Investigation of systemic folate status, impact of alcohol intake and levels of DNA damage in mononuclear cells of breast cancer patients

Effects of physical activity on systemic oxidative/DNA status in breast cancer survivors

Physical activity offers a paradoxical hormetic effect and a health benefit to cancer survivors; however, the biochemical mechanisms have not been entirely elucidated. Despite the well-documented evidence implicating oxidative stress in breast cancer, the association between health benefits and redox status has not been investigated in survivors who participate in dragon boating. The present study investigated the plasmatic systemic oxidative status (SOS) in breast cancer survivors involved in two distinct physical training exercises. A total of 75 breast cancer survivors were allocated to one of three groups: Control (resting), dragon boat racing and walking group; the latter is a type of aerobic conditioning exercise often advised to cancer patients. Various biochemical oxidative stress markers were examined, including oxidant status (hydroperoxide levels, lipid oxidation) and antioxidant status (enzymatic activities of superoxide dismutase and glutathione peroxidase, reduced glutathione levels and antioxidant capability). In addition, the individual DNA fragmentation and DNA repair capability of nucleotide excision repair (NER) systems were examined by comet assays. According to the results, all patients exhibited high levels of oxidative stress. Physical activity maintained this oxidative stress condition but simultaneously had a positive influence on the antioxidant component of the SOS, particularly in the dragon boat racing group. DNA fragmentation, according to the levels of single- and double-strand breaks, were within the normal range in the two survivor groups that were involved in training activities. Radiation-induced damage was not completely recognised or repaired by NER systems in any of the patients, probably leading to radiosensitivity and/or susceptibility of patients to cancer. These findings suggest that physical activity, particularly dragon boat racing, that modulates SOS and DNA repair capability could represent a strategy for enhancing the quality of life and improving the long-term health benefits for breast cancer survivors.

Extracellular amyloid beta 42 causes necrosis, inhibition of nuclear division, and mitotic disruption under both folate deficient and folate replete conditions as measured by the cytokinesis-block micronucleus cytome assay

Alzheimer's disease is associated with accumulation of extracellular beta amyloid peptide 42 (Aβ42) which may induce DNA damage and reduce cellular regenerative potential. These effects may be exacerbated under conditions of folate deficiency. The aim of this study was to investigate whether extracellular Aβ42 induces DNA damage and cell death in human peripheral lymphocytes and whether there is an interactive effect between extracellular Aβ42 and folic acid status. Peripheral blood lymphocytes were cultured in medium under conditions of both low and high folate (20 and 200 nM, respectively) and challenged with either Aβ42 or the physiologically normal form Aβ40 (both at 5, 10, 15 µM). Genome stability and cytotoxicity events were investigated using the cytokinesis-block micronucleus cytome (CBMN-cyt) assay. Outcome measures scored included the nuclear division index (NDI), necrosis, apoptosis, binucleated cells with micronuclei (MN), nucleoplasmic bridges (NPB), and nuclear buds (NBUD) and abnormally shaped nuclei (circular, (CIR) and horse-shoe, (HS) that may be indicative of mitotic disruption. Folic acid deficiency significantly reduced NDI (P < 0.001) and increased all the DNA damage biomarkers (MN, NPB, NBUD, HS, CIR), (P < 0.001). In contrast, exposure to Aβ40 had no impact on CBMN cytome biomarkers but Aβ42 significantly reduced NDI (P < 0.01), increased necrosis (P < 0.05) and frequency of cells with circular nuclei (P < 0.01). There was no evidence of an interaction between Aβ42 and folic acid with respect to CBMN cytome biomarkers. Extracellular Aβ42 appears to have cytotoxic and cytostatic effects but its effect on chromosomal instability appears to be small relative to folate deficiency.

Does chemotherapy-induced oxidative stress improve the survival rates of breast cancer patients?

