Sister chromatid exchanges and chromosomal aberrations induced by mitomycin C in mouse lymphocytes carrying a leukemogenic virus

The induction of chromosomal damage (sister chromatid exchanges (SCEs), chromosomal aberrations, and micronuclei) in T lymphocytes from mouse spleen was analyzed after treatment in vivo with different concentrations of mitomycin C (MMC). Lymphocytes were derived from BALB/Mo mice, which carry an endogenous type C retrovirus (Moloney murine leukemia virus, M-MuLV), and from BALB/c mice (controls, M-MuLV-free). Chromosomal damage was determined in vitro on lymphocytes stimulated with concanavalin A (Con A) and incubated for two generation cycles with bromodeoxyuridine (BUdR). The baseline frequency of SCEs was significantly higher in untreated BALB/Mo than in BALB/c lymphocytes. The frequencies of SCEs were significantly increased by increasing doses of MMC in both BALB/c and BALB/Mo T lymphocytes. Treatment with a low dose of MMC (0.3 mg/kg) produced an additive effect on SCE frequency in BALB/Mo lymphocytes, which was gradually suppressed by increasing the MMC concentration (3-5 mg/kg). Indeed, the levels of SCEs became significantly lower in BALB/Mo than in BALB/c lymphocytes at the highest MMC concentration tested (10 mg/kg), indicating that a negative synergistic effect was eventually produced. Chromosomal aberrations (breaks and total aberrations) were significantly increased by the highest MMC doses (5-10 mg/kg) and were more frequent in BALB/Mo than in BALB/c lymphocytes at 10 mg/kg MMC. The frequencies of micronuclei were increased by all MMC doses and were significantly higher in BALB/Mo than in BALB/c lymphocytes at 10 mg/kg MMC. These results are referred to interferences of M-MuLV and MMC with the function of enzymes, such as DNA topoisomerases, involved in the mechanism of SCE production.     

Sister chromatid exchange in human lymphocytes induced by propoxur following plant activation by Vicia faba

Because the carbamate insecticide propoxur induced sister chromatid exchanges (SCE) in Vicia faba but was ineffective in producing SCE in lymphocytes in culture, it was hardly suspected that plant metabolism was involved. Experiments were conducted in which metabolic activation was afforded by Vicia faba roots, and SCE in human lymphocytes in vitro was used to assess cytogenetic damage. Several concentrations of propoxur (250, 500, 1, 000, 1, 500, and 2, 000 ppm) were applied for 4 hr to the roots of Vicia faba. Extracts prepared from these treatments were added to the lymphocyte cultures and a significant increase of SCE frequencies with a concentration-response relationship could be detected. The lymphocyte proliferation kinetics and the proliferation rate index (PRI) were not affected (except in the highest concentration, of 2, 000 ppm). This general behavior was in agreement with the presence of an enzymatic system (SI0 fraction) in Vicia roots capable of metabolizing or activating the propoxur. With 2, 000 ppm, cell necrosis was produced in Vicia; therefore, this extract did not induce SCE in lymphocytes. However, lymphocyte proliferation kinetics were delayed and PRI was significantly decreased. Ethanol, a promutagen activated by this plant, was applied directly to the lymphocyte cultures as a positive control, and the response was negative. On the other hand, the extracts of roots treated with ethanol increased the SCE to more than twice that of the negative control, but the lymphocyte proliferation kinetics and PRI were not affected. © 1995 Wiley-Liss, Inc.     

Sister chromatid exchange induced by several types of coffees in Chinese hamster ovary cells

Different brands of commercial caffeinated and decaffeinated coffees (roasted, high roast, blend ground, and instant coffees) were studied. These coffees were tested for their ability to induce sister chromatid exchanges (SCE) in CHO-K1 cells. Tests were performed in the presence and in the absence of a metabolic activation system (S-9 mix). Results were compared to the roasting procedure because genotoxic products could be formed from these processes. Our results indicate that caffeinated instant coffees showed higher genotoxic activity than decaffeinated coffees. Non-significant genotoxic activity was detected with the green coffee (unroasted). The highest increase of the frequency of SCE occurred when the caffeinated instant coffee was tested in the absence of metabolic activation system. The repeatability of the test was checked through three assays with the same sample.     

