Background: Liver metastasis is a major cause of mortality in colorectal cancer (CRC). Epigenetic alternations could serve as biomarkers for cancer diagnosis and prognosis. In this study, we analyzed microarray data in order to identify core genes and pathways which contribute to liver metastasis in CRC under epigenetic regulations.
Materials and methods: Data of miRNAs (GSE35834, GSE81582), DNA methylation (GSE90709, GSE77955), and mRNA microarrays (GSE68468, GSE81558) were downloaded from GEO database. Differentially expressed genes (DEGs), differentially expressed miRNAs (DEMs), and differentially methylated genes (DMGs) were obtained by GEO2R. The target genes of DEMs were predicted by miRWalk. Functional and enrichment analyses were conducted by DAVID database. Protein-protein interaction (PPI) network was constructed in STRING and visualized using Cytoscape.
Results: In liver metastasis, miR-143-3p, miR-10b-5p, miR-21-5p, and miR-518f-5p were down-regulated, while miR-122-5p, miR-885-5p, miR-210-3p, miR-130b-5p, miR-1275, miR-139-5p, miR-139-3p, and miR-1290 were up-regulated compared with primary CRC. DEGs targeted by altered miRNAs were enriched in pathways including complement, PPAR signaling, ECM-receptor interaction, spliceosome, and focal adhesion. In addition, aberrant DNA methylation-regulated genes showed enrichment in pathways of amino acid metabolism, calcium signaling, TGF-beta signaling, cell cycle, spliceosome, and Wnt signaling.
Conclusion: Our study identified a series of differentially expressed genes which are associated with epigenetic alternations of miRNAs and DNA methylation in colorectal liver metastasis. Up-regulated genes of SLC10A1, MAPT, SHANK2, PTH1R, and C2, as well as down-regulated genes of CAB39, CFLAR, CTSC, THBS1, and TRAPPC3 were associated with both miRNA and DNA methylation, which might become promising biomarker of colorectal liver metastasis in future.
Keywords: Colorectal cancer; DNA methylation; Epigenetics; MicroRNA.