CCL2 and bone giant cell tumor: According to recent analyses, neoplastic spindle cells of bone giant cell tumors may secrete a variety of cytokines and differentiation factors, including MCP1 (monocyte chemoattractant protein 1), ODF (osteoclast differentiation factor) and M-CSF (macrophage colony-stimulating factor): these are monocyte chemo-attractants and are essential for osteoclast differentiation.