Antineoplastic agents induce oxidative stress leading to lipid, carbohydrate, protein, and DNA damage. We sought to explore the role of drug-induced oxidative stress on breast cancer patient's survival. We observed that neoadjuvant patients presented a marked raise in DNA damage and protein carbonyl levels after chemotherapy, whereas postchemotherapy DNA repair activity of the KU86 enzyme and total antioxidant capacity of the plasma were higher in the adjuvant group. With respect to patient's survival, we observed that increasing levels of KU86 and antioxidant capacity of the plasma during chemotherapy significantly influenced the survival rates of the patients, protecting from disease recurrence and death. Our results suggest that chemotherapy induces a certain level of systemic oxidative stress, which is maintained along successive clinical interventions and could influence the clinical outcome of the patients.

Noninvasive subcellular imaging in breast cancer risk assessment: construction of diagnostic windows

AIM

Breast cancer is the most common cause of cancer-related death among women. Delayed diagnosis leads to development of metastasis and impairs the outcome. This study was designed to utilize subcellular DNA imaging by 'comet assay' and determine pathology-specific comet patterns as the robust biomarker to distinguish between high and low risk for breast cancer development among predisposed individuals with benign breast alterations.

MATERIALS & METHODS

A total of 161 patients were grouped as follows: benignancy, premenopause (n = 59); benignancy, postmenopause (n = 20); breast cancer, premenopause (n = 19); breast cancer, postmenopause (n = 63). On average, 800-1000 comets were evaluated per patient.

RESULTS & CONCLUSION

The qualitative comet assay is an innovative approach for breast cancer risk assessment that can be utilized for the screening of highly predisposed individuals among patients with benign breast alterations. Pathology-specific comet patterns have been identified as the robust biomarker for breast cancer risk. Mathematic model-based diagnostic windows have been constructed for their clinical application.

Impact of spinach consumption on DNA stability in peripheral lymphocytes and on biochemical blood parameters: results of a human intervention trial

INTRODUCTION

A controlled intervention trial was conducted to assess the impact of spinach consumption on DNA stability in lymphocytes and on health-related biochemical parameters.

METHODS

The participants (n = 8) consumed homogenised spinach (225 g/day/person) over a period of 16 days. DNA migration was monitored in single cell gel electrophoresis-comet assays under standard conditions, which reflect single- and double-strand breaks, after treatment of nuclei with lesion-specific enzymes (formamidopyrimidine glycosylase, FPG and endonuclease III, ENDO III) and after treatment of intact cells with H(2)O(2) before, during and after intervention.

RESULTS

While no reduction in DNA damage was observed under standard conditions after different time intervals of spinach intake, other endpoints, namely ROS sensitivity and DNA migration attributable to the formation of oxidatively damaged DNA bases (i.e. pyrimidines-ENDO III-sensitive sites and purines-FPG sensitive sites) were reduced 6 h after consumption of the first portion and after 11 days of continuous consumption. In the case of ENDO III-sensitive sites, also after 16 days, a decrease in comet formation was observed. At the end of a 40 days washout period, the DNA stability parameters were not significantly different from the background values. Other biochemical parameters which were significantly altered by spinach intake were the folate (+27%) and homocysteine (-16%) concentrations in blood, and it was found in an earlier human study that folate may prevent oxidative damage to DNA bases.

CONCLUSIONS

Taken together, our results show that moderate consumption of spinach causes protection against oxidative DNA damage in humans and that this phenomenon is paralleled by alterations of health-related biochemical parameters.

Radiosensitivity and repair kinetics of gamma-irradiated leukocytes from sporadic prostate cancer patients and healthy individuals assessed by alkaline comet assay

BACKGROUND

Impaired DNA repair mechanism is one of the main causes of tumor genesis. Study of intrinsic radiosensitivity of cancer patients in a non-target tissue (e.g. peripheral blood) might show the extent of DNA repair deficiency of cells in affected individuals and might be used a predictor of cancer predisposition.

METHODS

Initial radiation-induced DNA damage (ratio of Tail DNA/Head DNA), dose-response curves and kinetics of DNA repair in leukocytes from healthy volunteers and prostate cancer patients were assessed using alkaline comet assay after exposure to 60Co gamma rays.

