Micronucleus Count Research Articles

Development of a dual-cure mineral trioxide aggregate-based cement: Biological, physical, and mechanical properties.

Purpose:The purpose of this study is to compare the physical, mechanical, and biocompatibility properties of a new dual-cure white mineral trioxide aggregate (D-W-MTA) and a commercial W-MTA.Materials and Methods:Diametral tensile strength (DTS), water sorption (WSp), and water solubility (WSl) tests were performed. Cytotoxicity was observed in primary culture of human pulp fibroblasts (HPFs) and mouse 3T3/NIH fibroblast lineage. Specimens of both materials were embedded in 1 mL of Dulbecco's modified essential medium for 24 h. Cells were incubated for 24 h with the eluates. Cytotoxicity was evaluated by the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay and genotoxicity by micronucleus (MN) formation. Data were analyzed by ANOVA and Kruskal–Wallis tests considering P < 0.05.Results:D-MTA and W-MTA not showed cytotoxic effect on the two cell lines. However, D-MTA stimulated HPF growth. The MN count was similar to that of the control group for D-MTA and W-MTA. D-MTA presented lower DTS and WSl. Nevertheless, WSp was similar in the two groups.Conclusion:The results suggest that D-MTA is a promising material for pulp capping. Thus, in vivo tests should be performed to evaluate the performance of this material.

Evaluation of cytogenic damage in the form of micronuclei in oral exfoliated buccal cells in tobacco users.

Variety of substances such as tobacco, UV radiation, infrared rays, X-radiations, and chemicals on oral induction results in chromosomal aberrations and production of micronucleus (MN). Among them, tobacco-specific nitrosamines are potent mutagenic agents causing oral cancer. The objective of the study is to compare the genotoxicity in buccal mucosal cells, i.e. the MN count of all groups and to find the incidence of micronucleated cells (MNCs) in accordance to duration and frequency of tobacco usage and timing of contact of tobacco in the oral mucosa. Individuals without any oral diseases were divided into 3 groups having 25 in each group: smoking, chewing, and control. Smears were made from buccal exfoliated cells and stained with DNA-specific Feulgen stain. Frequency on MNC per 500 cells was assessed with one-way ANOVA and Tukey HSD multiple comparisons test and mean rank with Kruskal-Wallis test. The mean micronucleus MN revealed that chewers had 8.00, smokers had 7.20 and controls had 0.4. The ANOVA test for mean frequency of micronucleated cell MNC revealed High significance (<0.001) for between groups comparison. The mean rank by Kruskal Wallis test revealed the MNC increases as the duration and frequency of habit increases. An increase in MNC in accordance to time of contact with buccal mucosa increases as the duration and time increases. Estimation of MN serve as an indicator of genetic damage and points that tobacco in chewing form induce genotoxic effect. This is studied in an easily accessible tissue- buccal mucosa in a non invasive manner.

Micronucleus Assay in Urothelial Cells in Cancer Cervix.

Cancer ranks third among the ten leading global causes of death. To evaluate the genotoxic risks, observed as DNA damages, can be assessed by Micronucleus (MN) test. To identify the occurrence of MN in normal and cancer cervix and find the correlation between MN and stage of cancer. A total of 60 females were included in the study and visual examination of the cervix was done. Based on the examination two groups were formed: A- Normal cervix (n-23) and B- Presence of erosion or growth or ulcer etc., in cervix (n-37). Midstream urine sample was collected and centrifuged from the cases after getting the informed consent. Slides were prepared from the pellet, were fixed in methanol, glacial acetic acid fixative and stained with Giemsa and May Grunwald stain. Statistical analysis was done by student's t-test and chi-square test. A linear association was noted between the mean MN count and cancer cervix stage. Almost 18.2% of the Group A cases had significant MN count. Sensitivity and specificity of MN count in Group A was 83.8% and 82.6% respectively. The efficiency was 83.3%. A statistically significant MN count was seen in the different stages of cancer cervix. There are cases who had normal findings on visual inspection of cervix but with significant MN count are prone for malignant transformation. MN assay is an easy, non-invasive, cost-effective method and can be used as a screening test for a large population.

