Similarities Found in Genes of Humans, Dogs, and Horses with Melanoma Tumors

First of its kind study suggests commonalities for humans, dogs, and horses with melanoma.

Mucosal melanoma is a rare and poorly understood subtype of melanoma, representing only 1% of the 15,400 people annually diagnosed with the disease in the UK. For the first time, researchers and their collaborators at the Wellcome Sanger Institute have compared cancer genes in mucosal melanoma in humans, dogs, and horses.

The study, published in Nature Communications, described how researchers sequenced genomes of the same cancer across the species in order to determine the key genes, to gain insights on how the cancer evolves, and to guide the development of new therapies.

By using the genomic data from 46 human, 65 canine, and 28 equine melanoma tumors, all in the primary stage of cancer, scientists found common genes in all species.

"Genomics gives us a unique view into the hidden similarities and differences of cancer between species,” said corresponding author David Adams, PhD, in a prepared statement. “The genetic changes, or mutations, we found in mucosal melanoma tumors across humans, dogs and horses suggests they are important enough to be conserved between species. These key mutations are likely to drive the cancer and could be targets for the development of new drugs."

Mucosal melanoma results from melanoctyes, the cells that are responsible for producing pigment found in skin as well as mucosal surfaces such as sinuses, nasal passages, and the mouth. The risk factors for the disease are unknown, as there is no known link to ultraviolet light exposure or family history. Patients with the cancer often present late in the progression of the disease and the main treatment for mucosal melanoma is surgical removal of the tumor.

For unknown reasons, immunotherapy has not been effective with the subtype, despite its effects on melanoma. According to the press release, researchers now suggest that unlike skin melanoma, mucosal melanoma tumors carry few mutations so they remain hidden to the immune system and do not spark the immune response needed to target the cancer.

This study is the first to sequence horse tumors and the first genomic experiment of this scale on dog tumors, according to the authors. Although gray horses are genetically predisposed to developing melanoma, the cancer in equines is non-metastatic, unlike humans and dogs.

"Spontaneous tumors in dogs are gaining recognition as 'models' of human cancers for the development of therapies that can benefit both species,” said corresponding author Geoffrey Wood, in a prepared statement. “This study shows the importance of understanding the genetic similarities and differences of cancers across species so that the most biologically relevant drug targets are prioritized."


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