MMP3 and cancer: CCN2/CTGF up-regulates MMP family proteins in cancer [27], while MMP3 regulates CCN2/CTGF by two mechanisms, including (i) intracellular MMP3, which directly activates the CCN2/CTGF gene to induce the production of CCN2/CTGF protein in chondrocytes [28,29] and (ii) MMPs, which cleave CCN2/CTGF to generate bioactive fragments essential for angiogenesis and osteoclastogenesis [30,31].