1. ¹Molecular Urology and Therapeutics Program, Department of Urology and Winship Cancer Institute, Emory University School of Medicine, 1365B Clifton Road, NE, Atlanta, GA 30322, USA;
2. ²Department of Pathology, University of Alabamn, Birmingham, AL 35294, USA

Correspondence: Haiyen E Zhau, Tel: +1-404-778-4319; Fax: +1-404-778-3675 E-mail: hzhau@emory.edu; Leland WK Chung, Tel: +1-404-778-4319; Fax: +1-404-778-3675 E-mail: lwchung@emory.edu

Received 11 April 2007; Revised 11 July 2007; Re-revised 3 March 2008; Accepted 7 March 2008.

Abstract

Epithelial-mesenchymal transition (EMT) in cancer describes the phenotypic and behavioral changes of cancer cells from indolent to virulent forms with increased migratory, invasive and metastatic potential. EMT can be induced by soluble proteins like transforming growth factor 1 (TGF1) and transcription factors including Snail and Slug. We utilized the ARCaP_E/ARCaP_M prostate cancer progression model and LNCaP clones stably overexpressing Snail to identify novel markers associated with EMT. Compared to ARCaP_E cells, the highly tumorigenic mesenchymal ARCaP_M and ARCaP_M1 variant cells displayed a higher incidence of bone metastasis after intracardiac administration in SCID mice. ARCaP_M and ARCaP_M1 expressed mesenchymal stromal markers of vimentin and N-cadherin in addition to elevated levels of Receptor Activator of NF-B Ligand (RANKL). We observed that both epidermal growth factor (EGF) plus TGF1 treatment and Snail overexpression induced EMT in ARCaP_E and LNCaP cells, and EMT was associated with increased expression of RANKL protein. Finally, we determined that the RANKL protein was functionally active, promoting osteoclastogenesis in vitro. Our results indicate that RANKL is a novel marker for EMT during prostate cancer progression. RANKL may function as a link between EMT, bone turnover, and prostate cancer skeletal metastasis.