Increased plasma miR-370-3p expression in poor-outcome patients with pancreatic ductal adenocarcinoma

To determine whether circulating microRNAs (miRNAs) can be used as prognostic biomarkers for pancreatic ductal adenocarcinoma (PDAC). Patients with PDAC (N = 120) who underwent surgical resection at Hiroshima University Hospital between November 2006 and January 2020 were enrolled in this study and grouped based on their overall survival (OS) into two groups: favorable prognosis group (F group; OS ≥ 18 months) and unfavorable prognosis group (U group; OS < 18 months). Blood plasma samples were collected prior to surgery. To identify candidate prognostic miRNAs, next-generation sequencing (NGS) analysis was used to evaluate the expression levels of miRNAs in seven of the plasma samples. Using quantitative real-time PCR (qRT-PCR), the expression levels of the selected miRNAs were determined in the remaining 113 patient plasma samples, and the relationship between miRNA expression and survival was statistically evaluated. NGS analysis and qRT-PCR revealed significantly upregulated plasma miR-370-3p expression in the U group compared to that in the F group (p = 0.028 and p = 0.005, respectively). Moreover, miR-370-3p expression and lymph node metastasis showed a statistically significant association (p = 0.028). In a multivariate analysis of OS and recurrence-free survival (RFS), the upregulation of miR-370-3p expression in plasma was identified as an independent risk factor for poor OS (HR2.13, p = 0.004) and RFS (HR1.84, p = 0.015). Plasma miR-370-3p expression upregulation correlates with poor prognosis in patients with PDAC.