Despite the well-known transcriptional regulation of the cyclin D1 gene by E2 treatment in hormone-sensitive breast cancer cells [45,46,47], it does not present any ERE sequence in the promoter region [41,59], and it was clarified that hormone induction of cyclin D1 is under the control of a DNA binding-independent effect of ERα relying on the receptor membrane rapid signaling [41]. This evidence concerns the gene ESR1 and breast cancer.