Image may be NSFW.
Clik here to view.
Canine cancer has been traced all the way back to one inbred dog who lived 11,000 years ago.
“We do not know why this particular individual gave rise to a transmissible cancer,” said Dr. Elizabeth Murchison in a press release. “But it is fascinating to look back in time and reconstruct the identity of this ancient dog whose genome is still alive today in the cells of the cancer that it spawned.”
Dr. Murchison, along with her colleagues at the Wellcome Trust Sanger Institute and the University of Cambridge, made the discovery in a study that was published in this week’s Science magazine.
Based on the genetic information that is still contained in that genome thousands of years later, researchers believe the dog had a short, straight coat that was either brown or black, and probably resembled a modern-day Alaskan Malamute or Husky. They could not, however, determine if the dog was a male or female.
The ground-zero prehistoric dog carried the canine transmissible venereal tumor (CTVT), which causes genital cancer. The dog transmitted it to another dog while mating with it. Because the cancer wasn’t always fatal, it could be spread to other dogs. CTVT is possibly the world’s longest-surviving cancer, according to Murchison.
CTVT is unusual in that it carries about 2 million mutations, whereas the typical human cancer carries between 1,000 and 5,000. The researchers were able to determine how long the cancer has existed by studying a type of CTVT mutation known as a “molecular clock,” which accumulates steadily over time.
“The genome of this remarkable long-lived cancer has demonstrated that, given the right conditions, cancers can continue to survive for more than 10,000 years, despite the accumulation of millions of mutations,” Murchison said in the press release.
Transmissible cancers are very rare. In fact, besides CTVT, there is only one other known type that naturally occurs: a facial cancer that can be spread by Tasmanian devils when they bite each other. The vast majority of cancers in both animals and humans are caused by the mutation of a single cell, and cannot leave the body and be transmitted to others.
How did canine cancer start affecting dogs worldwide? For thousands of years, it existed in only one isolated group of dogs. “It spread around the world within the last 500 years, possibly carried by dogs accompanying seafarers on their global explorations during the dawn of the age of exploration,” Murchison said.
The discovery by Murchison and her colleagues will help researchers to determine what causes cancers to become transmissible.
“Although transmissible cancers are very rare, we should be prepared in case such a disease emerged in humans or other animals,” Sir Mike Stratton, the study’s senior author and director of the Sanger Institute, said in the press release.
“Furthermore, studying the evolution of this ancient cancer can help us to understand factors driving cancer evolution more generally.”
PHOTO: Maraudeur
The post Canine Cancer Traced Back 11,000 Years to Ground-Zero Dog appeared first on Find A Vet.
