MicroRNA expression profiles of seminoma from paraffin-embedded formalin-fixed tissue

In this study, we used microRNA (miRNA) microarrays in an unbiased screen for aberrantly expressed miRNAs in seminoma, a primitive type of germ cell tumor. Formalin-fixed and paraffin-embedded (FFPE) surgical samples from 11 cases of normal testicular tissue resected for nonneoplastic causes and from 11 cases of seminoma were assessed for miRNA expression. Normal testicular tissue and seminoma were paired by race. We found 112 miRNAs to be differentially expressed between seminoma and normal testicular tissue; 52 miRNAs were overexpressed, and 60, downregulated in seminoma. We did not observe significant differences between black and white populations in our race-paired study. The upregulation of the expression of hsa-mir-21, hsa-mir-372, hsa-mir-373, has-mir-221, and hsa-mir-222 was validated by reverse transcription and real-time PCR. Hsa-mir-372 was upregulated around 1,270-fold (95 % confidence interval (CI) 525.2-3,064.8; p = 8.1e-5 by Mann-Whitney U test). Hsa-mir-373 was upregulated around 1,530-fold (95 % CI 620.5-3,785.6; p = 8.0e-5 by Mann-Whitney U test), consistent with previous reports, indicating that the miRNAs in FFPE are well preserved, and FFPE can be a valuable source for the miRNA study of seminoma. In addition, expression of hsa-mir-21 (12.2-fold, 0.0095), hsa-mir-221 (3.8-fold, 0.014) and hsa-mir-222 (3.8-fold, 0.019) was found elevated in seminoma compared to normal testicular tissue.