Validation of single cell gel assay in human leukocytes with 18 reference compounds

Comet assay and hormesis

The paper provides the first assessment of the occurrence of hormetic dose responses using the Comet assay, a genotoxic assay. Using a priori evaluative criteria based on the Hormetic Database on peer-reviewed comet assay experimental findings, numerous examples of hormetic dose responses were obtained. These responses occurred in a large and diverse range of cell types and for agents from a broad range of chemical classes. Limited attempts were made to estimate the frequency of hormesis within comet assay experimental studies using a priori entry and evaluative criteria, with results suggesting a frequency in the 40% range. These findings are important as they show that a wide range of genotoxic chemicals display evidence that is strongly suggestive of hormetic dose responses. These findings have significant implications for study design issues, including the number of doses selected, dose range and spacing. Likewise, the widespread occurrence of hormetic dose responses in this genotoxic assay has important risk assessment implications.

Histopathological, Immunohistochemical, And Molecular Alterations In Brain Tissue And Submandibular Salivary Gland Of Atrazine-Induced Toxicity In Male Rats

Atrazine (ATZ) is herbicide that has been widely used for different crops. This extensive use has resulted in severe deleterious effects in different species. In this work, we investigated the potentially harmful effect of atrazine herbicide on the brain and submandibular salivary gland. Our investigation was carried out on 20 adult male albino rats that were equally divided into two groups. The first group received distilled water as control, while the second group received ATZ at 200 mg/kg body weight/ day via stomach gavage for 30 successive days of the experiment; the oral LD50 for ATZ is 3090 mg/kg. Our findings revealed the ability of ATZ to cause damage to the cerebrum, hippocampus, and submandibular salivary gland. This damage resulted from the induced oxidative stress, which was indicated by a significant elevation in malondialdehyde (MDA) concentration, DNA fragmentation, tumor necrotic factor-alpha (TNF-α) expression, with a significant decrease in reduced glutathione (GSH) level and reduction of B cell lymphoma 2 (BCL2), dopamine receptor D1 (Drd1), cAMP-responsive element-binding protein 1 (Creb1) genes expression after ATZ exposure. Moreover, degeneration of cells, cytoplasmic vacuolation, congestion of blood vessels, a strong immune reaction to caspase 3, and negligible immune expression of a glial fibrillary acidic protein (GFAP) were also noticed in the ATZ-treated group. We concluded that ATZ induces oxidative stress and has a toxic and apoptotic effects on the cerebrum, hippocampus, and salivary gland of adult male albino rats.

Genotoxic effects of urban pollution in the Iguaçu River on two fish populations

Environmental impacts on water resources and discharges of pollutants are some of the main problems of aquatic ecosystems. Currently, the Iguaçu River is considered the second most polluted river in Brazil, therefore, given the importance of understanding the effects of water pollution on living organisms, this study aimed to analyze the possible genotoxic effects in Astyanax bifasciatus (Characiformes; Characidae) and Geophagus brasiliensis (Perciformes: Cichlidae) in response to the water quality of the Iguaçu River. Four sampling points were determined on the Iguaçu River, with different levels of environmental impact. The micronuclei and nuclear abnormalities were quantified by counting 2000 erythrocytes from each specimen. There was a statistical difference in the frequency of nuclear abnormalities both for A. bifasciatus (Kruskal-Wallis _3;30 = 10.9; p = 0.01) and for G. brasiliensis (Kruskal-Wallis _3;26 = 12.27; p = 0.006), with point 1 (critically degraded) showing a higher frequency of nuclear abnormalities and point 4 (moderately degraded) showing a lower frequency of nuclear abnormalities for both species, showing genotoxic potential in fish erythrocytes. This result demonstrates the need for further discussion on the conservation of the Iguaçu River as well as broadening the discussion on its potability.

Suitability of Nanoparticles to Face Benzo(a)pyrene-Induced Genetic and Chromosomal Damage in M. galloprovincialis. An In Vitro Approach

Benzo(a)pyrene (B(a)P) is a well-known genotoxic agent, the removal of which from environmental matrices is mandatory, necessitating the application of cleaning strategies that are harmless to human and environmental health. The potential application of nanoparticles (NPs) in the remediation of polluted environments is of increasing interest. Here, specifically designed NPs were selected as being non-genotoxic and able to interact with B(a)P, in order to address the genetic and chromosomal damage it produces. A newly formulated pure anatase nano-titanium (nano-TiO2), a commercial mixture of rutile and anatase, and carbon black-derived hydrophilic NPs (HNP) were applied. Once it had been ascertained that the NPs selected for the work did not induce genotoxicity, marine mussel gill biopsies were exposed in vitro to B(a)P (2 μg/mL), alone and in combination with the selected NPs (50 µg/mL nano-TiO2, 10 µg/mL HNP). DNA primary reversible damage was evaluated by means of the Comet assay. Chromosomal persistent damage was assessed on the basis of micronuclei frequency and nuclear abnormalities by means of the Micronucleus-Cytome assay. Transmission Electron Microscopy (TEM) was performed to investigate the mechanism of action exerted by NPs. Pure Anatase n-TiO2 was found to be the most suitable for our purpose, as it is cyto- and genotoxicity free and able to reduce the genetic and chromosomal damage associated with exposure to B(a)P.

