Fluorescence imaging to assess the matrix metalloproteinase activity and its inhibitor in vivo

Matrix metalloproteinases (MMPs) are a kind of secretory proteinases. Degradation of the extracellular matrix (ECM) by MMPs enhances tumor invasion and metastasis. To monitor MMPs activity and assess the MMP inhibitor effects in vivo, we constructed a plasmid that encoded a secretory fluorescent sensor named DMC (DsRed2-MSS-CFP expressed from pDisplay vector) that DsRed2 and cyan fluorescent protein (CFP) linked by MMP substrate site (MSS). MDA-MB 435s cells highly expressing endogenetic secretory MMP were transfected with the DMC plasmid so that the DMC could be cleaved by endogenetic MMP and the fluorescence ratio of DsRed2 to CFP was decreased. Treating the cells with GM6001, an MMP inhibitor, blocked the cleavage of DMC and caused an increase of the DsRed2/CFP ratio. The same result was achieved by using an in vivo tumor model that stable DMC-expressing MDA-MB 435s cells inoculated onto the chorioallantoic membrane of developing chick embryos to form primary tumors on the membrane. Thus, the fluorescent sensor DMC is able to sensitively monitor MMP activity and assess MMP inhibitors for anticancer research in vivo. This proves a novel method to efficiently screen and assess the anticancer drug MMP inhibitor in living cells and in vivo tumor models.