Abstract
BACKGROUND: MicroRNAs (miRNAs) function as post-transcriptional gene expression regulators and influence the development and progression of several cancers, yet their roles in pediatric sarcomas remain poorly defined. METHODS: RNA extracted from formalin-fixed paraffin-embedded tumor tissue scrolls of 108 pediatric tumors, including 32 osteosarcoma (OS), 26 Ewing's sarcoma (EWS), and 50 rhabdomyosarcoma (RMS) cases, were analyzed for microRNA expression using the NanoString multiplex nCounter platform that yielded information on 827 human miRNAs. The expression of candidate miRNAs was validated with in situ hybridization (miRNA-ISH) and QuPath quantification on tissue microarray slides comprising an independent set of 48 OS, 17 EWS, and 104 RMS adult and pediatric cases collectively. RESULTS: The differential expression analysis of nCounter data identified 23 miRNAs enriched in RMS, 33 in EWS, and 45 in OS (>3 fold change and p < 0.01). miR-206 was most strongly associated (>55 fold change, p < 1 × 10(-9)) with RMS and demonstrated the highest sensitivity and specificity in distinguishing RMS from EWS and OS; this finding was also confirmed by miRNA-ISH. A combined signature of differentially expressed miRNAs reliably separated alveolar from embryonal RMS. The expression of miR-9-5p in EWS and miR-140-5p in OS discriminated among the different tumors and correlated with adverse patient outcome. The nCounter assay exhibited greater sensitivity than miRNA-ISH in detecting miR-206 and miR-140-5p expression. CONCLUSIONS: Collectively, these findings demonstrate that distinct miRNA profiles can differentiate pediatric sarcoma types and subtypes and offer clinically relevant insights into tumor biology, prognosis, and potential diagnostic application.