Among the top 50 BC smoking-dysregulated genes, ordered by absolute difference in gene expression, were several related to oxidative stress, including glutathione peroxidase (GPX1) which was up-regulated, and microsomal glutathione S-transferase 1 (MGST1), which was one of the few genes down-regulated by smoking (Table 1). Here, MGST1 is linked to breast cancer.