ACKR3 and breast neoplasm: Addressing the roles of CXCR7/ACKR3, the other CXCL12 receptor, the study of murine breast tumor cells demonstrated that CXCL12 has induced the functional expression of MMP9 through CXCR7/ACKR3 in vitro and that CXCR7/ACKR3 inhibition has led to reduced tumor growth and MMP9 expression in tumors in vivo (106).