In MM, CXCR4 is involved in myeloma cell homing, bone marrow retention, angiogenesis and metastasis, while collective evidence from several studies support the pivotal role of CXCR4 in different stages of MM, disease progression, development of therapeutic resistance and MRD, as well as poor prognosis [59,60,61,62,63,64,65,66]. The gene discussed is CXCR4; the disease is plasma cell myeloma.