Proliferative characteristics and sister chromatid exchange (SCE) of colony-forming cells (CFU-S) in acute myelogenous leukemia

Sister chromatid exchange (SCE) and cell cycle progression of colony-forming cells (CFU-S) from patients with acute myelogenous leukemia were studied using bromodeoxyuridine (BrdU) incorporation and sister chromatid differential staining. The mean SCE rate of CFU-S was 7.99, which is similar to that reported for human peripheral blood lymphocytes. Cultures treated with BrdU at culture initiation and then harvested 72-120 hr later indicated a cell cycle time (TC) of approximately 60 hr. However, cells allowed to proliferate for 72-120 hr prior to the addition of BrdU showed TC values of 12-36 hr. Analysis of serial cultures from one patient revealed a heterogeneous population with a mean TC of 19.5 hr. These cell cycle times are considerably shorter than previously published reports and suggest that leukemic cells have the potential to divide rapidly.     

Increased spontaneous and mitomycin C-induced sister chromatid exchanges in patients with cancer of the cervix uteri, with special reference to stage of cancer

The frequencies of spontaneous and mitomycin C (MMC)-induced sister chromatid exchange (SCE) were examined in 35 patients with cancer of the cervix uteri (stage 0, eight cases; stage I, nine cases; stage II, nine cases, and stage III, nine cases) before they had undergone cancer treatment, as well as in seven patients with uterine myoma and 18 healthy women as controls. The frequency of SCE was analyzed in reference to the stage of cancer in the cancer group and in reference to chromosome group in the cancer and normal groups. The frequencies of spontaneous and MMC-induced SCE in the cancer group were 10.0 +/- 1.8 and 20.7 +/- 2.6, respectively, and both were significantly higher than in the myoma (8.1 +/- 0.8 and 17.6 +/- 1.8) and normal (7.6 +/- 0.8 and 17.6 +/- 2.3) groups. Furthermore, the frequency of SCE in the cancer group increased with cancer stage. All chromosome groups contributed equally to the increase in SCE in the cancer group. These results indicate that an increase in the frequency of SCE in patients with cervical cancer is related to the presence of cancer, but is not related to a predisposition to cancer.     

SCE and UDS studies in a family with retinoblastoma: a case study

The frequencies of both spontaneous and mitomycin C (MMC)-induced sister chromatid exchanges (SCE) were analyzed in mixed lymphocyte cultures from a kindred with retinoblastoma. Both the affected daughter and male proband, as well as two normal controls, were studied. No differences were observed in the spontaneous or in the MMC-induced SCE frequencies obtained from the peripheral lymphocytes of these patients compared to the normal controls. Unscheduled DNA synthesis (UDS) was observed in the lymphocytes treated with varying concentrations of both MMC and M-methyl-N-nitro-N-nitrosoguanidine (MNNG). Whereas no differences were observed in the rate of [3H]thymidine incorporation in the retinoblastoma-derived lymphocytes exposed to MMC when compared to the controls, differences were seen in the response to MNNG. Our data suggest that cells from these retinoblastoma patients respond like normal cells to damage induced by MMC, but that they are unable to repair damage induced by MNNG.     

Effects of acute and chronic administration of mitomycin C on the induction of sister chromatid exchanges in vivo

Frequencies of sister chromatid exchanges (SCE) were analyzed in bone marrow cells of mice injected with mitomycin C (MMC) both before and during infusion with bromodeoxyuridine (BrdU). Administration of MMC at 1, 6.5, and 13 hours after the onset of BrdU infusion resulted in the induction of approximately 45 SCE/cell, independent of time of administration. When MMC was injected 26 hours prior to BrdU infusion, only baseline levels of SCE were noted. The effects of multiple doses of MMC (chronic administration) were examined in mice treated with 1–5 mg/kg on a weekly or bimonthly basis. SCE analysis was performed one week after the final injection. At all doses and with all treatment regimes, SCE frequencies did not differ from control levels. The results indicate that most or all MMC-induced DNA damage that results in SCE formation is removed in a single cell cycle after its administration.     

