CXCR4 and neoplasm: However, increasingCXCR4 concentration in the cell membrane promotes receptor homodimerization.13 While CXCR4 is overexpressed in many tumor cells,5,6 it has been detected in the homodimer form in malignant cells.14 Consequently, both forms of CXCR4 should beinvestigated for drug design and targeting.