The Role of the Interleukin-6 Family of Cytokines in Bone Remodeling and Bone Cancer

Publisher Summary Cytokines of the interleukin (IL)-6 family are recognized as pleiotropic factors influencing many biological events in several organs, especially bone. Since its discovery, the list of IL-6 effects is still growing and recent in vivo and genetic data have challenged our concept saying that IL-6 was a major positive regulator of bone resorption. Adding to our confusion, other IL-6-type cytokines can have opposite effects on bone pathophysiology, despite their overlapping biological effects. Not surprisingly, these cytokines are also implicated in various bone cancers. However, clinical trials have been performed either using these cytokines as anti-cancer adjuvants or neutralizing their unwanted effects on tumor growth and osteolysis. This chapter describes the dual effects of IL-6-type cytokines in bone remodeling and cancer and discusses recent data on IL-6 signaling, which may have therapeutic implications.