MicroRNA expression profiling of thymic epithelial tumors.

Thymic epithelial tumors (TET) are the most frequent human primary mediastinal tumors in adults. A deep biological characterization of the processes at the basis of the transformed phenotype could strongly improve our understanding of the morphological and clinical heterogeneity of these diseases. MicroRNAs (miRNAs) are non-coding RNAs involved in post-transcriptional regulation and their altered expression accounts for the pathogenesis of several tumors. The aim of this study was to identify the miRNAs that are differentially expressed in tumor vs normal thymic tissues or among the different tumor histotypes and that could impact on the biology of TET. microRNAs expression profiling was performed by microarray analysis of formalin-fixed paraffin embedded (FFPE) tissue from 54 thymic tumor samples and 12 normal counterparts, derived from two patient cohorts. We identified groups of miRNAs differentially expressed between: (i) TET and normal thymic tissues, (ii) thymomas and thymic carcinomas, (iii) histotype groups. Moreover, we identified putative molecular pathways targeted by these differentially expressed miRNAs that could be involved in thymic carcinogenesis and in the maintenance and spreading of this tumor.