ESR1 and neoplasm: These mechanisms that sustain altered ER signalling in endocrine-resistant tumours can result in further unbalanced activity of ER co-regulator, ligand-independent ER activation, and altered ER-dependent transcriptional reprogramming to further support endocrine resistance (Massarweh et al. 2008, Evans et al. 2010, Lupien et al. 2010, Nardone et al. 2015).