To determine if Ets1 expression was sufficient to alter the growth characteristics of ER-positive breast cancer cell lines, we evaluated a panel of breast cancer cell lines including BT-474, MCF7, MDA-MB-157, MDA-MB-231, MDA-MB-453, T-47D and ZR-75-1 as well as the human non-tumorigenic mammary cell line MCF10A for expression of ERα and Ets1. Here, ESR1 is linked to breast cancer.