Evaluation of Micronuclei in Buccal Mucosa – Comparing Smokers And Non Smokers

According to WHO over 1 billion people are associated with tobacco smoking and it accounts for approximately 4 - 5 million deaths a year worldwide which is estimated to increase to 10 million by 2030. Tobacco is a known causative agent in numerous cancers one of the major being oral cancer. Buccal mucosal cells are easily accessible and their response to the carcinogenic substances in cigarette can be studied easily for risk assessment with the help of a biomarker. Biomarker is a measurable DNA and RNA characteristic that can help study biologic and pathologic damage. Micronucleus count is a potentially useful candidate for such a biomarker. Micronuclei are fragments or whole chromosomes which did not reach spindle poles during mitosis and remain encapsulated at telophase in a separate nucleus. This study showed the usefulness of micronuclei for risk assessment due to genotoxic damage in smokers in comparison to non smokers. Not only was a significant increase in micronuclei found in smokers but also an increase in micronuclei with respect to age , duration of exposure and frequency of exposure was observed. Our study concludes that post standardization micronuclei may be used as screening tool for oral cancers.

Cytogenetic effects of radioiodine therapy: a 20-year follow-up study

The purpose of this study was to compare cytogenetic data in a patient before and after treatment with radioiodine to evaluate the assays in the context of biological dosimetry. We studied a 34-year-old male patient who underwent a total thyroidectomy followed by ablation therapy with (131)I (19.28 GBq) for a papillary thyroid carcinoma. The patient provided blood samples before treatment and then serial samples at monthly intervals during the first year period and quarterly intervals for 5 years and finally 20 years after treatment. A micronucleus assay, dicentric assay, FISH method and G-banding were used to detect and measure DNA damage in circulating peripheral blood lymphocytes of the patient. The results showed that radiation-induced cytogenetic effects persisted for many years after treatment as shown by elevated micronuclei and chromosome aberrations as a result of exposure to (131)I. At 5 years after treatment, the micronucleus count was tenfold higher than the pre-exposure frequency. Shortly after the treatment, micronucleus counts produced a dose estimate of 0.47 ± 0.09 Gy. The dose to the patient evaluated retrospectively using FISH-measured translocations was 0.70 ± 0.16 Gy. Overall, our results show that the micronucleus assay is a retrospective biomarker of low-dose radiation exposure. However, this method is not able to determine local dose to the target tissue which in this case was any residual thyroid cells plus metastases of thyroidal origin.

Treatment of cosmetic effluent in different configurations of ceramic UF membrane based bioreactor: Toxicity evaluation of the untreated and treated wastewater using catfish (Heteropneustes fossilis).

Extensive usage of pharmaceutical and personal care products (PPCPs) and their discharge through domestic sewage have been recently recognized as a new generation environmental concern which deserves more scientific attention over the classical environmental pollutants. The major issues of this type of effluent addressed in this study were its colour, triclosan and anionic surfactant (SDS) content. Samples of cosmetic effluent were collected from different beauty treatment salons and spas in and around Kolkata, India and treated in bioreactors containing a bacterial consortium isolated from activated sludge samples collected from a common effluent treatment plant. Members of the consortium were isolated and identified as Klebsiella sp., Pseudomonas sp., Salmonella sp. and Comamonas sp. The biotreated effluent was subjected to ultrafiltration (UF) involving indigenously prepared ceramic membranes in both side-stream and submerged mode. Analysis of the MBR treated effluent revealed 99.22%, 98.56% and 99.74% removal of colour, triclosan and surfactant respectively. Investigation of probable acute and chronic cyto-genotoxic potential of the untreated and treated effluents along with their possible participation in triggering oxidative stress was carried out with Heteropneustes fossilis (Bloch). Comet formation recorded in both liver and gill cells and micronucleus count in peripheral erythrocytes of individuals exposed to untreated effluent increased with duration of exposure and was significantly higher than those treated with UF permeates which in turn neared control levels. Results of this study revealed successful application of the isolated bacterial consortium in MBR process for efficient detoxification of cosmetic effluent thereby conferring the same suitable for discharge and/or reuse.

Comparative Evaluation of Micronuclei in Exfoliated Urothelial Cells in Patients with Smoking and Smokeless Tobacco-associated Lesions: A Prospective Quantitative Study

