The effect of decitabine on DNA methylation and expression in breast cancer cell lines. A) Composite graphs showing the DNA methylation levels across the ESR1 gene in three ER-neg cell lines treated with DAC (yellow) compared to DMSO-treated controls (red). Data was collected in triplicate in each cell line at each locus, and the standard error of the mean was then calculated (error bars); *p < 0.05, Bonferroni corrected t-test. B) DNA methylation across the ESR1 gene in ER-pos cell lines treated with DAC (purple) compared to untreated (blue). C, D) qRT-PCR gene expression in individual cell lines treated with DAC (ER-neg = yellow, ER-pos = purple) compared to DMSO-treated controls (ER-neg = red; ER-pos = blue). Expression increased significantly in ER-neg cell lines, but was significantly reduced in all three ER-pos cell lines (p < 0.05).