Sister chromatid exchange in normal and Ph1-positive leukemic cells after mitomycin-C treatment in vitro

The sister chromatid exchange (SCE) frequency was investigated in normal bone marrow and Ph1-positive cells of chronic myelocytic leukemia (CML) patients with and without mitomycin-C (MMC) treatment in vitro. Even though the spontaneous SCE frequency was found to be significantly lower in CML cells, the absolute SCE values after MMC treatment did not differ between leukemic and normal cells, and this seems to indicate an equilization of SCE rates. However, the fact that leukemic cells with lower spontaneous SCE rates need a further increase of SCE to reach values equal to those of normal cells might indicate a somewhat higher susceptibility of leukemic cells to DNA damage by MMC. This interpretation appears to be confirmed by the fact that the inhibition of cellular proliferation at higher MMC doses considerably reduced the number of leukemic cells that was able to divide twice during a given culture time.     

Cytogenetic and cytokinetic analysis of lymphocytes from patients with hereditary adenomatosis of the colon and rectum

The frequencies of chromosome aberrations, sister chromatid exchanges (SCEs), and cell cycle kinetics were examined in cultured lymphocytes from five patients with hereditary adenomatosis of the colon and rectum (ACR) [three patients with Gardner's syndrome (GS) and two patients with familial polyposis coli (FPC)]. The frequency of numerical chromosome aberrations was no different in metaphase cells at the first and second replication cycles (M1 and M2) in the ACR patients and control subjects. The percentage of structural chromosome aberrations in both M1 and M2 cells was somewhat higher in the ACR patients as compared with the controls. Neither spontaneous nor mitomycin C-induced SCE frequencies in the patients with ACR were different from the controls, except for one patient with GS, who showed a remarkably high spontaneous SCE frequency. This patient is the mother of a son who had hepatoblastoma. The cell replication index (RI) was lower in the GS patients than in the controls. However, the RI in the FPC patients did not differ from that of the controls.     

Increased sensitivity to mitomycin C-induced sister chromatid exchange in lymphocytes from patients undergoing hyperbaric oxygen therapy

Treatment of cells with hyperbaric oxygen (HBO) results in the generation of reactive oxygen species and the induction of DNA damage. In the present study, we have evaluated the sister chromatid exchange (SCE) frequencies in lymphocytes from patients undergoing hyperbaric oxygen therapy (HBOT). In addition, we have determined the sensitivity of lymphocytes from those patients to SCE induction by 20 and 40 ng/ml mitomycin C (MMC). Patients undergoing HBOT for diabetic feet were exposed to 10 consecutive daily HBO treatments according to a routine therapy protocol. The study began with 12 patients; however, it was not possible to sample all of the patients at all HBOT sessions, and the number of patients gradually decreased towards the end of the HBOT. We observed a statistically significant induction in mean SCE/cell (P < 0.05; n = 11) immediately after the first session of HBOT. Relative to its frequency after the 1st treatment, the mean SCE frequency gradually decreased after the 5th and 10th HBOT sessions and reached baseline (pretherapy) levels 1 day after the last treatment in the four patients that were sampled. The mean MMC-induced SCE frequency was highest in lymphocytes sampled immediately after the first HBOT session, and significantly higher than the MMC-induced SCE frequency in cells sampled before HBOT. Unlike the case with untreated cells, MMC-induced SCE frequencies remained high in lymphocytes sampled at later stages of therapy and mean MMC-induced SCE frequencies were significantly higher (P < 0.05; n = 4) in lymphocytes sampled 1 day after the last session of HBOT than in lymphocytes sampled from these patients prior to beginning the therapy. The results indicate that HBOT induces SCE and that lymphocytes retain increased sensitivity to the genotoxicity of MMC one day after completing the HBOT.     

Induction of chromosome aberrations and specific locus mutation but not sister chromatid exchanges in Chinese hamster ovary cells by neocarzinostatin

The induction of chromosome aberrations, sister chromatid exchanges (SCE), cytotoxicity, and 6-thioguanine-resistant mutation by neocarzinostatin (NCS) in Chinese hamster ovary cells was analyzed. It was observed that within the same concentration range of 0.01-0.1 mu/ml NCS, the drug induced a significant increase in all analyzed end-points except in SCE frequencies. There was no increase in SCE frequencies even when the cells were treated at the G1/S border in the first cell cycle and when aberrations were observed in the same cell showing a second cycle differential staining pattern. Our study indicates that the cellular damage induced by NCS leads to expression in chromosome aberrations, cytotoxicity, and mutagenicity but not in sister chromatid exchanges.     

Estrogen effects on chromosome number and sister chromatid exchanges in uterine epithelial cells and kidney cells from neonatal mice.

