ESR1 and cancer: There was a strong correlation between ESR1 ChIP-seq peaks in primary cancer samples and the number of shared datasets for each ESR1 binding site in cell lines (r2 = 0.74, p < 0.0001), which was preserved when restricting analysis to only the central 200 basepairs of each ESR1 binding site (r2 = 0.73, p < 0.0001).