RESULTS

Results showed that higher levels of baseline and gamma rays induced DNA damage in leukocytes of prostate cancer cases than in controls. A similar dose response was obtained for both groups. After a repair time of 24 h following in vitro irradiation, samples from the healthy individuals showed no residual DNA damage in their leukocytes, whereas prostate cancer patients revealed more than 20 percent. Although similar initial radiosensitivity was observed for both groups, the repair kinetics of radiation induced DNA damage of leukocytes from prostate cancer cases and healthy subjects were statistically different.

CONCLUSION

These results support the hypothesis that men affected by prostate cancer may have a constitutional genomic instability.

G0 and G2 chromosomal assays in the evaluation of radiosensitivity in a cohort of Italian breast cancer patients

Breast cancer (BC) is the most common type of malignancy in female patients and radio-treatment is the conventional therapy even if a great number of studies reported that enhanced sensitivity to ionizing radiation as measured as chromosome effects is present in a significant proportion of cancer patients, including breast cancer ones. In this study we analysed whether peripheral blood lymphocytes from sporadic BC patients and healthy subjects showed a different sensitivity to ionizing radiation and whether cytogenetic radiosensitivity may serve as a breast cancer risk biomarker. To test this hypothesis, the in vitro radiation sensitivity was measured by using both G(0) and G(2) chromosome radiosensitivity assays, on 46 subjects (23 BC patients and 23 healthy subjects). Results show that cancer patients are more radiosensitive than healthy controls and that G(2) assay could be more appropriate to define the individual radiosensitivity if compared to G(0) assay.

Association between global DNA hypomethylation in leukocytes and risk of breast cancer

Background: Global DNA hypomethylation may result in chromosomal instability and oncogene activation, and as a surrogate of systemic methylation activity, may be associated with breast cancer risk. Methods: Samples and data were obtained from women with incident early-stage breast cancer (I–IIIa) and women who were cancer free, frequency matched on age and race. In preliminary analyses, genomic methylation of leukocyte DNA was determined by measuring 5-methyldeoxycytosine (5-mdC), as well as methylation analysis of the LINE-1-repetitive DNA element. Further analyses used only 5-mdC levels. Logistic regression models were used to estimate odds ratios (ORs) and 95% confidence intervals (CIs) for risk of breast cancer in relation to amounts of methylation. Results: In a subset of samples tested (n = 37), 5-mdC level was not correlated with LINE-1 methylation. 5-mdC level in leukocyte DNA was significantly lower in breast cancer cases than healthy controls (P = 0.001), but no significant case–control differences were observed with LINE-1 methylation (P = 0.176). In the entire data set, we noted significant differences in 5-mdC levels in leukocytes between cases (n = 176) and controls (n = 173); P value < 0.001. Compared with women in the highest 5-mdC tertile (T3), women in the second (T2; OR = 1.49, 95% CI = 0.84–2.65) and lowest tertile (T1; OR = 2.86, 95% CI = 1.65–4.94) had higher risk of breast cancer (P for trend ≤0.001). Among controls only and cases and controls combined, only alcohol intake was found to be inversely associated with methylation levels. Conclusion: These findings suggest that leukocyte DNA hypomethylation is independently associated with development of breast cancer.

Association between DNA damage, DNA repair genes variability and clinical characteristics in breast cancer patients

