Faculty Bibliography

Catalase is an endogenous antioxidant enzyme that neutralizes hydrogen peroxide and is induced by oxidative challenge. A -262C --> T polymorphism in the promoter region of the gene (CAT) is associated with risk of several conditions related to oxidative stress. We sought to determine the functional effects of the CAT polymorphism on enzyme activity in erythrocytes and the potential modifying effects of demographic and lifestyle factors on genotype/phenotype relationships, using specimens and data from controls from breast and prostate cancer studies in Arkansas (n = 420). There was a dose-response reduction in catalase activity by genotype, with geometric means of 115.4 units/mg hemoglobin for those with CC genotypes, 82.1 units/mg for those with CT genotypes, and 73.5 units/mg for those with TT genotypes. Associations were only observed among Caucasians (P < 0.0001), with no effects among African Americans (P = 0.91), and were stronger among women than men, although numbers in stratified analyses were small. Differences in catalase activity by genotype were most pronounced among those in the highest tertiles of consumption of fruits and vegetables (-35%, P = 0.003), with weaker relationships among those who were lower consumers (-21.8%, P = 0.16). Among those with CC genotypes, there was no change in activity by consumption, but there were notable decreases in activity by tertiles of consumption for those with at least one T allele. These data indicate that the CAT -262C --> T polymorphism predicts a portion of catalase phenotype, which may be limited to Caucasians. Associations between genotype and phenotype were modified by dietary factors, illustrating the biochemical complexity of studies of genetic polymorphisms and disease risk

Glutathione S-transferases (GSTs) are phase II enzymes that are involved in the detoxification of a wide range of carcinogens. The novel GSTA1*A and GSTA1*B genetic polymorphism results in differential expression, with lower transcriptional activation of GSTA1*B (variant) than that of GSTA1*A (common) allele. Considering that cruciferous vegetables induce GSTs, which metabolize tobacco smoke carcinogens, we hypothesized that the variant GSTA1*B genotype may predispose women to breast cancer, particularly among low cruciferous vegetable consumers and among smokers. Thus, we evaluated potential relationships between GSTA1 polymorphisms and breast cancer risk, in relation to vegetable consumption and smoking status in the Long Island Breast Cancer Study Project (1996-1997), a population-based case-control study. Genotyping (1036 cases and 1089 controls) was performed, and putative breast cancer risk factors and usual dietary intakes were assessed. Having GSTA1*A/*B or *B/*B genotypes was not associated with increased breast cancer risk, compared to having the common *A/*A genotype. However, among women in the lowest two tertiles of cruciferous vegetable consumption, *B/*B genotypes were associated with increased risk (OR (95% CI)=1.73 (1.10-2.72) for 0-1 servings/week), compared to women with *A/*A genotypes. Among women with *B/*B genotypes, a significant inverse trend between cruciferous vegetable consumption and breast cancer risk was observed (P for trend=0.05), and higher consumption (4+ servings/week) ameliorated the increased risk associated with the genotype. Current smokers with *B/*B genotypes had a 1.89-fold increase in risk (OR (95% CI)=1.89 (1.09-3.25)), compared with never smokers with *A/*A genotypes. These data indicate that GSTA1 genotypes related to reduced GSTA1 expression are associated with increased breast cancer primarily among women with lower consumption of cruciferous vegetables and among current smokers

