microRNAs in Uveal Melanoma: in vivo findings and computational analysis

Background: Uveal melanoma (UM) is the most prominent primary eye cancer in adults, featuring a high mortality rate and poor prognosis. The role of miRNAs as potential biomarkers in UM patients has drown increasing attention and recent computational analyses have shown the prognostic significance of a cluster of deregulated miRNAs in UM patients. Purpose: The aim of the study was to assess whether the evaluation of the expression levels of the up-regulated miRNA hsa-miR-199a-5p and of down-regulated miRNAs hsa-miR-508-3p and hsa-miR-514a-3p could be useful biomarker in uveal melanoma (UM) patients. Methods: Expression profile of miRNAs hsa-miR-199a-5p, hsa-miR-508-3p and hsa-miR-514a-3p was performed in serum of 30 patients newly diagnosed with UM and compared to 10 healthy controls. Of the 30 UM patients, 11 underwent enucleation and Formalin-Fixed Paraffin-Embedded (FFPE) UM samples were analyzed to assess the expression levels of the three miRNAs under investigation. Droplet digital PCR (ddPCR) was used for both liquid biopsy and tissue samples. A novel computational analysis for the three selected miRNAs was performed in order to corroborate the experimental results. Results: Significantly higher expression levels of miRNAs hsa-miR-199a-5p were found in serum samples of UM patients compared with healthy controls. Receiver Operating Characteristics (ROC) analysis revealed that a diagnostic test based on the evaluation of hsa-miR-199a-5p circulating levels would have a moderate accuracy (AUC=0.7433), and limited specificity and sensitivity (63.33% and 70%, respectively). No circulating levels of both miRNAs hsa-miR-508-3p and hsa-miR-514a-3p were detected. ddPCR analyses confirmed significantly upregulated expression of miRNA hsa-miR-199a-5p in UM tissue samples, whereas miRNAs hsa-miR-508-3p and hsa-miR-514a-3p were found significantly downregulated. The bioinformatics results confirmed the prognostic value of the three miRNAs under investigation and showed a plethora of targeted genes involved in different physio-pathological processes. Conclusions: The present study demonstrated the diagnostic value of hsa-miR-199a-5p in liquid biopsy samples from UM patients. While hsa-miR-508-3p and hsa-miR-514a-3p have no role as circulating biomarkers, they were found significantly down-regulated in FFPE UM samples, suggesting their potential prognostic role in those patients treated with enucleation.