The expression of connective tissue growth factor (CTGF/CCN2) gene is triggered in BM by PTHrP and TGF-β released by breast cancer cells through PKA-PKC-dependent activation of the ERK1/2 pathway, augmenting osteoclastogenesis by binding αvβ3 integrin on OCL progenitors [12]. This evidence concerns the gene CCN2 and breast cancer.