Sister chromatid exchange analysis in the Prader-Labhart-Willi syndrome

The number of sister chromatid exchanges (SCE) and cell kinetics in lymphocytes were investigated from 16 Prader-Labhart-Willi syndrome (PLWS) patients [8 with 15q12 deletion (4 females, 4 males; mean age = 12.9y with age range of 0.3 to 24y), and 8 non-deletion (2 females, 6 males; means age = 16.8y with age range of 5 to 26y)], 18 parents of PLWS patients and age-matched control individuals. The average SCE frequency and standard deviation in PLWS patients with and without the chromosome 15 deletion was 6.6 +/- 1.3 and 6.2 +/- 0.8, respectively. Therefore no significant difference in SCE frequency or replicative index was found between the two PLWS subgroups. There was also no significant difference in SCE frequency or replicative index between the 16 PLWS patients and age-matched control subjects. The average SCE frequency and standard deviation in 8 fathers who were previously identified to have donated the chromosome 15 with the deletion in the child was 7.5 +/- 1.2, which was not significantly different from 8.5 +/- 2.0 seen in age-matched control subjects. There was also no significant difference in the SCE frequency or replicative index of 18 parents of PLWS patients with and without the chromosome 15 deletion when compared with age-matched control subjects.     

Sister chromatid exchange and chromosome abnormalities in uremic patients

Chronic renal failure heightens the risk of malignancy. We therefore examined lymphocytes from 44 uremic patients and 24 normal controls for chromosome abnormalities and sister chromatid exchange (SCE) rate. This is the first report of SCE in uremia. Uremia was found to increase structurally abnormal chromosomes and elevate the rate of SCE. These cytogenetic changes in uremia may play a role in the heightened risk of cancer.     

Apparent enhanced response to the induction of sister chromatid exchange by mitomycin C in myotonic dystrophy.

The spontaneous and mitomycin C (MMC) induced sister chromatid exchange (SCE) frequencies were examined in five adults with myotonic dystrophy (MD). There was no significant difference in the spontaneous incidence of SCE between MD patients and controls. However, a significantly enhanced response to the induction of SCE by MMC was observed in three of the five MD patients who were severely affected, while no such enhancement was observed in the other two mildly affected cases. These results suggest that the raised response may be a secondary consequence associated with disease progression. No differences were observed between the proliferating rate in vitro of lymphocytes of severe and mild cases of MD and controls, but the severe cases showed a significant increase in the proportion of T cells in peripheral blood. It is suggested that the observed enhanced response to MMC may reflect an increase in the proportion of a more sensitive subset of T cells in the peripheral blood.     

Sister chromatid exchange induction and the course of DNA duplication,two mechanisms of sister chromatid exchange induction by ENU and the role of BrdU

The aims of the present study were to establish the following: (i) the course of sister chromatid exchange (SCE) induction by ethylnitrosourea (ENU) in the first, second and third divisions as a function of the exposure time; (ii) the persistence of SCE-inducing lesions and the determination of whether or not they are always involved in SCE formation; (iii) the effect of bromodeoxyuridine (BrdU) incorporation on the induction and persistence of SCE. Three-way differential staining of sister chromatids in murine bone marrow cells in vivo was used in the present study. The results indicate the following: (i) SCE induction in each cell division depends on the course of DNA duplication, suggesting that SCE occurs at the replication fork; (ii) the cell population under study could be considered synchronous and had a cell cycle duration of nearly 9 h; (iii) in the second and third cell divisions ENU preferentially induced SCE in the cycle in which the exposure occurred; (iv) lesions induced by exposure to ENU did not cause SCE at the same site in subsequent divisions; (v) ENU was also capable of producing a long-lasting induction of SCE in BrdU-unsubstituted DNA; (vi) the sensitivity to SCE induction by the mutagen increases nearly proportionally to BrdU incorporation into DNA.     

Sister chromatid exchange and chromosome breakage in complete hydatidiform moles.

