Within this group we identifed three genes encoding soluble ligands with established roles in bone-related processes, IL-11, CSF-2 and SOST. IL-11 and GM-CSF (encoded by CSF-2) are osteoclastogenic cytokines whose expression by metastatic breast cancer cells is known to stimulate bone resorption by osteoclasts [30,31]. This evidence concerns the gene CSF2 and breast carcinoma.