Estrogensignaling has dual roles in MECs and breast cancer cells; on one hand it has anoncogenic role by promoting proliferation of ER+ luminal breast cancercells, on the other hand it also has a tumor suppressor role by promoting MECdifferentiation and inhibiting metastasis of breast cancer cells (Chimge and Frenkel, 2013). The gene discussed is ESR1; the disease is breast cancer.