DNA methylome analysis identifies accelerated epigenetic ageing associated with postmenopausal breast cancer susceptibility.

AIM OF THE STUDY: A vast majority of human malignancies are associated with ageing, and age is a strong predictor of cancer risk. Recently, DNA methylation-based marker of ageing, known as 'epigenetic clock', has been linked with cancer risk factors. This study aimed to evaluate whether the epigenetic clock is associated with breast cancer risk susceptibility and to identify potential epigenetics-based biomarkers for risk stratification. METHODS: Here, we profiled DNA methylation changes in a nested case-control study embedded in the European Prospective Investigation into Cancer and Nutrition (EPIC) cohort (n = 960) using the Illumina HumanMethylation 450K BeadChip arrays and used the Horvath age estimation method to calculate epigenetic age for these samples. Intrinsic epigenetic age acceleration (IEAA) was estimated as the residuals by regressing epigenetic age on chronological age. RESULTS: We observed an association between IEAA and breast cancer risk (OR, 1.04; 95% CI, 1.007-1.076, P = 0.016). One unit increase in IEAA was associated with a 4% increased odds of developing breast cancer (OR, 1.04; 95% CI, 1.007-1.076). Stratified analysis based on menopausal status revealed that IEAA was associated with development of postmenopausal breast cancers (OR, 1.07; 95% CI, 1.020-1.11, P = 0.003). In addition, methylome-wide analyses revealed that a higher mean DNA methylation at cytosine-phosphate-guanine (CpG) islands was associated with increased risk of breast cancer development (OR per 1 SD = 1.20; 95 %CI: 1.03-1.40, P = 0.02) whereas mean methylation levels at non-island CpGs were indistinguishable between cancer cases and controls. CONCLUSION: Epigenetic age acceleration and CpG island methylation have a weak, but statistically significant, association with breast cancer susceptibility.

Dietary intake of acrylamide and epithelial ovarian cancer risk in the european prospective investigation into cancer and nutrition (EPIC) cohort.

Acrylamide, classified in 1994 by the International Agency for Research on Cancer (IARC) as "probably carcinogenic" to humans, was discovered in 2002 in some heat-treated, carbohydrate-rich foods. The association between dietary acrylamide intake and epithelial ovarian cancer risk (EOC) has been previously studied in one case-control and three prospective cohort studies which obtained inconsistent results and could not further examine histologic subtypes other than serous EOC. The present study was carried out in the European Prospective Investigation into Cancer and Nutrition (EPIC) subcohort of women (n = 325,006). Multivariate Cox proportional hazards models were used to assess the association between questionnaire-based acrylamide intake and EOC risk. Acrylamide was energy-adjusted using the residual method and was evaluated both as a continuous variable (per 10 µg/d) and in quintiles; when subgroups by histologic EOC subtypes were analyzed, acrylamide intake was evaluated in quartiles. During a mean follow-up of 11 years, 1,191 incident EOC cases were diagnosed. At baseline, the median acrylamide intake in EPIC was 21.3 µg/d. No associations and no evidence for a dose-response were observed between energy-adjusted acrylamide intake and EOC risk (HR10µg/d,1.02; 95% CI, 0.96-1.09; HRQ5vsQ1, 0.97; 95% CI, 0.76-1.23). No differences were seen when invasive EOC subtypes (582 serous, 118 endometrioid, and 79 mucinous tumors) were analyzed separately. This study did not provide evidence that acrylamide intake, based on food intake questionnaires, was associated with risk for EOC in EPIC. Additional studies with more reliable estimates of exposure based on biomarkers may be needed.

Dietary fat intake and risk of epithelial ovarian cancer in the European Prospective Investigation into Cancer and Nutrition.

There are inconsistent and limited data available to assess the relationship between fat intake and risk of epithelial ovarian cancer (EOC). We examined the consumption of total fat, fat sources and fat subtypes in relation to risk of EOC and its major histologic subtypes in the European Prospective Investigation into Cancer and Nutrition which includes incident invasive (n=1095) and borderline (n=96) EOC. Cox proportional hazards regression was used to estimate hazard ratios (HRs) and 95% confidence intervals (CIs). In multivariate models, we observed no association with consumption of total fat, animal or plant fat, saturated fat, cholesterol, monounsaturated fat, or fatty fish and risk of invasive EOC. There was, however, an increased risk of invasive EOC in the highest category of intake (Quartile 4 vs. Quartile 1) of polyunsaturated fat (HR=1.22, 95% CI=1.02-1.48, P(trend)=0.02). We did not observe heterogeneity in the risk associations in comparisons of serous and endometrioid histologic subtypes. This study does not support an etiological role for total fat intake in relation to EOC risk; however, based on observations of a positive association between intake of polyunsaturated fat and invasive EOC risk in the current and previous studies, this fat subtype warrants further investigation to determine its potential role in EOC development.

