Preliminary Study: Proteomic Profiling Uncovers Potential Proteins for Biomonitoring Equine Melanocytic Neoplasm

SIMPLE SUMMARY: Equine melanocytic neoplasm (EMN) affects grey horse worldwide, with the highest prevalence of approximately 80% in older grey horses. However, the efficiencies of both therapeutic and prevention strategies are not high. We investigated a less invasive technique to detect EMN using proteomics via serum protein expression. The serum sample can be used for proteomics analysis to identify and quantify differences in the expression of proteins between normal and EMN grey horses. In addition, it can detect the expressed patterns of proteins and relevant pathophysiology pathways of EMN. We summarised the differential protein expression in each stage, with the overall aim to identify potential proteins in the early stage of EMN and the severity stage of EMN. The potential proteins could be used for biomonitoring EMN, facilitating prevention and treatment based on the preliminary results in this study. ABSTRACT: Equine melanocytic neoplasm (EMN) is a cutaneous neoplasm and is mostly observed in aged grey horses. This preliminary study aimed to identify potential proteins to differentiate normal, mild and severe EMN from serum proteomic profiling. Serum samples were collected from 25 grey horses assigned to three groups: normal (free of EMN; n = 10), mild (n = 6) and severe EMN (n = 9). To explore the differences in proteins between groups, proteomic profiling and analysis were employed. Accordingly, 8241 annotated proteins out of 8725 total proteins were compared between normal and EMN groups and inspected based on differentially expressed proteins (DEPs). Through DEP analysis, 95 significant DEPs differed between normal and EMN groups. Among these DEPs, 41 significant proteins were categorised according to protein functions. Based on 41 significant proteins, 10 were involved in metabolism and 31 in non-metabolism. Interestingly, phospholipid phosphatase6 (PLPP6) and ATPase subunit alpha (Na+/K+-ATPase) were considered as potential proteins uniquely expressed in mild EMN and related to lipid and energy metabolism, respectively. Non-metabolism-related proteins (BRCA1, phosphorylase B kinase regulatory subunit: PHKA1, tyrosine-protein kinase receptor: ALK and rho-associated protein kinase: ROCK1) correlated to melanoma development differed among all groups. The results of our study provide a foundation for early EMN biomonitoring and prevention.