Micronuclei in lymphocytes of prostate cancer patients undergoing radiation therapy

To further verify the applicability of the micronucleus (MN) assay in biodosimetry, we measured the MN yield in cytokinesis-blocked (CB) peripheral blood lymphocytes (PBL) of eight prostate cancer (PC) patients. These patients had no previous chemotherapy or radiotherapy (xRT). They were treated with standardized schemes of fractionated pelvic xRT. Before xRT, and at one random time-point during the course of xRT, blood samples were collected from each patient for the following purposes: (1) to verify the relationship between the MN yield in PBL and the estimated equivalent (EQ) total-body absorbed dose; and (2) to evaluate the individual differences of ex vivo radiation dose-response (1-4 Gy) relationship of MN yield in PBL before xRT. The number of xRT fractions, cumulative tumor dose, and EQ total-body absorbed doses of these patients represented a wide range. We found in PBL of these patients that (1) MN yield (Y) increased linearly with the estimated EQ total-body absorbed dose as Y=14.6+9.2D (R(2)=0.7, p=0.007); the distributions of MN yield were overdispersed; the ratio of relative increment of MN yield per 1000 binucleated (BN) PBL ranged from 0.9 to 8.2 (median: 4.1) folds above that of the respective baseline levels; and (2) before xRT, the MN yields also increased linearly with the ex vivo radiation dose; at each radiation dose level, the distributions of MN yield were overdispersed in most patients. In two of the three patients with xRT-induced early side effects (cystitis, diarrhea), the MN yield in PBL induced by ex vivo irradiation before xRT was significantly higher than in the other patients without xRT-induced side effects. These findings suggest that MN yields in CB PBL can be used as an in vivo biodosimeter. Since the differences in individual ex vivo radiation dose-response relationship of MN yield in PBL before xRT appeared to be significant, our preliminary results also suggest that it may be possible to identify individual intrinsic radiosensitivity before the start of xRT.     

Effect of blood storage on radiation-induced micronuclei in human lymphocytes.

To evaluate the effect of blood storage on the yield of micronuclei (MN) in both irradiated (in vivo and ex vivo) and unirradiated peripheral blood lymphocytes (PBL), we applied the MN assay in cytokinesis-blocked (CB) PBL obtained from healthy subjects (n=11), and from cancer patients (n=10) who were undergoing fractionated partial-body radiotherapy (xRT). The heparinized blood samples were exposed to 137Cs-irradiation (0 Gy or 2 Gy) immediately after blood collection and were stored upright in test tubes either at room temperature (22 degrees C) or in the refrigerator (5 degrees C). Duplicate whole blood cultures from each sample were set up at 0 h, 96 h, and 120 h after ex vivo irradiation. Giemsa (10%) stained slides were prepared from each culture. MN yield was determined per 1000 binucleated cells. As compared to that obtained from the corresponding fresh blood samples, we found that (1) the 22 degrees C blood storage temperature did not affect MN yields in PBL of either healthy subjects or cancer patients up to 96 h, either with or without ex vivo irradiation; and (2) while blood samples were stored at 5 degrees C, the MN yield increased significantly in PBL of healthy subjects (with or without ex vivo irradiation) at 120 h, and in cancer patients (with ex vivo irradiation) at 96 h and 120 h. Since handling of the blood sample is important for CBMN assay during shipment or in the laboratory, our findings showed that blood storage at 22 degrees C or at 5 degrees C up to 96 h appeared to provide insignificant variations of the MN results as compared to fresh blood samples. However, the 96 h of blood storage at 5 degrees C elevated the MN frequency in ex vivo irradiated PBL of cancer patients who were undergoing xRT.     