Mitochondrial DNA copy number and future risk of B-cell lymphoma in a nested case-control study in the prospective EPIC cohort.

It has been suggested that mitochondrial dysfunction and DNA damage are involved in lymphomagenesis. Increased copy number of mitochondrial DNA (mtDNA) as a compensatory mechanism of mitochondrial dysfunction previously has been associated with B-cell lymphomas, in particular chronic lymphocytic leukemia (CLL). However, current evidence is limited and based on a relatively small number of cases. Using a nested case-control study, we extended these findings with a focus on subtype-specific analyses. Relative mtDNA copy number was measured in the buffy coat of prospectively collected blood of 469 lymphoma cases and 469 matched controls. The association between mtDNA copy number and the risk of developing lymphoma and histologic subtypes was examined using logistic regression models. We found no overall association between mtDNA and risk of lymphoma. Subtype analyses revealed significant increased risks of CLL (n = 102) with increasing mtDNA copy number (odds ratio = 1.34, 1.44, and 1.80 for quartiles 2-4, respectively; P trend = .001). mtDNA copy number was not associated with follow-up time, suggesting that this observation is not strongly influenced by indolent disease status. This study substantially strengthens the evidence that mtDNA copy number is related to risk of CLL and supports the importance of mitochondrial dysfunction as a possible mechanistic pathway in CLL ontogenesis.

Methylome analysis and epigenetic changes associated with menarcheal age.

Reproductive factors have been linked to both breast cancer and DNA methylation, suggesting methylation as an important mechanism by which reproductive factors impact on disease risk. However, few studies have investigated the link between reproductive factors and DNA methylation in humans. Genome-wide methylation in peripheral blood lymphocytes of 376 healthy women from the prospective EPIC study was investigated using LUminometric Methylation Assay (LUMA). Also, methylation of 458877 CpG sites was additionally investigated in an independent group of 332 participants of the EPIC-Italy sub-cohort, using the Infinium HumanMethylation 450 BeadChip. Multivariate logistic regression and linear models were used to investigate the association between reproductive risk factors and genome wide and CpG-specific DNA methylation, respectively. Menarcheal age was inversely associated with global DNA methylation as measured with LUMA. For each yearly increase in age at menarche, the risk of having genome wide methylation below median level was increased by 32% (OR:1.32, 95%CI:1.14-1.53). When age at menarche was treated as a categorical variable, there was an inverse dose-response relationship with LUMA methylation levels (OR(12-14 vs. ≤11 yrs):1.78, 95%CI:1.01-3.17 and OR(≥15 vs. ≤11 yrs):4.59, 95%CI:2.04-10.33; P for trend<0.0001). However, average levels of global methylation as measured by the Illumina technology were not significantly associated with menarcheal age. In locus by locus comparative analyses, only one CpG site had significantly different methylation depending on the menarcheal age category examined, but this finding was not replicated by pyrosequencing in an independent data set. This study suggests a link between age at menarche and genome wide DNA methylation, and the difference in results between the two arrays suggests that repetitive element methylation has a role in the association. Epigenetic changes may be modulated by menarcheal age, or the association may be a mirror of other important changes in early life that have a detectable effect on both methylation levels and menarcheal age.

The associations of advanced glycation end products and its soluble receptor with pancreatic cancer risk: a case-control study within the prospective EPIC Cohort.

BACKGROUND: Advanced glycation end products (AGE) and their receptors (RAGE) have been implicated in cancer development through their proinflammatory capabilities. However, prospective data on their association with cancer of specific sites, including pancreatic cancer, are limited. METHODS: Prediagnostic blood levels of the AGE product Nε-(carboxymethyl)lysine (CML) and the endogenous secreted receptor for AGE (esRAGE) were measured using ELISA in 454 patients with exocrine pancreatic cancer and individually matched controls within the European Prospective Investigation into Cancer and Nutrition (EPIC). Pancreatic cancer risk was estimated by calculating ORs with corresponding 95% confidence intervals (CI). RESULTS: Elevated CML levels tended to be associated with a reduction in pancreatic cancer risk [OR = 0.57 (95% CI, 0.32-1.01) comparing highest with lowest quintile), whereas no association was observed for esRAGE (OR = 0.98; 95% CI, 0.62-1.54). Adjustments for body mass index and smoking attenuated the inverse associations of CML with pancreatic cancer risk (OR = 0.78; 95% CI, 0.41-1.49). There was an inverse association between esRAGE and risk of pancreatic cancer for cases that were diagnosed within the first 2 years of follow-up [OR = 0.46 (95% CI, 0.22-0.96) for a doubling in concentration], whereas there was no association among those with a longer follow-up (OR = 1.11; 95% CI, 0.88-1.39; P(interaction) = 0.002). CONCLUSIONS AND IMPACT: Our results do not provide evidence for an association of higher CML or lower esRAGE levels with risk of pancreatic cancer. The role of AGE/RAGE in pancreatic cancer would benefit from further investigations.