Reversibility of Epithelial-Mesenchymal Transition in Prostate Cancer

Northport Va Medical Center, Northport NY

Investigators

Abstract

It has been proposed that transition of cancer cells to a metastatic phenotype within the primary tumor site involves the loss of the epithelial phenotype and the acquisition of a mesenchymal (fibroblast-like) phenotype (epithelial-mesenchymal transition: EMT). A crucial role for the tumor microenvironment (hypoxia, stromal factors, inflammation) in the induction of EMT has been proposed. Thus, adaptive rather than selective pressures are operative. Based on the retarded growth of EMT converted cells, epithelial function needs to be regained at the metastatic site to facilitate tumor growth. This has led to the assumption that EMT is reversible and mesenchymal-epithelial transition (MET) occurs at the metastatic site. These experimental observations are consistent with pathologic examination of human cancer tissues revealing remarkable resemblance between primary and metastatic tumors. Experimental models and clinical correlations of different types of cancers have implicated numerous mechanistic factors in EMT; these data suggest that a one size fits all approach is overly simplistic. Membrane type 1-matrix metalloproteinase (MT1-MMP) is among the most prominent factors implicated in cancer invasion and metastasis. Based on data from several labs including our own, we propose that microenvironmental factors within primary prostate cancers, result in activation of MT1-MMP on the cancer cell surface, which initiates a series of events, leading to EMT and metastasis. The signaling pathways involved in MT1-MMP induced EMT include Wnt5a, Rac1, and generation of reactive oxygen species (ROS). We propose that following removal of the initiating events e.g. hypoxia, downregulation of MT1-MMP occurs at the metastatic site, leading to MET. The primary goal of this proposal is to characterize the MT1-MMP, Wnt5a, ROS pathway leading to EMT/MET and metastasis of prostate cancer. To accomplish this goal, we will employ our recently published prostate cancer model displaying MT1-MMP induced EMT. Expression of MT1-MMP in human LNCaP prostate cancer cells induces EMT-like phenotypic changes associated with loss of E-cadherin at the primary tumor site. Using cDNA microarray and shRNA strategies, we demonstrated that Wnt5a is a downstream effector of MT1-MMP induced EMT. Reactive oxygen species are increased in this EMT model, leadig to DNA damage. The three major aims proposed in this grant are to: (1) Characterize the reversibility and mechanism of MT1-MMP/Wnt5a Induced EMT in Prostate Cancer; (2) Delineate the role of hypoxia and the generation of ROS in the EMT Pathway of Prostate Cancer. Assess the role of mitochondrial versus NAD(P)H oxidase sources of ROS in prostate cancer. Examine the role of ROS in inducing genomic instability. (3) Employ immunohistochemial markers of EMT and hypoxia in human prostate cancer specimens and determine if these markers correlate with stage of disease and biochemical failure (rise in PSA).