Plasma MicroRNAs as Novel Biomarkers for Patients with Intraductal Papillary Mucinous Neoplasms of the Pancreas

Abstract

Pancreatic ductal adenocarcinoma (PDAC) is one of the most fatal cancers worldwide, partly because methods are lacking to detect disease at an early, operable stage. Noninvasive PDAC precursors called intraductal papillary mucinous neoplasms (IPMN) exist, and strategies are needed to aid in their proper diagnosis and management. Data support the importance of miRNAs in the progression of IPMNs to malignancy, and we hypothesized that miRNAs may be shed from IPMN tissues and detected in blood. Our primary goals were to measure the abundance of miRNAs in archived preoperative plasma from individuals with pathologically confirmed IPMNs and healthy controls and discover plasma miRNAs that distinguish between IPMN patients and controls and between "malignant" and "benign" IPMNs. Using novel nCounter technology to evaluate 800 miRNAs, we showed that a 30-miRNA signature distinguished 42 IPMN cases from 24 controls [area underneath the curve (AUC) = 74.4; 95% confidence interval (CI), 62.3-86.5, P = 0.002]. The signature contained novel miRNAs and miRNAs previously implicated in pancreatic carcinogenesis that had 2- to 4-fold higher expression in cases than controls. We also generated a 5-miRNA signature that discriminated between 21 malignant (high-grade dysplasia and invasive carcinoma) and 21 benign (low- and moderate-grade dysplasia) IPMNs (AUC = 73.2; 95% CI, 57.6-73.2, P = 0.005), and showed that paired plasma and tissue samples from patients with IPMNs can have distinct miRNA expression profiles. This study suggests feasibility of using new cost-effective technology to develop a miRNA-based blood test to aid in the preoperative identification of malignant IPMNs that warrant resection while sparing individuals with benign IPMNs the morbidity associated with overtreatment.

Figure 1. A 30-miRNA signature discriminates IPMN Cases (N=42) from Healthy Controls (N=24)

A) Percentage of variation explained in the first 5 principal components using the 30 miRNA signature. B) Association of the 30-miRNA signature with case-control status. Box plots were used to display the distribution of the IPMN-risk malignancy score within each group. Two-sample t-tests were used to determine associations between the continuous PC1 score and case-control status. C) Receiver operating characteristic (ROC) curve analysis using miRNA expression to discriminate IPMN cases from healthy controls. The 30-miRNA signature PC1 yielded an area underneath the curve (AUC) value of 74.4 (95% CI: 62.3-86.5) in differentiating between groups.

Figure 2

Heatmap of the 30-miRNA signature in IPMN cases and non-diseased controls.

Figure 3

Heatmap of the KEGG pathways enriched for genes targeted by the 30 differentially expressed miRNAs.