Surprisingly, despite the strong in vitro effects, CXCR7 did not influence colorectal tumour growth in vivo, at least in a mouse xenograft model (Meijer et al, 2008), whereas CXCR7 RNAi significantly reduced the tumour growth of lung and mammary carcinomas (Miao et al, 2007). The gene discussed is ACKR3; the disease is neoplasm.