Women with complete hydatidiform moles (CHM) are at a 10% risk for developing persistent trophoblastic disease or choriocarcinoma. We studied sister chromatid exchange (SCE) as a prognostic indicator for malignancy in peripheral blood lymphocytes (PBL) from women with CHM and their husbands, but found no differences from normal control couples. SCE levels in cultured tissue derived from 11 CHM (avg. 7.9) and 2 choriocarcinomas (avg. 6.8) were not significantly different from those of 8 normal skin fibroblast cultures (avg. 7.8). These same tissues were then examined for chromosome breakage which was significantly higher for CHM (0.48/cell) and choriocarcinoma (0.87/cell) than normal fibroblasts (0.33/cell). Chromosome breaks occurred at 50-60% known fragile sites and at 50-55% of cancer breakpoints. Whereas SCE was only associated with 13% of breaks in the three tissues, half of these were at known fragile sites. Our results suggest that SCE is not an indicator of malignancy in PBL or cultured cells from CHM or choriocarcinoma and that the level of SCE is not elevated in CHM or choriocarcinoma. However, our results confirm the increased breakage seen in the latter two tissues which may represent general DNA instability predisposing to choriocarcinoma and its accompanying chromosomal rearrangements.     

Sister chromatid exchange evaluation as an aid to the diagnosis and exclusion of Fanconi''s anaemia by induced chromosome damage analysis.

Evaluation of chromatid aberrations induced in culture by DNA cross linking agents provides the most reliable method currently available for the diagnosis and exclusion of Fanconi's anaemia. However, at appropriate concentrations of clastogenic agent the aberration frequency in an unaffected subject may be very low and thus it may be difficult to confirm that the treatment was effective. Data are presented to show that sister chromatid exchange analysis can be used to monitor the effectiveness of the clastogen treatment and thereby increase the reliability and efficiency of the assay.     

Sister chromatid exchange frequency in B-cells stimulated by TPA in chronic lymphocytic leukemia

Chronic lymphocytic leukemia (CLL) is characterised by the clonal proliferation and accumulation of neoplastic B-lymphocytes. The median age of the patients is 65 years, and more men than women are affected. The overwhelming majority of CLLs are of B-cell origin. Chromosomal aberrations have been detected in more than 50% of the B-cells obtained from peripheral blood samples after appropriate stimulation with polyclonal B-cell mitogens. The analysis of sister chromatid exchange is a cytogenetic technique used to show DNA damage due to an exchange of DNA fragments between sister chromatids. In this study, lymphocytes from 22 patients with CLL-B (7 female, 15 male; mean age 64.09 +/- 7.56 years) were stimulated by a B-cell mitogen (TPA) and BrdU added at the 24 h of the culture. Metaphase chromosomes were stained with a fluorescence plus Giemsa technique after a standard harvest procedure. The frequency of sister chromatid exchange was found to be increased significantly P =.02) in patients with CLL-B (8.24 +/- 1.36 per metaphase) compared to controls (7.25 +/- 1.42 per metaphase). We conclude that the increased frequency of sister chromatid exchange in chronic lymphocytic leukemia after stimulation with a B-cell mitogen (TPA) may reflect DNA instability and defective DNA repair in these patients.     

Sister chromatid exchange and chromosome fragility in the nevoid basal cell carcinoma syndrome

Previous studies of chromosome stability in the nevoid basal cell carcinoma syndrome have yielded inconsistent results and suffered from small sample sizes and less than optimal controls. We investigated chromosome fragility and sister chromatid exchange in 20 affected individuals from five multiplex pedigrees, and 15 first- or second-degree unaffected relatives. The percentage of case and control cells showing breaks or rearrangements was compared using a test of proportions. A similar procedure was used to compare site-specific sister chromatid exchanges in baseline cultures from affected persons and controls. No significant differences were noted for either chromosome fragility or sister chromatid exchange between the two groups. These results suggest that cancer susceptibility in the nevoid basal cell carcinoma syndrome is not caused by or manifested as chromosome instability.     

Sister chromatid exchange and lym phocyte proliferation in a Down syndrome mosaic

The number of SCE was compared in the normal and trisomic cell lines of a trisomy 21 mosaic case. It was found that in the trisomic cells the SCE-frequency was twice as high as in the normal cells. The mitoses with high numbers of SCE (above 10) were increased 4-5 fold. Differential chromatid staining also allowed us to determine the mitotic cycle of the mitoses. The percentage of mitoses from the fourth or a later mitotic cycle was significantly higher in the trisomic cell line than in the normal one. From this result, it can be concluded that the cell cycle time was distinctly shortened in the cells with trisomy 21.     

