Modifying effects of oxidative stress and DNA repair variants on physical activity and breast cancer risk

Purpose. The mechanisms driving the inverse association between recreational physical activity (RPA) and breast cancer risk are unclear. Exercise both increases reactive oxygen species production, which may transform normal epithelium to a malignant phenotype, and enhances antioxidant capacity, which could protect against subsequent oxidative insult. Physical activity may also improve damage repair systems, particularly those that operate on oxidative damage. Given the paradoxical and complex effects of physical activity both oxidative stress and DNA repair pathways are of interest. Polymorphisms in these pathways may modify the association between RPA and breast cancer incidence. Methods. We estimated interactions between RPA and several polymorphisms in oxidative stress-related genes (CAT, COMT, GPX, GSTP1, GSTA1, GSTM1, GSTP1, MPO, and MnSOD) as well as DNA repair genes (ERCC1, MGMT, MLH1, MSH2, MSH3, OGG1, XPA, XPC, XPD, XPF, XPG, and XRCC1). Data were from the Long Island Breast Cancer Study Project, a population-based, case-control study with interview and biomarker data available on 1053 cases and 1102 controls. Results. Six variants in antioxidant and DNA repair pathway genes (CAT rs1001179, GSTP1-Ile105Val, XPC-Ala499Val, XPF-Arg415Gln, XPG-Asp1104His and MLH1-lle219Val) interacted with postmenopausal RPA (p=0.043, 0.006, 0.048, 0.022, 0.012, and 0.010, respectively). Highly active women with genotypes related to reduced antioxidant capacity were at increased risk of breast cancer (CAT OR=1.61; 95% CI, 1.06-2.45) while risk reductions were observed among moderately active women with genotypes related to enhanced antioxidant capacity (GSTP1 OR=0.56; 95% CI, 0.38-0.84). With respect to DNA repair we found risk reductions for highly active women with common genotypes for XPC (OR=0.57; 95% CI, 0.38-0.84) and XPF (OR=0.64; 95% CI, 0.46-0.89) compared to non-active women homozygous for the major alleles. Non-significant risk reductions were observed among active women with at least one variant allele for XPG and MLH1, respectively. Conclusions. Genes involved in antioxidant and DNA repair pathways may modify the RPA-breast cancer risk association. While the functional significance of many polymorphisms with respect to breast cancer remains largely unknown, the observed associations are biologically plausible and consistent across multiple indicators of physical activity reducing the likelihood that these findings are attributable to chance. Our results merit further investigation.Doctor of Philosoph

Maternal B vitamins: effects on offspring weight and DNA methylation at genomically imprinted domains

Abstract Background Inadequate maternal nutrition during early fetal development can create permanent alterations in the offspring, leading to poor health outcomes. While nutrients involved in one-carbon cycle metabolism are important to fetal growth, associations with specific nutrients remain inconsistent. This study estimates associations between maternal vitamins B12, B6 (pyridoxal phosphate [PLP] and 4-pyridoxic acid [PA]), and homocysteine (Hcy) concentrations, offspring weight (birth weight and 3-year weight gain), and DNA methylation at four differentially methylated regions (DMRs) known to be involved in fetal growth and development (H19, MEG3, SGCE/PEG10, and PLAGL1). Methods Study participants (n = 496) with biomarker and birth weight data were enrolled as part of the Newborn Epigenetics STudy. Weight gain data were available for 273 offspring. Among 484 mother-infant pairs, DNA methylation at regulatory sequences of genomically imprinted genes was measured in umbilical cord blood DNA using bisulfite pyrosequencing. We used generalized linear models to estimate associations. Results Multivariate adjusted regression models revealed an inverse association between maternal Hcy concentration and male birth weight (β = −210.40, standard error (SE) = 102.08, p = 0.04). The offspring of the mothers in the highest quartile of B12 experienced lower weight gain between birth and 3 years compared to the offspring of the mothers in the lowest (β = −2203.03, SE = 722.49, p = 0.003). Conversely, maternal PLP was associated with higher weight gain in males; higher maternal PLP concentrations were also associated with offspring DNA methylation levels at the MEG3 DMR (p < 0.01). Conclusions While maternal concentrations of B12, B6, and Hcy do not associate with birth weight overall, they may play an important role in 3-year weight gain. This is the first study to report an association between maternal PLP and methylation at the MEG3 DMR which may be an important epigenetic tag for maternal B vitamin adequacy

