Epithelial to Mesenchymal Transition of a Primary Prostate Cell Line with Switches of Cell Adhesion Modules but without Malignant Transformation Xi-Song Ke1., Yi Qu1., Naomi Goldfinger2, Kari Rostad 1 , Randi Hovland3, Lars A. Akslen1,4, Varda Rotter2, Anne Margrete Øyan1,5, Karl-Henning Kalland1,5* 1 The Gade Institute, University of Bergen, Bergen, Norway, 2 Department of Molecular Cell Biology, Weizmann Institute of Science, Rehovot, Israel, 3 Center of Medical Genetics and Molecular Medicine, Haukeland University Hospital, Bergen, Norway, 4 Department of Pathology, Haukeland University Hospital, Bergen, Norway, 5 Department of Microbiology and Immunology, Haukeland University Hospital, Bergen, Norway Abstract Background: Epithelial to mesenchymal transition (EMT) has been connected with cancer progression in vivo and the generation of more aggressive cancer cell lines in vitro. EMT has been induced in prostate cancer cell lines, but has previously not been shown in primary prostate cells. The role of EMT in malignant transformation has not been clarified. Methodology/Principal Findings: In a transformation experiment when selecting for cells with loss of contact inhibition, the immortalized prostate primary epithelial cell line, EP156T, was observed to undergo EMT accompanied by loss of contact inhibition after about 12 weeks in continuous culture. The changed new cells were named EPT1. EMT of EPT1 was characterized by striking morphological changes and increased invasion and migration compared with the original EP156T cells. Gene expression profiling showed extensively decreased epithelial markers and increased mesenchymal markers in EPT1 cells, as well as pronounced switches of gene expression modules involved in cell adhesion and attachment. Transformation assays showed that EPT1 cells were sensitive to serum or growth factor withdrawal. Most importantly, EPT1 cells were not able to grow in an anchorage-independent way in soft agar, which is considered a critical feature of malignant transformation. Conclusions/Significance: This work for the first time established an EMT model from primary prostate cells. The results show that EMT can be activated as a coordinated gene expression program in association with early steps of transformation. The model allows a clearer identification of the molecular mechanisms of EMT and its potential role in malignant transformation. Citation: Ke X-S, Qu Y, Goldfinger N, Rostad K, Hovland R, et al. (2008) Epithelial to Mesenchymal Transition of a Primary Prostate Cell Line with Switches of Cell Adhesion Modules but without Malignant Transformation. PLoS ONE 3(10): e3368. doi:10.1371/journal.pone.0003368 Editor: Stefan W o¨lfl, Universita¨t Heidelberg, Germany Received June 24, 2008; Accepted September 3, 2008; Published October 13, 2008 Copyright: 2008 Ke et al. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. Funding: This study was funded by the following grants: Helse Vest (Grants 911005, 911227 and 911401), The Research Council of Norway (Grants 154942/310, 163920/V50, 185676/V40, The Norwegian Cancer Society (grants HS01-2006-0446 and HS01-2006-0468) and the University of Bergen. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript. Competing Interests: The authors have declared that no competing interests exist. * E-mail: Kalland@gades.uib.no . These authors contributed equally to this work. Introduction Epithelial to mesenchymal transition (EMT) is a developmental process characterized by loss of epithelial markers, gain of mesenchymal markers and changes in cellular morphology and phenotype with increased ability to migrate and invade [1–3]. EMT is an important physiological process during embryogenesis and wound healing, but may be exploited to play a central role in cancer progression (reviewed in [2,4–7]). During progression to metastatic competence, carcinoma cells acquire mesenchymal adhesive properties and the activation of proteolysis and motility, which allows the tumor cells to metastasize and establish secondary tumors at distant sites [3–5]. Several models have been proposed to show that EMT contributes to the progress of established tumours in transformed cells [6,8,9]. The relationship between EMT and early carcinogenesis has not been clarified, and has so far been addressed by very few studies [10,11]. Recently, it was described that EMT has strong and significant associations with multiple end points of prostate cancer progression and cancer-specific death [12]. It is therefore interesting to establish an EMT model based on prostate cells in vitro. EMT has been described in prostate cancer cells, including LNCaP [13,14], DU145 [15] and PC3 cells [16–18]. However, multiple genomic rearrangements have accumulated in these cell lines during long term passages in different laboratories, and they are likely to differ significantly from the original patient cells. For PC3 cells, e.g., both mesenchymal to epithelial transition (MET) [19] and EMT has been reported. More exact analysis of EMT will benefit much from cell lines that are very close to prostate cells in vivo. PLoS ONE | www.plosone.org 1 October 2008 | Volume 3 | Issue 10 | e3368