Ginseng reduces the micronuclei yield in lymphocytes after irradiation

To assess the effect of Chinese ginseng in modifying the radiation-induced micronuclei (MN) yield in human G(o) peripheral blood lymphocytes (PBL), we conducted the cytokinesis-blocked (CB) MN assay in blood samples obtained from healthy volunteers (n=4). Before (137)Cs ex vivo irradiation, mononuclear cell cultures from each sample were incubated 24 h with different concentrations (0-2000 microg ml(-1)) of crude water extract of ginseng dry root. We found that (1) at 0 Gy and without the presence of ginseng, MN yield (mean+/-S.E.M.) was 11.7+/-2.7 per 1000 binucleated (BN) cells. Different concentrations of ginseng crude water extract did not affect the MN yields and the proliferative activity of PBL; (2) after 1 and 2 Gy exposure, radiation alone sharply increased the MN yields, respectively, to 119.6+/-17.4 and 340.5+/-20.9 per 1000 BN cells. However, treatment with ginseng for 24 h before radiation exposure, resulted in a significant linear decline of MN yields as ginseng concentration increases. Compared to radiation alone, the extent to which ginseng water extract reduced the MN yields induced by 1 Gy exposure was 46.0% at 1500 microg ml(-1) and 61.5% at 2000 microg ml(-1), and with 2 Gy exposure, it was 38.6% at 1500 microg ml(-1) and 46.5% at 2000 microg ml(-1); (3) MN data suggested a tendency for overdispersion relative to the Poisson model; and (4) over the different levels of ginseng concentrations, the trend in micronucleated BN index was as similar as that of the MN yields. These results indicated that (1) ginseng crude water extract exerts no apparent cytogentic effect on human PBL at concentrations up to 2000 microg ml(-1) as evaluated by the CBMN assay; and (2) the protection of ginseng water extract against (137)Cs-induced MN in human PBL is concentration-dependence. Therefore, our findings indicated that ginseng may have therapeutic value as a possible radioprotector for normal tissue during radiotherapy of cancer patients.     

Relative biological effectiveness of fission neutrons for induction of micronucleus formation in mouse reticulocytes in vivo

Following whole-body irradiation of ICR mice with various doses of fission neutrons or X-rays, the frequency of micronuclei (MNs) in peripheral blood reticulocytes was measured at 12 h intervals beginning immediately after irradiation and ending at 72 h after irradiation. The resulting time-course curve of MN frequency had a clear peak 36 h after irradiation, irrespective of the type of radiation applied and the dose used. The MN frequency, averaged as the unweighted mean over the experimental time course, showed a linear increase with increasing dose of either fission neutrons or X-rays. The linear response to X-rays supports reported conclusion that induction of MN formation in reticulocytes is a dose-rate independent phenomenon. The relative biological effectiveness (RBE) of fission neutrons to X-rays for MN induction was estimated to be 1.9 +/- 0.3. This value is considerably lower than the RBE value of 4.6 +/- 0.5 reported for the same fission neutrons for induction of lymphocyte apoptosis in the thymus of ICR mice that represents dose-rate independent, one-track event. Based on these results, we propose that MNs increased in reticulocytes after irradiation mostly represent acentric fragments caused by single chromosome breaks, and that some confounding factor is operating in erythroblasts for the formation of aberrations from non-rejoining DNA double-strand breaks more severely after high-LET radiation than after low-LET radiation.     

The interaction between X-rays and 3 MeV neutrons in the skin of the mouse foot

Mouse feet were irradiated with mixtures of 3 MeV neutrons and 140 kVp X-rays given simultaneously or within 24 hours of each other. The effects of different treatments were contrasted by comparing the doses required to give equal skin reactions. Irradiation was given as 1, 2, 4 or 8 equal fractions, in order to assess r.b.e. and the shapes of the underlying dose-response curves for mixed beams over a wide range of dose per fraction. All dose-effect curves were well fitted by a linear-quadratic (alpha, beta) model. For X-rays and neutrons given simultaneously, the linear coefficient (alpha) decreased by a factor of 4.80 while the quadratic coefficient (beta) increased by a factor of only 1.44 when the proton contamination in the beam increased from 11 to 100 per cent, with alpha/beta changing from 95.0 to 13.8. The data from simultaneous X-ray and neutron irradiation were consistent with full interaction of those effects from the two radiations which give rise to the total quadratic component of effect. When the two radiations are separated by up to 24 h, this interaction decreases but does not entirely disappear.     

