ESR1 and breast cancer: We have previously shown that PGR is not only an ERα‐target gene but is also an ERα‐associated protein that can reprogram ERα DNA binding and transcriptional responses in breast cancer and, importantly, used the PDE model to study the transcriptome and growth effects of this ERα reprogramming by PGR (Mohammed et al., 2015; Singhal et al., 2016).