ESR1 and breast cancer: In another study, Leeet al(54), demonstrated that an estrogen-downregulated miRNA, miR-34b, acts as an oncosuppressor that targets cyclin D1 and Jagged-1 (JAG1) in an ERα-positive/wild-type p53 breast cancer cell line (MCF-7), as well as in ovarian and endometrial cells, but not in ERα-negative or mutant p53 breast cancer cell lines (T47D, MBA-MB-361 and MDA-MB-435).