Natural cytotoxicity and interferon production in human cancer: deficient natural killer activity and normal interferon production in patients with advanced disease

Natural cytotoxicity was measured in 51 adult patients with solid epithelial malignant tumors and in 27 normal subjects. Peripheral blood leukocytes (PBL) from 31% of the patients and 7% of the controls failed to kill target cells (K562) in a short-term chromium-release assay. When patients were classified according to clinical stage, PBL from 12% of patients with localized cancers, but 50% of patients with advanced disease, failed to exhibit cytotoxicity within the normal range. Pretreatment of PBL with interferon alpha (IFN alpha) or with Newcastle Disease Virus (NDV), a potent inducer of IFN alpha, enhanced cytotoxicity from all normal subjects. Of patients whose PBL lacked spontaneous cytotoxicity, half were able to kill normally after pretreatment of PBL with IFN alpha or NDV. Virtually all the patients whose PBL were unable to kill despite pretreatment with IFN alpha or virus had disseminated malignancies. IFN alpha production by PBL exposed to NDV and to K562 cells was normal in all the patients regardless of stage of disease or ability to kill K562 cells. The observed defect in natural cytotoxicity is thus unlikely to be due to a failure of PBL to produce IFN alpha.     

A survey on the cytogenetic status of the Croatian general population by use of the cytokinesis-block micronucleus assay

The cytokinesis-block micronucleus assay (CBMN) was used to assess the variability and determine possible influences of external and internal factors on the background levels of cytogenetic damage in peripheral blood lymphocytes (PBL) of 50 healthy volunteers selected at random from the general population of Croatia. The mean MN frequency for all subjects was 4.74+/-0.31 per 1000 cells and the mean cytokinesis-block proliferation index (CBPI) was 1.82+/-0.01. The mean frequency of nucleoplasmic bridges (NPB) for all subjects was 0.06+/-0.04 and of nuclear buds (NB) 0.12+/-0.05. The canonical correlation analyses indicate a positive non-significant correlation between the MN frequency and age, gender and smoking habits. Results of factor structure and canonical weights showed that age and gender rather than smoking habits control the incidence of MN in PBL of healthy volunteers. The lowest median value of MN was observed in subjects younger than 30 years (both smoking and non-smoking). Generally, non-smokers had lower median values of MN compared to smokers. In non-smokers, males showed lower micronucleus incidence than females. Within the non-smokers smaller differences in the median values of MN between subgroups (male and female; age subgroups) were observed. Among smokers, females had a two-fold higher median value of MN frequency than males, but this difference was not significant (p=0.2643, Mann-Whitney U test). Canonical correlation analyses indicate a strong and significant correlation between cell proliferation parameters (M1-M4 and CBPI) and age, gender and smoking habits. The most sensitive parameters were M3 and M4. Age had the strongest effect on M3, while M4 was highly influenced by smoking habits. Gender had an equal non-significant effect on both parameters. The usefulness of the new criteria for the cytokinesis-block MN assay measuring DNA damage as a sensitive biomarker in biomonitoring studies is confirmed.     

The association between micronucleus,nucleoplasmic bridges,and nuclear buds frequency and the degree of uterine cervical lesions

Background and aim: The loss of genomic stability plays an important role in carcinogenesis. Therefore, it is imperative to use certain biomarkers of DNA damage due to genomic instability in order to predict cancer risk. The aim of this study was the evaluation of genomic instability in patients with cervical lesions.

Materials and methods: We investigated the genetic damages in 80 subjects: 40 patients with high-grade squamous intraepithelial lesions (HSIL), 20 patients with invasive squamous cervical cancer (SCC) and 20 healthy women with a biomarker in two different tissues; the micronucleus (MN) test in peripheral blood lymphocytes (PBL), and in buccal exfoliated cells (BEC). This study also examined the frequency of other nuclear anomalies such as nucleoplasmic bridges (NPBs) and nuclear bunds (NBUDs) in PBL.

Results: The frequency of MN in BEC, MN in PBL, NPB in PBL and NBUD in PBL were significantly higher (p?Conclusion: Although larger studies are needed, our data support the predictive value of MN, NPB and NBUD as biomarkers of genomic instability for evaluation of risk level of cancer diseases.     