Polycyclic aromatic hydrocarbons and postmenopausal breast cancer: An evaluation of effect measure modification by body mass index and weight change

Polycyclic aromatic hydrocarbons (PAHs) have been linked to breast cancer in many, but not all, previous studies. PAHs are lipophilic and stored in fat tissue, which we hypothesized may result in constant low-dose exposure to these carcinogens. No previous studies have evaluated whether obesity modifies associations between multiple measures of PAHs and breast cancer incidence

Polycystic ovarian syndrome (PCOS), related symptoms/sequelae, and breast cancer risk in a population-based case–control study

Despite the overlap between the clinical symptoms/sequelae of polycystic ovarian syndrome (PCOS) and many known reproductive risk factors for breast cancer, the relationship between PCOS and breast cancer remains unclear, possibly because of the complex heterogeneity and challenges in diagnosing PCOS over time. We hypothesized that PCOS, specific PCOS-related symptoms/sequelae, or clusters of PCOS-related symptoms/sequelae, may be differentially associated with pre- vs. postmenopausal breast cancer risk

Cross-Sectional Associations between Body Size, Circulating Sex-Steroid Hormones and IGF Components among Healthy Chinese Women

The incidence of breast cancer has increased in Asian countries and rates of hormone receptor (HR) negative breast cancer exceed those of Western countries. Epidemiologic data suggest that the association between body size and BC risk may vary by HR status, and could differ geographically. While body size may influence BC risk by moderating the synthesis and metabolism of circulating sex-steroid hormones, insulin-like growth factor (IGF)-1 and related binding proteins, there is a dearth of literature among Asian women. We aimed to examine these specific associations in a sample of Chinese women. In Sichuan Province 143 women aged ≥40 years were recruited through outpatient services (2011–2012). Questionnaires, anthropometric measurements, and blood samples were utilized for data collection and linear regression was applied in data analyses. Among women <50 years we observed a non-monotonic positive association between body mass index (BMI) and 17β-estradiol, and a reversed J-shaped association between BMI and IGF-1 (p ≤0.05). We observed similar associations between waist-to-hip ratio and these markers. Our finding of augmented IGF-1 among women with low body mass may have implications for understanding breast tumor heterogeneity in diverse populations and should be evaluated in larger prospective studies with cancer outcomes

Reproductive characteristics modify the association between global DNA methylation and breast cancer risk in a population-based sample of women

DNA methylation has been implicated in breast cancer aetiology, but little is known about whether reproductive history and DNA methylation interact to influence carcinogenesis. This study examined modification of the association between global DNA methylation and breast cancer risk by reproductive characteristics. A population-based case-control study assessed reproductive history in an interviewer-administered questionnaire. Global DNA methylation was measured from white blood cell DNA using luminometric methylation assay (LUMA) and pyrosequencing assay (long interspersed elements-1 (LINE-1). We estimated adjusted odds ratios (ORs) and 95% confidence intervals (CIs) among 1 070 breast cancer cases and 1 110 population-based controls. Effect modification was assessed on additive and multiplicative scales. LUMA methylation was associated with elevated breast cancer risk across all strata (comparing the highest to the lowest quartile), but estimates were higher among women with age at menarche ≤12 years (OR = 2.87, 95%CI = 1.96–4.21) compared to >12 years (OR = 1.66, 95%CI = 1.20–2.29). We observed a 2-fold increase in the LUMA methylation-breast cancer association among women with age at first birth >23 years (OR = 2.62, 95%CI = 1.90–3.62) versus ≤23 years (OR = 1.32, 95% CI = 0.84–2.05). No modification was evident for parity or lactation. Age at menarche and age at first birth may be modifiers of the association between global DNA methylation and breast cancer risk

