Biologists reconstruct genome of 11,000-year-old “almost immortal” sexually-transmitted dog cancer

Canine transmissible venereal tumours (CTVT) is one of only two natural transmissible cancers, and could hold the key to better organ transplants in humans.

Veterinary biologists have discovered that a sexually-transmitted cancer found in dogs around the world first originated 11,000 years ago, making it potentially the oldest living mammalian creature.

The study from the Wellcome Trust’s Sanger Institute, published in Science, analysed the genome of canine transmissable venereal tumours (CTVT), a disease that is one of only two known cancers of its type to have been observed in the natural world (the other, transferred via bites, affecting Tasmanian devils). It’s not a cancer caused by the transfer of a virus, like with cervical cancer and the HPV virus in humans - it’s the transfer of actual cancerous dog cells from dog to dog.

“They are actually a parasite, they need to have their host in order to survive, but they’re actually derived from the same species as their host,” Dr Elizabeth Murchison, the study’s lead author, explained to me. “They’re quite a strange disease. They are an infectious disease, but they’re originally from the same species as their host, which makes them a kind of very tricky to combat.”

“It’s the oldest continually surviving mammalian lifeform that we know of,” she said. “It is almost immortal.”

Genome analysis of samples from a dog in Brazil and another Australia found that the cancer had undergone a huge number of mutations, in the order of two million, since it first began metastasising within the first dog to contract it.

Murchison said: “Between humans we each have about three million mutations, the natural variance that makes us different to other people. Similarly dogs have about three million natural variants that make one dog different to another dog. But cancers themselves, in humans, don’t tend to differ from their host very much. They usually have between 1,000 and 5,000 mutations in the genome that makes the cancer different to the host. Whereas this dog cancer has acquired about two million, which is almost making it like a different individual to the original host that gave rise to it.”

Relying on recent research which found that, within cancer patients, the number of mutations within a cancer correlates both to the type of cancer and the age of the patient, the study team were able to trace back in time to the point at which mutations must have started - giving the age of CTVT at 11,000 years.

Yet CTVT stayed within the small population where it first emerged for roughly 10,500 years, until suddenly spreading elsewhere around the globe - a time that coincides with the beginnings of the European age of exploration. While there’s no way to know where in the world the cancer first appear (yet), the earliest known historical mention of it is by a London doctor in 1810.

With the information from the origin dog’s genome, the team was able to create an image of what it probably looked like. Here's a video from the team further explaining their work:

What’s more, the cancer appears to have been caused by in-breeding.

“It was a relatively inbred individual,” explains Murchison. “Similarly, the Tasmanian devils are relatively inbred population - they live on an island, and they have a small population. The cancer might have originated in a dog that lived in an in-bred population, but from there it managed to adapt into all sorts of out-bred dogs. It can even survive in other species of canids, including jackals and coyotes and foxes. It’s pretty remarkable.”

Theoretically, this type of cancer could emerge at any time in any species, Murchison pointed out, but the experience of the dog and Tasmanian devil transmissible cancers - and from a third variant, which emerged briefly in a population of laboratory hamsters in the 1960s - seems to indicate that in-bred populations are more at risk. There are human populations which suffer from low genetic diversity around the world, and this research could be important in understanding transmissible cancers in the case of a variant appearing.

“These cancers have to overcome one of the most fundamental immunological barriers, and how they do it is still a mystery,” Murchison said. “It’s incredibly important to understand how they do it, as it has implications for how cancers evade the immune system, but also potentially how other infectious diseases might work, and have implications for how to design better methods for helping transplant recipient patients not to reject their graft transplant organs.”

Murchison is also keen to see if further research could help the endangered Tasmanian devil, whose variant is much more aggressive than CTVT and which can kill its host in a matter of months.

What the first dog to get CTVT may have looked like. (Image: Sanger Institute)

Ian Steadman is a staff science and technology writer at the New Statesman. He is on Twitter as @iansteadman.

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Buying into broadband’s bigger picture

Reliable internet access must be viewed as a basic necessity, writes Russell Haworth, CEO of Nominet.

 

As we hurtle towards a connected future, in which the internet will underpin most aspects of our daily lives, connectivity will become a necessity and not a luxury. As a society, we need to consider the wider benefits of enabling internet connections for all and ensure no corner of the county is left out of the digital loop.

Currently, despite government incentive schemes and universal service obligations, the rollout of broadband is left largely to the market, which relies on fixed and wireless network operators justifying deployment based on their own business models. The commercial justification for broadband deployment relies on there being sufficient demand and enough people to pay for a broadband subscription. Put flippantly, are there enough people willing to pay for Netflix, or Amazon? However, rather than depending on the broad appeal of consumer services we need to think more holistically about the provision of internet services. If road building decisions followed the same approach, it would equate to only building a road if everyone living in the area bought yearly gym membership for the leisure centre at the end of the new tarmac. The business case is narrow, and overlooks the far-reaching and ultimately more impactful benefits that are available.

Internet is infrastructure as much as roads are, and could easily prove attractive to a wider range of companies investing in digital technology who stand to gain from internet-enabled communities. Health services are one of the most compelling business cases for internet connectivity, especially in remote, rural communities that are often in the “final five per cent” or suffering with below average internet speeds. Super-fast broadband, defined as 30 Mbps, is now available to 89 per cent of UK homes, but only 59 per cent of rural dwellings can access these speeds.

We mustn’t assume this is a minority; rural areas make up 85 per cent of English land and almost ten million people (almost a fifth of the population) live in rural communities. This figure is rising, and ageing ‒ on average, 23.5 per cent of the rural population is over 65 compared to 16.3 per cent in urban areas ‒ and this presents complicated healthcare challenges for a NHS already struggling to meet demand. It goes without saying that accessibility is an issue: only 80 per cent of rural residents live within 4km of a GP’s surgery compared to 98 per cent of the urban population.

While the NHS may not have the resources to build more surgeries and hospitals, robust broadband connections in these areas would enable them to roll out telehealth options and empower their patients with healthcare monitoring apps and diagnostic tools. This would lower demand on face-to-face services and could improve the health of people in remote areas; a compelling business case for broadband.

We can’t afford to rely on “one business case to rule them all” when it comes to internet connectivity – the needs run far beyond Netflix and Spotify, and the long-term, economic and social benefits are vast. It’s time to shift our thinking, considering internet connectivity as essential infrastructure and invest in it accordingly, especially when it comes to the needs of the remote, rural areas of the country.

Russell Haworth joined Nominet as CEO in 2015. He leads the organisation as it develops its core registry business, explores the potential of new technologies in the global internet sector, and delivers on its commitment to ensuring the internet is a force for good.

This article was taken from a New Statesman roundtable supplement "The Internet as Infrastructure: Why rural connectivity is crucial to the UK’s success"

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