Diaziquone-induced micronuclei in cytochalasin B-blocked mouse peripheral blood lymphocytes

A mouse peripheral blood lymphocyte (PBL) micronucleus (MN) test was developed using a modification of the technique for assessing MN in human PBLs described by Fenech and Morley (1985). Male C57Bl/6 mice (5/dose) were injected i.p. with either 0, 2.5, 5.0, 7.5, or 10.0 mg diaziquone (AZQ)/kg. After 24 h the mice were bled by cardiac puncture, PBLs were isolated on a Ficoll-density gradient and then cultured in RPMI 1640 medium using 8 micrograms phytohemagglutinin/ml. In some cultures cytochalasin B (CYB) was added at 21 h during the medium change to block cytokinesis. In other cultures, CYB was omitted to compare the sensitivity of analyzing MN in binucleate versus unblocked mononucleate cells. All doses of AZQ yielded significant increases in MN-containing binucleated PBLs. The use of CYB in the mouse PBL MN test increased the sensitivity approximately 3-fold. The MN test in mouse PBLs should be useful in comparative cytogenetic studies of mice and humans.     

Baseline and therapy-induced chromosome damages in peripheral blood lymphocytes of breast cancer patients assessed by the micronucleus assay

Purpose: Radiotherapy (RT) alone or in combination with chemotherapy (CT) leads nearly always to increase of DNA damage in cancer patients. The purpose of this study was to determine the variability rate and individual sensitivity of breast cancer (BC) patients to the applied RT and RT in combination with CT. Methods: The analysed sample included 30 women with histologically confirmed BC. The frequency of micronuclei (MN) was estimated in peripheral blood lymphocytes (PBL) by using the cytokinesis-block micronucleus (CBMN) assay before the administered therapy and one month later. Results: The mean therapy-induced MN value was significantly higher (p < 0.001) compared with mean baseline MN. Both therapies (RT and combined RT+CT) significantly increased the MN frequency in patients' lymphocytes (p<0.001), but without significant differences in the therapy-induced MN frequency between these two groups (p > 0.05). The administered therapy induced significant difference in cell kinetics (p < 0.05). The results showed a wide range of inter-individual variability in both baseline and the therapy-induced MN frequency. Conclusion: The applied therapies increased the MN frequency in PBL in BC patients, and the presented data indicate absence of synergistic effect of these two therapies. None of the variation factors (age, smoking and therapy type) had influence on the noticed variability.     

Validation of micronuclei frequency in peripheral blood lymphocytes as early cancer risk biomarker in a nested case-control study

Aim of this work was to assess the predictive value of micronuclei (MN) frequency in peripheral blood lymphocytes (PBL) for the risk of cancer death in disease-free individuals. Blood samples from 1650 subjects selected from the general population of Pisa, Italy, were collected between June 1991 and November 1993. The follow-up until January 2005 recorded a total of 111 deaths (52 for cancer). MN frequency was assessed for 49 cancer cases and 101 matched controls. A significantly higher MN frequency was found in cancer cases (4.7+/-3.4 MN/1000 BN cells) versus controls (1.5+/-1.7; p<0.0001). Donors were stratified in two classes and multivariate logistic regression analysis confirmed that individuals with high MN frequency (>2.5 MN/1000 BN cells) had a significantly increased risk of cancer death (OR=10.7; 95% CI=4.6-24.9; p<0.0001) when compared to individuals with low MN frequency (相似文献   

Long term depleted uranium exposure in Gulf War I veterans does not cause elevated numbers of micronuclei in peripheral blood lymphocytes

Depleted uranium (DU) is a high density heavy metal that has been used in military munitions since the 1991 Gulf War. DU is weakly radioactive and chemically toxic. Long term exposure can cause adverse health effects. This study assessed genotoxic effects in DU exposed Gulf War I veterans as a function of uranium (U) body burden. Levels of urine U were used to categorize the cohort into low and high exposure groups. Exposure to DU occurred during friendly fire incidents in 1991 involving DU munitions resulting in inhalation and ingestion exposure to small particles of DU and soft tissue DU fragments from traumatic injuries. All of these Veterans are enrolled in a long term health surveillance program at the Baltimore Veterans Administration Medical Center. Blood was drawn from 35 exposed male veterans aged 36-59 years, then cultured and evaluated for micronuclei (MN) using the cytokinesis block method. The participants were divided into two exposure groups, low and high, based on their mean urine uranium (uU) concentrations. Poisson regression analyses with mean urine U concentrations, current smoking, X-rays in the past year and donor age as dependent variables revealed no significant relationships with MN frequencies. Our results indicate that on-going systemic exposure to DU occurring in Gulf War I Veterans with DU embedded fragments does not induce significant increases in MN in peripheral blood lymphocytes compared to MN frequencies in Veterans with normal U body burdens.     

