Prostate cancer (CaP) is the most common malignancy in men in US and the second leading cause of cancer mortality. To reduce the significant morbidity and mortality, new strategies for CaP prevention and treatment depend on the determination of specific molecular mechanisms involved in this disease. 8-Catenin is a unique armadillo (ARM)domain-containing protein in that it is neural specific and primarily expresses in the brain. However, 8-catenin expression increases in prostatic adenocarcinomas, redistributes E-cadherin/120ctn from the cell-cell junction, and promotes CaP cell growth and invasion. To investigate this largely unexplored area of neuronal catenin gene expression in peripheral tissues of cancers, the overall goal of this project is to test the hypothesis that 8-catenin promotes CaP formation and progression by interacting with multiple cellular machineries, including cell-cell and cell-matrix adhesion, cell growth/survival, and invasion. There are three specific aims in this proposal.
Specific Aim 1 will determine how 8-catenin promotes cell growth/survival and motility in response to the hepatocyte growth factor and/or androgen using CWR22 tumor xenografts and their derived cell lines. We will broadly screen and profile the S-catenin induced alteration of signaling molecules by array technology. These studies will identify cancer specific pathways that 8-catenin is involved in and will investigate their interactions with S-catenin using protein co-immunoprecipitation and yeast two-hybrid analyses.
Specific Aim 2 will determine how 8-catenin interacts with Rho family small GTPases to disrupt adherens junction and promote CaP cell growth/survival and invasion. We will first identify the 8-catenin sequence responsible for this action. Then, the analyses of 8-catenin RNAi or its mutants that are defective in Rac-1 or E-cadherin binding will determine the interactions between GTP-Rac-1/IQGAP-1 and E-cadherin/p120ctn pathways to reveal possible differential modulations on cell-cell adhesion and cell growth/survival and invasion. We will also determine the cytoplasmic accumulation and nuclear signaling of (3-catenin that is released from E- cadherin complexes by IQGAP-1.
Specific Aim 3 will apply Y311, a unique (dePhospho-specific) monoclonal antibody, and site-directed mutagenesis to determine how 8-catenin modifications occur and what are their roles in CaP. We will also investigate S-catenin proteolytic fragments and their potentials as DNA binding proteins and nuclear signaling for gene expression. Finally, we will generate transgenic mice displaying prostate tissue specific S-catenin expression to approach these questions at the animal level. These studies will place 8-catenin into the broad context of growth factor and kinase signaling machineries relevant to CaP. Understanding the posttranslational modifications that control 8-catenin functions will unravel mechanisms by which S-catenin modulates gene expression and promotes CaP in vivo.
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