ESR1 and breast cancer: Because a previous study demonstrated that ZMYND8 physically binds ERα in breast cancer [34], and because we found that mRNA levels of ZMYND8 were positively correlated with expression levels of the ESR1 (estrogen receptor 1) gene (Spearman correlation coefficient (r) of 0.34 in TCGA breast cancer samples), we tested whether ZMYND8 is a downstream target of the ER pathway.