DNA methylation age in paired tumor and adjacent normal breast tissue in Chinese women with breast cancer.

BACKGROUND: Few studies have examined epigenetic age acceleration (AA), the difference between DNA methylation (DNAm) predicted age and chronological age, in relation to somatic genomic features in paired cancer and normal tissue, with less work done in non-European populations. In this study, we aimed to examine DNAm age and its associations with breast cancer risk factors, subtypes, somatic genomic profiles including mutation and copy number alterations and other aging markers in breast tissue of Chinese breast cancer (BC) patients from Hong Kong. METHODS: We performed genome-wide DNA methylation profiling of 196 tumor and 188 paired adjacent normal tissue collected from Chinese BC patients in Hong Kong (HKBC) using Illumina MethylationEPIC array. The DNAm age was calculated using Horvath's pan-tissue clock model. Somatic genomic features were based on data from RNA sequencing (RNASeq), whole-exome sequencing (WES), and whole-genome sequencing (WGS). Pearson's correlation (r), Kruskal-Wallis test, and regression models were used to estimate associations of DNAm AA with somatic features and breast cancer risk factors. RESULTS: DNAm age showed a stronger correlation with chronological age in normal (Pearson r = 0.78, P < 2.2e-16) than in tumor tissue (Pearson r = 0.31, P = 7.8e-06). Although overall DNAm age or AA did not vary significantly by tissue within the same individual, luminal A tumors exhibited increased DNAm AA (P = 0.004) while HER2-enriched/basal-like tumors exhibited markedly lower DNAm AA (P = < .0001) compared with paired normal tissue. Consistent with the subtype association, tumor DNAm AA was positively correlated with ESR1 (Pearson r = 0.39, P = 6.3e-06) and PGR (Pearson r = 0.36, P = 2.4e-05) gene expression. In line with this, we found that increasing DNAm AA was associated with higher body mass index (P = 0.039) and earlier age at menarche (P = 0.035), factors that are related to cumulative exposure to estrogen. In contrast, variables indicating extensive genomic instability, such as TP53 somatic mutations, high tumor mutation/copy number alteration burden, and homologous repair deficiency were associated with lower DNAm AA. CONCLUSIONS: Our findings provide additional insights into the complexity of breast tissue aging that is associated with the interaction of hormonal, genomic, and epigenetic mechanisms in an East Asian population.

The Health of Women (HOW) Study®: a web-based survey of breast cancer risk factors, diagnosis, and treatment.

PURPOSE: Although improvements in breast cancer detection and treatment have significantly increased survival, important questions related to breast cancer risk, prognosis, and survivorship remain. This brief report describes the Health of Women (HOW) Study® methodology and characterizes the participants who completed the My Health Overview and My Breast Cancer modules. METHODS: The HOW Study® was a collection of cross-sectional, web-based modules designed to survey a large number of participants with and without breast cancer. RESULTS: A total of 42,540 participants completed the My Health Overview module, of whom 13,285 (31.2%) reported a history of breast cancer. The majority of participants were white (94.3%), female (99.5%), married (74.1%), college educated (73.2%), post-menopausal (91.1%), parous (68.8%), and reported breastfeeding their children (56.0%). A total of 11,670 participants reported a history of breast cancer in the My Breast Cancer module. The majority of survivors reported on their primary breast cancer and were diagnosed over the age of 40 years (83.5%), had either Stage I or Stage II breast cancer (63.1%), and were treated with surgery (98.8%), radiation (64.8%), and/or chemotherapy (62.3%). CONCLUSIONS: The HOW Study® provides an innovative framework for collecting large amounts of epidemiological data in an efficient and minimally invasive way. Data are publicly available to researchers upon request. IMPLICATIONS FOR CANCER SURVIVORS: The HOW Study® can be leveraged to answer important questions about survivorship, and researchers are encouraged to utilize this new data source.