TNFSF11 and cystic fibrosis: The RANKL-RANK-OPG signaling pathway for osteoclastogenesis10 is believed to be heavily involved in the development of CF.31 The receptor activator of nuclear factor-κβ ligand (RANKL) binds and activates the receptor activator of nuclear factor-κβ (RANK), causing it to cluster and recruit TNF receptor–associated factor 6 (TRAF6) (Figure 1).