Serum exosomal hsa-let-7f-5p: A potential diagnostic biomarker for metastatic pancreatic cancer detection.

BACKGROUND: Exosomal microRNAs (miRNAs) have emerged as promising biomarkers for cancer diagnosis due to their stability, tumor specificity, and accessibility. However, the diagnostic potential of serum exosomal miRNAs in metastatic pancreatic cancer remains underexplored. AIM: To investigate the diagnostic potential of serum exosomal miRNAs in metastatic pancreatic cancer. METHODS: A total of 36 patients were enrolled, comprising 8 patients in the discovery phase (4 with metastatic and 4 with non-metastatic pancreatic cancer) and 28 in the validation cohort (15 non-metastatic and 13 metastatic cases). Exosomes were isolated using the exoEasy Maxi Kit and characterized by transmission electron microscopy, nanoparticle tracking analysis, and western blotting. High-throughput sequencing was conducted to identify differentially expressed serum exosomal miRNAs, which were subsequently validated using TaqMan probe-based reverse transcription-quantitative polymerase chain reaction. Bioinformatic analyses were performed to predict downstream target genes and explore their roles in metastatic progression. RESULTS: Transmission electron microscopy revealed that the isolated exosomes were predominantly round or oval with well-defined membrane boundaries. Nanoparticle tracking analysis showed a peak particle size of approximately 138 nm, accounting for 99.2% of total particles, consistent with the typical size range of exosomes. Western blotting confirmed the expression of exosome-specific markers CD63 and CD81. High-throughput sequencing identified 42 differentially expressed exosomal miRNAs between metastatic and non-metastatic groups. Among them, hsa-let-7f-5p was significantly upregulated in metastatic pancreatic cancer (P = 0.007), as validated by reverse transcription-quantitative polymerase chain reaction. Target gene prediction indicated that hsa-let-7f-5p may be involved in metastasis through its interactions with nerve growth factor, cyclin-dependent kinase inhibitor 1A, high mobility group AT-hook 2, insulin-like growth factor 2 mRNA-binding protein 1, and insulin-like growth factor 2 mRNA-binding protein 3. CONCLUSION: The elevated expression of serum exosomal hsa-let-7f-5p in metastatic pancreatic cancer suggests its potential as a non-invasive biomarker for distinguishing metastatic from non-metastatic disease.