ESR1 and breast cancer: Interestingly, a subset of ER- breast cancer cell lines (MCF-12A, MDA-MB-468, BT-549, Hs-578T, HCC1143 and MDA-MB-231) expressed substantial amount of EglN2, albeit slightly lower level than ER+ breast cancer cell lines including T47D, BT474 and ZR-75-1 (Figure 2A).