Increased aggressiveness of human prostate PC-3 tumor cells expressing cell surface localized membrane type-1 matrix metalloproteinase (MT1-MMP)

Membrane type-1 matrix metalloproteinase (MT1-MMP) is a multidomain transmembrane endopeptidase with a major role in physiological and pathological processes through proteolysis of extracellular matrix and other pericellular proteins. We examined cell surface function of MT1-MMP in PC-3 human prostate tumor cells selected for metastasis in nude mice (PC-3-LN4), or transfected with the full-length wild-type (WT) MT1-MMP or with the mutant form lacking the cytoplasmic tail (ΔC-MT1-MMP). Enhanced cell surface MT1-MMP was determined by fluorescence-activated cell sorting analysis and evidenced mechanistically by increased activation of proMMP-2 and invasion into type-I collagen gels. PC-3 cells overexpressing MT1-MMP grew faster than mock-transfected control cells subcutaneously in nude mice. MT1-MMP localized in caveolae, as judged by immunofluorescence microscopy and sucrose-gradient, detergent-resistant cell fractionation. ΔC-MT1-MMP was strongly associated with caveolae, whereas the WT form was present in both caveolae and noncaveolae fractions. The role of plasma membrane MT1-MMP was supported by localization of MT1-MMP by immunofluorescence microscopy at the cell surface of tumor cells in primary prostate cancers. Increased plasma membrane localization of MT1-MMP, either in caveolae or in other lipid raft structures, is a mechanism to localize this proteinase in contact with extracellular matrix and other pericellular proteins, the cleavage of which can facilitate prostate cancer cell invasion and metastasis.