BACKGROUND: Manganese superoxide dismutase (MnSOD) plays a critical role in the detoxification of mitochondrial reactive oxygen species, constituting a major cellular defense mechanism against agents that induce oxidative stress. A genetic polymorphism in the mitochondrial targeting sequence of this gene has been associated with increased cancer risk and survival in breast cancer. This base pair transition (-9 T > C) leads to a valine to alanine amino acid change in the mitochondrial targeting sequence. A polymorphism has also been identified in the proximal region of the promoter (-102 C>T) that alters the recognition sequence of the AP-2 transcription factor, leading to a reduction in transcriptional activity. The aim of our study was to investigate possible associations of the -102 C>T polymorphism with overall and relapse-free breast cancer survival in a hospital-based case-only study. MATERIALS AND METHODS: The relationship between the MnSOD -102 C>T polymorphism and survival was examined in a cohort of 291 women who received chemotherapy and/or radiotherapy for incident breast cancer. The MnSOD -102 C>T genotype was determined using a TaqMan allele discrimination assay. Patient survival was evaluated according to the MnSOD genotype using Kaplan-Meier survival functions. Hazard ratios were calculated from adjusted Cox proportional hazards modeling. All statistical tests were two-sided. RESULTS: In an evaluation of all women, there was a borderline significant reduction in recurrence-free survival with either one or both variant alleles (CT + TT) when compared with patients with wild-type alleles (CC) (odds ratio, 0.65; 95% confidence interval, 0.42-1.01). When the analysis was restricted to patients receiving radiation therapy, there was a significant reduction in relapse-free survival in women who were heterozygous for the MnSOD -102 genotype (relative risk, 0.40; 95% confidence interval, 0.18-0.86). Similarly, when the homozygous and heterozygous variant genotypes were combined, there remained a significant reduction in relapse-free survival in this group (hazard ratio, 0.42; 95% confidence interval, 0.20-0.87). CONCLUSION: The MnSOD -102 variant allele appears to be associated with an improved recurrence-free survival in all patients, and more dramatically in subjects who received adjuvant radiation therapy

PURPOSE: Because radiotherapy exerts cytotoxic effects via generation of massive oxidative stress, we hypothesized that catalase, manganese superoxide dismutase, myeloperoxidase (MPO), and endothelial nitric oxide synthase (eNOS) genotypes might result in greater risk of radiotoxicity. EXPERIMENTAL DESIGN: Cases (n = 446) were Caucasian women with breast cancer who received radiotherapy following lumpectomy. Genotypes were determined by matrix-assisted laser desorption/ionization time-of-flight. The development of acute reactions (moist desquamation) associated with genotypes was modeled using the Cox proportional hazards model, accounting for cumulative biologically effective radiation dose. RESULTS: Genotypes associated with higher levels of reactive oxygen species (ROS) were not associated with risk of radiotoxicity. However, relationships between overweight/obesity [body mass index (BMI), >25] and radiotoxicity risk seemed to be modified by eNOS and MPO genotypes associated with higher generation of nitric oxide and ROS, respectively. Women with high BMI (>25) and eNOS GG genotypes were at more than a 6-fold increase in risk (hazard ratio, 6.39; 95% confidence interval, 2.53-16.15) compared with those with BMI <25, and for MPO, those with high BMI (>25) and GG genotypes also had greater risk of radiotoxicity (hazard ratio, 3.61; 95% confidence interval, 1.78-7.35) compared with those with BMI <25. Overweight/obesity was not a strong risk factor among women with other eNOS and MPO genotypes. Exploratory analysis using classification and regression trees indicated that total number of risk alleles contributed, in part, to acute toxicity outcomes among a subgroup of women. CONCLUSIONS: Associations between BMI and radiotoxicity risk may be most apparent among women with genotypes related to higher levels of oxidative stress. Regression trees may be useful in future studies to examine the contributions of multiple factors to individual susceptibility to adverse effects of cancer treatment

