Transmissible cancer dates back 11,000 years, scientists say
Scientists have discovered the world's longest surviving cancer first arose in a dog 11,000 years ago.
Research published in the journal Science reveals the transmissible genital cancer survived after the death of its oriental host as it was sexually transmitted to others.
According to genetic analysis, the dog is thought to have resembled an Alaskan Malamute or husky, with a short, straight coat coloured either grey/brown or black. While scientists could not determine the sex of the dog, it is believed to have been a relatively inbred individual.
"We do not know why this particular individual gave rise to a transmissible cancer," said lead author Dr Elizabeth Murchison, from the Wellcome Trust Sangar Institute and the University of Cambridge.
"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."
It is very rare for cancer cells to spread from their original host to other individuals. An aggressive transmissible facial cancer spread by biting in Tasmanian devils is the only other known example.
Researchers say the genome of this cancer carries about two million mutations, compared to the majority of human cancers which have between 1,000 and 5,000 mutations.
"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," explained Dr Murchison.
According to the Sangar Institute, the research findings have helped scientists to further understand how transmissible dog cancer has spread, becoming a common disease in dogs today.
Dr Murchison said: "The patterns of genetic variants in tumours from different continents suggested that the cancer existed in one isolated population of dogs for most of its history.
"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."
Professor Sir Mike Stratton, senior author and director of the Sangar Institute, added: "The genome of the transmissible dog cancer will help us to understand the processes that allow 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. Furthermore, studying the evolution of this ancient cancer can help us to understand factors driving cancer evolution more generally."
Image courtesy of Genome Research Ltd.
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