ESR1 and breast cancer: However, autocrine regulation in hippocampal neurons by locally produced E2 (Prange-Kiel et al., 2003), the regulation of luteinizing hormone (LH) production in ovarian follicle granulosa cells by local estrogens (Kessel et al., 1985), and autocrine regulation of cell proliferation in estrogen-dependent breast cancer cells via ERα (Tan et al., 2009), are examples of intrinsic actions.