ABSTRACTObjectiveTo clinically evaluate various tobacco-associated lesions and to evaluate and compare the micronucleus (MN) assay in exfoliated urothelial cells in patients with smoking and smokeless tobacco-associated lesions.Materials and MethodsThis study was conducted in the Department of Oral Pathology and Microbiology, Mahatma Gandhi Mission's Dental College and Hospital, Navi Mumbai, from October 2012 to June 2013. One hundred cases having tobacco habits (smoking or smokeless) and clinically detectable tobacco-associated lesions were included. Exfoliated urothelial cytosmears were prepared, stained with Papanicolaou and slides were scored for MN.ResultsAll cases (n = 100) were found to have tobaccoassociated lesions that were clinically detectable. Voided urine samples were collected from all cases (n = 100) who indulged in smoking and smokeless tobacco habit, with males (n = 71) and females (n = 29), whose ages ranged from 19 to 75 years. We observed that out of the 100 cases evaluated, 12 cases showed the presence of MN in the urine cytosmear. Of these 12 cases, n = 10 were bidi smokers and n = 2 were betel quid chewers. Owing to insufficient population of urothelial cells in the cytosmear, MN evaluation could not be statistically proved.ConclusionAlthough, MN score in the urothelial cells could not be statistically assessed, due to insufficient number of urothelial cells, our observations reveal that MN count seems to be increased in smokers than smokeless tobacco users. Thus, we urge the need for further studies to highlight the comparative evaluation of MN score between smokers and smokeless tobacco on urothelial cells.How to cite this articleIyer JS, Pathak J, Patel S, Poonja L, Swain N. Comparative Evaluation of Micronuclei in Exfoliated Urothelial Cells in Patients with Smoking and Smokeless Tobacco-associated Lesions: A Prospective Quantitative Study. J Contemp Dent 2015;5(2):93-97.

Role of micronucleus in oral exfoliative cytology.

In the last few years, the interest for oral cytology as a diagnostic and prognostic methodology, for monitoring patients in oral potentially malignant disorders and oral cancer has re-emerged substantially. In 1983, buccal mucosal micronuclei assay was first proposed to evaluate genetic instability. There are biomarkers that predict if a potentially malignant disorder is likely to develop into an aggressive tumor. These genotoxic and carcinogenic chemicals have been reported to be potent clastogenic and mutagenic agents which are thought to be responsible for the induction of chromatid/chromosomal aberrations resulting in the production of micronuclei. Various studies have concluded that the gradual increase in micronucleus (MN) counts from normal oral mucosa to potentially malignant disorders to oral carcinoma suggested a link of this biomarker with neoplastic progression. MN scoring can be used as a biomarker to identify different preneoplastic conditions much earlier than the manifestations of clinical features and might specifically be exploited in the screening of high-risk population for a specific cancer. Hence, it can be used as a screening prognostic and educational tool in community centers of oral cancer.

Assessing the suitability of 8-OHdG and micronuclei as genotoxic biomarkers in chromate-exposed workers: a cross-sectional study

ObjectivesWe aimed to investigate suitable conditions of 8-hydroxy-2′-deoxyguanosine (8-OHdG) and micronucleus (MN) as genotoxic biomarkers at different levels of occupational chromate exposure.DesignA cross-sectional study was used.Participants84 workers who were exposed...

Estimation of Genotoxic Effects from GSM Base Stations on Four Successive Generations (F1 F4) of Albino Mice, Mus Musculus Using RAPD Bands and Micronucleus Assay

The levels of radiofrequency radiations from the telecommunication base station and its potential genotoxic effects on DNA content and micronucleus induction in four generations of albino mice, Mus musculus were carried out. The level of radiofrequency radiations around the GSM base station ranged between 1.3 - 2.0⇥ 10 3 µW/m 2 respectively. The genotoxic effects of radiofrequency radiation on four mice generations were based on random amplified polymorphic DNA (RAPD) and gel electrophoresis, results showed gradual depreciation in DNA band intensity of exposed mice across generations when compared to control groups. The micronucleus assay using acridine orange stain showed increased in micronucleus count and cytotoxic effects on exposed mice being significantly (PCE/NCE P<0.05) higher when compared to the control . Statistical analysis also revealed that significant genotoxic effects were induced (p<0.05) in exposed mice compared with control over the four generations,the results indicated that the RAPD and micronucleus assay could be a suitable bio-molecular marker for the detection of potential long-term genotoxic effects of radiofrequency radiations on exposed mammalian organisms.

Comparative Study of Genotoxicity in Different Tobacco Related Habits using Micronucleus Assay in Exfoliated Buccal Epithelial Cells.

