EGR1 and breast carcinoma: Surprisingly, although an estrogen response element (ERE) has been identified on the Egr1 promoter, the induction of Egr1 transcription by estrogen is mediated by SRF and Elk1 binding to SRE rather than binding of estrogen receptors to their ERE, and is blocked by a MAPK but not PI3K pathway inhibitor in rat cardiomyocytes or MCF-7 human breast cancer cells (Slade and Carter, 2000; Chen et al., 2004), indicating that EGR1 is a downstream target of estrogen’s non-genomic effects.