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Dysfunctional Transforming Growth Factor-β Receptor II Accelerates Prostate Tumorigenesis in the TRAMP Mouse Model

Departments of ¹ Surgery/Urology, ² Toxicology, ³ Pathology, and ⁴ Molecular and Cellular Biochemistry, and ⁵ Markey Cancer Center, University of Kentucky College of Medicine, Lexington, Kentucky

Requests for reprints: Natasha Kyprianou, Division of Urology, MS283, University of Kentucky Medical Center, 800 Rose Street, Lexington, KY 50536. Phone: 859-323-9812; Fax: 859-323-1944; E-mail: nkypr2{at}uky.edu.

Key Words: apoptosis • cell proliferation • TGF-β signaling • membrane receptors • transgenic mouse model • prostate cancer • metastasis

The contribution of a dysfunctional transforming growth factor-β type II receptor (TGFβRII) to prostate cancer initiation and progression was investigated in an in vivo mouse model. Transgenic mice harboring the dominant-negative mutant TGF-β type II receptor (DNTGFβRII) in mouse epithelial cell were crossed with the TRAMP prostate cancer transgenic mouse to characterize the in vivo consequences of inactivated TGF-β signaling on prostate tumor initiation and progression. Histopathologic diagnosis of prostate specimens from the TRAMP+/DNTGFβRII double transgenic mice revealed the appearance of early malignant changes and subsequently highly aggressive prostate tumors at a younger age, compared with littermates TRAMP+/Wt TGFβRII mice. Immunohistochemical and Western blotting analysis revealed significantly increased proliferative and apoptotic activities, as well as vascularity and macrophage infiltration that correlated with an elevated vascular endothelial growth factor and MCP-1 protein levels in prostates from TRAMP+/DNTGFβRII+ mice. An epithelial-mesenchymal transition (EMT) effect was also detected in prostates of TRAMP+/DNTGFβRII mice, as documented by the loss of epithelial markers (E-cadherin and β-catenin) and up-regulation of mesenchymal markers (N-cadherin) and EMT-transcription factor Snail. A significant increase in the androgen receptor mRNA and protein levels was associated with the early onset of prostate tumorigenesis in TRAMP+/DNTGFβRII mice. Our results indicate that in vivo disruption of TGF-β signaling accelerates the pathologic malignant changes in the prostate by altering the kinetics of prostate growth and inducing EMT. The study also suggests that a dysfunctional TGFβRII augments androgen receptor expression and promotes inflammation in early stage tumor growth, thus conferring a significant contribution by TGF-β to prostate cancer progression. [Cancer Res 2009;69(18):7366–74]