Oral cancer is one of the most debilitating diseases afflicting mankind. Consumption of tobacco in various forms constitutes one of the most important etiological factors in initiation of oral cancer. When the focus of today's research is to determine early genotoxic changes in human cells, micronucleus (MN) assay provides a simple, yet reliable indicator of genotoxic damage. To identify and quantify micronuclei in the exfoliated cells of oral mucosa in individuals with different tobacco related habits and control group, to compare the genotoxicity of different tobacco related habits between each group and also with that of control group. In the present study buccal smears of 135 individuals with different tobacco related habits & buccal smears of 45 age and sex matched controls were obtained, stained using Giemsa stain and then observed under 100X magnification in order to identify and quantify micronuclei in the exfoliated cells of oral mucosa. The mean Micronucleus (MN) count in individuals having smoking habit were 3.11 while the count was 0.50, 2.13, and 1.67 in normal control, smoking with beetle quid and smokeless tobacco habit respectively. MN count in smokers group was 2.6 times more compared to normal controls. MN count was more even in other groups when compared to normal control but to a lesser extent. From our study we concluded that tobacco in any form is genotoxic especially smokers are of higher risk and micronucleus assay can be used as a simple yet reliable marker for genotoxic evaluation.

Predictive value of micronucleus count in cervical intraepithelial neoplasia and carcinoma

A micronucleus is a small additional nucleus formed due to chromosomal loss or fragmentation. The aim of this study was to assess the utility of micronucleus count as a screening tool in cervical cancer. A total of 132 cases consisting of 42 pre-neoplastic and neoplastic cases and 90 non-neoplastic cases were studied. Only routine Papanicolaou-stained cervical smears were used. In each smear, the number of micronucleated cells and binucleated cells were counted under oil immersion and expressed as a count per 1,000 cells. The micronucleated and binucleated cell counts in pre-neoplastic, neoplastic and non-neoplastic categories were compared for statistical significance. The counts were also correlated with age, duration of marital life, number of pregnancies and abortions. The micronucleus count and the binucleated cell count were significantly higher in the high -grade squamous intraepithelial lesion (HSIL) and invasive carcinoma categories compared to low -grade squamous intraepithelial lesion (LSIL) and non-neoplastic cases. Receiver operating characteristic (ROC) curve analysis revealed that micronucleus count and binucleated cell count possess a high degree of sensitivity and specificity for identifying HSIL and invasive carcinoma. Our results reveal that micronucleus evaluation in routine Pap smears is a very useful biomarker in cervical cancer screening. The binucleated cell count increases the predictive value of this simple test.

Microcystin bioaccumulation can cause potential mutagenic effects in farm fish

This study investigated the bioaccumulation of microcystin and its potential mutagenic effects in cage-reared fish. For six months, three reservoirs (Acauã, Cordeiro and Camalau) in arid regions of Brazil were monitored. After five months, 10 fish (Oreochromis niloticus) were collected from each tank, and the amounts of microcystin in their muscles and viscera were analysed. Mutagenic effects were also evaluated. Species of cyanobacteria were present during all months of our study. The highest biovolume of cyanobacteria and microcystin in water occurred in the Acauã Reservoir; this was followed by Cordeiro and Camalau. All fish sampled contained microcystin, ranging from 16.01 to 37.09ngg−1 in muscle and 228.2–804.0μgg−1 in liver. We observed significant differences between the micronucleus count in experimental and control fish (p<0.05), suggesting a potential mutagenetic effect in the experimental fish. In all reservoirs, the fish microcystin level was well above the World Health Organization (WHO) tolerable daily intake, indicating a serious risk to consumers.

Daño celular en una población infantil potencialmente expuesta a pesticidas

ABSTRACT Cell damage in a pediatric population potentially exposed to pesticidas Introduction: Pesticides can cause acute or chronic effects on human health. Many pesticides can cause da-mage to genetic material. These changes in genetic information have been associated with an increased risk of cancer. Objective: To investigate damage to genetic material in a population of children potentially expo-sed to pesticides in the environment. Method: The study design was observational and cross sectional. We studied 48 children potentially exposed to pesticides and 46 unexposed children. Samples of the oral mucosa were obtained to determine damage to genetic material using micronucleus frequency (MN). Results: Higher average micronucleus counts were found in the group potentially exposed to pesticides (5.1 ± 2.9 vs 1.8 ± 2.0, p < 0.0001), along with a higher average of binucleate cells (3.5 ± 2.7 vs 1.4 ± 1.4 p < 0.0001), higher frequen-cy of karyorrhexis (18.2 ± 18.4 vs 5.8 ± 18.4, p < 0.004) and pyknosis (24.8 ± 18.0 vs 17.1 ± 8.3; p < 0.03). Of the children potentially exposed to pesticides, 40% (19/47) had an exposure time of 6 years.

