Dysregulation of microRNA expression during the progression of colorectal tumors

MicroRNAs (miRNAs) are potential biomarkers of neoplastic lesions, but additional information on dysregulated miRNA expression during progression of the adenoma–adenocarcinoma sequence may be helpful to identify the role of miRNAs in this sequence. We examined the expression levels of 13 miRNAs (hsa‐miRNA‐19a‐3p, hsa‐miRNA‐21‐5p, hsa‐miRNA‐27a‐3p, hsa‐miRNA‐27b‐3p, hsa‐miRNA‐31‐5p, hsa‐miRNA‐34b‐3p, hsa‐miRNA‐125b‐5p, hsa‐miRNA‐143‐3p, miRNA‐191‐5p, hsa‐miRNA‐193b‐3p, hsa‐miRNA‐195‐5p, hsa‐miRNA‐206 and hsa‐let‐7a‐5p) that are closely associated with colorectal carcinogenesis in 40 conventional adenomas (tubular and tubulovillous adenomas), 20 intramucosal carcinomas (IMCs) and 60 invasive colorectal cancers (iCRCs) using reverse‐transcription polymerase chain reaction. These 120 tumors were divided into two cohorts, that is, cohort 1 (60 cases) and cohort 2 (for validation; 60 cases). We analyzed the expression levels of these miRNAs in the first step (adenoma→IMC) and second step IMC→iCRC) of the adenoma–carcinoma sequence in both cohorts. Although no significant differences in the expression of any of the 13 miRNAs were found between adenomas and IMCs consistently in both cohorts, the expression levels of hsa‐miRNA‐125b‐5p, hsa‐miRNA‐143‐3p, and hsa‐miRNA‐206 were significantly upregulated in iCRC in both cohorts compared with those in IMC. The current results suggest that certain miRNAs, including hsa‐miRNA‐125b‐5p, hsa‐miRNA‐143‐3p and hsa‐miRNA‐206, are candidate markers that play critical roles in the progression of IMC to iCRC.