Non-Invasive miRNA Profiling for Differential Diagnosis and Prognostic Stratification of Testicular Germ Cell Tumors

Testicular germ cell tumors (TGCT) are common in young adult men and have high cure rates. Conventional serum tumor markers and imaging are not able to differentiate between histologic subtypes of the disease, which portend different prognoses and require distinct therapeutic strategies. Micro-RNAs (miRNAs) are small non-coding transcripts involved in the post-transcriptional regulation of gene expression, which have emerged as promising biomarkers in a variety of tumors. This study aimed to assess the potential of differentially expressed miRNAs in differential diagnosis and prognostication among TGCT patients with various histologic subtypes.

Transcriptomic analysis of 134 patients from The Cancer Genome Atlas (TCGA)-TGCT database was conducted. miRNA differential expression analysis among seminomatous, embryonal carcinoma, mixed GCT, and teratoma was performed, followed by ROC curve analysis of the most significantly up- and downregulated miRNAs, respectively. Statistical associations of miRNA expression with AJCC stage were also investigated along with miRNA target network analysis and evaluation of miRNA detection in patients' fluids.

Upregulation of seven miRNAs (hsa-mir-135a-1, hsa-mir-135a-2, hsa-mir-200a, hsa-mir-200b, hsa-mir-203b, hsa-mir-375, hsa-mir-582) and downregulation of seven additional miRNAs (hsa-mir-105-1, hsa-mir-105-2, hsa-mir-4433a, hsa-mir-548x, hsa-mir-5708, hsa-mir-6715a, hsa-mir-767) were identified. miRNAs displayed a high sensitivity/specificity of 0.94/1.0 (AUC = 0.98) for the upregulated and 0.97/0.94 (AUC = 0.96) for the downregulated signature. Deregulated expression of these miRNAs was significantly associated with AJCC stage and distant organ metastasis (p < 0.001), overall supporting their prognostic strength. Both signatures were detectable in body fluids, particularly urine. miRNA target network analysis supported the functional role of these miRNAs in the regulation of cancer-related processes such as cell proliferation via deregulation of pivotal oncogenes.

These findings support the clinical value of two novel miRNA signatures in differential diagnosis and prognostic stratification of various histologic subtypes of TGCT, with potential treatment implications.