Analyses of key target genes involved in the tumor–bone vicious cycle showed similar patterns of gene expression in the vehicle-treated Cont-4T1 and Pth1rKD-4T1 tumors except for Il6, Ackr3 (encoding CXCR7), and Cyp19a1, which were reduced in the Pth1rKD-4T1 cells (Figure 6A). This evidence concerns the gene ACKR3 and neoplasm.