CXCR4 and neoplasm: Dysregulated Notch signaling promotes MM through several mechanisms: (1) enhanced proliferation via IL-6 and cyclin D upregulation, (2) increased tumor-initiating potential by inhibiting p21 and p27, (3) activation of pro-survival pathways like CXCR4/SD-1, (4) alterations enabling bone marrow infiltration and drug resistance, and (5) release of Notch components in exosomes.