The OGG1 gene encodes the enzyme 8-oxoguanine, a mutagenic base byproduct that occurs as a result of exposure to reactive oxygen. This is a repair enzyme for oxidatively damaged DNA and is involved in human carcinogenesis
OGG1 methylation levels in blood cells were measured in a prospective study of 582 US Veterans, median age 72, and followed for 13 years. High OGG1 methylation at a particular promoter region was associated with increased risk for any cancer, and in particular for risk of prostate cancer. Reduced OGG1 enzymatic activity has been linked to lung, breast, and skin cancer. It is important to view your genotype in this gene in conjunction with XRCC1, BRCA1, and BRCA2 genotypes in order to pre-determine your risk.
Increased levels of 8-oxo-dG in tissue can serve as a biomarker of oxidative stress. They also noted that increased levels of 8-oxo-dG are frequently found during carcinogenesis.