That OGG1 levels can vary in vivo has recently been demonstrated by the identification of a common single nucleotide polymorphism (SNP rs2304277) at the 3′ end of the OGG1 gene that is associated with a lower expression of the enzyme and that has been linked to an increased ovarian cancer risk in breast cancer patients carrying mutations in BRCA1 (35). This evidence concerns the gene BRCA1 and breast cancer.