This cancer, which causes grotesque genital tumours in dogs around the world, first arose in a single dog that lived about 11,000 years ago. The cancer survived after the death of this dog by the transfer of its cancer cells to other dogs during mating.
The genome of this 11,000-year-old cancer carries about two million mutations – many more mutations than are found in most human cancers, the majority of which have between 1,000 and 5,000 mutations. The team used one type of mutation, known to accumulate steadily over time as a “molecular clock”, to estimate that the cancer first arose 11,000 years ago.
“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,” said Dr Elizabeth Murchison from Cambridge’s Department of Veterinary Medicine and the Wellcome Trust Sanger Institute, who is lead author on the study, published today in the journal Science.
The genome of the transmissible dog cancer still harbours the genetic variants of the individual dog that first gave rise to the cancer 11,000 years ago. Analysis of these genetic variants revealed that this dog may have resembled an Alaskan Malamute or Husky. It probably had a short, straight coat that was coloured either grey/brown or black. Its genetic sequence could not determine if this dog was a male or a female, but did indicate that it was a relatively inbred individual. Read more..