Transformation of mammalian cells by alpha particles.

Mammalian cells in culture have been shown here for the first time to be transformed by alpha irradiation. Mouse embryo (C3H 10T1/2) cells were transformed with 5.6 MeV alpha particles from a Tandem Van de Graaff machine. Malignant tumours were induced following inoculation of the transformed cells into syngeneic hosts. Unirradiated control cells failed to produce tumours. The morphology of the transformed foci was similar to that obtained by X-rays and chemicals but different from virally transformed cells. The transformation frequency increased approximately as the cube of the dose to a maximum of about 4 per cent ofthe surviving cells which occurred between 1.5 and 2.5 x 10(7) alpha particles per cm2 (205-342 rad). It appears that alpha particle irradiation may exert a direct effect on the genome of the cell to produce malignancy without any external immunological or hormonal influences.     

Micronucleus induction and reproductive death in a human cell line exposed to low-energy argon beam

Little is known about the action of charged particles of very high linear energy transfer (LET) on human cells and, in particular, the relationship between DNA damage and reproductive death. The aim of this study was to measure the biological efficiency of a low-energy argon beam (E=7.1 MeV/nucleon, LET= 1590 keV/µm) produced at GSI, Darmstadt, on a human melanoma cell line (CAL4) established in our Institute. Two different methods were used: the micronucleus (MN) test and the colonyforming assay. The MN test, using the cytochalasin-block method, is a measure of genotoxic damage. MN are scored in binucleate cells (BNC) and are formed from acentric fragments or whole chromosomes that have not been incorporated into daughter nuclei at mitosis. The colonyforming assay quantifies reproductive death. Parallel experiments were run with cobalt gamma-rays for comparison. After Co irradiation, the MN-free BNC dose-response curve coincided with that of the loss of colony-forming ability, suggesting the potential of the former as a predictive test of cell killing. After Ar irradiation, there was a dissociation between the two effects, especially at high doses: cell death was greater than the frequency of BNC with MN. The inactivation cross-section was 74 µm²; it was 39 µm² for MN yield. Therefore, the relative biological effectiveness (RBE) was higher for cell killing than for MN yield (0.8 and 0.5, respectively, at a Co dose of 3 Gy). The total MN count in BNC followed the same pattern of response as the fraction of BNC with MN. However, multiple (>2) MN in BNC were more frequently observed after low-dose Ar irradiation than after gamma-ray exposure (RBE>1). Moreover, the frequency of multiple MN induction exceeded that expected from a Poisson distribution attribution at all dose levels of Ar irradiation. These results indicate that (1) cell killing after 7.1-MeV Ar beam irradiation is less effective than after Co irradiation at an equivalent average energy deposition; (2) unlike gamma-rays, Ar particles are more efficient at cell killing than in producing MN; (3) the frequent scoring of multiple MN suggests the production of multiple damage sites, even at low fluences of Ar particles.     

Mutation induction by different types of radiation at the Hprt locus

Mutation induction at the Hprt locus in Chinese hamster cells was studied after exposure to ultraviolet light, X-rays and alpha particles. While mutant frequency as a function of dose or fluence followed a linear–quadratic relationship with UV and X-rays, it showed a linear dependence for alpha particles. If mutant frequency is plotted vs. the logarithm of surviving fraction, a linear relationship is found in all cases although with different slopes. These are about equal with the two types of ionising radiations but about 10 times larger for UV. They can be used as a measure of mutagenic potential and are termed “mutagenicity”. It is shown that this parameter is correlated with the maximum of mutant yield, i.e., the number of mutants per cell at risk. It is concluded from this analysis that the maximum mutant yield is always found at doses or fluences which lead to 37% survival irrespective of the kind of radiation. If mutation induction is measured in X-irradiated cells after pre-exposure to UV, mutant frequency is higher than expected on the basis of independent action of the two radiations. Deletion spectra were determined by using multiplex polymerase chain reaction. It was found that the background of spontaneous mutants varied considerably and showed frequently repetitive patterns, presumably because of clonal expansion of pre-formed mutants. UV-induced mutants did not contain any deletions, while those with both X-rays and alpha particles the majority displayed partial and total deletions. Based on a total number of 134 X-ray- and 192 alpha-induced mutants, it is concluded that the total fraction of mutant clones without deletions (partial or total) is about 40% for X-rays and only about 20% for alpha-particles.     