Statistics of Interlaboratory In Vitro Toxicological Studies

Interlaboratory studies are common in toxicology, particularly for the introduction of alternative assays. Numerous papers are available on the statistical analysis of interlaboratory studies, but these deal primarily with the case of a replicated single sample studied in several laboratories. This approach can be used for some assays, but for the majority, the results will be unsatisfactory, i.e. involving great variability between both the dose groups and the laboratories. However, the primary objective of toxicological assays is to achieve similarity between the sizes of effects, rather than to determine absolute values. In the parametric model, the sizes of effects are the studentised differences from the negative control or, for the commonly used dose-response designs, the similarity of the slopes of the dose-response curves. Standard approaches for the estimation of intralaboratory and interlaboratory variability, including Mandel plots, are introduced, and new approaches are presented for demonstrating similarity of effect sizes, with or without assuming a dose-response model. One approach is based on a modification of the parallel-line assay, the other is based on a modification of the interaction contrasts of the analysis of variance. SAS programs are given for all approaches, and real data from an interlaboratory immunotoxicological study are analysed as a demonstration.

Investigating unmetabolized polycyclic aromatic hydrocarbons in adolescents' urine as biomarkers of environmental exposure

Polycyclic aromatic hydrocarbons (PAHs) are of interest to human biomonitoring studies due to their carcinogenic potential. Traditionally metabolites of these compounds, like 1-hydroxypyrene, are monitored in urine, but recent methods allow the determination of the parent compounds in urine, which give additional information regarding sources and toxicity of PAHs. In order to assess the feasibility of incorporating these methods in a human biomonitoring study, the 16 USEPA parent PAHs were determined in 20 urine samples. These samples were obtained from 10 boys and 10 girls aged 14-16 years, participating in the third Flemish Environment and Health Study (Flanders, Belgium). Of these 16 parent PAHs, nine could be determined in more than 95% of the samples and three (including benzo(a)pyrene) in more than 50%. Several correlations were found between different PAHs, but not between pyrene and its metabolite 1-hydroxypyrene. Diagnostic PAH ratios in urine and air samples pointed towards combustion sources and are in line with the ratios in environmental samples. Benzo(a)pyrene, naphthalene and fluorene have the highest carcinogenic potential in our cohort, when using toxic equivalency factors. Some associations between PAH congeners and determinants of exposure were found, while fluorene and acenaphthylene were positively associated with thyroid hormone levels and benzo(a)pyrene showed a positive correlation with DNA damage by comet assay. These results confirm that parent PAHs in urine are useful as biomarkers of exposure in biomonitoring studies.

Quantitative genotoxicity assays for analysis of medicinal plants: A systematic review

ETHNOPHARMACOLOGICAL RELEVANCE

Medicinal plants are known to contain numerous biologically active compounds, and although they have proven pharmacological properties, they can cause harm, including DNA damage.

AIM OF THE STUDY

Review the literature to evaluate the genotoxicity risk of medicinal plants, explore the genotoxicity assays most used and compare these to the current legal requirements.

MATERIAL AND METHODS

A quantitative systematic review of the literature, using the keywords "medicinal plants", "genotoxicity" and "mutagenicity", was undertakenQ to identify the types of assays most used to assess genotoxicity, and to evaluate the genotoxicity potential of medicinal plant extracts.

RESULTS

The database searches retrieved 2289 records, 458 of which met the inclusion criteria. Evaluation of the selected articles showed a total of 24 different assays used for an assessment of medicinal plant extract genotoxicity. More than a quarter of those studies (28.4%) reported positive results for genotoxicity.

CONCLUSIONS

This review demonstrates that a range of genotoxicity assay methods are used to evaluate the genotoxicity potential of medicinal plant extracts. The most used methods are those recommended by regulatory agencies. However, based on the current findings, in order to conduct a thorough study concerning the possible genotoxic effects of a medicinal plant, we indicate that it is important always to include bacterial and mammalian tests, with at least one in vivo assay. Also, these tests should be capable of detecting outcomes that include mutation induction, clastogenic and aneugenic effects, and structural chromosome abnormalities. In addition, the considerable rate of positive results detected in this analysis further supports the relevance of assessing the genotoxicity potential of medicinal plants.

