CXCR7 is a recently described second receptor for CXCL12 and was shown to promote lung cancer growth in vivo (Miao et al, 2007) but this receptor might rather modulate CXCR4-mediated responses than act as an independent CXCL12 receptor (Hartmann et al, 2008). This evidence concerns the gene ACKR3 and lung cancer.