Female mice of the NMRI strain were treated with a high dose (5 micrograms) or a low dose (10(-2) micrograms) of the synthetic estrogen diethylstilbestrol (DES) or estradiol-17 beta (E2) 48 and 24 hr, 24 hr, or 12 hr before death on day 3 after birth. Cultures of epithelium from the uterine cervix and uterine horns as well as of kidney cells were set up, and, after a culture period of 3 days, cells were studied for chromosome number and sister chromatid exchanges. Cervical cells from control females had a distinct peak of tetraploid cells, which was depressed after DES treatment but less so after E2 treatment. The tetraploid peak was lower in uterine horn epithelium and was less influenced by DES. No indications were obtained for an estrogen-induced aneuploid cell population in the uterine horn epithelium or cervical epithelium. The incidence of cells with a high number of sister chromatid exchanges (HFCECs) was only about one-fifth in uterine horn epithelium from control females compared with cervical epithelium from the same females. In the cervical epithelium, DES at both dose levels and E2 at the high dose induced an increased and similar incidence of HFCECs (from about 12.5% in controls to about 35%), which was not related to estrogen exposure time. In uterine horn epithelium, the incidence of HFCECs increased from 2.5% in controls to 8.5% after DES treatment. It is postulated that there is a more pronounced genomic plasticity in the cervical epithelium compared with the uterine horn epithelium. The estrogens had no effect on chromosome number or HFCECs in kidney cells.     

Sister chromatid exchange in aplastic anemia

The incidence of sister chromatid exchanges (SCE) in the lymphocytes of patients with aplastic anemia (AA) was determined before and after exposure to mitomycin C (MMC). The “baseline” SCE rate was significantly higher in AA, but MMC-induced SCE rate was not different compared to controls. It is suggested that some patients with AA may have an underlying DNA damage.     

Factors underlying variation in spontaneous and clastogen-induced sister chromatid exchanges and chromosome breakage frequencies.

The latent "factors" influencing spontaneous and clastogen-induced genetic damage, measured by rates of sister chromatid exchange (SCE) and chromosome breakage (CB), were investigated in a small sample of 20 unrelated, healthy individuals. The covariation of spontaneous and clastogen-induced (bleomycin [BLM], streptonigrin [SN], mitomycin-C [MMC], 4-nitroquinoline-1-oxide [4NQO]) SCEs and CBs was analyzed by maximum-likelihood factor analysis. A single-factor model resulted in large standardized regression coefficients of measured variables on the factor for spontaneous and BLM- and SN-induced SCE frequencies, and a modest regression coefficient for MMC-induced SCEs. A two-factor model, after varimax rotation, yielded one factor strongly associated with spontaneous and BLM- and SN-induced SCE frequencies, and a second factor associated with spontaneous and BLM- and SN-induced CBs. A bootstrap analysis of this data set indicated the statistical significance of one regression coefficient (i.e., P less than or equal to 0.05) and borderline significance (0.07 less than or equal to P less than or equal to 0.11) of three other regression coefficients on the first factor, to be interpreted as an effector of SCE frequencies. However, for the second factor, none of the bootstrapped regression coefficients was significant (P greater than 0.22). Due to the modest sample utilized in this study, the validity of this model should be further explored using additional, larger data sets.     

Baseline and mitomycin-c-induced sister chromatid exchanges in a melanoma and a colon tumor cell line

Baseline and mitomycin C (MMC)-induced sister chromatid exchanges (SCEs) in two human tumor cell lines (a colon tumor and a melanoma) and in a normal fibroblast cell line were analyzed and compared. The tumor cells showed numerical and structural chromosomal abnormalities. Their baseline SCE rate was slightly, but not significantly, higher than that of the control. Each tumor cell line showed a dose-dependent increase in SCE frequency above the spontaneous level in its own specific manner. The response in the malanoma cell was consistantly below that of the control, but only the response to the highest dose of MMC (10^?9 M) was significantly lower than that of the control. The response of the colon tumor cells varied with respect to that of the control. Thus, it appears that karyotypic instability in tumor cells is not necessarily associated with elevated baseline or induced SCE/chromosome rates. In addition, within each cell line dose group, the SCE frequency was proportional to the number of chromosomes. Thus, the SCE/chromosome is a better expression of genetic damage than SCE/metaphase in analyses involving heteroploid cells.     

Effect of the dithiocarbamate pesticide zineb and its commercial formulation azzurro. I. Genotoxic evaluation on cultured human lymphocytes exposed in vitro.

