Expression of CCND1, the gene encoding cyclin D1, is stimulated by treatment of cells with E2. Expression is dependent on ESR1-mediated signaling through the PKA and AKT pathways, and consistent with this, levels of phosphorylated CREB1 increase upon treatment with E2. The CCND1 promoter has a CRE element that is bound by phosphorylated CREB1 upon E2 treatment as assessed by electrophoretic mobility shift assay (Park et al, 2001; Felty et al, 2005).