One of the most surprising findings from the study related to how mitochondrial DNA transfers – and mixes – between the tumour and the host. The researchers found that mitochondrial DNA molecules from host cells that have migrated into tumour cells occasionally fuse with the tumour’s own mitochondrial DNA, sharing host and tumour DNA in a process known as ‘recombination’. This is the first time this process has been observed in cancers.
Máire Ní Leathlobhair, the study’s co-first author, explains: “Mitochondrial DNA recombination could be happening on a much wider scale, including in human cancers, but it may usually be very difficult to detect. When recombination occurs in transmissible cancers, two potentially very different mitochondrial DNAs – one from the tumour, one from the host – are merging and so the result is more obvious. In human cancer, the tumour’s mitochondrial DNA is likely to be very similar to the mitochondrial DNA in the patient’s normal cells, so the result of recombination would be almost impossible to recognise.”
Although the significance of mitochondrial DNA recombination in cancer is not yet known, its discovery is now leading scientists to explore how this process may help cancer cells to survive – and if blocking it may stop cancer cells from growing.
Dr Elizabeth Murchison, senior author of the study, said: “The genetic changes in CTVT have allowed us to reconstruct the global journeys taken by this cancer over two thousand years. It is remarkable that this unusual and long-lived cancer can teach us so much about the history of dogs, and also about the genetic and evolutionary processes that underlie cancer more generally.”
The research was funded by the Wellcome Trust, the Leverhulme Trust and the Royal Society. - See more at: https://www.cam.ac.uk/research/news/a-shaggy-dog-story-the-contagious-cancer-that-conquered-the-world#sthash.AfFmV01g.dpuf