complexity of AML, 14 this is a step forward to an easier and highly efficacious GEP-driven therapeutic strategy. 15 CONFLICT OF INTEREST The authors declare no conflict of interest. ACKNOWLEDGEMENTS Celgene provided lenalidomide free of charge. This study was supported in part by AIL Pesaro Onlus, AIRC (5xMille 10007 and IG10519) and FIRB Futura 2011. AUTHORS’ CONTRIBUTIONS GV, FF and AI designed the research and wrote the manuscript; FDR, MRC, CR and GS treated the patients, collected the data and commented on the manuscript; FL and AV collected and analyzed the data and commented on the manuscript; PPP and MR performed the statistical analysis. AG, MR, and MAL generated GEP; FF performed GEP data analysis; SP performed EBM diagnostic accuracy analysis; PPP, SAP, AI and GV designed the molecular analysis and funded it, analyzed GEP data and wrote the manuscript. G Visani 1 , F Ferrara 2 , F Di Raimondo 3 , F Loscocco 1 , G Sparaventi 1 , S Paolini 4 , F Fuligni 4 , A Gazzola 4 , M Rossi 4 , MA Laginestra 4 , MR Caraci 3 , C Riccardi 2 , M Rocchi 5 , A Visani 4 , SA Pileri 4 , PP Piccaluga 4,6 and A Isidori 1,6 1 Hematology and Hematopoietic Stem Cell Transplant Center, AORMN, Pesaro, Italy; 2 Hematology, Cardarelli Hospital, Napoli, Italy; 3 Hematology, Catania University, Catania, Italy; 4 Hematopathology Section, Department of Experimental, Diagnostic, and Specialty Medicine, S. Orsola-Malpighi Hospital, Bologna University School of Medicine, Bologna, Italy and 5 Institute of Biomathematics, Urbino University, Urbino, Italy E-mail: giuseppe.visani@ospedalimarchenord.it 6 These authors contributed equally to this work. REFERENCES 1 Estey EH. How to manage high-risk acute myeloid leukemia. Leukemia 2012; 26: 861–869. 2 Blum W, Klisovic RB, Becker H, Yang X, Rozewski DM, Phelps MA et al. 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Gene expression profiling in MDS and AML: potential and future avenues. Leukemia 2011; 25: 909–920. This work is licensed under a Creative Commons Attribution- NonCommercial-ShareAlike 3.0 Unported License. To view a copy of this license, visit http://creativecommons.org/licenses/by-nc-sa/3.0/ Supplementary Information accompanies this paper on the Leukemia website (http://www.nature.com/leu) MSC-derived exosomes: a novel tool to treat therapy-refractory graft-versus-host disease Leukemia (2014) 28, 970–973; doi:10.1038/leu.2014.41 Approximately 35–50% of the patients receiving matched related or unrelated allogeneic stem cell transplantation, develop severe forms of graft-versus-host disease (GvHD; Grade II–IV) that cannot be controlled with corticosteroids in up to 50% of the GvHD patients. 1 Owing to the lack of confirmed treatment options Le Blanc et al. 2 introduced mesenchymal stem cells (MSCs) as a strategy to treat severe therapy-refractory acute GvHD. Since then, a number of different studies have addressed the impact of MSC administration on GvHD with different outcomes. 3 New data suggest that the beneficial effects of MSCs rather derive from secreted, immune response-modulating factors than from their tissue intercalation themselves. 3 On the basis of a preclinical myocardial infarction model, evidence was provided that the immune-modulating factors of MSCs are also secreted ex vivo and Accepted article preview online 21 January 2014; advance online publication, 21 February 2014 Letters to the Editor 970 Leukemia (2014) 935 – 979 & 2014 Macmillan Publishers Limited