The in vitro cytogenetic effects exerted by the dithiocarbamate fungicide zineb and one of its commercial formulations currently used in Argentina, azzurro, were studied in whole blood human lymphocyte cultures. The genotoxicity of the fungicides was measured by analysis of the frequency of chromosomal aberrations and sister chromatid exchanges (SCEs) and cell cycle progression assays. Both zineb and azzurro activities were tested within the range 0.1-100.0 microg/ml immediately after in vitro lymphocyte stimulation. Only concentrations of 50.0 and 100.0 microg/ml zineb and azzurro induced a significant increase in SCE frequency over control values. Furthermore, this genotoxicity appears to be correlated with its cytotoxicity, measured as cell cycle kinetics, since both a significant delay in cell cycle progression and a significant reduction in proliferative rate index were only observed in those cultures treated with these fungicide concentrations. For both chemicals, a progressive dose-related inhibition of the mitotic activity of cultures was observed when increasing the fungicide concentration. Moreover, only the mitotic activity statistically differed from control values when doses of zineb or azzurro <10 microg/ml were employed. For both fungicides the mitotic index reached the minimal value at doses of 100 microg/ml. Both products induced a significant dose-dependent increase in the number of abnormal cells, chromatid-type and chromosome-type aberrations as well as in the total number of aberrations in the 0.1-100.0 microg/ml dose range. Based on these results, the evaluation of zineb as a controversial genotoxic/non-genotoxic compound for human health should be reconsidered. Instead, we demonstrate that the fungicide induces large DNA alterations and should be considered as a clastogenic mutagen.     

Vitamin E prevents ethylene bis(dithiocarbamate) pesticide zineb-induced sister chromatid exchange in Chinese hamster ovary cells

The in vitro effect of the antioxidant alpha-tocopherol, vitamin E, on deleterious effects induced by the dithiocarbamate fungicide zineb and its commercial formulation azzurro on Chinese hamster ovary (CHO) cells was studied by using frequency of sister chromatid exchanges (SCEs), cell cycle progression and mitotic index (MI) as genetic end points. Both zineb and azzurro activities were tested within the range 0.1-100.0 microg/ml on exponentially growing CHO cells preincubated for 24 h in the presence or absence of 50.0 microg/ml vitamin E. SCE frequencies increased significantly over control values in a concentration-dependent manner in zineb- and azzurro-treated cultures at concentrations of 0.1-10.0 and 0.1-25.0 microg/ml, respectively. When target cells were preincubated with vitamin E, the number of SCEs was significantly lower than that observed in cells exposed only to 1.0-10.0 microg/ml zineb or 1.0-25.0 microg/ml azzurro, but higher than control values. Cytotoxicity was observed at concentrations higher than 25.0 and 50.0 microg/ml zineb and azzurro, respectively, regardless of the absence or presence of vitamin E. Regression analysis showed that the proliferative rate index decreased as a function of the concentration of zineb (0.1-10.0 microg/ml concentration range) and azzurro (0.1-25.0 microg/ml concentration range) titrated into cultures. For both chemicals, progressive concentration-related inhibition of the mitotic activity from cultures was observed when 10.0 microg/ml zineb or 1.0-25.0 microg/ml azzurro was employed. However, no significant alteration in cell cycle progression or MI was observed between vitamin E-preincubated cultures and those treated only with zineb and azzurro.     

Fibroblast cultures of patients with basal cell epithelioma exhibit a normal sensitivity to the genotoxic effect of ultraviolet irradiation.

Fibroblast cultures of 16 basal cell epithelioma (basalioma, BCE) patients with an unusually young age at onset of disease (29-51 years; 42.5 +/- 7.04), and healthy normal controls (27-55 years; 40.73 +/- 9.52) were studied for chromosome instability induced by ultraviolet rays (UV). We used an UV source that emitted predominantly UV-A and UV-B at an intensity of 375 J/m2 and evaluated the induction of micronuclei (MN) and sister chromatid exchange (SCE). Young basalioma patients and normal controls showed no significant differences in MN and SCE frequencies, neither with respect to spontaneous nor to UV-induced values (MN spontaneous: 10.80 +/- 5.65 vs. 11.32 +/- 8.21; UV-induced increase: 7.36 +/- 4.40 vs. 9.93 +/- 7.55; SCE spontaneous: 10.28 +/- 1.61 vs. 10.72 +/- 1.09; UV-induced increase: 7.30 +/- 2.19 vs. 7.55 +/- 2.14). We conclude from these data that an enhanced UV sensitivity as observed in cells from patients with cutaneous malignant melanoma and xeroderma pigmentosum is not a constitutive risk factor in basalioma patients.     

