CXCR4 and plasma cell myeloma: CXCR4 signalling modulators, e.g., plerixafor, an anti-CXCR4 antibody, is being tested in clinical studies in both solid and haematologic cancers (e.g., acute myeloid leukaemia (AML), chronic lymphatic leukaemia (CLL) and multiple myeloma (MM) [26,32,33].