ESR1 and neoplasm: In a previous study from our group, we showed that ATF2 silencing leads to a loss in the growth-inhibitory effects of tamoxifen in the ER-positive, tamoxifen-sensitive MCF7 cell line and that tamoxifen treatment caused a dose-dependent phosphorylation of ATF2 within its activation domain, enhancing its transcriptional activity, suggesting a tumour-suppressive role of ATF2 in ER-positive breast cancer [25].