Sister chromatid exchange analysis in lung and peripheral blood lymphocytes of mice exposed to methyl isocyanate by inhalation

Mice were exposed to 1, 3, or 6 ppm methyl isocyanate (MIC) for 6 hr/day for four consecutive days. Lung cells and peripheral blood lymphocytes (PBLs) were removed and cultured for analysis of sister chromatid exchange (SCE) and cell cycle kinetics. MIC caused a small but significant increase in SCE frequency of cultured lung cells from mice exposed to 1, 3, or 6 ppm MIC. MIC did not significantly increase SCE levels in PBLs of mice exposed to concentrations as high as 6 ppm. In cultured PBLs, MIC had a stimulatory effect on cell cycling rates as measured by the replicative index, and it caused a significant reduction in mononuclear leucocyte counts and the mitotic indices.     

The restriction endonuclease AluI induces sister chromatid exchange in Chinese hamster ovary cells.

Chinese hamster ovary (CHO) cells were exposed to the restriction endonuclease AluI in the presence of 1.1 M glycerol. Chromosomal aberrations and sister chromatid exchange (SCE) were scored in first post-treatment metaphases following recovery times of 6-18 h. At all recovery times chromosomal aberrations were induced by the enzyme. In AluI-treated damaged cells significant elevations of SCE frequencies were found after recovery times of 12-18 h. These results indicate that SCE, unlike chromosomal aberrations, are induced only in late G1 and early S phase of the cell cycle. The lesions producing SCE are postulated as DNA single-strand breaks and gaps induced by AluI in canonical structures of DNA and in DNA-RNA hybrids.     

Sister chromatid exchange levels and cell cycle time in human bone marrow cells and lymphocytes

The frequency of sister chromatid exchange (SCE) and the cell-cycle-specific pattern of mitoses were analyzed at the same time in normal bone marrow cells and lymphocytes of six healthy donors. The SCE frequency was found to be significantly higher in lymphocytes. The cell-cycle-specific pattern revealed significantly shorter cell cycle times for normal bone marrow cells as compared with those of phytohemagglutinin (PHA) stimulated lymphocytes. Chromosomes of bone marrow metaphases displayed a more contracted morphology.     

Sister chromatid exchanges in peripheral lymphocytes from women with carcinoma of the uterine cervix

Sister chromatid exchanges (SCE) are reciprocal exchanges between sister chromatids. It has been reported that in patients with cervical cancer, the frequency of SCE in peripheral lymphocytes is significantly higher than that in normal individuals; however, other studies have shown no significant difference. The aim of this unmatched case-control study was to compare the mean number of SCE per metaphase in lymphocytes from women with and without carcinoma of the cervix uteri. The SCE specimens were prepared by the fluorescence plus giemsa technique in peripheral lymphocytes from 28 women with carcinoma of cervix uteri and 28 controls. The mean number of SCE per metaphase in women with carcinoma of cervix uteri (7.80 +/- 1.05) was higher than the control group (6.98 +/- 1.13) (P < 0.05; t-test). This study had a statistical power of 0.80 and an alpha value of 0.05. This finding suggests that an increased number of SCE in peripheral lymphocytes is associated with cervical cancer. We consider that the lack of reported association of SCE and cervical cancer might be attributed to the none determination of the statistical power and sample size.     

Monocytes affect cell-cycle progression but not baseline frequency of sister chromatid exchanges of pig lymphocytes

The effect of pig monocytes (MNs) on the baseline frequency of sister chromatid exchanges (SCEs) and cell-cycle progression of pig lymphocytes was studied in plasma leukocyte (PLCs) and whole blood leukocyte cultures (WBCs). No variation in SCE frequency was observed between control WBC and PLC, nor did the addition of pig MNs to PLCs modify the baseline frequency of SCEs. Cell proliferation was slower in PLCs than in WBCs. Variations in cell-cycle progression of pig lymphocytes from PLC were observed both in the absence and presence of adherent cells in the culture. In MN-free cultures, lymphocytes proliferated foster than in parallel PLC cultures. However, when MNs were seeded into the cultures, cell-cycle progression gradually slowed as a function of the concentration of adherent cells present in the cultures. This finding shows that pig MNs modulate the in vitro cell-cycle progression of pig lymphocytes in a dose-dependent manner and that the low baseline SCE frequency of pig lymphocytes is independent of the presence or absence of MNs in the culture.