MicroRNA Expression Profile Reveals miR-17-92 and miR-143-145 Cluster in Synchronous Colorectal Cancer

Abstract

The expression of abnormal microRNA (miRNA, miR) is a ubiquitous feature of colorectal cancer (CRC). The pathological features and clinical behaviors of synchronous CRC have been comprehensively described; however, the expression profile of miRNA and small nucleolar RNA (snoRNA) in synchronous CRC has not been elucidated. In the present study, the expression profile of miRNA and snoRNA in 5 synchronous CRCs, along with the matched normal colorectal tissue was evaluated by microarray. Function and pathway analyses of putative targets, predicted from miRNA-mRNA interaction, were performed. Moreover, we analyzed clinicopathological and molecular characteristics of 22 patients with synchronous CRC and 579 solitary CRCs in a retrospective cohort study. We found a global dysregulation of miRNAs, including an oncogenic miR-17-92 cluster and oncosuppressive miR-143-145 cluster, and snoRNAs in synchronous CRC. Differential miRNA rather than snoRNA expression was robust enough to distinguish synchronous cancer from normal mucosa. Function analysis of putative targets suggested that miRNA clusters may modulate multiple effectors of oncogenic pathways involved in the pathogenesis of synchronous CRC. A comparison of normal mucosa between synchronous and solitary CRC suggested a differential genetic background of synchronous CRC from solitary CRC during carcinogenesis. Compared with solitary cancer patients, synchronous cases exhibited multiple extra-colonic cancers (P = 0.012), coexistence of adenoma (P = 0.012), microsatellite instability (P = 0.024), and less glucose transporter 1 (P = 0.037). Aberrant miRNA expression profiles could potentially be used as a diagnostic tool for synchronous CRC. Our findings represent the first comprehensive miRNA and snoRNA expression signatures for synchronous CRC, implicating that the miRNAs and snoRNAs may present therapeutic targets for synchronous CRC.

FIGURE 1

An overview of our experimental design.

FIGURE 2

Unsupervised hierarchical clustering and PCA of miRNA and snoRNA expression. (A) Hierarchical clustering of 10 samples and 24 differentially expressed miRNA transcripts. (B) PCA of dysregulated miRNA transcripts. (C) Hierarchical clustering of 10 samples and 24 differentially expressed snoRNAs. (D) PCA of dysregulated snoRNAs. In clustering analysis, colored bars indicate the range of normalized log2-based signals, with red indicating high expression and green low expression. PCA = principal component analysis, snoRNA = small nucleolar RNA, miRNA, miR = microRNA.

FIGURE 3

Molecular functions and canonical pathways were associated with the intersecting targets derived from the comparison of predicted targets of microRNA (miRNA) clusters with mRNA expression profiles. The top 10 molecular functions (A) and 10 pathways (B) are shown. A larger value on the X-axis indicates a higher degree of significance. The pink vertical line crossing all the bars indicates the threshold of significance, bars above this line represents P < 0.05.

FIGURE 4

Network interaction map based on combined microRNA (miRNA) cluster expression, target prediction, and mRNA expression data for tumor and normal samples. Red symbols are assigned for upregulated and green symbols are for downregulated genes.

FIGURE 5

Kaplan–Meier curves for overall survival of CRC patients according to synchronicity status (A) and of synchronous CRC patients according to MSI status (B). CRC = colorectal cancer, MSI = microsatellite instability.