At least seven genes (IL-11, CTGF, CXCR4, MMP-1, PTHrP, VEGF, and PTGS2/COX2) have been identified as drivers of human breast cancer bone metastases in the MDA-MB-231 model, and each of these genes is transcriptionally regulated by and dependent on TGFβ signaling in vivo [20]. Here, TGFB1 is linked to breast carcinoma.