TNFSF11 and breast neoplasm: Breast tumor cells can secrete many different cytokines or factors (e.g., IL-1β, IL-6, IL-8, IL-11, IL-17, M-CSF, TNFα, parathyroid hormone-releasing protein (PTHrP), prostaglandin E2 (PGE2)) that cause increased RANKL production by stromal cells in the bone microenvironment and osteoblasts [46,47].