Travelling tumours: New research on 6,000 year old canine cancer

CTVTs spread due to early maritime activity.
Copyright: iStock/s-eyerkaufer

The sexually transmitted cancer, “canine transmissible venereal tumour” (CTVT), is currently undergoing vigorous research at the University of Cambridge. Researchers have found indication from this that there could be another way to combat cancerous tumours.

CTVTs have been predicted to have originated around 6,000 years ago is Asia and has since spread globally. Due to the nature of the cancer transfer between dogs, the cancer cells from dogs today have the same DNA as the original infected dog.

Researchers from the Transmissible Cancer Group (TCG) at the University of Cambridge have been researching CTVTs in the hopes that they can learn more from one of the most prolific cancer lineages in nature.

CTVTs manifest as genital tumours in both female and male domestic dogs and so researchers tested 546 male and female dogs from across the globe. This large research group was intended to help scientists track where the disease originated and at what time.

PHD student, Adrian Baez-Ortega, is part of the study on CTVT. He said: “This tumour has spread to almost every continent, evolving as it spreads…changes to its DNA tell a story of where it has been and when, almost like a historical travel journal.”

What’s new?

Using the data collected in this study, scientists created a phylogenetic tree. This tree allowed researchers to create a tree of origin.

Originating in Asia, the disease then is believed to have transferred to Europe due to the maritime activity at the time. Scientist have predicted that the disease then spread to the Americas around 500 years ago when European settlers first arrived at the continent by sea.

Researchers from the University of Cambridge have found indication that all tumours found in North, Central and South America have the same origin point from the same introduction event.

After being transferred to the Americas, it is believed that the disease was then spread to Africa and back to India.

Over the years, tumour DNA mutates, and the unique signatures change under various factors. Researchers have identified five factors that have change CTVT DNA. The first four have previously been identified in humans and have been linked to UV exposure. However, the fifth signature has yet to be identified in any other mammal. The signature referred to as “Signature A” caused tumour mutations and damaged the tumour’s DNA a very long time ago. The signature is believed to be linked to environmental factors that have not since been identified.

Leader of the Transmissible Cancer Group at the University of Cambridge, Dr Elizabeth Murchison said “This is really exciting – we’ve never seen anything like the pattern caused by this carcinogen before…It looks like the tumour was exposed to something thousands of years ago that caused changes to its DNA for some length of time and then disappeared. It’s a mystery what the carcinogen could be. Perhaps it was something present in the environment where the cancer first arose.”

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