# Unique miRNA Expression Profile in MSI- and EMAST-Unstable Sporadic Colon Cancer

## TL;DR

This study identifies unique miRNA expression patterns in different types of sporadic colon cancer based on their instability status.

## Contribution

The first report on miRNA expression differences between MSS/EMAST-S, MSS/EMAST-H, and MSI-H/EMAST-H colorectal cancer subgroups.

## Key findings

- miR-92a-3p and miR-224-5p are significantly downregulated in MSI-H/EMAST-H tumors.
- miR-518c-3p is upregulated in MSS/EMAST-H tumors compared to other subgroups.
- miR-143-3p and miR-145-5p are consistently downregulated in tumors compared to normal tissues.

## Abstract

MicroRNAs (miRNAs) are critical post-transcriptional gene regulators and their involvement in sporadic colon cancer (CRC) tumorigenesis has been confirmed. In this study we investigated differences in miRNA expression in microsatellite stable (MSS/EMAST-S), microsatellite unstable marked by high elevated microsatellite alterations at selected tetranucleotide repeats (MSS/EMAST-H), and high microsatellite unstable (MSI-H/EMAST-H) tumor subgroups as well as in tumors with different clinicopathologic characteristics. An RT-qPCR analysis of miRNA expression was carried out on 45 colon cancer and adjacent normal tissue samples (15 of each group). Overall, we found three differentially expressed miRNAs between the subgroups. miR-92a-3p and miR-224-5p were significantly downregulated in MSI-H/EMAST-H tumors in comparison to other subgroups. miR-518c-3p was significantly upregulated in MSS/EMAST-H tumors in comparison to stable and highly unstable tumors. Furthermore, we showed that miR-143-3p and miR-145-5p were downregulated in tumors in comparison to normal tissues in all subgroups. In addition, we showed overexpression of miR-125b-5p in well-differentiated tumors and miR-451a in less advanced tumors. This is the first report on differences in miRNA expression profiles between MSS/EMAST-S, MSS/EMAST-H, and MSI-H/EMAST-H colorectal cancers. Our findings indicate that the miRNA expression signatures differ in CRC subgroups based on their instability status.