Significant inhibition of OGG1 mRNA expression by E2 was demonstrated in mammary tissues of rats treated with E2 for 7 days and OGG1 mRNA expression further decreased in mammary tissues as well as in mammary tumors of rats treated with E2 for 240 days, compared to age-matched mammary tissues from control animals (Figure 1A). Here, OGG1 is linked to breast cancer.