Faecal Proteomics and Functional Analysis of Equine Melanocytic Neoplasm in Grey Horses

Abstract

Equine melanocytic neoplasm (EMN) is a common disease in older grey horses. The purpose of this study was to examine the potential proteins throughout EMN stages from faecal proteomic outlining using functional analysis. Faecal samples were collected from the rectum of 25 grey horses divided into three groups; normal group without EMN (n = 10), mild EMN (n = 6) and severe EMN (n = 9). Based on the results, 5910 annotated proteins out of 8509 total proteins were assessed from proteomic profiling. We observed differentially expressed proteins (DEPs) between the normal group and the EMN group, and 109 significant proteins were obtained, of which 28 and 81 were involved in metabolic and non-metabolic functions, respectively. We found 10 proteins that play a key role in lipid metabolism, affecting the tumour microenvironment and, consequently, melanoma progression. Interestingly, FOSL1 (FOS like 1, AP-1 transcription factor subunit) was considered as a potential highly expressed protein in a mild EMN group involved in melanocytes cell and related melanoma. Diacylglycerol kinase (DGKB), TGc domain-containing protein (Tgm2), structural maintenance of chromosomes 4 (SMC4) and mastermind-like transcriptional coactivator 2 (MAML2) were related to lipid metabolism, facilitating melanoma development in the severe-EMN group. In conclusion, these potential proteins can be used as candidate biomarkers for the monitoring of early EMN, the development of EMN, further prevention and treatment.

Keywords: equine melanocytic neoplasm; faecal proteome; functional analysis; lipid metabolism.

Figure 1

The proteomic framework from EMN faecal sample towards protein identification and quantification.

Figure 2

The comparative protein expression levels across a normal grey horse group, mild EMN group and severe EMN group. The heatmap is generated from the intensity of significant proteins database for each group using the CLUE program (https://clue.io/command, accessed on 10 September 2021). N, M and S represent normal, mild and severe, respectively.

Figure 3

Contribution of DGKB, MAML2, SMC4, TGM2 and MAGED2 in networks of protein-protein interaction and protein-chemotherapy interaction of Equus caballus. Abbreviations: DGKA; diacylglycerol kinase alpha, DGKB; diacylglycerol kinase beta, MAML2; mastermind like transcriptional coactivator 2, SMC4; structural maintenance of chromosomes 4, TGM2; transglutaminase 2, MAGED2; melanoma antigen family D2 in Equus caballus that computational prediction between organism and interaction aggregated by the Stitch program (www.stitch.embl.de, accessed on 10 September 2021) Version 5.0.