Introduction Cholangiocarcinoma (CCA) is a primary biliary ductal cancer which is often difficult to diagnose and which carries a poor prognosis. New diagnostic tests are urgently needed to improve patient outcome. Bile is a rich source of potential novel biomarkers for CCA, due to its intimate proximity to the malignant lesion. However, there are no biliary biomarkers for CCA currently available.

MicroRNAs (miRNAs) are key post-transcriptional regulators, and influence tumorogenesis. Studies on cell lines and tissue have identified several potential miRNA signatures for CCA, and recently miR-9 was identified as elevated in bile from CCA compared with benign disease¹.

In this study we aimed to measure specific miRNA expression in bile from patients with CCA, gallstone disease and pancreatic adenocarcinoma (PA) and to assess their performance in differentiating these causes of biliary obstruction.

Methods Bile was collected at endoscopic retrograde cholangiopancreatography (ERCP) from patients with CCA (n = 6), PA (n = 10) and gallstones (n = 8; benign control). Bile was prepared as previously described1 and total RNA was 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 highly expressed in bile from patients with CCA compared to those with gallstones. MiR-155 was not significantly upregulated in malignancy. In discriminating CCA from benign disease, miR-106a had sensitivity and specificity of 83.3% [95% CI 36–100] and 88% [95% CI 47–100] respectively, with an AUC of 0.83 (cut-off level > 6.05). OncomiR-21 was also upregulated in the bile of both tumour types, but was not as reliable. Neither miRNA discriminated significantly between PA and CCA.

Conclusion MiRNA can be reliably isolated from bile pellets. Both miR-106a and oncomiR-21 are potential novel biliary biomarkers for CCA, and could improve differentiation of benign from malignant disease at ERCP. Further work is required to validate these findings in a larger cohort and against other disease groups, and to investigate possible correlations between miRNA profile and disease course.

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.