CXCR4 and bone neoplasm: To further explore the transactivation of HER2 by CXCL12, we investigated the role of the small GTP protein Gαi2 in Src and HER2 phosphorylation in lipid raft membrane microdomains and the significance of CXCR4 inhibition by plerixafor, a bone stem cell mobilizer, in prostate cancer bone tumor growth.