A novel strategy to tag MMPs-positive cells for in vivo imaging of tumor cells

Matrix metalloproteinases (MMPs) are endopeptidases responsible for degrading the extracellular matrix (ECM) and remodeling tissue in both physiological and pathological processes. MMP2 and membrane-type 1 MMP (MT1-MMP) have been associated with tumor invasion, metastasis and angiogenesis; therefore, a molecular imaging strategy assessing their activity may help to predict the malignancy of tumors. Here, we established a novel method of specifically tagging the surface of MMP2- and MT1-MMP-positive cells, and applied it to the development of an optical imaging probe. We constructed a protein-based probe. In vitro and in vivo experiments demonstrated that the probe was cleaved and specifically remained in tumor xenografts in a MMP-dependent manner.