Investigation of Extracellular Vesicular Small RNAs to Identify Biomarkers for Pancreatic Ductal Adenocarcinoma

Pancreatic ductal adenocarcinoma (PDAC) has a poor prognosis and unmet needs for clinical biomarkers. Extracellular vesicles (EVs) contain diverse biomolecules, including several kinds of small RNAs (smRNAs). We investigated EV-containing smRNAs (EV-smRNAs) as novel PDAC biomarkers. SmRNA-seq showed that the total count of EV-smRNAs was remarkably downregulated in PDAC when it was compared with normal controls. Among them, the expression of microRNAs (miRNAs) including miR-125a-5p, miR-30e-5p, miR-16-2-3p, miR-98-5p and let-7 family were considerably attenuated in PDAC, and especially decreased miR-142-5p and let-7f-5p were significantly related to the early stage of PDAC. Also, upregulated long non-coding RNAs (lncRNAs) such as DDX59-AS1, SNHG25, LDLRAD4-AS1, and LYPLAL1-DT, and downregulated miRNAs such as miR-766-3p, miR-148b-3p and miR-337-3p were associated with metastatic PDAC. Considering the prognosis, lncRNA CARS1-AS1 and miRNA miR-142-5p were upregulated in patients with better responses to treatment. Moreover, we found a set of miRNA-lncRNA-target gene candidates, consisting of miRNA let-7c-5p and miR-98-5p, lncRNA OLMALINC, and target genes BACH1 and CCND1. In PDAC cell lines and PDAC organoids, they played a role in mainly cell migration during PDAC progression. We suggested some potential EV-smRNA biomarkers involved in PDAC development, metastasis and prognosis, and also underlined mechanistic insights into PDAC progression. Overall design: Peripheral blood was collected from 51 patients with PDAC and 15 normal controls. Extracted EV-smRNAs were analyzed using small RNA sequencing (smRNA-seq), and their target genes were validated with PDAC cell lines and organoids.