Identification of mammary epithelial cells subject to chronic oxidative stress in mammary epithelium of young women and teenagers living in USA

Abstract

Current knowledge of changes in the mammary epithelium relevant to breast carcinogenesis is limited to when histological changes are already present because of a lack of biomarkers needed to identify where such molecular changes might be ongoing earlier during the decades-long latent stages of breast carcinogenesis. Breast reduction tissues from young women and teenagers, representative of the USA's high breast cancer incidence population, were studied using immunocytochemistry and a targeted PCR array in order to learn whether a marker of chronic oxidative stress [protein adducts of 4-hydroxy-2-nonenal (4HNE)] can identify where molecular changes relevant to carcinogenesis might be taking place prior to any histological changes. 4HNE-immunopositive (4HNE+) mammary epithelial cell-clusters were identified in breast tissue sections from most women and from many teenagers (ages 14–30 y) and, in tissues from women ages 17–27 y with many vs. few 4HNE+ cells, the expression of 30 of 84 oxidative stress associated genes represented in SA Bioscience RT2 Oxidative Stress and Antioxidant PCR array was decreased and only one was increased > 2-fold. This is in contrast to increased expression of many of these genes known to be elicited by acute oxidative stress. The findings validate using 4HNE-adducts to identify where molecular changes of potential relevance to carcinogenesis are taking place in histologically normal mammary epithelium and highlight differences between responses to acute vs. chronic oxidative stress. We posit that the altered gene expression in 4HNE+ tissues identified reflects adaptive responses to chronic oxidative stress that enable some cells to evade mechanisms that have evolved to prevent propagation of cells with oxidatively-damaged DNA and to accrue heritable changes needed to establish a cancer.