ORIGINAL ARTICLE Epigenetic-induced repression of microRNA-205 is associated with MED1 activation and a poorer prognosis in localized prostate cancer T Hulf 1,7 , T Sibbritt 1 , ED Wiklund 1,2 , K Patterson 1 , JZ Song 1 , C Stirzaker 1 , W Qu 1 , S Nair 1 , LG Horvath 1,3 , NJ Armstrong 1,4 , JG Kench 1,5 , RL Sutherland 1 and SJ Clark 1,6 Deregulation of microRNA (miRNA) expression can have a critical role in carcinogenesis. Here we show in prostate cancer that miRNA-205 (miR-205) transcription is commonly repressed and the MIR-205 locus is hypermethylated. LOC642587, the MIR-205 host gene of unknown function, is also concordantly inactivated. We show that miR-205 targets mediator 1 (MED1, also called TRAP220 and PPARBP) for transcriptional silencing in normal prostate cells, leading to reduction in MED1 mRNA levels, and in total and active phospho-MED1 protein. Overexpression of miR-205 in prostate cancer cells negatively affects cell viability, consistent with a tumor suppressor function. We found that hypermethylation of the MIR-205 locus was strongly related with a decrease in miR-205 expression and an increase in MED1 expression in primary tumor samples (n ¼ 14), when compared with matched normal prostate (n ¼ 7). An expanded patient cohort (tumor n ¼ 149, matched normal n ¼ 30) also showed significant MIR-205 DNA methylation in tumors compared with normal, and MIR-205 hypermethylation is significantly associated with biochemical recurrence (hazard ratio ¼ 2.005, 95% confidence interval (1.109, 3.625), P ¼ 0.02), in patients with low preoperative prostate specific antigen. In summary, these results suggest that miR-205 is an epigenetically regulated tumor suppressor that targets MED1 and may provide a potential biomarker in prostate cancer management. Oncogene advance online publication, 6 August 2012; doi:10.1038/onc.2012.300 Keywords: microRNA; miR-205; MED1; epigenetics; prostate cancer INTRODUCTION A prevailing concern in prostate cancer prognosis and treatment decisions is the absence of reliable markers for disease progres- sion. In recent years, epigenetic modifications, such as DNA methylation and chromatin modification, have been shown to be sufficient to drive cancer phenotypes 1 and be of prognostic value. 2 MiRNAs (microRNAs) are noncoding RNAs that regulate gene expression in many biological processes including growth, differentiation, metabolism and development. MiRNAs typically exert a physiological effect through targeting mRNAs for repression. The paradigm for miRNA function at an mRNA target describes the degree of Watson–Crick base pairing between the miRNA seed sequence 2–8 and the target mRNA 3 0 -UTR determining the method of repression; with perfect complimen- tarity permitting Argonaut catalyzed degradation, and imperfect pairing promoting repression of translation. 3 Recent studies have indicated that miRNAs are mechanistically involved in many human cancers, 4 including prostate cancer. 5 Moreover, miRNA expression profiles have proved to be superior to mRNA profiling for tissue and disease categorization. 6 However, a great many challenges remain in deciphering the regulation and role of miRNAs in normal and neoplastic tissue. MiR-205 exemplifies the challenge of understanding the role of miRNAs in cancer, in that studies on a range of cancers and cell lines have shown both positive and negative correlations between miR-205 expression and disease state. We recently identified both primary and mature miR-205 expression to be downregulated in prostate cancer cells. 7 MiR-205 expression has also been reported to be downregulated in a number of other cancers and cancer cell-line studies including: breast, 8–10 prostate, 11 bladder, 12 head and neck squamous cell carcinoma 13 and esophageal. 14 Conversely, miR- 205 has been reported to be overexpressed in endometrial carcinoma, 15 ovarian, 16 non-small-cell lung cancer, 17–19 head and neck squamous cell carcinoma, 20–22 bladder, 23,24 and esophageal squamous mucosa. 25 A number of explanations may account for this, including the difficultly in controlling for normal tissue contaminating tumor samples. However, it is plausible that miR- 205 expression levels are intrinsically linked with tumor progression and that different published expression changes may reflect tumor staging of individual cohorts. This possibility is supported by the fact that miR-205 is typically robustly expressed in epidermal tissues, 24 and is downregulated during epithelial to mesenchymal transition, 26 a mechanism whereby cells undergo loss of cell adhesion and increased cell mobility in a manner similar to the initiation of metastasis. Individual miRNAs may target numerous mRNA targets. 27,28 MiR-205 has previously been cited as targeting HER3 (ERBB3), 9 PKCe, 11 SHIP2 (INPPL1), 21 VEGF-A, 8 SIP1 and ZEB1 26 for repression. In addition, miR-205 has been 1 Epigenetics Group, Cancer Research Program, Garvan Institute of Medical Research, Darlinghurst, New South Wales, Australia; 2 Department of Molecular Biology, Aarhus University, Aarhus, Denmark; 3 Department of Medical Oncology, Sydney Cancer Center, Royal Prince Alfred Hospital, Camperdown, New South Wales, Australia; 4 School of Mathematics and Statistics, University of New South Wales, Sydney, New South Wales, Australia; 5 Department of Tissue Pathology, Royal Prince Alfred Hospital, Camperdown, New South Wales, Australia and 6 St Vincent 0 s Clinical School, University of NSW, St Vincent 0 s Hospital, Darlinghurst, New South Wales, Australia. Correspondence: Professor SJ Clark, Epigenetics Group, Cancer Research Program, Garvan Institute of Medical Research, 384 Victoria Street, Darlinghurst, New South Wales 2010, Australia. E-mail: s.clark@garvan.org.au 7 Current address: Sydney Medical School, Edward Ford Building (A27), Fisher Road, The University of Sydney, New South Wales 2006, Australia. Received 2 November 2011; revised 15 May 2012; accepted 27 May 2012 Oncogene (2012), 1–9 & 2012 Macmillan Publishers Limited All rights reserved 0950-9232/12 www.nature.com/onc