Lifetime exposure to ambient air pollution and methylation of tumor suppressor genes in breast tumors

Highlights: • DNA was extracted from breast tumor tissue and methylation of nine genes was measured. • Total suspended particulates and traffic exposures throughout life were considered. • Exposure to TSP of a woman's first birth was associated with higher methylation of SYK and lower methylation of SCGB3A1. • Traffic exposure was associated with methylation of certain genes. • Our observed associations were not statistically significant after adjustment for multiple comparisons. We previously reported increased risk of breast cancer associated with early life exposure to two measures of air pollution exposure, total suspended particulates (TSP) and traffic emissions (TE), possible proxies for exposure to polycyclic aromatic hydrocarbons (PAHs). Exposure to PAHs has been shown to be associated with aberrant patterns of DNA methylation in peripheral blood of healthy individuals. Exposure to PAHs and methylation in breast tumor tissue has received little attention. We examined the association of early life exposure to TSP and TE with patterns of DNA methylation in breast tumors.