MGMT and cancer: Xie et al. used mtDNA-deficient (ρ0) prostate adenocarcinoma cell (LNCaP) and ρ0 human breast adenocarcinoma cell (MCF-7) models to demonstrate that mtDNA can influence the expression of DNA methyltransferase 1 (DNMT1),128 altering the methylation of genes that are relevant to cancer and cancer progression.128 For example, mtDNA deficiency induced DNMT1 expression, which led to the hypermethylation of the promoters for endothelin B receptor, O6-methylguanine-DNA methyltransferase and E-cadherin, ultimately silencing the expression of these genes.