We recently isolated two cell lines from luminal T47Dco xenografts grown in ovx’d NSG mice: EWD8 consisting mainly of luminobasal ER–PR–CK5+ cells derived from a tumor in EWD mice; and E3 consisting mainly of luminal ER+PR+CK5– cells derived from a tumor in E-replenished mice [13]. Here, ESR1 is linked to neoplasm.