Sister-chromatid exchange in human B- and T-lymphocytes exposed to bleomycin, cyclophosphamide, and ethyl methanesulfonate

Synthesis and in vitro anticancer evaluation of novel flavonoid-based amide derivatives as regulators of the PI3K/AKT signal pathway for TNBC treatment

Aberrant activation of the PI3K/AKT pathway is considered in many malignant tumors and plays a crucial role in mediating malignancy progression, metastasis, and chemoresistance. Consequently, development of PI3K/AKT pathway targeted drugs is currently an attractive research field for tumor treatment. In this study, twenty-six flavonoid-based amide derivatives were synthesized and evaluated for their antiproliferation effects against seven cancer cell lines, including MDA-MB-231, MCF-7, HCC1937, A549, HepG2, GTL-16 and HeLa. Among them, compound 7t possessed the best specific cytotoxicity against triple negative breast cancer MDA-MB-231 cells with an IC₅₀ value of 1.76 ± 0.91 μM and also presented inhibitory ability on clonal-formation, migration and invasion of MDA-MB-231 cells. Further cell-based mechanistic studies demonstrated that compound 7t caused cell cycle arrest of MDA-MB-231 cells at the G₀/G₁ phase and induced apoptosis. Meanwhile, the western blot assay revealed that compound 7t could down-regulate the expression of p-PI3K, p-AKT, and Bcl-2 and up-regulate the production of PTEN, Bax, and caspase-3. Molecular docking also showed a possible binding mode of 7t with PI3Kα. Together, compound 7t was eligible as a potential TNBC therapeutic candidate for further development.

Differential DNA damage induced by H2O2 and bleomycin in subpopulations of human white blood cells

The purpose of this study was to characterize the differential sensitivities of various subpopulations of human white blood cells after exposure to H2O2 (an oxidant agent) and bleomycin (a radiomimetic glycopeptide), in vitro, using single-cell gel electrophoresis (SCGE). Human peripheral blood was fractionated into mononuclear cells, which were further separated into monocytes, CD4+ T-cells, CD8+ T-cells, B-cells and natural killer cells (NK cells). The separated fractions were exposed to different doses of H2O2 and bleomycin, and then used to measure levels of induced and basal DNA damage. There was a significant increase in the amount of DNA damage in CD4+ T-cells, CD8+ T-cells, NK cells and B-cells when treated with H2O2 and bleomycin, whereas monocytes had the lowest sensitivity to H2O2 compared with the other cell fractions, but no lower sensitivity to bleomycin. Furthermore, CD4+ T-cells and CD8+ T-cells had the highest levels of basal DNA damage. When basal DNA damage was taken into account, NK cells tended to show a higher sensitivity to H2O2 than CD4+ T-cells, CD8+ T-cells and monocytes. In addition, B-cells, which showed lower sensitivity to H2O2 than CD4+ T-cells, CD8+ T-cells and NK cells when exposed to lower doses of H2O2 (<10 microM), showed higher sensitivity to H2O2 at higher doses (>20 microM). On the other hand, B-cells showed the highest sensitivity to bleomycin.

Increased rates of spontaneous sister chromatid exchange in lymphocytes of BRCA2+/- carriers of familial breast cancer clusters

Heterozygous carriers of germ-line mutations of the BRCA2 breast cancer susceptibility gene are predisposed to breast, ovarian, pancreatic and other cancers. The BRCA2 protein is implicated in the maintenance of chromosome stability through its essential function in double-strand DNA repair and recombination. Our previous studies had revealed multiple intrachromosomal rearrangements, duplications, inversions and deletions on 9p23-24 in lymphocytes and fibroblasts of BRCA2+/- members from independently ascertained familial breast cancer clusters. In pursuit of evaluating if there is a subtle genomic instability in BRCA2+/- individuals, we have determined frequencies of spontaneous sister chromatid exchanges (SCEs) in BRCA2 wild-types and BRCA2 mutation carriers of two familial breast cancer clusters. Here, we demonstrate an average increase of 65% of spontaneous SCEs in BRCA2+/- versus BRCA2+/+ family members. In one cluster, the number of metaphases with multiple SCEs was 5-times higher in BRCA2+/- compared to wild-type members, while in the second cluster BRCA2+/- members had 8.9% of metaphases with multiple SCEs compared to a level below detection in BRCA2 wild types. To investigate the correlation between SCE and genomic instability in 9p, we performed fluorescence detection of SCEs and FISH analysis with 9p probes. The frequency of SCE in 9p of BRCA2 mutation carriers was 3-4 fold (P = 0.005) higher compared to BRCA2 wild-types. Collectively, the increased rates of SCE in BRCA2 heterozygous mutation carriers indicate a BRCA2 haploinsufficiency, which might be an important factor for the accumulation of structural chromosomal alterations with the consequence of damage in as yet unidentified genes.

