KCNA3 and breast cancer: Although the selection of subtype‐specific methylation markers was based on the top significant CpG's indicative of different breast cancer subtypes (not taking into account their effects on gene expression), we find that the proxy markers KCNA3, ZNF132, TENC1 and ZNF671 are down‐regulated in association with promoter methylation based on RNA sequencing and methylation data from the TCGA cohort (Supplementary Figure 5).