Protein profiling could be used to monitor equine melanoma in grey horses, allowing early detection and treatment, according to researchers.
Melanomas, or equine melanocytic neoplasms, are common skin tumors in horses that can affect up to 80% of older grey horses. Most are benign initially but up to two-thirds can start to show malignant behavior if left untreated. The efficiencies of both therapeutic and prevention strategies are not high.
The cancer arises from uncontrolled melanin metabolism that affects melanoblast overproduction in the base layer of the skin and the outer root sheath of hair follicles.
Melanomas in horses are typically identified at specific locations, such as underneath the tail, between the anus and genitals, around the anus, and at the muzzle, lip and eyelid.
Consequently, the condition is treated at a late stage by surgery, immunotherapy and immune modulation or chemotherapy, Parichart Tesena and her fellow researchers wrote in the journal Animals. To overcome this, there is an urgent need for early detection, they said.
Researchers, in a preliminary study centered at Kasetsart University in Thailand, explored a less invasive technique to detect equine melanomas by investigating protein production.
They wanted to identify the presence of potential proteins in horse serum that might differentiate between normal, mild and severe melanomas.
Serum samples were collected from 25 grey horses, 10 of whom were classed as free of melanoma, six with mild melanomas, and nine who were affected severely.
In all, 8241 annotated proteins out of 8725 total proteins were compared between the normal and melanoma-affected groups, looking at the ratios in which the proteins were present.
The ratios of 95 proteins differed significantly between the normal and melanoma-affected groups. Among these, 41 significant proteins were categorised according to protein functions.
Based on 41 significant proteins, 10 were involved in metabolism and 31 in non-metabolism.
Phospholipid phosphatase6 (PLPP6) and ATPase subunit alpha (Na+/K+-ATPase) were considered as potential proteins uniquely expressed in mild cases of melanomas, showing particular promise for early detection. The first is related to lipid metabolism, the second to energy metabolism.
Based on the results, the data from the analysis suggests that signalling and receptor protein pathways in the cell microenvironment are the key processes of equine melanoma development. To prevent tumour (or cancer) development, these processes need to be inhibited.
Melanoma cells can use a variety of energy sources to maintain tumour growth and progression. They increase the rate of lipid metabolism for progression. Thus, lipid metabolism may offer novel potential proteins for monitoring levels of cancer cells, in particular PLCH1, HMGCS2 and PLPP6.
The authors said their study provides a foundation for early biomonitoring and prevention of equine melanomas.
The proteomic profiling achieved in this study revealed potential proteins for the biomonitoring of early melanomas, facilitating rapid prevention and treatment, they concluded.
The study team comprised Tesena, Amornthep Kingkaw, Wanwipa Vongsangnak, Surakiet Pitikarn, Narumon Phaonakrop, Sittiruk Roytrakul and Attawit Kovitvadhi.
Tesena, P.; Kingkaw, A.; Vongsangnak, W.; Pitikarn, S.; Phaonakrop, N.; Roytrakul, S.; Kovitvadhi, A. Preliminary Study: Proteomic Profiling Uncovers Potential Proteins for Biomonitoring Equine Melanocytic Neoplasm. Animals 2021, 11, 1913. https://doi.org/10.3390/ani11071913