The proximate cause of cancer cell death by radiation therapy and a number of therapeutic agents is through generation of reactive oxygen species, resulting in DNA damage as well as mitochondrial membrane disruption, triggering the apoptotic cascade. Because mitochondrial manganese superoxide dismutase catalyzes conversion of superoxide radicals to H(2)O(2), with catalase neutralizing H(2)O(2) and myeloperoxidase converting H(2)O(2) to highly reactive hypochlorous acid, we hypothesized that gene variants could impact the efficacy of treatment for breast cancer and improve survival. Women who were treated with radiation and/or chemotherapy for incident breast cancer at the Arkansas Cancer Research Center from 1985 to 1996 were identified. DNA was extracted from paraffin-embedded normal tissue (n = 279), and MnSOD, CAT, and MPO genotypes were determined using mass spectrometry. Cox proportional hazards models were adjusted for age, race, stage with node status, and estrogen receptor and progesterone receptor status. Women who were homozygous for MPO G alleles, associated with increased transcription, had better survival (hazard ratio, 0.60; 95% confidence interval, 0.38-0.95; P = 0.03) than those with common alleles. Both CAT TT and MnSOD CC genotypes were associated with nonsignificant reduced hazard of death. When we combined genotypes associated with higher levels of reactive oxygen species for MnSOD and MPO, women with MnSOD CC and MPO GG genotypes had a 3-fold decrease in hazard of death (hazard ratio, 0.33; 95% confidence interval, 0.13-0.80; P = 0.01). These data indicate that gene variants that impact oxidative stress modify prognosis after treatment for breast cancer

Tamoxifen has been a mainstay of adjuvant therapy for breast cancer for many years. We sought to determine if genetic variability in the tamoxifen metabolic pathway influenced overall survival in breast cancer patients treated with tamoxifen. We examined functional polymorphisms in CYP2D6, the P450 catalyzing the formation of active tamoxifen metabolites, and UGT2B15, a Phase II enzyme facilitating the elimination of active metabolite in a retrospective study of breast cancer patients. We also examined whether the combination of variant alleles in SULT1A1 and UGT2B15 had more of an impact on overall survival in tamoxifen-treated patients than when the genes were examined separately. We conducted a retrospective study using archived paraffin blocks for DNA extraction and data from pathology reports and hospital tumor registry data for information on clinical characteristics, treatment, and outcomes (162 patients receiving tamoxifen and 175 who did not). Genotypes for CYP2D6 and UGT2B15 were obtained and Cox proportional hazards modeling was performed. After adjusting for age, race, stage of disease at diagnosis, and hormone receptor status, we found no significant association between CYP2D6 genotype and overall survival in either group of breast cancer patients. Tamoxifen-treated patients with UGT2B15 high activity genotypes had increased risk of recurrence and poorer survival. When UGT2B15 and SULT1A1 'at-risk' alleles were combined, women with two variant alleles had significantly greater risk of recurrence and poorer survival than those with common alleles. These studies indicate that genetic variation in Phase II conjugating enzymes can influence the efficacy of tamoxifen therapy for breast cancer

Observed weak or null associations between fruit and vegetable intake and breast cancer risk could be due to heterogeneity in endogenous antioxidant capabilities. The authors evaluated potential relations between a functional polymorphism in catalase, an antioxidant enzyme, and breast cancer risk, particularly in relation to fruit and vegetable intake and supplement use. Women (1,008 cases and 1,056 controls) in the Long Island Breast Cancer Study Project (1996-1997) were interviewed, completed a food frequency questionnaire, and provided blood for genotyping. The high-activity catalase CC genotype was associated with an overall 17% reduction in risk of breast cancer compared with having at least one variant T allele (odds ratio = 0.83, 95% confidence interval: 0.69, 1.00). Vegetable and, particularly, fruit consumption contributed to the decreased risk associated with the catalase CC genotype. Associations were more pronounced among women who did not use vitamin supplements, with a significant multiplicative interaction (p(interaction) = 0.02) for the CC genotype and high fruit intake (odds ratio = 0.59, 95% confidence interval: 0.38, 0.89), and there was no association among supplement users. These results indicate the importance of diet, rather than supplement use, in concert with endogenous antioxidant capabilities, in the reduction of breast cancer risk. CC genotypes were prevalent in approximately 64% of controls; thus, the preventive potential for fruit consumption has widespread implications