Increased levels of chromosomal aberrations and DNA damage in a group of workers exposed to formaldehyde

Formaldehyde (FA) is a commonly used chemical in anatomy and pathology laboratories as a tissue preservative and fixative. Because of its sensitising properties, irritating effects and cancer implication, FA accounts probably for the most important chemical-exposure hazard concerning this professional group. Evidence for genotoxic effects and carcinogenic properties in humans is insufficient and conflicting, particularly in regard to the ability of inhaled FA to induce toxicity on other cells besides first contact tissues, such as buccal and nasal cells. To evaluate the effects of exposure to FA in human peripheral blood lymphocytes, a group of 84 anatomy pathology laboratory workers exposed occupationally to FA and 87 control subjects were tested for chromosomal aberrations (CAs) and DNA damage (comet assay). The level of exposure to FA in the workplace air was evaluated. The association between genotoxicity biomarkers and polymorphic genes of xenobiotic-metabolising and DNA repair enzymes were also assessed. The estimated mean level of FA exposure was 0.38±0.03 ppm. All cytogenetic endpoints assessed by CAs test and comet assay % tail DNA (%TDNA) were significantly higher in FA-exposed workers compared with controls. Regarding the effect of susceptibility biomarkers, results suggest that polymorphisms in CYP2E1 and GSTP1 metabolic genes, as well as, XRCC1 and PARP1 polymorphic genes involved in DNA repair pathways are associated with higher genetic damage in FA-exposed subjects. Data obtained in this study show a potential health risk situation of anatomy pathology laboratory workers exposed to FA (0.38 ppm). Implementation of security and hygiene measures may be crucial to decrease risk. The obtained information may also provide new important data to be used by health care programs and by governmental agencies responsible for occupational health and safety.

Sodium copper chlorophyllin (SCC) induces genetic damage in postmeiotic and somatic wing cells of Drosophila melanogaster

There is no apparent evidence to indicate that sodium copper chlorophyllin (SCC) is mutagenic. The aim of the present study was thus to determine the mutagenic effect of SCC, in postmeiotic germ cells of the adult male Drosophila. This investigation was based on the ability to examine whether SCC induced sex-linked recessive lethal mutations (SLRL), as well as the somatic mutation and recombination test (SMART). Four different SCC concentrations were used: 0, 45, 69, 80, and 100 mM. For SLRL, two broods were generated to test sperm and primarily spermatids. Results showed a significant frequency of recessive lethal mutations compared with control sperm cells with SCC at 69, 80, and 100 mM. In contrast, the frequency of somatic mutations rose by 0.21 only with 100 mM of SCC. These findings provide evidence that SCC is a weak mutagen in both cell lines. The differential response may be attributed to repair mechanisms that are active in somatic cells but almost absent in germ cells.

The effect of nitrobenzene on antioxidative enzyme activity and DNA damage in tobacco seedling leaf cells

Nitrobenzene, although widely used in industry, is a highly toxic environmental pollutant. To evaluate the toxicity of nitrobenzene to tobacco seedlings, seedlings were exposed to varying concentrations of nitrobenzene (0-100 mg/L) for 24 h. The contents of reactive oxygen species (hydrogen peroxide [H(2)O(2)] and superoxide anion [O2(-)]) and the activities of antioxidative enzymes (superoxide dismutase [SOD], guaiacol peroxidase [POD], and catalase [CAT]) were measured in leaf cells. Damage to DNA was assessed by single-cell gel electrophoresis (comet assay). Compared with the control, the contents of H(2) O(2) increased significantly with nitrobenzene concentrations ranging from 5 to 100 mg/L. Activity of SOD was induced by 50 to 100 mg/L of nitrobenzene but not by 10 to 25 mg/L. Activity of POD was stimulated by nitrobenzene at 10 to 50 mg/L but inhibited at 100 mg/L. Activity of CAT was increased significantly only by 100 mg/L. Lipid peroxidation increased with 50 to 100 mg/L, which indicated that nitrobenzene induced oxidative stress in tobacco leaf cells. Comet assay of the leaf cells showed a significant enhancement of the head DNA (H-DNA), tail DNA (T-DNA), and olive tail moment (OTM) with increasing doses of nitrobenzene. The values of H-DNA, T-DNA, and OTM exhibited significant differences from the control when stress concentrations were higher than 10 mg/L. The results indicated that nitrobenzene caused oxidative stress, which may be one of the mechanisms through which nitrobenzene induces DNA damage.

Genotoxic effect induced by hydrogen peroxide in human hepatoma cells using comet assay

Background

Hydrogen peroxide (H₂O₂) is a common reactive oxygen intermediate generated by various forms of oxidative stress.

