In view of these dual roles of CXCL12, it is expected that the CXCL12-CXCR4 pair will be instrumental in regulating osteoclastogenesis and osteolysis in tumors, but currently this aspect was mainly investigated in multiple myeloma (141, 144) and needs to be extensively addressed in future studies. This evidence concerns the gene CXCL12 and plasma cell myeloma.