The cell's susceptibility to DNA damage and its ability to repair this damage are important for cancer induction, promotion and progression. In the present work we determined the level of basal (total endogenous) and endogenous oxidative DNA damage as well as polymorphism of the DNA repair genes: RAD51 (135 G/C), XRCC3 (Thr241Met), OGG1 (Ser326Cys) and XPD (Lys751Gln) in peripheral blood lymphocytes of 41 breast cancer patients and 48 healthy individuals. DNA damage was evaluated by alkaline comet assay with DNA repair enzymes: Endo III and Fpg, preferentially recognizing oxidized DNA bases. The genotypes of the polymorphisms were determined by restriction fragment length polymorphism PCR. We observed a strong association between breast cancer occurrence and the genotypes C/C of the RAD51-135G/C polymorphism, Ser/Ser of the OGG1-Ser326Cys and Lys/Gln of the XPD-Lys751Gln, whereas the genotypes G/C of the RAD51-135G/C and Lys/Lys of the XPD-Lys751Gln exerted a protective effect against breast cancer. We also found that individuals with the G/C genotype of the RAD51-135G/C polymorphism and with the Lys/Lys genotype of the XPD-Lys751Gln polymorphism displayed a lower extent of basal and oxidative DNA damage. A strong association between higher level of oxidative DNA damage and the Lys/Gln genotype of the latter polymorphism was found. We also correlated genotypes with clinical characteristics of breast cancer patients. We observed a strong association between the G/C genotype of the RAD51-135 G/C polymorphism and the expression of the progesterone receptor and between both alleles of the OGG1-Ser326Cys polymorphism and lymph node metastasis. Our results suggest that the polymorphism of the RAD51, OGG1 and XPD genes may be linked with breast cancer by the modulation of the cellular response to oxidative stress and these polymorphisms may be considered as markers in breast cancer along with the genetic or/and environmental indicators of oxidative stress.

Hyperhomocysteinemia in women with advanced breast cancer

Patients with malignancy have an increased risk of venous thromboembolic disease but the pathophysiology of this association has not been precisely defined. Hyperhomocysteinemia has become established as one of the commonest conditions associated with venous and arterial thrombosis. We examined the prevalence of hyperhomocysteinemia in women with early (group A, n = 31), metastatic breast cancer (group B, n = 41) and in a group of healthy females (group C, n = 29). Blood samples were collected at diagnosis or prior to treatment. We measured both total plasma homocysteine (tHcy) and red cell folate (RCF). The Mean (SD) tHcy were group A - 9.43 micromol/l (5.6), group B - 11.34 micromol/l (5.1) and group C - 7.9 micromol/l (1.5). A total of 39% of patients with metastatic and 22.6% with early breast cancer had tHcy concentrations above the upper limit of normal. Women with metastatic disease had significantly higher tHcy compared with controls (P < 0.01) but not when compared with women with early breast cancer. Also, no difference was observed when women with early disease were compared with controls. We found no correlation between age and tHcy. Lower RCF levels were identified in group B compared with group A, but this does not fully explain the increased tHcy levels seen within the same group. We conclude that hyperhomocysteinemia is common in women with advanced breast cancer. This observation could explain the high rate of venous thrombosis in women with metastatic breast malignancy.

Radiation sensitivity of leukocytes from healthy individuals and breast cancer patients as measured by the alkaline and neutral comet assay

Initial radiation-induced DNA damage, dose-response curves and kinetics of DNA repair in leukocytes from healthy volunteers and breast cancer patients, was assessed using alkaline and neutral comet assay after exposure to (60)Co gamma rays. Both versions of comet assay showed higher levels of baseline DNA damage in leukocytes of breast cancer cases than in controls. Gamma ray induced initial DNA damage in leukocytes of cancer cases was not significantly different from that of healthy donors. A similar dose-response was obtained with both versions of comets for two groups. After a repair time of 24h, following irradiation, samples from the healthy individuals showed no residual DNA damage in their leukocytes, whereas breast cancer patients revealed more than 20%. Although similar initial radiosensitivity was observed for both groups but the repair kinetics of radiation-induced DNA damage of leukocytes from breast cancer cases and healthy subjects was statistically different.

