Comprehensive Analysis of microRNA Expression During the Progression of Colorectal Tumors

Background No effective early diagnostic biomarkers are available for colorectal cancer (CRC). Therefore, we sought to identify new biomarkers that could identify CRC from progression as a pre-cancerous lesion to its invasive form. Recent studies have shown that microRNAs (miRs) are associated with the onset of cancer invasion and progression. Aims We hypothesized that the identification of miRs associated with CRC might be useful to detect this disease at early stages. Methods We conducted an integrated analysis of 79 isolated colorectal tumor glands, including adenomas, intramucosal cancers, and invasive CRCs that showed a microsatellite stable phenotype using GeneChip miRNA 4.0 microarray assays. The colorectal tumors we examined were divided into 2 cohorts (42 in the first cohort and 37 in the second cohort). Results First, cluster analysis was performed to stratify expression patterns of multiple miRs that were pooled according to the following criteria: fold change in expression (< -2.0 or > 2.0), p < 0.05, and mature miRs. As a result, the expression patterns of pooled miRs were subdivided into 3 subgroups that were correlated with tumor grade. Each subgroup was characterized by specific miRs. In addition, we found that specific miRs, including miR-140-3p and miR-378i, were closely associated with cancer invasion. Finally, we analyzed paired dysregulated miRs between adenomatous and cancerous components present within the same tumor. Discussion We showed that several miRs were dysregulated during progression from adenoma to intramucosal cancer. Specific miRs may have key roles in progression from intramucosal tumor to invasive CRC.