Abstract
MicroRNA (miRNA) dysregulation is implicated in testicular germ cell tumor (TGCT) pathogenesis. Here, we characterized miRNA expression profiles across TGCT histologic subtypes using miRNA-sequencing on 43 formalin-fixed paraffin-embedded (FFPE) tissue samples (31 primary, 12 metastases) from 29 patients to identify diagnostic markers and their regulatory functions. From 20 seminomas (SEM), 14 non-seminomatous germ cell tumors (N-SEM), and 9 teratomas, we profiled a total of 2606 miRNAs. Compared to teratomas, 154 miRNAs (targeting 657 genes) were enriched in SEM, and 141 miRNAs (targeting 358 genes) in N-SEM. miR-200-3p, targeting the DNA methyltransferase DNMT3B, was enriched in N-SEM versus SEM. Our findings showed high concordance with The Cancer Genome Atlas (TCGA)-TGCT data (Pearson R > 0.66, p < 1e-10). miRNA expression was largely similar between primary and metastatic tissues and between chemotherapy-treated and untreated teratomas, reflecting teratoma chemo-resistance. Using novel candidates, miRNA-based logistic regression classifiers distinguished viable GCT (SEM/N-SEM) from teratoma (Area Under the Curve [AUC] > 0.96) and SEM from N-SEM (AUC = 0.81), outperforming well-known miRNA markers. Target gene analysis implicated FOXO and RUNX1 regulation, somatotroph signaling, and height-related pathways. Overall, our comprehensive tissue-level miRNA profiling in TGCTs identified potential diagnostic biomarkers for histologic subtypes, offering insights into miRNA-mediated transcriptional dysregulation.