Aberrant epigenetic regulation in clear cell sarcoma of the kidney featuring distinct DNA hypermethylation and EZH2 overexpression

// Jenny Karlsson 1, * , Anders Valind 1, * , Caroline Jansson 1 , Maureen J. O’Sullivan 2 , Linda Holmquist Mengelbier 1 , David Gisselsson 1, 3 1 Department of Clinical Genetics, Lund University, University and Regional Laboratories, Lund, Sweden 2 National Children’s Research Centre, Our Lady’s Children’s Hospital, Crumlin, Dublin 12, Ireland 3 Department of Pathology, Skåne Regional and University Laboratories, Lund, Sweden * These authors have contributed equally to this work Correspondence to: Jenny Karlsson, e-mail: jenny.karlsson@med.lu.se Keywords: CCSK, Wilms tumor, pediatric tumors, hypermethylation, EZH2 Received: September 30, 2015 Accepted: January 23, 2016 Published: February 03, 2016 ABSTRACT The global methylation profile and the mutational status of 633 specific epigenetic regulators were analyzed in the pediatric tumor clear cell sarcoma of the kidney (CCSK). Methylation array analyses of 30 CCSKs revealed CCSK tumor DNA to be globally hypermethylated compared to Wilms tumor, normal fetal kidney, and adult kidney. The aberrant methylation pattern of CCSKs was associated with activation of genes involved in embryonic processes and with silencing of genes linked to normal kidney function. No epigenetic regulator was recurrently mutated in our cohort, but a mutation in the key epigenetic regulator EZH2 was discovered in one case. EZH2 mRNA was significantly higher in CCSK compared to Wilms tumor and normal kidney, and the EZH2 protein was strongly expressed in more than 90 % of CCSK tumor cells in 9/9 tumors analyzed. This was in striking contrast to the lack of EZH2 protein expression in Wilms tumor stromal elements, indicating that EZH2 could be explored further as a diagnostic marker and a potential drug target for CCSK.