Moderate folate depletion modulates the expression of selected genes involved in cell cycle, intracellular signaling and folate uptake in human colonic epithelial cell lines

Folate deficiency may affect gene expression by disrupting DNA methylation patterns or by inducing base substitution, DNA breaks, gene deletions and gene amplification. Changes in expression may explain the inverse relationship observed between folate status and risk of colorectal cancer. Three cell lines derived from the normal human colon, HCEC, NCM356 and NCM460, were grown for 32-34 days in media containing 25, 50, 75 or 150 nM folic acid, and the expression of genes involved in cell-cycle checkpoints, intracellular signaling, folate uptake and cell adhesion and migration was determined. Expression of Folate Receptor 1 was increased with decreasing media folate in all cell lines, as was p53, p21, p16 and beta-catenin. With decreasing folate, the expression of both E-cadherin and SMAD-4 was decreased in NCM356. APC was elevated in NCM356 but unchanged in the other lines. No changes in global methylation were detected. A significant increase in p53 exon 7-8 strand breaks was observed with decreasing folate in NCM460 cells. The changes observed are consistent with DNA damage-induced activation of cell-cycle checkpoints and cellular adaptation to folate depletion. Folate-depletion-induced changes in the Wnt/APC pathway as well as in genes involved in cell adhesion, migration and invasion may underlie observed relationships between folate status and cancer risk.

BRCA1 and TP53 mutation spectrum of breast carcinoma in an ethnic population of Kashmir, an emerging high-risk area

Breast cancer shows geographical variation in its incidence, even within areas of ethnic homogeneity. Kashmir valley (India), over past few years, witnesses an increase in incidence and occurrence of familial, early onset, and male breast cancer in its unexplored ethnic population. Here, we make a preliminary attempt to estimate the nature and frequency of BRCA1 and TP53 gene mutations of breast cancer patients from Kashmir. PCR-SSCP analysis followed by direct sequencing revealed the presence of only two germline intronic variations (c.199+67T>C and c.5396+187T>C) in BRCA1 gene in only 5.26% (2/38) patients while as 44% (11/25) of sporadic breast cancer patients harboured significant amount of somatic mutations in TP53 (p=0.0074; OR=0.053). The 17 mutations found in TP53 in 11 patients, comprised of 13 substitutions [11 single-base (9 transitions+2 transversions), 1 double-base and 1 complex] and four insertions. The 11 substitutions represent missense mutations, leading to aminoacid substitution while as rest two were silent mutations. The four insertions represented three frame-shifts and one non-sense mutation. The mutation effect data was found to be significant (p=0.0002). Significant amount of mutations were found in exon 6 (p=0.04; OR=0.273) and a combination of exons 6 and 7 (p=0.0145; OR=14.22) of TP53. Comparison of mutation profile with other ethnic populations and regions reflected both differences and similarities indicating co-exposure to a unique set of risk factors. The differences could be due to exposure to particular environmental carcinogens; different lifestyle, reproductive pattern; dietary or cultural practices of Kashmiri women that need further investigations. The infrequent presence of germline BRCA1 mutations in our study agree with the idea that a great proportion of moderate risk breast cancer population could be due to the susceptibility genes distinct from BRCA1. However, high frequency of somatic TP53 gene mutations implicates TP53 as a predominant factor for breast carcinogenesis in moderate risk ethnic Kashmiri population. The study also suggests TP53 as a potential molecular marker and prognostic tool, at least in a subset of sporadic breast tumors.

Radiosensitivity in breast cancer assessed by the Comet and micronucleus assays

Spontaneous and radiation-induced genetic instability of peripheral blood mononuclear cells derived from unselected breast cancer (BC) patients (n=50) was examined using the single-cell gel electrophoresis (Comet) assay and a modified G2 micronucleus (MN) test. Cells from apparently healthy donors (n=16) and from cancer patients (n=9) with an adverse early skin reaction to radiotherapy (RT) served as references. Nonirradiated cells from the three tested groups exhibited similar baseline levels of DNA fragmentation assessed by the Comet assay. Likewise, the Comet analysis of in vitro irradiated (5 Gy) cells did not reveal any significant differences among the three groups with respect to the initial and residual DNA fragmentation, as well as the DNA repair kinetics. The G2 MN test showed that cells from cancer patients with an adverse skin reaction to RT displayed increased frequencies of both spontaneous and radiation-induced MN compared to healthy control or the group of unselected BC patients. Two patients from the latter group developed an increased early skin reaction to RT, which was associated with an increased initial DNA fragmentation in vitro only in one of them. Cells from the other BC patient exhibited a striking slope in the dose–response curve detected by the G2 MN test. We also found that previous RT strongly increased both spontaneous and in vitro radiation-induced MN levels, and to a lesser extent, the radiation-induced DNA damage assessed by the Comet assay. These data suggest that clinical radiation may provoke genetic instability and/or induce persistent DNA damage in normal cells of cancer patients, thus leading to increased levels of MN induction and DNA fragmentation after irradiation in vitro. Therefore, care has to be taken when blood samples collected postradiotherapeutically are used to assess the radiosensitivity of cancer patients.

