CCN2 and cancer: TGF-β has an additional role in cancer to promote bone metastasis by regulating many of the tumor-secreted factors that stimulate tumor growth and bone destruction [5] (Table 1), such as PTHrP [6], IL-11, connective tissue growth factor (CTGF), the CXC chemokine receptor 4 (CXCR4), and others [7]–[10].