Patterns of miRNA Expression in Primary and Metastatic Wilms Tumor

BACKGROUND Wilms tumor (WT) development and the ability to form distant metastases are thought to be governed by a wide range of molecular factors, with prominent involvement of microRNAs (miRNAs). However, very few studies have explored alterations in miRNA expression between primary and metastatic WT, and all of them focused on a narrow set of miRNAs. MATERIAL AND METHODS We investigated miRNA expression in primary (10) and metastatic WT (6) and in healthy kidney specimens (10) using formalin-fixed, paraffin-embedded (FFPE) samples. miRNA was extracted from FFPE samples using miRNeasy FFPE Kits by Qiagen. Following reverse transcription, cDNA was amplified using miRCURY LNA miRNA Focus PCR Panels by Qiagen, which included primers against 84 specific miRNA targets, of which 81 were successfully amplified. Expression in metastatic WT was compared with primary tumors and healthy kidney tissue. RESULTS Differential expression was particularly evident for 5 miRNAs (miR-17-3p, miR-34b-3p, miR-34c-5p, miR-375-3p, miR-616-3p). Our findings regarding the miR-34 family seem noteworthy in light of the limited existing literature, which similarly reports elevated expression of these miRNAs in WT, although they are more commonly downregulated in many other cancer types. CONCLUSIONS While the sample size in this study was modest, our findings suggest that metastatic tumors exhibit distinct miRNA expression patterns, which may have value for identifying tumors at risk of metastasis. We encourage further studies to validate or refute the role of the miRNAs proposed here in the development of metastasis.