Aim

The aim of this study was to investigate the DNA damage capacity of H₂O₂ in HepG2 cells.

Methods

Cells were treated with H₂O₂ at concentrations of 25 µM or 50 µM for 5 min, 30 min, 40 min, 1 h, or 24 h in parallel. The extent of DNA damage was assessed by the comet assay.

Results

Compared to the control, DNA damage by 25 and 50 µM H₂O₂ increased significantly with increasing incubation time up to 1 h, but it was not increased at 24 h.

Conclusions

Our findings confirm that H₂O₂ is a typical DNA damage-inducing agent and thus is a good model system to study the effects of oxidative stress. DNA damage in HepG2 cells increased significantly with H₂O₂ concentration and time of incubation but later decreased likely due to DNA repair mechanisms and antioxidant enzymes.

Genotoxicity of glyphosate assessed by the comet assay and cytogenetic tests

It was evaluated the genotoxicity of glyphosate which up to now has heterogeneous results. The comet assay was performed in Hep-2 cells. The level of DNA damage in the control group (5.42±1.83 arbitrary units) for tail moment (TM) measurements has shown a significant increase (p<0.01) with glyphosate at a range concentration from 3.00 to 7.50mM. In the chromosome aberrations (CA) test in human lymphocytes the herbicide (0.20-6.00mM) showed no significant effects in comparison with the control group. In vivo, the micronucleus test (MNT) was evaluated in mice at three doses rendering statistical significant increases at 400mg/kg (13.0±3.08 micronucleated erythrocytes/1000 cells, p<0.01). In the present study glyphosate was genotoxic in the comet assay in Hep-2 cells and in the MNT test at 400mg/kg in mice. Thiobarbituric acid reactive substances (TBARs) levels, superoxide dismutase (SOD) and catalase (CAT) activities were quantified in their organs. The results showed an increase in these enzyme activities.

Genotoxic damage in pathology anatomy laboratory workers exposed to formaldehyde

Formaldehyde (FA) is a chemical traditionally used in pathology and anatomy laboratories as a tissue preservative. Several epidemiological studies of occupational exposure to FA have indicated an increased risk of nasopharyngeal cancers in industrial workers, embalmers and pathology anatomists. There is also a clear evidence of nasal squamous cell carcinomas from inhalation studies in the rat. The postulated mode of action for nasal tumours in rats was considered biologically plausible and considered likely to be relevant to humans. Based on the available data IARC, the International Agency for Research on Cancer, has recently classified FA as a human carcinogen. Although the in vitro genotoxic as well as the in vivo carcinogenic potentials of FA are well documented in mammalian cells and in rodents, evidence for genotoxic effects and carcinogenic properties in humans is insufficient and conflicting thus remains to be more documented. To evaluate the genetic effects of long-term occupational exposure to FA a group of 30 Pathological Anatomy laboratory workers was tested for a variety of biological endpoints, cytogenetic tests (micronuclei, MN; sister chromatid exchange, SCE) and comet assay. The level of exposure to FA was evaluated near the breathing zone of workers, time weighted average of exposure was calculated for each subject. The association between the biomarkers and polymorphic genes of xenobiotic metabolising and DNA repair enzymes was also assessed. The mean level of exposure was 0.44+/-0.08ppm (0.04-1.58ppm). MN frequency was significantly higher (p=0.003) in the exposed subjects (5.47+/-0.76) when compared with controls (3.27+/-0.69). SCE mean value was significantly higher (p<0.05) among the exposed group (6.13+/-0.29) compared with control group (4.49+/-0.16). Comet assay data showed a significant increase (p<0.05) of TL in FA-exposed workers (60.00+/-2.31) with respect to the control group (41.85+/-1.97). A positive correlation was found between FA exposure levels and MN frequency (r=0.384, p=0.001) and TL (r=0.333, p=0.005). Regarding the genetic polymorphisms studied, no significant effect was found on the genotoxic endpoints. The results of the present biomonitoring study emphasize the need to develop safety programs.

