Diane Palmieri, Ph.D.

Dissertation research performed under the guidence of Dr. Frank C. Church

ABSTRACT
    Cancer is a multistep process including metastasis of the primary tumor to a distant site.  For a cancer cell to metastasize there must be a cascade of complex enzymatic events that break down cell-extracellular matrix protein interactions.  These events are mediated by a variety of proteases, including serine proteases. Serine proteases and their specific inhibitors, serpins (serine protease inhibitors) are the focus of this dissertation.
    Serpins are involved in a wide range of disease processes and serpins in cancer is an emerging field.  Specifically, one group of serpins, known as plasminogen activator inhibitors (PAIs), has received attention because proteolytic members of the plasminogen activator (PA) system regulate extracellular matrix degradation.  This has linked several members of the PA system to increased metastatic disease and to decreased overall survival in breast cancer.  A paradox exists between the clinical findings for PAI -1 (PAI-1) and the function of PAI-1 as a protease inhibitor.  It is contradictory that increased expression of a protease inhibitor, that inhibits extracellular matrix degradation, is a negative prognostic indicator.  To understand the paradox, we hypothesized a role for PAI-1 in breast cancer that was independent of its protease inhibitory activity.  We investigated the expression of PA family members in breast and gynecologic cancer cell lines and expressed wild type and a non-inhibitory mutant form of PAI-1 in the invasive MDA-MB-435 breast cancer cell line.  The effect of PAI-1 on cell proliferation, adhesion, and motility was assessed.  We also investigated a possible role for the related serpin, PAI-3 in breast cancer in parallel experiments.
    The results show that expression of wt-PAI-1 and wt-PAI-3 in MDA-MB-435 cells decreased in vitro proliferation but increased adhesion and motility on the extracellular matrix proteins vitronectin and fibronectin.  This increased adhesion and motility was the result of the increased expression of several members of the integrin family.  The non-inhibitory PAI-1 and PAI-3 mutants were not capable of mediating the same changes in proliferation, adhesion, and motility.  Collectively, these results suggest that expression of these serpins may create a cell that acts independently of its protease inhibitory function to promote tumor cell invasion and metastasis.