Sister chromatid exchange induction and cell cycle inhibition by aniline and its metabolites in human fibroblasts

Sister chromatid exchange (SCE) and cell cycle analyses in human fibroblasts were used to ascertain the relative genotoxicity and cytotoxicity of aniline and its metabolites. Fibroblasts were allowed to attach to plastic petri dishes for 4 hr and exposed in serum-free medium for 2 hr to the following: aniline HCl (0.05–10.0 mM), acetanilide (0.1–10.0 mM), o-hydroxyacetanilide (0.01–2.0 mM), p-hydroxyacetanilide (0.1–10.0 mM), o-aminophenol (0.01–0.3 mM), p-aminophenol (0.005–0.2 mM), N-phenylhydroxylamine (0.001–0.5 mM). Triethylenemelamine (TEM; 0.25 and 0.49 μM) was used as a positive control. The treatment medium was replaced with complete medium containing 5-bromo-deoxyuridine (10 μM), and cells were allowed to grow for 48 hr with Colcemid present for the final 4.5 hr. Cell cycle analyses (percentage of cells in first, second, or third division) revealed that p-hydroxyacetanilide (10mM), p-aminophenol (≥0.1 mM), o-aminophenol (≥0.1 mM), N-phenylhydroxylamine (≥ mM), and TEM (0.49 μM) inhibited cell proliferation. Cell death was seen at doses of 0.5 mM N-phenylhydroxylamine, 0.2 mM p-aminophenol, and 0.3 mM o-aminophenol. Significant increases (P0.05) in SCE frequencies were found with aniline HCl, o-aminophenol, N-phenylhydroxylamine, and TEM. On an SCE/mmole basis at the highest concentrations examined, o-aminophenol was 270 times more potent than aniline in inducing SCE, whereas TEM was about 390 times more potent than o-aminophenol. Furthermore, fibroblasts treated with o-aminophenol responded in a dose-dependent fashion and exhibited a 2-fold increase in SCE frequency. N-phenylhydroxylamine induced a less clear-cut, dose-related increase in SCE frequency with a 1.4-fold elevation. Only marginal increases in SCE were observed with aniline at the highest doses. Using these data, we propose that aniline may exert its tumorigenic potential in rats through the production of both genotoxic and cytotoxic metabolites.     

Sister chromatid exchange (SCE) of the kinetochore carrying segment, KS

The mechanism of SCE discussed in previous papers (3, 4) is adapted to account for the absence of kinks on chromatids experiencing an exchange limited to their KSs. The paper ends with a brief digression on kinks. Equivalent to solitons, such dynamic malformations can function as carriers of information along the chromatid stack.     

Sister chromatid exchanges induced in rabbit lymphocytes by ethylene oxide after inhalation exposure

Ethylene oxide, which is the simplest epoxide and an extremely important commercial compound, has been used by many investigators as a model compound to study mutagenicity by alkylation of DNA. Knowledge of in vivo dose-effect relations under experimental conditions may provide further insight into the dynamics of the sister chromatid exchange (SCE) response. It may also provide information on temporal aspects of sampling design for human worker populations. Groups of four male New Zealand white rabbits were exposed in inhalation chambers to 0, 10, 50, and 250 parts per million (ppm) ethylene oxide for 6 hr a day, 5 days a week, for 12 weeks. Peripheral blood samples were taken before the start of exposure, at intervals during exposure, and up to 15 weeks after the end of exposure to measure SCE rates in peripheral lymphocytes as well as standard hematological endpoints. Additionally, the level of reduced glutathione (GSH) in liver and blood was measured in a set of concurrently exposed animals at the end of the 12-week exposure. Results show that exposure to 10 ppm does not cause a detectable increase in SCE rates. However, exposure to 50 and 250 ppm does cause an increase in SCEs that decreases after exposure ends, but still remains above baseline levels 15 weeks after exposure. Hematological and GSH measurements did not differ between control and exposed groups. These results indicate that inhalation exposure to the mutagenic alkylating agent ethylene oxide results in a dose-related SCE effect, and that SCE is a more sensitive indicator of exposure than either standard hematological end points or GSH levels.     