Folate, vitamin B(6), and vitamin B(12) intake and the risk of breast cancer among Mexican women

BACKGROUND

High intake of folate, vitamin B(6), and vitamin B(12) have been hypothesized to lower the risk for breast cancer. We conducted a population-based case-control study to evaluate the risk for breast cancer among Mexican women with relatively low vitamin intakes.

METHODS

We included 475 women (median age, 53 years; range, 23-87 years) diagnosed with incident breast cancer through six hospitals in Mexico City and interviewed them to obtain data on breast cancer risk factors and their usual diet using a food frequency questionnaire. We selected 1,391 (median age, 49 years; range, 18-82 years) controls from the Mexico City population using a national sampling frame.

RESULTS

Compared with women in the lowest quartile, the odds ratio for breast cancer for women in the highest quartile of folate intake was 0.64 [95% confidence intervals (CI), 0.45-0.90; P, test for trend = 0.009] and 0.32 (95% CI, 0.22-0.49; P, test for trend < 0.0001) for vitamin B(12) intake. Among postmenopausal women, intakes of folate and vitamin B(12) were associated with a lower risk of breast cancer and those associations were stronger than among premenopausal women. The inverse association of folate and breast cancer was stronger among women who consumed a high level of vitamin B(12) as compared with women consuming diets low in vitamin B(12). No association was observed for vitamin B(6) intake.

CONCLUSIONS

In this population, high intakes of folate and vitamin B(12) were independently associated with decreased breast cancer risk, particularly among postmenopausal women.

Chronic cigarette smoking is associated with diminished folate status, altered folate form distribution, and increased genetic damage in the buccal mucosa of healthy adults

BACKGROUND

Smoking causes genetic damage in buccal cells and increases the risk of oral cancer. Because folate is instrumental in DNA synthesis and repair, it is a determinant of genetic stability and therefore might attenuate the genotoxic effects of smoking.

OBJECTIVE

Our aim was to compare the presence of folate metabolites and select indicators of genetic damage in the mouths of chronic smokers and nonsmokers.

DESIGN

Dietary, biochemical, and molecular correlates of folate status were measured in healthy smoker (n = 35) and nonsmoker (n = 21) groups of comparable age, sex, and body mass indexes.

RESULTS

After correction for dietary intake, the smokers displayed lower plasma, erythrocyte, and buccal mucosal cell (BMC) folate (20%, 32%, and 50% lower, respectively; P < 0.05) and lower plasma vitamin B-12 and pyridoxal 5-phosphate (P < 0.05) than did nonsmokers. Folate in the BMCs of smokers comprised significantly greater proportions of pteroylmonoglutamate, formyltetrahydrofolate, and 5,10-methenyltetrahyrofolate than did folate in the BMCs of nonsmokers. Although the degree of genomic methylation and uracil incorporation in the buccal cells of the 2 groups were not significantly different, the BMC micronucleus index, a cytologic indicator of genetic damage, in the smokers was 2-fold that of the nonsmokers (9.57 compared with 4.44 micronuclei/1000 cells; P < 0.0001). Neither systemic nor oral folate status was an independent predictor of micronuclei.

CONCLUSIONS

Chronic smoking is associated with a lower systemic status of several B vitamins, reduced oral folate, and changes in folate form distribution in the mouth. However, the cytologic damage that is evident in the mouths of smokers does not correlate with oral folate status.