CXCR4 and neoplasm: Augmenting evidence accumulates that CXCL12 and its receptors, both CXCR4 and CXCR7, are involved in cancer development, affecting tumor cell adhesion, trans-endothelial migration, neovascularization and cell survival.18,29,35 In different tumor cell types, depending on differentiation status and environment, CXCR4 and CXCR7 may be expressed uniquely or in combination.29,28 As a result, studies on the cellular function of CXCR7 to date has produced a rather puzzling picture.