Gamma ray induced DNA damage in human and mouse leucocytes measured by SCGE-Pro: a software developed for automated image analysis and data processing for Comet assay

The studies reported in this communication had two major objectives: first to validate the in-house developed SCGE-Pro: a software developed for automated image analysis and data processing for Comet assay using human peripheral blood leucocytes exposed to radiation doses, viz. 2, 4 and 8 Gy, which are known to produce DNA/chromosome damage using alkaline Comet assay. The second objective was to investigate the effect of gamma radiation on DNA damage in mouse peripheral blood leucocytes using identical doses and experimental conditions, e.g. lyses, electrophoretic conditions and duration of electrophoresis which are known to affect tail moment (TM) and tail length (TL) of comets. Human and mouse whole blood samples were irradiated with different doses of gamma rays, e.g. 2, 4 and 8 Gy at a dose rate of 0.668Gy/min between 0 and 4 degrees C in air. After lyses, cells were electrophorased under alkaline conditions at pH 13, washed and stained with propidium iodide. Images of the cells were acquired and analyzed using in-house developed imaging software, SCGE-Pro, for Comet assay. For each comet, total fluorescence, tail fluorescence and tail length were measured. Increase in TM and TL was considered as the criteria of DNA damage. Analysis of data revealed heterogeneity in the response of leucocytes to gamma ray induced DNA damage both in human as well as in mouse. A wide variation in TM and TL was observed in control and irradiated groups of all the three donors. Data were analyzed for statistical significance using one-way ANOVA. Though a small variation in basal level of TM and TL was observed amongst human and mouse controls, the differences were not statistically significant. A dose-dependent increase in TM (P<0.001) and TL (P<0.001) was obtained at all the radiation doses (2-8 Gy) both in human and mouse leucocytes. However, there was a difference in the nature of dose response curves for human and mouse leucocytes. In human leucocytes, a linear increase in TM and TL was observed up to the highest radiation dose of 8 Gy. However, in case of mouse leucocytes, a sharp increase in TM and TL was observed only up to 4 Gy, and there after saturation ensued. In human samples, the dose response of both TM and TL showed best fits with linear model (r(TM)=0.999 and r(TL)=0.999), where as in mouse, the best fit was obtained with Sigmoid (Boltzman) model. From the present data on leucocytes with increase in TM and TL as the criteria of DNA damage, it appears that mouse is relatively more sensitive to radiation damage than humans.

Comparison of DNA damage in peripheral blood and spleen lymphocytes using the single-cell gel assay

The alkaline single-cell gel (SCG) or 'comet' assay has been applied to the detection of DNA damage from a number of chemical and biological factors in vivo and in vitro. In the past, a number of cell types has been used with peripheral blood lymphocytes being the most readily accessible. This study was designed to determine whether lymphocytes sequestered in the spleen might prove more sensitive to DNA damage than those in the peripheral circulation. This would result in a more effective SCG assay. Baseline DNA length to width ratios for peripheral blood and splenic lymphocytes did not differ significantly from each other (1.27 and 1.21, respectively). Neither did ratios of lymphocytes from the two sources, sampled 20 and 48 h after injection with 100 mg/kg methyl methanesulfonate (MMS) (3.81 and 3.62 at 20 h, respectively; and 1.96 and 2.21 at 48 h, respectively). Recovery from MMS damage at 168 h postinjection was also not different in the two groups of cells (1.13 and 1.16, respectively). However, an examination of cell profiles of DNA damage showed that splenic lymphocytes had a significantly higher percentage of damaged cells (63.33%) than did peripheral blood lymphocytes (40.67%) 48 h postinjection. Of the hypotheses proposed for this difference, the most likely seems to involve the different proportions of B- and T-lymphocytes present in the peripheral blood and the spleen. Since the difference between peripheral blood and splenic lymphocytes was seen only at 48 h postinjection, the use of splenic lymphocytes in the SCG assay is not advantageous under most circumstances.

