ESR1 and breast cancer: Interestingly, in breast cancer, estrogen receptor‐bound SEs are also bound by MED1 and FOXA1, which act as facilitators for the interaction with neighboring enhancers (Bojcsuk et al., 2017), and lists of highly active SEs which potentially play a critical role in this tumor type have just been reported (Hazan et al., 2019; Li et al., 2019).