RANKL contributes to bone metastasis by not only activating osteoclastic bone resorption but also stimulating the migration of tumour cells to bone.15–18 RANK is expressed at high levels on many different epithelial tumour cells that preferentially metastasize to bone, including MDA-MB-231 cells and the murine melanoma cell line B16F10. This evidence concerns the gene TNFSF11 and neoplasm.