Unexpected DNA damage caused by polycyclic aromatic hydrocarbons under standard laboratory conditions

The genotoxicity of 15 polycyclic aromatic hydrocarbons was determined with the alkaline version of the comet assay employing V79 lung fibroblasts of the Chinese hamster as target cells. These cells lack the enzymes necessary to convert PAHs to DNA-binding metabolites. Surprisingly, 11 PAHs, i.e., benzo[a]pyrene (BaP), benz[a]anthracene, 7,12-dimethylbenz[a]anthracene, 3-methylcholanthrene, fluoranthene, anthanthrene, 11H-benzo[b]fluorene, dibenz[a,h]anthracene, pyrene, benzo[ghi]perylene and benzo[e]pyrene caused DNA strand breaks even without external metabolic activation, while naphthalene, anthracene, phenanthrene and naphthacene were inactive. When the comet assay was performed in the dark or when yellow fluorescent lamps were used for illumination the DNA-damaging effect of the 11 PAHs disappeared. White fluorescent lamps exhibit emission maxima at 334.1, 365.0, 404.7, and 435.8 nm representing spectral lines of mercury. In the case of yellow fluorescent lamps these emissions were absent. Obviously, under standard laboratory illumination many PAHs are photo-activated, resulting in DNA-damaging species. This feature of PAHs should be taken into account when these compounds are employed for the initiation of skin cancer. The genotoxicity of BaP that is metabolically activated in V79 cells stably expressing human cytochrome P450-dependent monooxygenase (CYP1A1) as well as human epoxide hydrolase (V79-hCYP1A1-mEH) could not be detected with the comet assay performed under yellow light. Likewise the DNA-damaging effect of r-7,t-8-dihydroxy-t-9,10-epoxy-7,8,9,10-tetrahydrobenzo[a]pyrene (anti-BaPDE) observed with the comet assay was only weak. However, upon inhibition of nucleotide excision repair (NER), which is responsible for the removal of stable DNA adducts caused by anti-BaPDE, the tail moment rose 3.4-fold in the case of BaP and 12.9-fold in the case of anti-BaPDE. These results indicate that the genotoxicity of BaP and probably of other compounds producing stable DNA adducts are reliably detected with the comet assay only when NER is inhibited.

Promoter hypermethylation for molecular nodal staging in non-small cell lung cancer

CONTEXT

Even among cases of non-small cell lung cancer (NSCLC) in the most favorable stage (IA), the disease-specific mortality is 25% or greater. One plausible explanation implicates the simplistic standard pathologic procedures used to designate lymph node involvement. A more sensitive assessment of the nodal status may improve staging.

OBJECTIVE

To determine the prognostic impact of detecting an abnormal molecular event (promoter hypermethylation in a set of relevant genes) in histologically uninvolved lymph nodes in resected NSCLC.

DESIGN

In this retrospective analysis of archived material, we examined DNA extracted from lymph nodes of stage I NSCLC (n = 180). Patients underwent surgery between 1991 and 1995 in a single institution. Methylation-specific polymerase chain reaction was used to detect promoter hypermethylation in a panel of 8 genes. Survival data were extracted from the computerized database at the Tumor Registry.

RESULTS

Evidence of promoter hypermethylation in at least 1 gene was detected in 67% of these N0 nodes. The most commonly hypermethylated gene was E-cadherin (53%). The hypermethylation frequency for the remaining genes were as follows: APC, 5%; p16, 9%; MGMT, 11%; hMLH1, 15%; RASSF1A, 4%; DAP kinase, 9%; and ATM, 19%. The presence of promoter hypermethylation in 2 or more genes did not influence the overall, median, or 5-year survival rates.

CONCLUSIONS

Identifying promoter hypermethylation (in our panel) in N0 lymph nodes in stage I NSCLC cannot be recommended for clinical decision making. Molecular abnormalities, including those found in cancer by qualitative methylation-specific polymerase chain reaction, are not synonymous with established, histologically detectable metastasis.

Influence of endogenous and synthetic female sex hormones on human blood cells in vitro studied with comet assay

The comet assay has been conducted with numerous cell lines to assess in vitro genotoxicity. In order to use the comet assay as part of an in vitro test for evaluating genotoxicity, however, there are cell-specific factors that need to be better understood. In this present study we have evaluated some factors that may impact upon the DNA damage detected in whole blood (WB) cells and lymphocytes (ILs). Experiments were conducted comparing responses of both cells, and investigating the effects of the female hormonal cycle, and oral contraceptive (OC) use on DNA damage detection in the in vitro comet assay, at three sampling time. No significant differences were detected in the basal levels of DNA damage detected in ILs and WB cells from women OC users and non-users and from men. Basal DNA damage in ILs was unaffected by gender and stage of the menstrual cycle or the stage of the treatment schedule. Our results also indicated that the H2O2 induces DNA damage in human lymphocytes independently of gender, low-dose OC use and hormonal fluctuation. However, data showed that in 3rd sampling of menstrual cycle, lymphocytes were more resistant to H2O2-induced DNA damage than those from OC users and men.

