We have shown that the chemokine receptor CXCR4, which regulates leukocytic and stem cell homing and cancer metastasis (18–20), and the multifunctional regulator DPP4, which controls the CXCR4 ligand CXCL12 (21, 22) are regulated by adenosine (23, 24) and selected eicosanoids (25) through pathways that we have identified (26–28). Here, CXCR4 is linked to cancer.