A Milestone Reached in Equine Eye Cancer Research
For a prey animal that instinctively depends on sight for survival, a horse’s loss of vision or even the loss of an eye is devastating. Yet, squamous cell carcinoma (SCC) is the most common cancer found in equine eyes and the second most common tumour in horses.
The disease originates in the junction between the cornea – the clear surface of the eyeball – and the conjunctiva that covers the white of the eye. In advanced cases, SCC can be locally invasive, spread to the orbit, and eat away at the bone and eventually the brain leading to loss of life.
But a recent genetic study led by scientists at the University of California, Davis, will help owners identify if their horses are at risk for SCC and make informed decisions on two levels. For horses with a known susceptibility to the disease, regular eye exams can lead to early diagnosis of a tumour, which can then be surgically removed and the eye saved. Secondly, knowledge of a horse’s susceptibility will allow owners to make critical decisions regarding breeding.
What makes this research all the more interesting is that the study also has implications for human health. The gene associated with equine SCC is also linked in humans to a disease characterized by sun sensitivity and increased risk of cutaneous SCC and melanoma.
“Mutations in the same gene that increase risk for limbal SCC in Haflingers (DDB2) have been shown to increase risk for SCC, basal cell carcinoma, and melanomas in humans,” says Bellone. “Several of the mutations identified in humans are in the same region of the gene as the horse mutation, illustrating the importance of this region in identifying UV damaged DNA.”
Emphasizing the importance of the parallel in humans with the mutation in this protein, she says that they now have the ability to understand why it’s affecting the eyes of horses as well as the skin of humans.
