The most recently discovered member of this family, CXCR7, is an atypical receptor lacking canonical G-protein signaling activation upon ligand binding10, but its expression is linked to aggressive tumor phenotypes in several cancer models, including colon cancer11 breast cancer12, 13, hepatocellular carcinoma14 and prostate cancer7, 15, 16. The gene discussed is ACKR3; the disease is cancer.