Researchers have looked at the "genome and evolution" of a sexually-transmitted canine cancer.
The team was able to look at the cancer's history as far back as 11,000 years ago, a Wellcome Trust Sanger Institute news release reported.
The researchers were able to sequence the gene of what is believed to be the "world's oldest continuously surviving cancer." The condition is transmitted sexually and causes tumors on the dogs' genitals.
The cancer's genome contains two million mutations; most cancers only have between 1,000 and 5,000. The team looked at one mutation's development as a "molecular clock" to determine how old the disease was.
"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," Doctor Elizabeth Murchison, first author from the Wellcome Trust Sanger Institute and the University of Cambridge, said in the news release.
The cancer still holds the genetic variants of the dog it originated in 11,000 years ago. The team determined this dog resembled an Alaskan malamute or Siberian Husky and had a short dark coat. The dog was believed to have been a product of inbreeding.
"We do not know why this particular individual gave rise to a transmissible cancer," Murchison said, "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."
The researchers hope to use this information to determine how the disease spread in the past.
"The patterns of genetic variants in tumors from different continents suggested that the cancer existed in one isolated population of dogs for most of its history," Murchison said. "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."
Transmissible cancers are incredibly rare. The only other known contagious form of cancer is a face condition in Tasmanian devils that can be spread through biting.
"The genome of the transmissible dog cancer will help us to understand the processes that allow cancers to become transmissible," Professor Sir Mike Stratton, senior author and Director of the Sanger Institute, said. "Although transmissible cancers are very rare, we should be prepared in case such a disease emerged in humans or other animals. Furthermore, studying the evolution of this ancient cancer can help us to understand factors driving cancer evolution more generally."
