The Prostate 67:547 ^ 556 (2007) EZH2 Promotes Proliferation and Invasiveness of Prostate Cancer Cells R.J. Bryant, 1,2 N.A. Cross, 2 C.L. Eaton, 2 F.C. Hamdy, 2 and V.T. Cunliffe 1 * 1 MRCCentre Development for Developmental and Biomedical Genetics,University of Sheff|eld, Firth Court,Western Bank, Sheff|eld,United Kingdom 2 Academic Urology Unit, Section of Oncology, School of Medicine and Biomedical Science, University of Sheff|eld, Sheff|eld,United Kingdom BACKGROUND. The transcriptional repressor EZH2 is implicated in control of cell proliferation in embryonic, immortalized and transformed cells. EZH2 expression in prostate cancer correlates with progression to hormone-refractory and metastatic disease, but it is unknown whether EZH2 plays a specific role in the acquisition of an advanced prostate cancer phenotype. METHODS. Using siRNA knockdown, we investigated the role of EZH2 in maintenance of prostate cancer cell proliferation and invasiveness. Using LNCaP cells with inducible EZH2 overexpression, we investigated whether EZH2 upregulation promotes an aggressive phenotype. RESULTS. Knockdown of endogenous EZH2 reduced proliferation of androgen-responsive and androgen-independent prostate cancer cells. EZH2 knockdown also inhibited prostate cancer cell invasion. However, overexpression of EZH2 in androgen-responsive cancer cells did not appreciably affect either proliferation or invasiveness. CONCLUSIONS. EZH2 promotes proliferation and invasion of prostate cancer cells, which can account for the correlation between EZH2 expression levels and an adverse prostate cancer prognosis. Prostate 67: 547 – 556, 2007. # 2007 Wiley-Liss, Inc. KEY WORDS: EZH2; prostate cancer; proliferation; invasion INTRODUCTION Prostate cancer is the most commonly diagnosed male malignancy and the second leading cause of cancer death in men in the Western world. In the United Kingdom alone, approximately 32,000 new cases of prostate cancer are diagnosed annually [1]. Whilst the introduction of serum prostate specific antigen measurement has allowed early detection of the disease, clinicians are unable to determine with certainty the potential aggressiveness of individual tumors, resulting in many patients being either over- treated or under-treated. It is imperative that the molecular events leading to advanced stages of the disease are appropriately elucidated. Improved under- standing of the biology of prostate cancer progression will enable the discovery of new prognostic markers and novel targets for future therapeutic manipulation. Aberrant transcriptional silencing is a hallmark of advanced prostate cancer. The Polycomb Group (PcG) of transcriptional silencing proteins is widely implicated in the establishment and maintenance of transcriptionally repressed chromatin during both normal embryonic development and tumorigenesis. Gene expression profiling of hormone-refractory Grant sponsor: MRC Clinical Research Training Fellowship; Grant sponsor: Royal College of Surgeons of Edinburgh, UK. *Correspondence to: Dr. V.T. Cunliffe, MRC Centre Development for Developmental and Biomedical Genetics, University of Sheffield, Firth Court, Western Bank, Sheffield S10 2TN, United Kingdom. E-mail: V.T.Cunliffe@sheffield.ac.uk Received 16 September 2006; Accepted 17 November 2006 DOI 10.1002/pros.20550 Published online 24 January 2007 in Wiley InterScience (www.interscience.wiley.com). ß 2007 Wiley-Liss, Inc.