ACKR3 and neoplasm: In turn, hypoxia initiates a lethal cascade of events consisting of the increased production of CXCL12, the subsequent recruitment of CXCR4 and CXCR7-positive bone marrow-derived monocytes and hematopoietic progenitor cells that differentiate into tumor-promoting macrophages and mediate vasculogenesis and tumor recurrence in mice (Tabatabai et al., 2006; Kioi et al., 2010; Tseng et al., 2011).