Receptor activator of NF-kB (RANK)-c regulates wild type (wt) RANK-dependent survival and inhibits cell motility and migration. A and B. MTT proliferation/viability assays for MDA-MB-231 and 293T transfected cells, after the addition of doxorubicin (Doxo) and/or RANK ligand (RANKL). Plasmid transfections and doxorubicin or RANKL treatments as indicated. C. RANK-c reduces the motility of MDA-MB-231 cells, compared to both wt RANK and mock-transfected cells as assessed by the wound-healing assay. D and E. Migration of mock- and isoform-transfected MDA-MB-231 cells towards RANKL (1 μg/ml) or 1% FBS was assessed with the use of 8-μm pore Transwell chambers. *P < 0.001 in comparison to wt RANK.