Differentially expressed microRNAs, including a large microRNA cluster on chromosome 24, are associated with equine sarcoid and squamous cell carcinoma.

This study explored how microRNA (miRNA) expression varies in the two most prevalent types of skin tumors in horses, equine sarcoid and squamous cell carcinoma, and how this could influence tumor development. Significant differences were found in miRNA expression between various different classes of these tumors and controls, suggesting potential use in diagnosis.

Objective and Methods

• This study’s goal was to analyze variations in miRNA expression in the two most common horse skin tumors, equine sarcoid (ES) and squamous cell carcinoma (SCC). The research also aimed to understand the potential impact of these variations on the tumor microenvironment. The tumors were divided into four groups for the study: mild equine sarcoid (ESM), aggressive equine sarcoid (ESA), ocular SCC (oSCC), and genital SCC (gSCC).
• Each subclass included three tumor samples and three control samples. Next-generation sequencing was employed to examine the miRNA profiles in these samples, followed by differential expression analysis using DESeq2. The pathways that the human matches of the identified dysregulated miRNAs could participate in were predicted using the DIANA-miRPath software program.

Findings

• The analysis revealed various miRNAs that were differentially expressed between tumor and control tissues for each of the four groups. A total of 57 miRNAs in ESM, six in ESA, 47 in oSCC, and none in gSCC were identified as differentially expressed, suggesting their possible role as tissue biomarkers for diagnosis.
• In terms of specific findings, ES lesions were generally associated with a reduced expression of the miR-200 family, which might trigger epithelial-mesenchymal transition, a process linked to tumor development and metastasis.
• In contrast, ESM lesions showed increased activity of a miRNA cluster on equine chromosome 24, which has been proposed to have tumor-suppressive properties.
• Notably, in oSCC tumors, this cluster was depressed, as was the miR-34 family, which may thus promote the metabolism of oSCC tumor cells.

Implications and Future Research

• This study suggests that miRNA fingerprints could serve as potential diagnostic tools for horse skin tumors. However, the biological effects of these miRNA fingerprints and their effectiveness as diagnostic tools need further validation.
• Future investigations should be performed on larger cohorts to affirm these findings and to delve deeper into the role of these microRNAs in the development and progression of equine skin tumors.