interacts with the DNA repair protein XPA. Physical exercise has been shown to decrease and even reverse these promoter hypermethylation, lowering the risk of the development of cancer. Decreased hypermethylation patterns reveal a transcriptionally accessible promoter region, allowing for increased expression of the tumor suppressing genes. Physical exercise increases levels of eustress, or good stress, on the body. This eustress stimulates epigenetic modifications affecting the DNA genome of cancer cells. Environmental conditions, such as eustress, strongly induces expression of the tumor suppressor TP53 gene by influencing epigenetic modifications to be made to the cancer cells genome. The TP53 gene codes for the p53 protein, a protein important in the apoptotic pathway of programmed cell death. The p53 protein is important for the regulation of cell growth and apoptosis, so hypermethylation of the TP53 promoter region are common markers associated with the development of cancer. Other than methylation patterns affecting expression of TP53, microRNAs and antisense RNAs control the levels of the p53 protein by regulating expression of the p53 coding TP53 gene. Breast cancer In a study on the epigenetic effects of physical exercise on breast cancer in women, blood samples from breast cancer patients were collected before and after 6 months of moderate-intensity aerobic exercise. The test group experienced 129 minutes of exercise on average per week compared to the control group’s 21.8 minutes a week. The study found 43 genes having significant changes in DNA methylation. Of the 43 genes, 3 of the genes experiencing reduced methylation levels were directly correlated with increased survival of breast cancer. The gene L3MBTL1, a known tumor suppressor, had methylation levels decreased by 1.48% in the exercise group while the limited exercise control group experienced a 2.15% increase in methylation. The 1.48% decrease in methylation of L3MBTL1 resulted in greater expression of the tumor suppressor while the 2.15% increase in methylation experienced by the limited exercise control group led to a decrease in expression. The findings of the study showed patients who exercised regularly had lower methylation levels and higher gene expression of L3MBTL1. These patients also experienced a greater than 60% reduction in risk of breast cancer death compared to patients in the limited exercise group. Effects on aging DNA methylation Epigenetic mechanisms affected by physical exercise have also been seen to be involved in age-related processes. A major component of aging is significant loss of DNA methylation over time. Methyl