Direct Crosstalk Between Cancer and Osteoblast Lineage Cells Fuels Metastatic Growth in Bone via Auto-Amplification of IL-6 and RANKL Signaling Pathways

作者:Zheng Yu*; Chow Shu Oi; Boernert Katja; Basel Dennis; Mikuscheva Anastasia; Kim Sarah; Fong Yee Colette; Trivedi Trupti; Buttgereit Frank; Sutherland Robert L; Dunstan Colin R; Zhou Hong; Seibel Markus J
来源:Journal of Bone and Mineral Research, 2014, 29(9): 1938-1949.
DOI:10.1002/jbmr.2231

摘要

The bone microenvironment and its modification by cancer and host cell interactions is a key driver of skeletal metastatic growth. Interleukin-6 (IL-6) stimulates receptor activator of NF-kappa B ligand (RANKL) expression in bone cells, and serum IL-6 levels are associated with poor clinical outcomes in cancer patients. We investigated the effects of RANKL on cancer cells and the role of tumor-derived IL-6 within the bone microenvironment. Using human breast cancer cell lines to induce tumors in the bone of immune-deficient mice, we first determined whether RANKL released by cells of the osteoblast lineage directly promotes IL-6 expression by cancer cells in vitro and in vivo. We then disrupted of IL-6 signaling in vivo either via knockdown of IL-6 in tumor cells or through treatment with specific anti-human or anti-mouse IL-6 receptor antibodies to investigate the tumor effect. Finally, we tested the effect of RANK knockdown in cancer cells on cancer growth. We demonstrate that osteoblast lineage-derived RANKL upregulates secretion of IL-6 by breast cancers in vivo and in vitro. IL-6, in turn, induces expression of RANK by cancer cells, which sensitizes the tumor to RANKL and significantly enhances cancer IL-6 release. Disruption in vivo of this auto-amplifying crosstalk by knockdown of IL-6 or RANK in cancer cells, or via treatment with anti-IL-6 receptor antibodies, significantly reduces tumor growth in bone but not in soft tissues. RANKL and IL-6 mediate direct paracrine-autocrine signaling between cells of the osteoblast lineage and cancer cells, significantly enhancing the growth of metastatic breast cancers within bone.