Many bone metastases genes that are regulated by TGF-β are also regulated by hypoxia (Table 1), including those identified by Kang et al. to comprise a bone-metastatic gene signature in breast cancer cells: CTGF, CXCR4, IL-11, and MMP-1 [8], [13], [24]–[26]. This evidence concerns the gene CXCR4 and breast carcinoma.