The cytogenetic effects of black tea and green tea on cultured human lymphocytes

In this study, the cytogenetic effects of black tea and green tea were determined in cultured peripheral blood lymphocytes. Results showed that black tea and green tea induced the mitotic and replication indexes and decreased micronuclei. But these data were not statistically significant for green tea. The effects of black tea on the micronucleus formation and mitotic index were statistically significant. The decrease in micronucleus counts indicated that black tea and green tea had considerable anticlastogenic and antigenotoxic effects as observed in vitro in human lymphocytes. Thus, it could be concluded that tea polyphenols protected the normal cells from genotoxic or carcinogenic agents, which indicated the therapeutic and antioxidative role of catechins, flavonoids or other tea compounds.

Abstract LB-336: High-content, high-throughput imaging cytometry for fully automated DNA damage analysis

Abstract Assessment of DNA damage is a vital part of oncology research and cancer drug development. In this study, we present a novel method using laser scanning cytometry (LSC) to automate a panel of DNA damage assays that are traditionally scored manually. The comet assay is one of the simplest and most widely-used methods to evaluate DNA damage. In order to fully automate this assay, we successfully developed the first algorithm that can reliably segment and quantify the amount of DNA present in the comet head versus the tail separately, providing a standardized and fully automated measurement of DNA damage. In the micronucleus (MN) assay, measurement of micronuclei formed from chromosome breakage and/or malsegregation provides an assessment of DNA damage and serves as a biomarker of genotoxicity and mutagenicity. Using simultaneous measurements by LSC of cellular morphology, nuclear and MN counts, precise DNA content, and specific molecular biomarker intensity, we developed a protocol to identify and quantify different cell sub-types within human buccal mucosa tissue consisting of basal cells, differentiated cells and bi-nucleated cells, as well as scoring cells which contain MN. The automated high-throughput generation of this data allows a high content analysis “cytome” assay of DNA damage, chromosome instability, cell death and the regenerative potential of human buccal mucosal tissue in response to exogenous and endogenous insults. The multiplexed DNA damage response assay combines DNA content measurement with assessment of ATM and H2AX phosphorylation. The integrated signal of each of the above markers allows correlation of the extent of DNA damage with the cell cycle phase. We employed LSC's automated imaging features to extend the dynamic range of measurable damage induced by various genotoxic agents, allowing identification and enumeration of DNA damage-reporting foci and analysis of expression and degree of overlap of these marker phospho-proteins in individual foci. Induction of cell senescence combined with reproductive cell death is the goal of chemotherapy and radiotherapy of solid tumors. The morphometric analytical capabilities of LSC were used to develop new biomarkers that reveal the degree (depth) of cell senescence based on senescence-characteristic morphological features. Combining these biomarkers with markers of DNA damage response, we assessed several factors that enhanced or attenuated senescence induced by anticancer drugs. In conclusion, we have developed a panel of LSC algorithms that allow previously unavailable automation and standardization of high-content, high-throughput DNA damage assays to be performed on a single platform. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 102nd Annual Meeting of the American Association for Cancer Research; 2011 Apr 2-6; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2011;71(8 Suppl):Abstract nr LB-336. doi:10.1158/1538-7445.AM2011-LB-336

High content flow cytometric micronucleus scoring method is applicable to attachment cell lines

A flow cytometric method for analyzing suspension cell cultures for micronucleus content has been previously reported (Avlasevich et al. [2006]: Environ Mol Mutagen 47: 56-66). The experiments described herein were undertaken to evaluate the compatibility of this method (In Vitro MicroFlow) with attachment cells. Initially, CHO-K1 cells were studied in nine independent experiments using mitomycin C and cyclophosphamide. The results demonstrated the effectiveness of the cell processing procedure, and also provided historical control data that were useful for setting criteria for making positive calls. Subsequently, CHO-K1 cells were treated with methyl methanesulfonate, mitomycin C, etoposide, vinblastine sulfate, dexamethasone, and sodium chloride. Whereas the four genotoxicants were each observed to increase micronucleus frequencies, the nongenotoxicants induced no such response up to cytotoxic concentrations. Following this initial work, inter-laboratory transferability was evaluated across three sites using a common cell staining and analysis protocol for CHO-K1 or V79 cells that had been treated with the ten chemicals listed in Annex 3 of the OECD Draft Proposal for a New Guideline 487: In Vitro Mammalian Cell Micronucleus Test. With the exception of benzo[a]pyrene at one site, each laboratory observed increased micronucleus frequencies for the genotoxicants, whereas no significant induction occurred with the non-genotoxicants. Interestingly, the method appeared to distinguish between genotoxic modes of action, as only aneugens increased the average micronucleus fluorescence intensity and the frequency of hypodiploid nuclei. Collectively, these data suggest that flow cytometry is capable of providing reliable micronucleus counts, and that additional information is obtained that appears to discern genotoxic modes of action.

