Introduction MicroRNAs (miRNAs) are short, non-coding RNAs with a key role in post-transcriptional regulation, and regulate multiple pathways of tumorogenesis. Expression profiling of malignant cell lines, fresh and formalin-fixed tumour have identified potential miRNA signatures for pancreatic ductal adenocarcinoma (PDAC), and RNA deep sequencing has demonstrated that miRNAs can be quantified from bile, in bilary tract cancers¹. Here, we report the first study of biliary miRNAs in PDAC.

Methods 3 target miRNAs known to be overexpressed in PDAC were selected. Bile was collected at endoscopic retrograde cholangiopancreatography (ERCP) from patients with PDAC (n = 10) or gallstones (n = 8; used as a benign control). Bile was prepared as described1 and total RNA isolated using TRIzol (Invitrogen, Paisley, UK). Quantitative real-time reverse-transcription polymerase chain reaction (RT-qPCR) was performed using Taqman mature miRNA primers and probes (Applied Biosystems, Cheshire, UK). Expression of oncomiR-21, miR-155 and miR-106a was measured. Cycle passing threshold (Ct) was recorded and normalised to RNU6B expression. Relative expression was calculated as 2Ct_miRNA-Ct_RNU6B. PCR reactions were carried out in duplicate.

Results miR-106a and oncomiR-21 were both highly expressed in the bile of patients with PDAC, compared to those with gallstones. miR-155 was not significantly upregulated in PDAC bile. Using miR-106a (cut-off level > 8.02), we discriminated PDAC from benign disease with a sensitivity and specificity of 80% [95% CI 44–98] and 100% [95% CI 63–100], respectively with an area under the curve (AUC) value of 0.88. OncomiR-21 was also upregulated in bile, but was not as reliable in discriminating diagnosis.

Conclusion This study demonstrates that bile miRNAs are well-suited analytes for the development of sensitive and specific tests in PDAC. Although tumour breach of the biliary epithelium was not always suspected in our cohort from clinical investigations, malignancy-specific miRNAs were found intraluminally. Of the 3 miRNAs tested, ROC analysis identified miR-106a as the best potential PDAC biomarker, with reliable diagnostic specificity and sensitivity. However, further study may also identify miRNAs that also discriminate prognoses and response to therapy, guiding individualised treatment.

Disclosure of Interest None Declared

Reference

1. Shigehara K, Yokomuro S, Ishibashi O, et al. Real-time PCR-based analysis of the human bile microRNAome identifies miR-9 as a potential diagnostic biomarker for biliary tract cancer. PloS one. 2011; 6(8):e23584.