Mutation induction by different types of radiation at the Hprt locus

Mutation induction at the Hprt locus in Chinese hamster cells was studied after exposure to ultraviolet light, X-rays and alpha particles. While mutant frequency as a function of dose or fluence followed a linear–quadratic relationship with UV and X-rays, it showed a linear dependence for alpha particles. If mutant frequency is plotted vs. the logarithm of surviving fraction, a linear relationship is found in all cases although with different slopes. These are about equal with the two types of ionising radiations but about 10 times larger for UV. They can be used as a measure of mutagenic potential and are termed “mutagenicity”. It is shown that this parameter is correlated with the maximum of mutant yield, i.e., the number of mutants per cell at risk. It is concluded from this analysis that the maximum mutant yield is always found at doses or fluences which lead to 37% survival irrespective of the kind of radiation. If mutation induction is measured in X-irradiated cells after pre-exposure to UV, mutant frequency is higher than expected on the basis of independent action of the two radiations. Deletion spectra were determined by using multiplex polymerase chain reaction. It was found that the background of spontaneous mutants varied considerably and showed frequently repetitive patterns, presumably because of clonal expansion of pre-formed mutants. UV-induced mutants did not contain any deletions, while those with both X-rays and alpha particles the majority displayed partial and total deletions. Based on a total number of 134 X-ray- and 192 alpha-induced mutants, it is concluded that the total fraction of mutant clones without deletions (partial or total) is about 40% for X-rays and only about 20% for alpha-particles.     

Assessment of the association between the frequency of micronucleus and p16INK4a/Ki-67 co-expression in patients with cervical intraepithelial lesions

Human papilloma virus (HPV) infection is the main etiological factor for cervical intraepithelial lesions (CIN). An important characteristic of this process is the loss of genome stability. Therefore, it is imperative to use biomarkers of DNA damage caused by genomic instability to identify high risk individuals. We investigated the frequency of micronuclei (MN) in peripheral blood lymphocytes (PBL) of 20 patients, diagnosed as histologically CIN 1 and 10 healthy controls. We also examined the frequency of other nuclear anomalies including nucleoplasmic bridges (NPBs) and nuclear buds (NBUDs) in PBL of patients with CIN 1 and healthy controls, and evaluated the benefits of p16^INK4a and Ki-67 (p16^INK4a/Ki-67) immunohistochemical double staining for identifying cervical squamous cells that express HPV E6/E7 oncogenes. We analyzed the association between the frequency of MN in PBL and the amount of p16^INK4a/Ki-67 co-expression in CIN 1 patients to establish genomic instability. Among CIN 1 subjects, 15% exhibited diffuse p16^INK4a/Ki-67 co-expression and were considered high positive, 25% of the CIN 1 cases exhibited p16^INK4a/Ki-67 co-expression restricted to the lower part of the epithelium and were considered low positive and the remaining 60% of cases were negative. The frequency of MN, NPBs and NBUDs differed significantly among groups. We found a statistically significant positive correlation between p16^INK4a/Ki-67 co-expression and the frequency of MN, NPBs and NBUDs in PBL. Our findings demonstrate the efficacy of p16^INK4a/Ki-67 double immunostaining for histological samples with CIN 1. MN frequency in PBL might be useful for detecting genomic instability in cases of HPV infection and CIN.     

