IKBKB and breast cancer: In the present study, we identified a novel circRNA, circIKBKB (hsa_circ_0084100), derived from the IKBKB gene (encoding inhibitor of NF-κB kinase subunit beta), which plays an important role in promotion of osteoclastogenesis and BC-BM through inducing bone pre-metastatic niche formation via specific upregulation of multiple bone remodeling factors.