Modification of the association between recreational physical activity and survival after breast cancer by promoter methylation in breast cancer-related genes

Background: Mechanisms underlying the inverse association between physical activity and survival after breast cancer are unresolved, but DNA methylation may play a role. We hypothesized that promoter methylation of breast cancer-related genes, as well as global methylation, may modify the association between prediagnostic recreational physical activity (RPA) and breast cancer mortality. Methods: Using a population-based sample of 1254 women diagnosed with first primary breast cancer, we examined modification of the RPA-mortality association by gene-specific promoter methylation and global methylation. Average lifetime RPA was assessed from menarche to diagnosis through structured in-home interviews. Promoter methylation of 13 breast cancer-related genes was evaluated in archived tumor by methylation-specific polymerase chain reaction and MethyLight assay. Global methylation in white blood cell DNA was determined at long interspersed nucleotide element 1 and by the luminometric methylation assay. After approximately 15 years of follow-up, 486 patients had died, and 186 of the deaths were breast cancer-related. We used Cox proportional hazards regression to estimate HRs and 95% CIs as well as likelihood ratio tests to assess multiplicative interactions. Results: All-cause mortality was lower only among physically active women with methylated promoter of APC (HR 0.60, 95% CI 0.40–0.80), CCND2 (HR 0.56, 95% CI 0.32–0.99), HIN (HR 0.55, 95% CI 0.38–0.80), and TWIST1 (HR 0.28, 95% CI 0.14–0.56) in tumors, but not among those with unmethylated tumors (significant interaction p < 0.05). We found no interaction between RPA and global methylation. Conclusions: The improved survival after breast cancer that is associated with RPA may be more pronounced in women with promoter tumor methylation in biologically plausible genes

Fat or fit: The joint effects of physical activity, weight gain, and body size on breast cancer risk

While physical activity reduces breast cancer risk, issues critical to providing clear public health messages remain to be elucidated. These include: the minimum duration and intensity necessary for risk reduction; the optimal time period for occurrence; as well as subgroup effects, particularly with regard to tumor heterogeneity and body size

A review of African American-white differences in risk factors for cancer: prostate cancer

African American men have higher prostate cancer incidence rates than White men, for reasons not completely understood. This review summarizes the existing literature of race-specific associations between risk factors and prostate cancer in order to examine whether associations differ

DNA methylation modifies the association between obesity and survival after breast cancer diagnosis

Mechanisms underlying the poor breast cancer prognosis among obese women are unresolved. DNA methylation levels are linked to obesity and to breast cancer survival. We hypothesized that obesity may work in conjunction with the epigenome to alter prognosis. Using a population-based sample of women diagnosed with first primary breast cancer, we examined modification of the obesity-mortality association by DNA methylation. In-person interviews were conducted approximately 3 months after diagnosis. Weight and height were assessed [to estimate body mass index (BMI)], and blood samples collected. Promoter methylation of 13 breast cancer-related genes was assessed in archived tumor by methylation-specific PCR and Methyl Light. Global methylation in white blood cell DNA was assessed by analysis of long interspersed elements-1 (LINE-1) and with the lumino-metric methylation assay (LUMA). Vital status among 1308 patients (with any methylation biomarker and complete BMI assessment) was determined after approximately 15 years of follow-up (N = 194/441 deaths due to breast cancer-specific/all-cause mortality). We used Cox proportional hazards regression to estimate hazard ratios (HRs) and 95 % confidence intervals (CIs) using two-sided p values of 0.05. Breast cancer-specific mortality was higher among obese (BMI ≥ 30) patients with promoter methylation in APC (HR = 2.47; 95 % CI = 1.43–4.27) and TWIST1 (HR = 4.25; 95 % CI = 1.43–12.70) in breast cancer tissue. Estimates were similar, but less pronounced, for all-cause mortality. Increased all-cause (HR =1.81; 95 % CI = 1.19–2.74) and breast cancer-specific (HR = 2.61; 95 % CI = 1.45–4.69) mortality was observed among obese patients with the lowest LUMA levels. The poor breast cancer prognosis associated with obesity may depend on methylation profiles, which warrants further investigation