Micronuclei, genetic polymorphisms and cardiovascular disease mortality in a nested case-control study in Italy

AIM: To validate the predictive value of micronuclei (MN) in peripheral blood lymphocytes (PBL) and glutathione-S-transferases (GSTs) polymorphisms (GSTM1 and GSTT1) for mortality risk (MR) of cardiovascular diseases (CVD). METHODS: Blood samples from 1650 healthy subjects selected from the general population were collected between June 1991 and November 1993, and slides were immediately prepared for MN assessment. The vital status, or the cause of death, was monitored for all subjects until January 2005. At the end of the follow-up, 111 deaths were recorded and 39 CVD cases were observed (age range=42-88 years). Two thousand binucleated (BN) cells/subject were scored for the MN assay and GSTs genotypes were assessed on the DNA extracted from the blood or serum samples. RESULTS: A significantly higher MN frequency was recorded for the case group in comparison with the control group (n=67, Kruskall-Wallis test, p=0.006) and GSTT1 null genotype was significantly less frequent in CVD patients (chi(2)-test, p=0.036). The influence of other factors were evaluated using a unconditional logistic regression that confirmed a significant association of GSTT1 positive genotype with an increased OR for CVD (OR=6.29, 95% CI 1.32-29.95) beside a significant effect of age (OR=1.13, 95% CI 1.03-1.26 year(-1)). Finally, subjects with an higher MN frequency showed a higher MR for CVD (Log-rank test, p=0.001). CONCLUSIONS: MN confirmed to be a suitable cytogenetic biomarker for early prediction of CVD death. The GSTT1 positive genotype is associated with an increased MR for CVD.     

Induction of micronuclei by X-radiation in human, mouse and rat peripheral blood lymphocytes

We compared the radiosensitivity of human, rat and mouse peripheral blood lymphocytes (PBLs) by analyzing micronuclei (MN) in cytochalasin B-induced binucleated (BN) cells. For each species and dose 4-ml aliquots of whole blood were X-irradiated to obtain doses of 38, 75, 150 or 300 cGy. Controls were sham-irradiated. After exposure to X-rays, mononuclear leukocytes were isolated using density gradients and cultured in RPMI 1640 medium containing phytohemagglutinin to stimulate mitogenesis. At 21 h cytochalasin B was added to produce BN PBLs, and all cultures were harvested at 52 h post-initiation using a cytocentrifuge. Significant dose-dependent increases in the percentage of micronucleated cells and the number of MN per BN cell were observed in all three species. The linear-quadratic regression curves for the total percentage of micronucleated cells for the three species were similar; however, the curve for the mouse PBLs had a larger quadratic component than either of the curves for the rat or human PBLs. Although the correlation between the percentage of cells with MN and those with chromosome aberrations was high (r2 greater than 0.95), the mouse and rat PBLs were over twice as efficient as human PBLs in forming MN from presumed acentric fragments. These data indicate that the induction of MN in BN cells following ionizing radiation is similar in human, rat and mouse PBLs, but care must be taken in using the MN results to predict frequencies of cells with chromosomal aberrations.     

Relative biological effectiveness of low-energy X-rays (25 kV) in mutant p53 cancer cells

Low-energy X-rays as used in radiation therapy and diagnostics such as mammography are associated with a certain risk of promoting tumour development, especially in patients with mutations in cancer-related genes like TP53. The present study therefore addressed the relative biological effectiveness (RBE) of low-energy X-rays for two human adenocarcinoma cell lines of the breast (MDA-MB-468) and pancreas (BxPC-3) with a mutation in the TP53 gene. Clonogenic survival and cytogenetic changes in terms of micronuclei (MN) formation were determined following irradiation with 25 kV X-rays and 200 kV reference irradiation in the dose range of 1–8 Gy. Except the frequency of MN-containing binucleated cells (BNC) (BNC?+?MN/BNC) in breast cancer cells yielding an RBE between 0.6 and 0.8, both cell lines displayed dose-dependent variations of RBE values between 1 and 2 for all biological end points (cell survival, (BNC?+?MN/BNC), MN/BNC, MN/(BNC?+?MN)) with increased effectiveness of 25 kV irradiation in pancreatic compared to breast cancer cells. The results confirm previous findings indicating increased effectiveness of low-energy X-rays and underline the necessity of careful risk estimation for cancer screening programmes.