Genetic differences in immune function in horses could explain why the virus linked to sarcoid skin tumors affects some animals and not others. The findings may also shed light on a related human condition, according to results from a new study.
Scientists at the Baker Institute for Animal Health at Cornell’s College of Veterinary Medicine and a research team looked at more than 50,000 sites in the horse genome in horses with and without sarcoids. The researchers found that certain regions tended to be different in horses diagnosed with sarcoids, which is the most common form of cancer found in the animals.
The findings show that a horse’s genes partly determine how susceptible it is to developing this cancer. Researchers published the data in a recent issue of the International Journal of Cancer.
Scientists led by Dr. Doug Antczak, a professor of equine medicine at Cornell, looked at 82 horses with sarcoids from the U.S. and U.K. and 272 control horses that did not have sarcoids. The researchers found that regions on chromosomes 20 and 22 were often different in horses diagnosed with sarcoids.
Chromosome 20 is in a part of the genome called the Major Histocompatibility Complex (MHC) class II region, which associated with immune function. Standardbred horses rarely have the MHC type linked to sarcoid vulnerability, so this could explain why this breed rarely gets a sarcoid diagnosis.
Still, “(m)ore than one genetic region is associated to susceptibility to sarcoids” and the regions “don’t completely determine whether or not a horse will develop the disease once it’s exposed” to bovine papillomavirus (BPV), or the virus linked to sarcoid tumors in horses, Antcak said in a statement.
The findings could also have implications for humans. Scientists have pointed to a link between the MHC class II region and cervical cancer in women, and “that should make a light bulb go off” for researchers studying the disease, Antczak said. “It suggests there's a common mechanism in both species for susceptibility to tumor progression that may involve subversion of the host immune response. By studying this phenomenon in horses you can learn about human cancer and vice versa,” Antczak said.