MMP1 and neoplasm: In addition to MMP-2 and -9, other MMP family members such as MMP-1, MMP-3, MMP-11 and MMP-14 have all been shown to be secreted by tumor cells in tumor microenvironments, serving to mediate the breakthrough of tissue barriers comprising cell–cell adherent junctions, basement membranes, and interstitial tissue stroma [38]–[40].