Sister chromatid exchange: Variation by age,sex, smoking,and breast cancer status

Variation in sister chromatid exchange (SCE) frequency in lymphocytes of 125 persons was compared using a multivariate general linear model. The study was performed to determine whether SCE frequency differs with respect to age, sex, smoking, and breast cancer status. Study subjects were divided into: members of two branches of families having an excess of cancer (primarily breast) including a brother and sister in one family who developed nonbreast malignancies within 1 yr of the study; women in both families successfully treated for breast cancer (all at least 5 yr posttreatment); and women from the general population with confirmed breast cancer.Controls consisted of spouses who married into the high-risk kindreds, hospital personnel, and others (primarily tradesmen without history of occupational exposure). Results show that: (1) Women with active breast cancer have a significantly higher mean SCE frequency than control women or women greater than 5 yr posttreatment for breast cancer; (2) Cigarette smokers show a significantly higher number of SCEs than was observed in nonsmokers; (3) The increase in SCE level in smokers is dose-related to exposure as measured by cumulative pack-years; (4) SCE values in both high-risk families are not significantly different from controls; (5) Neither the age nor sex of the individual affects SCE frequency; and (6) The observed distribution of exchanges agrees with that expected based on the proportion of the genome represented by each chromosome group.     

Sister chromatid exchanges induced by tertiary butyl hydroquinone in bone marrow cells of mice

Tertiary butyl hydroquinone (TBHQ)--a phenolic antioxidant, was evaluated by assessing the induction of sister chromatid exchanges (SCEs) in bone marrow metaphase cells of mice. Six concentrations, 0.5, 2, 20, 50, 100, and 200 mg/kg, of TBHQ were injected intraperitoneally. A positive dose-response effect in the SCE frequency was observed using the Cochran-Armitage trend test. Two mg/kg of TBHQ was found to be the minimum effective dose. Study of the cell-cycle kinetics showed a delay in cell cycle induced by the higher concentrations of TBHQ. Thus, TBHQ was found to be a DNA damage-inducing agent and also a cytotoxic chemical in vivo in mice.     

Sister chromatid exchange and proliferation pattern in stimulated lymphocytes of cutaneous malignant melanoma patients

Sister chromatid exchange (SCE) and the proliferative pattern of phytohemagglutinin-stimulated lymphocytes were examined in 36 nonfamilial cutaneous malignant melanoma (CMM) patients. One close relative of each of 27 CMM patients was also examined. All the patients had undergone surgical treatment for the neoplasm, but had received no chemotherapy or radiotherapy. The SCE rates were found to be higher and more variable in a significant fraction of CMM patients, and in relatively fewer unaffected relatives, which is in contrast to findings in unrelated subjects taken as controls. Also, variable and higher proportions of cells in metaphase of the first cell cycle (M1), after 72-hr culture in the presence of bromodeoxyuridine, were more often found among the CMM patients than in the controls; however, no effect of clinical progression of the neoplastic disease on SCE rates or on the lymphoproliferative pattern was observed. The present study indicates heterogeneity among subjects who develop CMM and suggests that the peculiarities of SCE rates and of the lymphoproliferative patterns observed in some of the CMM patients and in a few of their close relatives may be connected with the mechanism of onset of the neoplasm.     

Sister chromatid exchange induction near the baseline with low doses of the alkylating agent CCNU

Sister chromatid exchange (SCE) and cell-cycle kinetics were examined at near-baseline levels in human peripheral lymphocytes exposed to low doses of the potent SCE inducer 1-(2-chloroethyl)-3-cyclohexyl-1-nitrosourea (CCNU), in vitro. A preliminary SCE dose-response curve was determined with a broad range of doses of CCNU using a single donor. SCE induction was approximately linear over the entire dose range from 5 to 200 microM CCNU. Cell cycle kinetics were retarded in a dose-dependent manner. A second dose-response curve from the same donor was constructed using several doses of CCNU between 0.5 and 10 microM to evaluate linearity and uniformity of SCE response near baseline levels. SCE induction was approximately linear between 1.0 and 10.0 microM CCNU. Finally, SCE and cell-cycle kinetics were examined in 12 donors at doses of 1.0, 5.0, and 10.0 microM CCNU to evaluate the reproducibility of near-baseline SCE induction over a range of subjects. Cell-cycle kinetics were retarded at all three doses with a highly significant increase in SCE frequencies at 5.0 and 10.0 microM CCNU. These data suggest that increases in SCE less than twice background can be reliable indicators of genotoxic exposure.