Variation in arsenic-induced sister chromatid exchange in human lymphocytes and lymphoblastoid cell lines

This study was undertaken to compare the genotoxic effects of arsenite in cultured human lymphocytes and lymphoblastoid cell lines from a group of normal human volunteers. The goal was to determine whether, as found with other genotoxins, subgroups might exist which showed relative high or low sensitivity to induction of sister chromatid exchanges (SCEs) by this metal. Primary lymphoblast cultures were established by treatment with phytohemagglutinin (PHA-L). Lymphoblastoid cell lines were established by transformation with Epstein-Barr virus. Cultures were exposed for 40 h to sodium arsenite (AsIII) and SCEs assayed by 5-bromo-2'-deoxyuridine incorporation and staining by fluorescence plus Giemsa. SCEs were increased by arsenite in a dose-dependent manner over the concentration range of 10(-7)-10(-5) M. SCEs could not be scored above 10(-5) M because of cytotoxicity. Comparison of SCE frequency in primary lymphocyte cultures among individuals showed substantial variation in sensitivity to arsenite, with some showing no significant effect while others showed a 2-3-fold increase in SCE frequency. In one lymphoblastoid cell line especially sensitive to arsenite, arsenic acid (AsV) or dimethylarsinic acid (DMA) at concentrations up to 10(-5) M did not increase the SCE frequency suggesting that AsIII is the active form of arsenic. When pooled data from the primary lymphocytes was compared to that obtained with the lymphoblastoid cells, the slopes of the dose-response curves for ASIII-induced SCEs were similar. The sensitivity of the majority of the individual primary lymphocyte cultures to SCE induction by arsenite was correlated with the sensitivity of the lymphoblastoid cultures established from the same individual. However, in three individuals no correlation was found. Individual lymphoblastoid cell lines retained their As sensitivity after cryopreservation and subsequent revival. Whether the genotoxic response to As is genetically controlled or the result of phenotypic selection is being explored in these stable lymphoblastoid cell lines.

Sister-chromatid exchanges in cattle: breed, sex and BrdU dose effects

The spontaneous incidence of sister-chromatid exchanges (SCE) was investigated in a group of cattle, composed of 21 animals of both sexes and from two different breeds (Fleckvieh and Pirenaica). Peripheral lymphocytes of these animals were cultured in three different bromodeoxyuridine (BrdU) concentrations: 5, 15 and 30 micrograms/ml. The work was carried out following a randomized block design. Among the analyzed sources of variability, group, breed and BrdU dose factors had significant effects on the SCE frequency. No differences between sexes were found. Comparisons of the BdrU doses showed that the 5 micrograms/ml dose differed from both the 15 and 30 micrograms/ml doses, whereas the 15 and 30 micrograms/ml doses did not differ from each other. The results indicate that the breed of cattle as well as the BrdU dose chosen for the analysis must be considered when the SCE test is used for the biomonitoring of environmental mutagens.

Bleomycin sulfate-induced micronuclei in human, rat, and mouse peripheral blood lymphocytes

The sensitivity to micronucleus (MN) induction of human, mouse, and rat peripheral blood lymphocytes (PBLs) exposed to bleomycin sulfate (BLM) in vitro was compared in cytochalasin B-induced binucleated (BN) cells. For the PBLs of each species, either 0, 5, 10, 20, 40, 60, 80, or 160 micrograms/ml BLM was added to 5 ml aliquots of whole blood for 4 hr at 37 degrees C in a 5% CO2 atmosphere. Leukocytes were isolated on a density gradient and cultured in the presence of phytohemagglutinin to stimulate blastogenesis, and cytochalasin B was added to each culture at 21 hr postinitiation to prevent cytokinesis. A total of 4,000 BNs/concentration/species was analyzed for MN in two independent experiments. In addition, multiple-MN-BNs were quantitated, and the nucleation index was determined. Significant increases both in total MN-BNs and multiple-MN-BNs were observed at all concentrations in all species. All three species' concentration-response curves gave good fits (r2 values from 0.87 to 0.95) to either a linear or a square root model (y = mx + b or y = m[x]0.5 + b, respectively; where y = the percentage of MN-BN, m is the slope, and b is the y-intercept). The MN induction in the human and rat PBLs was not statistically different, but both were significantly less sensitive than the response shown by the BLM-exposed mouse PBLs. This difference in MN susceptibility was observed only at BLM test concentrations > or = 20 micrograms/ml. The nucleation index was significantly decreased in all species at either 80 or 160 micrograms/ml.

An analysis of gamma-ray-induced DNA damage in human blood leukocytes, lymphocytes and granulocytes

Lymphocytes and granulocytes were separated from human peripheral blood and irradiated with low doses of gamma-rays (0.05-0.5 Gy) from a 137Cs source. The magnitude and intercellular distribution of DNA damage, i.e., single-strand breaks and alkali-labile lesions, were compared with those obtained in unfractionated leukocytes irradiated in whole blood, using the alkaline single-cell gel-electrophoresis technique. Based on the extent of DNA migration, irradiation resulted in a linear and dose-dependent increase in DNA damage in all 3 cell populations, with a significant increase being detected at 0.05 Gy. The dose-dependent increase for DNA migration was not significantly different between separated lymphocytes and granulocytes, but their responses were significantly elevated over that obtained for leukocytes irradiated in whole blood. Based on an analysis of the ratio of the range to the standard deviation for each cell population at each dose of radiation, the distribution of damage among cells was relatively homogeneous and independent of dose and cell population. These results are consistent with a hypothesis that irradiation of leukocytes in whole blood partially protects against radical-induced DNA damage.

