PPARGC1A and breast cancer: The result with ESR1 is consistent with a report of decreased methylation and increased expression of ESR1 with in vitro arsenic exposure in a breast cancer model (Du et al. 2012), whereas the association with PPARGC1A is consistent with a report demonstrating up-regulation of this gene in arsenic-induced Bowen’s disease, a skin carcinoma (Lee et al. 2011).