Inhibition of spontaneous mutagenesis by vanillin and cinnamaldehyde in Escherichia coli: Dependence on recombinational repair

Vanillin (VAN) and cinnamaldehyde (CIN) are dietary antimutagens that effectively inhibit both induced and spontaneous mutations. We have shown previously that VAN and CIN reduced the spontaneous mutant frequency in Salmonella TA104 (hisG428, rfa, DeltauvrB, pKM101) by approximately 50% and that both compounds significantly reduced mutations at GC sites but not at AT sites. Previous studies have suggested that VAN and CIN may reduce mutations in bacterial model systems by modulating DNA repair pathways, particularly by enhancing recombinational repair. To further explore the basis for inhibition of spontaneous mutation by VAN and CIN, we have determined the effects of these compounds on survival and mutant frequency in five Escherichia coli strains derived from the wild-type strain NR9102 with different DNA repair backgrounds. At nontoxic doses, both VAN and CIN significantly reduced mutant frequency in the wild-type strain NR9102, in the nucleotide excision repair-deficient strain NR11634 (uvrB), and in the recombination-proficient but SOS-deficient strain NR11475 (recA430). In contrast, in the recombination-deficient and SOS-deficient strain NR11317 (recA56), both VAN and CIN not only failed to inhibit the spontaneous mutant frequency but actually increased the mutant frequency. In the mismatch repair-defective strain NR9319 (mutL), only CIN was antimutagenic. Our results show that the antimutagenicity of VAN and CIN against spontaneous mutation required the RecA recombination function but was independent of the SOS and nucleotide excision repair pathways. Thus, we propose the counterintuitive notion that these antimutagens actually produce a type of DNA damage that elicits recombinational repair (but not mismatch, SOS, or nucleotide excision repair), which then repairs not only the damage induced by VAN and CIN but also other DNA damage-resulting in an antimutagenic effect on spontaneous mutation.

SOS-red fluorescent protein (RFP) bioassay system for monitoring of antigenotoxic activity in plant extracts

An optical antigenotoxicity assay using genetically engineered red fluorescent bacteria is presented. Exposure of Escherichia coli RS4U to genotoxicants [mitomycin C (MMC), nalidixic acid (NA) and hydrogen peroxide (HP)] resulted in phenotypic red fluorescence proportional to the concentration of the inducer. Except for tannic acid (TA), co-treatment of the genotoxicant-activated bacteria with ascorbic acid (AA) and aqueous plant extracts (Mangifera indica, Psidium guajava and Syzygium cumini) afforded protection against all three genotoxicants. TA was effective in suppressing the genotoxic effect of MMC and HP. The antigenotoxic effect is seen as inhibition of the genotoxicant-triggered red fluorescence. The IC50 of the plant extracts and AA varied with the genotoxicant used. Rec assay verified the antigenotoxic activity of the plant extracts. Folin-Ciocalteu test, FeCl3 test and DPPH assay confirmed the presence of polyphenolic compounds and hydrolyzable tannins in the plant extracts and the antioxidant capacity of the plant samples.

Methylation profiling of archived non-small cell lung cancer: a promising prognostic system

PURPOSE

Enhanced prognostication power is becoming more desirable in clinical oncology. In this study, we explored the prognostic potential of multigene hypermethylation profiling in non-small-cell lung cancer.

EXPERIMENTAL DESIGN

We evaluated a panel of eight genes (p16, APC, ATM, hMLH1, MGMT, DAPK, ECAD, and RASSF1A) using methylation-specific PCR in 105 archived specimens of non-small-cell lung cancer representing all stages of the illness. We analyzed the effect of gene methylation status on outcome individually in a cumulative manner and in a combinatorial approach using recursive partitioning to identify methylation profiles, which affect overall survival.

RESULTS

In this data set, tumors harboring promoter hypermethylation at two or more genes exhibit similar survival trends to others in the cohort. Using recursive partitioning, three genes (APC, ATM, and RASSF1A) emerged as determinants of prognostic groups. This designation retained its statistical significance even when disease stage and age were entered into a multivariate analysis. Using this approach, patients whose tumors were hypermethylated at APC and those hypermethylated at only ATM (not also at APC or RASSF1A) enjoyed substantially longer 1- and 2-year survival than patients in the remaining groups. In 32 adjacent histologically normal lung tissue specimens, we detected similar methylation abnormalities.

CONCLUSION

Assessment of promoter hypermethylation aberrations may facilitate prognostic profiling of lung tumors, but validation in independent data sets is needed to verify these profiles. This system uses material that is abundantly available with linked outcome data and can be used to generate reliable epigenetic determinants.

