Some groups provided evidence that CXCR7 represents a scavenger or a decoy chemokine receptor, which is responsible for either sequestering extracellular CXCL1237,38 or modulating CXCR4 signalling by forming CXCR7–CXCR4 heterodimers.33,39 In contrast, others using various tumor cells demonstrated that CXCR7 can actively control cell growth and survival, as well as cell adhesion and transendothelial migration.18,25,26 In our opinion, the biological significance of CXCR7, its signal transduction and further effects obviously depend on malignant cell types investigated. The gene discussed is ACKR3; the disease is neoplasm.