ESR1 and breast cancer: We define a molecular pathway wherein activation of SXR inhibits proliferation of estrogen receptor positive (ER+) and p53 wild type (p53wt) breast cancer cell lines (MCF-7 and ZR-75-1) via induction of inducible nitric oxide synthase (iNOS), increased expression of nitric oxide (NO), and NO-dependent stabilization and accumulation of p53.