Genetic and epigenetic loss of microRNA-31 leads to feed-forward expression of EZH2 in melanoma

// Irfan A. Asangani 1,2,* ,Paul W. Harms 1,2,3,* , Lois Dodson 1 , Mithil Pandhi 1 , Lakshmi P. Kunju 2 , Christopher A. Maher 1,2,4 , Douglas R. Fullen 2,3 , Timothy M. Johnson 3 , Thomas J. Giordano 2 , Nallasivam Palanisamy 1,2,5,8 , Arul M. Chinnaiyan 1,2,5,6,7,8 1 Michigan Center for Translational Pathology 2 Department of Pathology, University of Michigan 3 Department of Dermatology, University of Michigan 4 Center for Computational Medicine and Bioinformatics 5 Comprehensive Cancer Center, University of Michigan Medical School 6 Howard Hughes Medical Institute, University of Michigan Medical School 7 Department of Urology, University of Michigan 8 Shared senior authors * These authors contributed equally to this work Correspondence: Arul M. Chinnaiyan, email: // Keywords : : microRNA-31, melanoma, tumor suppressor, EZH2, DZNep Received : August 15, 2012, Accepted : August 28, 2012, Published : August 31, 2012 Abstract MicroRNAs (miRs) play a key role in cancer etiology by coordinately repressing numerous target genes involved in cell proliferation, migration and invasion. The genomic region in chromosome 9p21 that encompasses miR-31 is frequently deleted in solid cancers including melanoma; however the expression and functional role of miR-31 has not been previously studied in melanoma. Here, we queried the expression status and performed functional characterization of miR-31 in melanoma tissues and cell lines. We found that down-regulation of miR-31 was a common event in melanoma tumors and cell lines and was associated with genomic loss in a subset of samples. Down-regulation of miR-31 gene expression was also a result of epigenetic silencing by DNA methylation, and via EZH2-mediated histone methylation. Ectopic overexpression of miR-31 in various melanoma cell lines inhibited cell migration and invasion. miR-31 targets include oncogenic kinases such as SRC, MET, NIK (MAP3K14) and the melanoma specific oncogene RAB27a. Furthermore, miR-31 overexpression resulted in down-regulation of EZH2 and a de-repression of its target gene rap1GAP; increased expression of EZH2 was associated with melanoma progression and overall patient survival. Taken together, our study supports a tumor suppressor role for miR-31 in melanoma and identifies novel therapeutic targets.