Altered miR-21, miRNA-148a Expression in Relation to KRAS Mutation Status as Indicator of Adenoma-Carcinoma Transitional Pattern in Colorectal Adenoma and Carcinoma Lesions

Sporadic colorectal cancer (CRC) is a fatal disease, mostly known as the silent killer, due to the fact that this disease is asymptomatic before diagnosis in advanced stage. Screening and the early detection of CRC and colorectal adenoma (CRA) by non-aggressive molecular biomarkers' signature is useful for improvement of survival rate in CRC patients. To achieve such a goal, a better understanding of distinct molecular abnormalities as candidate biomarkers in CRC development is crucial. In this study, seventy-five archived FFPE CRC samples, including colorectal adenocarcinoma, adenomatous polyps (adenoma), and adjacent non-neoplastic mucosa were collected for the investigation by Sanger sequencing at the DNA level and by real-time PCR at the RNA level. The results of the KRAS mutational analysis have shown that the majority of somatic mutations in the KRAS affect only one codon, mainly codon 12(p.G12D) with low frequency in adenomas (13.3%) versus CRCs (36%). The results of dysregulated epigenetic changes of miR-21 clearly showed upregulation of expression in colorectal adenocarcinoma, compared to non-neoplastic mucosa, in colorectal adenoma vs non-neoplastic mucosa: (p < 0.001) and in CRC versus adenoma (p < 0.001); while miR-148a expression were significantly downregulated in CRC, compared to non-neoplastic mucosa, in colorectal adenoma vs non-neoplastic mucosa, and in adenoma vs CRC (p < 0.001). Our findings support the important role of miR-21 in stages I-II of CRC, and the KRAS G12D mutant, and differential miR-148a expression, in advanced stages of CRC.