Differential promoter methylation profile of candidate genes in parental breast cancer cells (MCF7 P and SUM159 P) and putative breast CSC (MMO). Methylation status of 96 genes was analyzed using the Epitect Methyl qPCR Arrays (Qiagen). Methylation level is expressed in a 0-100% scale, with higher methylation shown in red and lower methylation shown in green. For MCF7, we identified a set of 19 genes differentially methylated in mammospheres compared to parental cells. 13 of these genes were hypermethylated and six genes were hypomethylated in mammospheres. For SUM159, we found only four differentially methylated genes and all these genes were hypomethylated in mammospheres.