STRUCTURE/FUNCTION OF METALLOPROTEINASE MT3/MMP

点击翻译按钮获取中文摘要

The long term objective of this proposal is to understand the proteolytic machinery employed by malignant tumor cells to traverse the dense structural barriers established by the extracellular matrix during the invasive and metastatic process. Despite improved surgical techniques against the primary tumors, failure to control the spread of cancer cells contributes to most of the cancer related death today. Cancer cells invade local tissues and metastasize to distant organs by regulating the expression of proteolytic enzymes that allow them to degrade their surrounding extracellular matrix barriers. One family of proteinases, known as the matrix-degrading metalloproteinases, have been implicated in cancer progression by virtue of their ability to degrade all proteinaceous components of the extracellular matrix including collagens, elastin and proteoglycans. While the majority of the MMPs are secreted enzymes, the recently identified MT-MMP subgroup contain potential transmembrane domains at their C-termini and therefore be able to anchor on the cell surface and form a localized proteolytic zone between the invading cells and their surrounding ECM barrier. The discovery of this subgroup clarified earlier suspicion that tumor cells utilize special proteolytic machinery anchored on their cell surfaces to clear a pathway during local invasion and metastasis. MT3-MMP, a recent addition to this subgroup, was recently identified from an malignant oral melanoma tissue by degeneraate RT-PCR strategy and found to be expressed by other cells and tissues. Furthermore, it has been proposed to play an important role in the development of invasive phenotype of tumor. To establish a causal relationship between MT3-MMP expression and the invasive phenotype, a comprehensive strategy is proposed in this application to 1) elucidate the mechanism(s) governing its conversion from zymogen to active form, 2) characterize its enzymic properties by expressing and isolating the enzyme in recombinant forms, and 3) assess the ability of MT3-MMP to regulate the invasive potential of tumor cells in an in vitro construct of the extracellular matrix. Insights from the characterization of MT3-MMP proteolytic activity, its activation mechanism as well as its ability to confer invasive potential on tumor cells should not only provide a thorough knowledge base on the role of this cell membrane associated metalloproteinase in human malignancies, but also its potential utility as a diagnotic marker or a target for new cancer therapies.