Detecting DNA repair capacity of peripheral lymphocytes from cancer patients with UVC challenge test and bleomycin challenge test

The objective of this study was to evaluate DNA repair capacity of cancer patients with the bleomycin (BLM) challenge test and the UVC challenge test. The human peripheral lymphocytes were collected from 33 patients with different kinds of cancers and 33 controls in the same hospital. The lymphocytes of each subject were divided into two groups: (1) In the BLM challenge test, the lymphocytes were treated with BLM (20 microgml(-1)) for 30 min, and repaired for 15 min. The DNA damage before and after BLM exposure was detected with comet assay to assess DNA repair capacity. (2) In the UVC challenge test, the lymphocytes were exposed to UVC (254 nm) at the dose of 1.5 Jm(-2). DNA damage of lymphocytes was measured before UVC exposure and at 90 and 240 min after UVC exposure using comet assay, then DNA repair percentage (DRP) was calculated. The results of this study indicate that the average DRPs of cancer patients were 75.63 +/- 3.11 and 68.98 +/- 4.19% calculated with tail length (TL) and tail moment (TM), respectively, in the BLM challenge test, which were significantly lower than those (91.11 +/- 1.09 and 88.19 +/- 1.71%) of controls (P < 0.01). Also, the mean DRPs of cancer patients were 49.19 +/- 3.47 and 58.27 +/- 3.64% calculated with TL and TM, respectively, in the UVC test, which were significantly lower than those (77.52 +/- 2.06 and 83.12 +/- 2.36%) of controls (P < 0.01). The correlation between the DRPs (%) drawn with TL and TM in the BLM test or between the DRPs (%) drawn with mean TL and mean TM in the UVC challenge test were significant (P < 0.05). The DNA repair capacity measured with the BLM and UVC challenge tests in 33 cancer patients was significantly lower than that in controls.

G2 arrest and apoptosis by 2-amino-N-quinoline-8-yl-benzenesulfonamide (QBS), a novel cytotoxic compound

We screened a library of 11,000 small molecular weight chemicals, looking for compounds that affect cell viability. We have identified 2-amino-N-quinoline-8-yl-benzenesulfonamide (QBS) as a potent cytotoxic compound that induces cell cycle arrest and apoptosis. Treatment of Jurkat T cells with QBS increased the levels of cyclin B1 as well as phosphorylated-cdc2, which was accompanied by reduced activity of cdc2 kinase, suggesting that QBS may induce cell cycle arrest at G2 phase. Structural analogues of QBS also exhibited similar effects on cell cycle progression and cell viability. Long-term treatment with QBS resulted in DNA fragmentation, cytochrome C release, and PARP cleavage, and an increase in the number of subdiploidy cells, indicative of cellular apoptosis. Moreover, QBS-induced apoptosis was blocked by z-VAD-fmk, a pan-caspase inhibitor. These results suggest that QBS is a novel and potent compound that induces G2 arrest and subsequent apoptosis, implicating it as a putative candidate for chemotherapy.

Lack of Genotoxicity of Formocresol, Paramonochlorophenol, and Calcium Hydroxide on Mammalian Cells by Comet Assay

Formocresol, paramonochlorophenol, and calcium hydroxide are widely used in dentistry because of their antibacterial activities in root canal disinfection. However, the results of genotoxicity studies using these materials are inconsistent in literature. The goal of this study was to examine the genotoxic potential of formocresol, paramonochlorophenol, and calcium hydroxide using mouse lymphoma cells and human fibroblasts cells in vitro by the comet assay. Data were assessed by Kruskal-Wallis nonparametric test. The results showed that all compounds tested did not cause DNA damage for the tail moment or tail intensity parameters. These findings suggest that formocresol, paramonochlorophenol, and calcium hydroxide do not promote DNA damage in mammalian cells and that the comet assay is a suitable tool to investigate genotoxicity.

Extended-term cultures of human T-lymphocytes and the comet assay: a useful combination when testing for genotoxicity in vitro?

Extended-term cultures of human lymphocytes provide a source of uniform human cells that can be used for several experiments performed over a long time, avoiding the variability arising from taking blood samples for individual experiments. The use of extended-term cultures of human T-lymphocytes in the alkaline single-cell gel electrophoresis assay (comet assay) was evaluated as a test for the potential genotoxicity of chemicals. The DNA-damaging effects of five DNA-reactive mutagens and clastogens (benzo[a]pyrene, cyclophosphamide, formaldehyde, 4-nitroquinoline-N-oxide (4NQO) and N-nitrosopiperidine) was determined and compared with the effects of one non-DNA-reactive mutagen (5-hydroxyurea), and one non-mutagenic agent (ethanol). The alkylating and/or DNA-adduct forming agents N-nitrosopiperidine, cyclophosphamide, 4-nitroquinoline-N-oxide and benzo[a]pyrene increased the DNA migration in a dose-dependent manner. In contrast, the DNA/protein-crosslinking agent formaldehyde decreased the migration of DNA during the electrophoresis. The lowest observed effect levels (LOELs) under the experimental conditions used in the present study, were: 0.0001 mM (4-nitroquinoline-N-oxide without S9), 0.05 mM (benzo[a]pyrene with S9), 0.1mM (formaldehyde without S9), 0.25 mM (cyclophosphamide with S9), and 0.5mM (N-nitrosopiperidine with S9), respectively. The antimetabolite 5-hydroxyurea was also found to increase the tail moment, but only in cells that had been exposed to rather high concentrations (> or =10mM) of the compound. Ethanol did not affect the tail moment, not even in cells that had been exposed to an apparently cytotoxic concentration (500 mM). The results of the present study are in qualitative agreement with those obtained using other cells in the alkaline comet assay and it is therefore concluded that extended-term cultures of human T-lymphocytes and the alkaline version of the single-cell gel electrophoresis assay is a useful combination when testing for the potential genotoxicity of chemicals.

