CXCL12 and cancer: Interestingly, as reported for Dkk3, CXCR7 expression is also upregulated in several cancers and tumor associated vasculature, which confers a proangiogenic role to CXCR7.44,45 Originally, CXCR7 was recognized as a mere scavenger receptor with the function to generate gradients of Sdf-1α.46,47 More recently, it is accepted as a functional receptor directly involved in cellular responses, including cell migration.33,36,48–50 In this study, knockdown of CXCR7 abrogated Dkk3-driven migration of progenitors, whereas CXCR7 overexpression increased Dkk3-mediated cell migration.