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.

Metro-Goldwyn-Mayer Pictures
Show Hide image

The one where she turns into a USB stick: the worst uses of tech in films

The new film Worst Tinder Date Ever will join a long tradition of poorly-thought-through tech storylines.

News just in from Hollywood: someone is making a film about Tinder. What will they call it? Swipe Right, perhaps? I Super Like You? Some subtle allusion to the app’s small role in the plotline? Nope – according to Hollywood Reporterthe film has been christened Worst Tinder Date Ever.

With the exception of its heavily branded title (You’ve Got Gmail, anyone?), Worst Tinder Date Ever follows neatly in the tradition of writers manhandling tech into storylines. Because really, why does it matter if it was a Tinder date? This “rom com with action elements” reportedly focuses on the couple’s exploits after they meet on the app, so the dogged focus on it is presumably just a ploy to get millennial bums on cinema seats.  

Like the films on this list, it sounds like the tech in Worst Tinder Date Ever is just a byword for “modern and cool” – even as it demonstrates that the script is anything but.

Warning: spoilers ahead.

Lucy (2014)

Scarlett Johansson plays Lucy, a young woman who accidentally ingests large quantities of a new drug which promises to evolve your brain beyond normal human limits.

She evolves and evolves, gaining superhuman powers, until she hits peak human, and turns into first a supercomputer, and then a very long USB stick. USB-Lucy then texts Morgan Freeman's character on his fliphone to prove that: “I am everywhere.”

Beyond the obvious holes in this plotline (this wouldn’t happen if someone’s brain evolved; texting a phone is not a sign of omnipotence), USB sticks aren’t even that good – as Business Insider points out: “Flash drives are losing relevance because they can’t compete in speed and flexibility with cloud computing services . . . Flashdrives also can’t carry that much information.”

Star Wars: The Force Awakens (2015)

If you stare at it hard enough, the plotline in the latest Star Wars film boils down to the following: a gaggle of people travels across space in order to find a map showing Luke Skywalker’s location, held on a memory stick in a drawer in a spherical robot. Yep, those pesky flash drives again.

It later turns out that the map is incomplete, and the rest of it is in the hands of another robot, R2-D2, who won’t wake up for most of the film in order to spit out the missing fragment. Between them, creator George Lucas and writer and director JJ Abrams have dreamed up a dark vision of the future in which robots can talk and make decisions, but can’t email you a map.

Willy Wonka and the Chocolate Factory (1971)

In which a scientist uses a computer to find the “precise location of the three remaining golden tickets sent out into the world by Willy Wonka. When he asks it to spill the beans, it announces: “I won’t tell, that would be cheating.


Image: Paramount Pictures. 

The film inhabits a world where artificial intelligence has been achieved, but no one has thought to pull Charlie's poor grandparents out of extreme poverty, or design a computer with more than three buttons.

Independence Day (1996)

When an alien invasion threatens Earth, David Levinson (Jeff Goldblum) manages to stop it by hacking the alien spaceship and installing a virus. Using his Mac. Amazing, really, that aliens from across the universe would somehow use computing systems so similar to our own. 

Skyfall (2012)

In the Daniel Craig reboot of the series, MI6’s “Q” character (played by Ben Whishaw) becomes a computer expert, rather than just a gadget wizard. Unfortunately, this heralded some truly cringeworthy moments of “hacking” and “coding” in both Skyfall and Spectre (2014).

In the former, Bond and Q puzzle over a screen filled with a large, complex, web shape. They eventually realise it’s a map of subterranean London, but then the words security breach flash up, along with a skull. File under “films which make up their own operating systems because a command prompt box on a Windows desktop looks too boring”.

An honourable mention: Nelly and Kelly Rowland’s “Dilemma” (2009)

Not a movie, but how could we leave out a music video in which Kelly Rowland texts Nelly on a Microsoft Excel spreadsheet on a weird Nokia palm pilot?


Image: Vevo.

You’ll be waiting a long time for that response, Kelly. Try Tinder instead.

Barbara Speed is a technology and digital culture writer at the New Statesman and a staff writer at CityMetric.