For the analysis, MCF-7 breast cancer cells, COLO-357 and PANC-1 pancreatic cancer cells and the non-cancerous HEK-293 cells were co-transfected with the reporter and either WT-ER or R269C-ER, grown in estrogen-depleted medium and treated with either vehicle control or E2. The gene discussed is ESR1; the disease is breast cancer.