Characterization of cytotoxic and genotoxic effects of different compounds in CHO K5 cells with the comet assay (single-cell gel electrophoresis assay)

Different variants of the comet assay were used to study the genotoxic and cytotoxic properties of the following eight compounds: chloral hydrate, colchicine, hydroquinone, DL-menthol, mitomycin C, sodium iodoacetate, thimerosal and valinomycin. Colchicine, mitomycin C, sodium iodoacetate and thimerosal induced genotoxic effects. The other compounds were found to be inactive. The compounds were tested in the standard comet assay as well as in the all cell comet assay (recovery of floating cells after treatment), designed in our laboratory for adherently-growing cells. This latter procedure proved to be more adequate for the assessment of the cytotoxicity for some of the compounds tested (hydroquinone, DL-menthol, thimerosal, valinomycin). Colchicine was positive in the standard comet assay (3h treatment) and in the all cell comet assay (24h treatment). Sodium iodoacetate and thimerosal were positive in the standard and/or the all cell comet assay. Chloral hydrate, hydroquinone, sodium iodoacetate, mitomycin C and thimerosal were also tested in the modified comet assay using lysed cells. Mitomycin C and thimerosal showed effects in this assay, whereas sodium iodoacetate was inactive. This indicates that it does not induce direct DNA damage. Compounds that are known or suspected to form DNA-DNA cross-links or DNA-protein cross-links (chloral hydrate, hydroquinone, mitomycin C and thimerosal) were checked for their ability to reduce ethyl methanesulfonate (EMS)-induced DNA damage. This mode of action could be demonstrated for mitomycin C only.

Genotoxicity of the Kishon River, Israel: the application of an in vitro cellular assay

The alkaline comet assay, a sensitive method for DNA strand breaks and alkali labile site detection in individual cells, was employed here as an ecotoxicological monitoring tool for evaluation of genotoxicity in the Kishon River, Israel. This river, the most polluted river in Israel, has recently elicited major public concern with regard to cancer incidences in people who have dived there over many years. Five water samples were collected every odd month throughout the year 2001, from four localities. The comet assay was employed on fish hepatoma cell line RTH-149. Cells were exposed for 2h, in triplicate, to Kishon water: medium (1:1) samples that were pre-adjusted for pH and salinity percentage levels. Three DNA damage parameters (comet percentages, score of damage, and cumulative tail lengths of the comet), revealed significantly higher genotoxic values in Kishon water-treated cells as compared with the controls (up to 2.4, 3.2, and 3.6-fold, respectively). Part of the sampling sites revealed higher genotoxicity than other polluted sites. The results of this study demonstrate that the comet assay with RTH-149 cells can be successfully applied to a variety of aquatic samples revealing freshwater, marine and estuary conditions. The method found to be fast, sensitive, and suitable for monitoring programs.

Genotoxic hazard of pollutants in cetaceans: DNA damage and repair evaluated in the bottlenose dolphin (Tursiops truncatus) by the Comet Assay

Single cell gel electrophoresis (or Comet Assay) was used for evaluation of the in vitro genotoxicity of hydrogen peroxide (used as a positive control), polychlorinated biphenyls (PCBs) (Aroclor 1254) and methyl mercury chloride, in isolated bottlenose dolphin leukocytes. Results showed that hydrogen peroxide and methyl mercury induced DNA strand breakage in a dose-dependent manner, while PCBs did not induce a clear dose-effect response at the low doses investigated. Efficiency in repairing DNA breakage induced by methyl mercury was also evaluated. Findings demonstrated that dolphin cells are characterized by higher efficiency in DNA repair when compared to human leukocytes. The observed resistance to methyl mercury toxicity in dolphins was hypothesized to be a defence strategy developed to combat high dietary exposure and compensate for limited capacity to excrete persistent pollutants.