CXCR4 and cancer: For cancer cells, the chemotaxis response following CXCL12 binding to CXCR4 was abolished, inhibiting CXCR4-mediated cell migration, if the receptor homodimerization was modulated by removing cholesterol or blocked by a TM4 peptide (an analog of the transmembrane (TM) helix 4 of CXCR4) [14, 15].