Abstract 997: PKD1-β3-integrin complex increases E-cadherin shedding through MMP-2 and −9 secretion in prostate cancer

Abstract

Abstract Introduction: We have previously reported that Protein Kinase D1 (PKD1), a serine threonine kinase, is down regulated in advanced prostate cancer (PC) and known complex with cell adhesion protein β3-integrin to influence cell motility. Cell motility in facilitated by degradation of extracellular matrix, which is accomplished through secretion of proteins such as Matrix Metalloproteinases (MMPs), which are neutral proteinases that catalyze degradation of various transmembrane and extracellular matrix proteins including E-cadherin at cell surface. Here, we demonstrate the presence of PKD1-β3-integrin complex in PC cells that increases MMP-2 and −9 secretion and consequently enhances E-cadherin shedding. Methods: Protein expression, phosphorylation and secretion studies using PC cell lines were done by western blot analysis or gelatin zymography. Cell proliferation was measured by MTS assay. In silico analysis was done to validate correlation between PKD1 and MMPs expression in human PC. Results: To find out the complex formation among PKD1 and β3-integrin in PC cell, we immunoprecipitated the PKD1 protein and immunoblotted with β3-integrin antibody and observed that the PKD1 and β3-integrin proteins were in same protein complex. Then we found that overexpression of PKD1 also colocalized in PC3 cells and that was suppressed with RGD peptide, a specific β3-integrin inhibitor, treated same cells. Additionally, we found that PKD1 overexpressed cell increased in secretion of MMP-2 and −9 as well as activation of Erk and Akt those were suppressed in RGD peptide treated cells. In contrast, we observed that downregulation of PKD1 by shRNA could suppress the phosphorylation of Erk and Akt as well as MMP-2 and MMP-9 secretion in DU145 cells. Interestingly, PKD1 enhanced the expression of E-cadherin and secretion of extracellular part of E-cadherin (sE-cadherin) in conditioned media of DU145 cells, which was suppressed by treatment by MMP-2 and −9 inhibitors. In addition, suppression of cell proliferation by PKD1 was augmented by recombinant MMP-2 and −9 proteins and rescued by MMP-2 and MMP-9 inhibitor in DU145 cells, suggesting a surprising antiproliferative role for MMP-2 and −9 in PC cells. In silico analysis of publicly available DNA microarray data set derived from human PC confirmed that expression of PKD1 and MMP-2 correlated directly in metastatic PC compared to benign prostate tissue. Conclusions: Our study has identified a novel role of PKD1-β3-integrin complex for secretion of MMP-2 and −9 in prostate cancer, which is associated with E-cadherin shedding. Our data also suggested that the proteins complex limits PC cell proliferation by modulation MMP-2 and −9 secretion. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 101st Annual Meeting of the American Association for Cancer Research; 2010 Apr 17-21; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2010;70(8 Suppl):Abstract nr 997.