Sister-chromatid exchanges induced by chloramphenicol on bovine lymphocytes

The induction of sister-chromatid exchanges (SCE) was studied in bovine lymphocyte cultures treated with chloramphenicol (CAP), an antibiotic agent in wide use in human and animal therapy. A total of six individuals, matched for sex, race, age and environmental conditions, were used for the analysis. Chloramphenicol was tested at four different concentrations (5, 10, 20 and 40 micrograms/ml) and acted for the last 24 h of the culture. Each experiment included two animals, each of which was exposed to all chloramphenicol doses, for a total of three repetitions. The results of the corresponding analysis of variance showed that this chemical had a small but statistically significant effect on the SCE frequency. In addition, the lymphocyte cultures responded strangely to this chemical: the highest SCE induction was produced by the lowest dose. However, the study of high frequency cells did not show the presence of this kind of cell which could explain this chloramphenicol response. In addition, chloramphenicol induced a high delay in the cell cycle.

Human biological monitoring of occupational genotoxic exposures

Human biological monitoring is a valuable tool for exposure assessment in groups of persons occupationally exposed to genotoxic agents. If the monitoring activity covers genetic material the term genetic monitoring is used. The methods used for genetic monitoring are either substance specific, e.g. the quantitation of identified DNA-adducts or substance unspecific as is the measurement of DNA-repair. The sample material used for analysis must be well characterized and subject to uniform processing for comparison of the results. Confounding factors of smoking, age and sex must be well controlled for and the biomonitoring results should preferentially be linked with accurate ambient air monitoring. In persons occupationally exposed to styrene the endpoints of DNA-damage and DNA-repair in genetic monitoring are methods of choice in exposure situations above the current Danish (25 ppm) or Finnish (20 ppm) occupational exposure limit value of styrene in ambient air. The consideration of ethical issues in human genetic monitoring is an important but often overlooked aspect. This includes the scientific and preventional relevance of performing a test on individuals, pre- and post study information of donors and confidentiality as well as ownership of the results.

Sister-chromatid exchange in highly purified human CD4+ and CD8+ lymphocytes

Sister-chromatid exchange (SCE) frequencies were determined in human peripheral blood CD4+ and CD8+ T lymphocyte subpopulations which were rapidly and highly purified from pooled T lymphocytes by immunological methods. The purified lymphocytes were stimulated with phytohemagglutinin (PHA) for 4 days. CD4+ lymphocytes showed significantly higher SCE frequencies than autologous CD8+ lymphocytes when measured simultaneously after identical bromodeoxyuridine (BrdU) incubation times. Differences in SCE frequencies between CD4+ and CD8+ lymphocytes were also detected when mitomycin C (MMC) was added to the cultures. Higher SCE frequencies in CD4+ lymphocytes were associated with lower proliferating rate indices (PRI) as compared to autologous CD8+ lymphocytes. Abnormalities in CD4+ T lymphocyte function and number in peripheral blood have been observed in several diseases characterized by immunological disorders. Thus, our data may suggest a link between some immunological disturbances and abnormal SCE frequencies in T lymphocyte subsets.

Clastogenic effects of bleomycin, cyclophosphamide, and ethyl methanesulfonate on resting and proliferating human B- and T-lymphocytes

The effects of bleomycin (BM), cyclophosphamide (CP), and ethyl methanesulfonate (EMS) on the frequencies of chromosomal aberrations were tested in mitogen-stimulated highly purified human B- and T-lymphocytes. In unstimulated G0/G1 B- and T-lymphocytes the clastogen induction of chromosome fragments was investigated in prematurely condensed chromosomes (PCC) induced by cell fusion with xenogenic mitotic cells. BM, CP (with metabolic activation), and EMS induced a significant increase in chromosome aberrations in proliferating human B- and T-lymphocytes. There were no significant differences in the BM-induced aberration rates between the cell populations. CP and EMS induced more aberrations in T- than in B-lymphocytes. In the PCC tests, BM-exposed G0/G1 lymphocytes showed dose-dependent high yields of chromosome fragments. No significant differences between B- and T-lymphocytes were observed. CP and EMS induced no clear increase in fragments in either cell population.