Epithelial to Mesenchymal Transition Is Mechanistically Linked with Stem Cell Signatures in Prostate Cancer Cells . . Dejuan Kong , Sanjeev Banerjee , Aamir Ahmad, Yiwei Li, Zhiwei Wang, Seema Sethi, Fazlul H. Sarkar* Department of Pathology, Karmanos Cancer Institute, Wayne State University School of Medicine, Detroit, Michigan, United States of America Abstract Background: Current management of patients diagnosed with prostate cancer (PCa) is very effective; however, tumor recurrence with Castrate Resistant Prostate Cancer (CRPC) and subsequent metastasis lead to poor survival outcome, suggesting that there is a dire need for novel mechanistic understanding of tumor recurrence, which would be critical for designing novel therapies. The recurrence and the metastasis of PCa are tightly linked with the biology of prostate cancer stem cells or cancer-initiating cells that is reminiscent of the acquisition of Epithelial to Mesenchymal Transition (EMT) phenotype. Increasing evidence suggests that EMT-type cells share many biological characteristics with cancer stem-like cells. Methodology/Principal Findings: In this study, we found that PCa cells with EMT phenotype displayed stem-like cell features characterized by increased expression of Sox2, Nanog, Oct4, Lin28B and/or Notch1, consistent with enhanced clonogenic and sphere (prostasphere)-forming ability and tumorigenecity in mice, which was associated with decreased expression of miR-200 and/or let-7 family. Reversal of EMT by re-expression of miR-200 inhibited prostasphere-forming ability of EMT-type cells and reduced the expression of Notch1 and Lin28B. Down-regulation of Lin28B increased let-7 expression, which was consistent with repressed self-renewal capability. Conclusions/Significance: These results suggest that miR-200 played a pivotal role in linking the characteristics of cancer stem-like cells with EMT-like cell signatures in PCa. Selective elimination of cancer stem-like cells by reversing the EMT phenotype to Mesenchymal-Epithelial Transition (MET) phenotype using novel agents would be useful for the prevention of tumor recurrence especially by eliminating those cells that are the ‘‘Root Cause’’ of tumor development and recurrence. Citation: Kong D, Banerjee S, Ahmad A, Li Y, Wang Z, et al. (2010) Epithelial to Mesenchymal Transition Is Mechanistically Linked with Stem Cell Signatures in Prostate Cancer Cells. PLoS ONE 5(8): e12445. doi:10.1371/journal.pone.0012445 Editor: Chad Creighton, Baylor College of Medicine, United States of America Received June 28, 2010; Accepted August 6, 2010; Published August 27, 2010 Copyright: 2010 Kong 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 work was funded by a grant from the National Cancer Institute, National Institutes of Health (NIH) (5R01CA083695-08 to FHS) (http:// projectreporter.nih.gov/reporter_searchresults.cfm). 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: fsarkar@med.wayne.edu . These authors contributed equally to this work. Introduction Emerging evidence suggest that most solid tumors including prostate cancer (PCa) may arise from cancer stem cells [1]. The cancer stem cells are cells within a tumor that possess the capacity of self-renewal and tumor-initiating capacity, and differentiate into the heterogeneous lineages of cancer cells that comprise in a tumor mass. These tumor-initiating cells could provide a reservoir for cells that cause tumor recurrence after therapy. Wang et al. have shown that the origin of PCa cells is from the differentiated luminal epithelial stem cells [2]. However, there is a greater degree of phenotypic heterogeneity of cells in PCa, especially within metastatic sites. Metastases often include rare cells that are phenotypically undifferentiated [3], suggesting that metastases- initiating cells may not be the only cells that are derived from androgen receptor-positive luminal cells. Although origin of PCa cells needs to be fully elucidated, a number of mounting evidence suggest that tumor-initiating cells or cancer stem cells play a critical role in the progression and recurrence of PCa to castrate resistant prostate cancer (CRPC) and its subsequent metastasis. Recent studies have indicated that somatic cells can be reprogrammed into pluripotent embryonic stem-like cells by co- expression of pluripotency stem cell markers such as Oct4, Sox2, Nanog and Lin28 [4,5], which raises the possibility that combined expression of stem cell-associated factors and special oncogenes could also induce a undifferentiated state in cancer cells. Interestingly, cell lines derived from human PCa specimen showed epithelial phenotype. However, immortalization of these cells by hTERT showed the expression of pluripotency stem cell markers, including Oct4, Nonag, and Sox2 [6], which could be associated with disease progression because over-expression of Oct4, Sox2, Nanog and c-myc has been found in poorly differentiated tumors [7]. Jeter et al. have shown that knock-down of Nanog in PCa cells significantly decreased long-term clonogenic growth and inhibited tumor growth [8]. Oct4 has also been shown to play important roles in the progression of PCa [9]. Epithelial to mesenchymal transition (EMT) is a vital process for morphogenesis during embryonic development, but more recently it has also been implicated in the conversion of early stage tumors into invasive malignancies [10]. Progression of most PLoS ONE | www.plosone.org 1 August 2010 | Volume 5 | Issue 8 | e12445