AA (measured as reduction of gamma ray-induced DNA migration) was determined by the comet assay. A small and reproducible but statistically not significant effect was measured for the AA concentration 20 mM. A clear and concentration-related increase in the frequency of sister chromatid exchange (SCE) and micronuclei (MN) was already measured at lower concentrations (0.2 and 0.5 mM, respectively). These results suggest that the comet assay has a low sensitivity for the detection of AA-induced DNA lesions leading to the induction of SCE and MN.     

The micronucleus assay in exfoliated buccal cells: application to occupational exposure to polycyclic aromatic hydrocarbons.

Many polycyclic aromatic hydrocarbons (PAHs) have been identified as cancer-inducing chemicals for animals and/or humans. Also, there is sufficient evidence that exposures in the occupational settings are carcinogenic or probably carcinogenic to human. Engine exhaust and used engine oils are major PAH sources in engine repair workshops and traffic. Analysis of micronucleus (MN) in exfoliated buccal cells is a sensitive method for monitoring genetic damage in human populations. In our study, we used three different occupational groups (Group 1; engine repair workers, Group 2; taxi drivers, Group 3; traffic police) and two controls (Control I for Group 1 and Control II for Group 2 and Group 3) for the exposed groups. We analysed MN frequencies in exfoliated buccal cells and compared the exposed groups (Group 1; n=34, Group 2; n=17, Group 3; n=15) and subjects not occupationally exposed to PAH (Control I; n=28, Control II; n=20). The mean (+/-S.D.) MN (%) frequencies in exfoliated buccal cells from Group 1 and Control I were 0.07+/-0.05 and 0. 05+/-0.04, respectively (p>0.05; Table 2). The mean (+/-S.D.) MN (%) frequencies in exfoliated buccal cells from Group 2, 3 and Control II were 0.12+/-0.05, 0.10+/-0.05 and 0.03+/-0.03, respectively (p<0. 0001, p<0.05; Table 2) Smokers and nonsmokers do not differ with respect to the incidence of MN in all groups.     

Cytogenetic analysis of buccal cells from shoe-workers and pathology and anatomy laboratory workers exposed to n-hexane, toluene, methyl ethyl ketone and formaldehyde.

People employed in the shoe manufacture and repair industry are at an increased risk for cancer, the strongest evidence being for nasal cancer and leukaemia. A possible causal role for formaldehyde is likely for cancer of the buccal cavity and nasopharynx. Exfoliated buccal cells are good source of tissue for monitoring human exposure to inhaled and ingested occupational and environmental genotoxicants. To assess the cytogenetic damage related to occupational exposure to airborne chemicals during shoe-making and the processes in pathology and anatomy laboratories, the micronuclei (MN) count per 3000 cells was measured in buccal smears from shoe-workers (group I, n = 22) exposed to mainly n-hexane, toluene and methyl ethyl ketone (MEK) and from anatomy and pathology staff (group II, n = 28) exposed to formaldehyde (FA). Eighteen male university staff were used as controls. The mean time-weighted average (TWA) concentrations of n-hexane, toluene and MEK in 10 small shoe workshops were 58.07 p.p.m., 26.62 p.p.m. and 11.39 p.p.m., respectively. The measured air concentrations of FA in the breathing zone of the anatomy and pathology laboratory workers were between 2 and 4 p.p.m. Levels of 2,5-hexadione (2,5-HD) and hippuric acid (HA), metabolic markers of n-hexane and toluene exposure, respectively, were significantly higher in the urine of workers in group I than in control subjects (p < 0.001 and p < 0.01, respectively). The mean (+/- SD) MN (0/00) [corrected] frequencies in buccal mucosa cells from workers in group I, group II and controls were 0.62 +/- 0.45%, 0.71 +/- 0.56% and 0.33 +/- 0.30%, respectively (p < 0.05 and p < 0.05 compared with controls for group I and group II, respectively). The effects of smoking, age and duration of exposure on the frequency of micronucleated buccal cells from workers in all three groups studied were also evaluated. Overall, the results suggest that occupational exposure to organic solvents, mainly n-hexane, toluene, MEK and FA, may cause cytogenetic damage in buccal cells and that use of exfoliated buccal cells seems to be appropriate to measure exposure to organic solvents.     

The micronucleus assay in human buccal cells as a tool for biomonitoring DNA damage: the HUMN project perspective on current status and knowledge gaps

The micronucleus (MN) assay in exfoliated buccal cells is a useful and minimally invasive method for monitoring genetic damage in humans. This overview has concluded that although MN assay in buccal cells has been used since the 1980s to demonstrate cytogenetic effects of environmental and occupational exposures, lifestyle factors, dietary deficiencies, and different diseases, important knowledge gaps remain about the characteristics of micronuclei and other nuclear abnormalities, the basic biology explaining the appearance of various cell types in buccal mucosa samples and effects of diverse staining procedures and scoring criteria in laboratories around the world. To address these uncertainties, the human micronucleus project (HUMN; see http://www.humn.org) has initiated a new international validation project for the buccal cell MN assay similar to that previously performed using human lymphocytes. Future research should explore sources of variability in the assay (e.g. between laboratories and scorers, as well as inter- and intra-individual differences in subjects), and resolve key technical issues, such as the method of buccal cell staining, optimal criteria for classification of normal and degenerated cells and for scoring micronuclei and other abnormalities. The harmonization and standardization of the buccal MN assay will allow more reliable comparison of the data among human populations and laboratories, evaluation of the assay's performance, and consolidation of its world-wide use for biomonitoring of DNA damage.     

Use of the micronucleus assay with exfoliated epithelial cells as a biomarker for monitoring individuals at elevated risk of genetic damage and in chemoprevention trials.

This review summarises the current database on the micronucleus (MN) assay with exfoliated cells (MEC assay) and evaluates the predictive value of this model for the detection of human cancer risks. The MEC test is a cost effective, non-invasive method, in which the formation of MN in exfoliated cells from different organs, such as oral and nasal cavity, bladder, cervix, and oesophagus is used as an endpoint to detect endogenous, lifestyle, occupational and environmental exposures to genotoxins as well as chemoprotection of various compounds in intervention studies. The results suggest that the MN assay might be a useful approach to identify antimutagens which are protective in humans. Based on the comparison of the data from MN experiments with results from epidemiological cancer studies, we conclude that the MEC assay is a useful biomarker for the detection of human cancer risk in organs to which the MEC test can be applied. However, the current data base is not sufficient to draw a firm conclusion on the specificity of this approach.     

Biomonitoring of the cytogenetic effect of antitumor therapy by means of micronucleus assay in exfoliated epithelial cells

Data are presented concerning the possibility of using the micronuclei (MN) level as a biomarker for cytogenetic effects in exfoliated epithelial cells of cancer patients under therapy. The number of MN in buccal cells of cancer patients under chemotherapy are very contradictory. A significant dose-dependent increment of MN in tumor and normal epithelial cells due to radiotherapy was shown in most investigations. Evaluation of MN induced by radiotherapy in exfoliated tumor cells can potentially identify the radiosensitivity of tumors and the outcome of treatment after the first fractions of irradiation. This technique is almost completely noninvasive and easily done in accessible primary cancers (oral cavity and uterine cervix). The text was submitted by the author in English.