Tannic acid prevents azidothymidine (AZT) induced hepatotoxicity and genotoxicity along with change in expression of PARG and histone H3 acetylation

Azidothymidine (AZT) is known to decrease HIV virus replication and is one of the most frequently prescribed antiretroviral drugs used for AIDS treatment. Dose-limiting toxicities are the major curse associated with AZT therapy. Recently, we have reported that tannic acid; a PARG inhibitor prevents cisplatin induced nephrotoxicity. The present work was conceived to study the effect of tannic acid on AZT induced hepatotoxicity and genotoxicity. AZT induces increase in plasma levels of ALT, AST and alkaline phosphatase along with increase in micronucleus (MN) count in peripheral blood. Suggesting, AZT is hepatotoxic and genotoxic to mice. Treatment of tannic acid protects AZT induced hepatotoxicity by decreasing the ALT, AST and alkaline phosphatase levels. It also significantly reduces the oxidative damage by preventing reduction in glutathione and decreasing the level of malondialdehyde in liver of AZT treated mice. In addition, tannic acid decreases the PARG expression, PARP cleavage and histone H3 acetylation in liver of AZT treated mice. Moreover, treatment of tannic acid also decreases MN count in peripheral blood, suggesting its anti-mutagenic effect. In light of these findings we suggest the potential role of tannic acid treatment in preventing AZT induced toxicity.

Reduced DNA repair in BRCA1 mutation carriers undetectable before onset of breast cancer?

Reduced DNA repair in BRCA1 mutation carriers undetectable before onset of breast cancer?

Proposed criteria for specific and non-specific chromosomal genotoxicity based on hydrophobic interactions

Tests for chromosomal damage are indispensable in the genotoxicity testing battery. Thus, positive results of clastogenicity or aneugenicity tests are of key relevance in safety assessment and product development. Schultz and Önfelt [N. Schultz, A. Önfelt, Sensitivity of cytokinesis to hydrophobic interactions. Chemical induction of bi- and multi-nucleated cells, Chem. Biol. Interact. 126 (2000) 97–123.] have studied the chemical induction of bi- and multi-nucleated cells in Chinese hamster V79 cells and compared non-specific agents with inducers acting through a known specific mechanism. They separated compounds with a specific action from those with a non-specific action based on lipophilicity, following a theory of hydrophobic interactions with processes of cytokinesis. It appeared possible to broaden the original database of this concept to include aneugenic as well as clastogenic compounds studied in the micronucleus (MN) test. The datasets used for this purpose were (A) the original dataset of Schultz and Önfelt [N. Schultz, A. Önfelt, Sensitivity of cytokinesis to hydrophobic interactions. Chemical induction of bi- and multi-nucleated cells, Chem. Biol. Interact. 126 (2000) 97–123.], and two sets (B, C) of our own data from studies in V79 cells in vitro. As the particular endpoints used were different (A: counts of bi- and multi-nucleated cells, B/C: micronucleus counts) the coherence of the experimental data sets was validated by including compounds belonging to both collections. Data set B included compounds with a specific effect on the mitotic spindle (nitrobenzene and benzonitrile) and data set C included the phytoestrogens genistein and daidzein, as well as a number of hormonal steroids with unknown mode of action. Taking all three data sets (A, B, C) together, the 33 compounds investigated covered a total lipophilicity range of log P between −0.51 (diamide) and 5.65 (17α-propylmesterolone). In order to separate statistical outliers (with a specific mode of action to be likely) from the large cluster of compounds with non-specific genotoxicity related to hydrophobic interactions, the method of robust regression was applied. It appeared that all compounds with a specific mode of action were in fact outliers of the lipophilicity rule. Genistein, a weak clastogen causing chromosomal aberrations and being discussed to induce topoisomerase-2 mediated DNA breaks, came close to the statistical borderline between compounds with specific and non-specific chromosomal genotoxicity. A general procedure is proposed, applicable in chemical product development, to screen specific and non-specific modes of action.