FOXA1 is expressed in some endometrial tumors and a role for FOXA1 as a pioneer factor in endometrial cancer cells has been proposed [83]; however, FOXA1 overlaps with less than 10% of ER-bound sites in endometrial cancer cells [78] and tumors [83], indicating that the pioneering role is minimal and does not explain most endometrial cancer-specific ER genomic binding. Here, ESR1 is linked to endometrial cancer.