Dr Kat Arney, The Naked Scientists
This week Kat Arney has been living up to our Naked theme and exposing the truth about the weird and wonderful naked mole-rat, which is said never to succumb to cancer...
Kat - Often described as wrinkly sausages with teeth, the unattractive appearance of Naked mole-rats masks their unusual biological properties. Pink and hairless, these extraordinarily long-lived rodents live pretty much their entire lives in the dark underground, up to an impressive 30 years in groups with similar social structures to insects such as ants and bees. Unusually, they can’t feel pain as they have no pain receptors in their skin and, unlike other mammals, they can adjust their body heat to match the temperature of the outside world.
But heterocephalus glaber, to use the Naked mole-rats latin name, is most famous for a health related trait - they never get cancer. Recent studies revealed that the cells of Naked mole-rats make a sticky substance called hyaluronan, which is thought to stop tumours in their tracks. And genetic studies have revealed that the animals carry exceptionally potent version of genes known as tumour suppressors, which stop cells growing out of control and forming cancers.
In 2013, the journal Science even named the Naked mole-rat “vertebrate of the year” thanks to their amazing cancer resistance. But, in 216, two papers turned up showing that this unbelievable ability is just that - unbelievable. Looking at 37 Naked mole-rats that had died between 1998 and 2015, vets at Disney’s Animal Kingdom in Florida, discovered four cases of cancer in the animals: one with liver cancer, another with a kidney tumour, a third with a type of cancer called lymphosarcoma, and another with what looked like oesophageal cancer.
Researchers from the University of Washington also announced they’d found two Naked mole-rats with cancer. One with a tumour that probably started in it’s salivary gland and another with a type of stomach cancer known as a neuroendocrine carcinoma. The first one is still alive and living in a zoo in Illinois but the second one died, probably as a result of the disease.
Proving it’s always risky to say something never happens in science, these discoveries show that although it’s still very rare for Naked mole-rats to get cancer, it can still happen. Even so, their unusual longevity and low, but still real, incidence of cancer makes them interesting animals to study to find out more about more about what’s going on and see if we can find any clues about our own human lifespan and cancer risk.
And they aren’t the only members of the animal kingdom to be rumoured to have inbuilt cancer resistance. Right at the start of this series I busted the myth that sharks don’t get cancer - they do. And elephants also have unusually low rates of tumours, yet the have many more cells than we do and live just as long - something known as Peto’s paradox after the great scientist Richard Peto.
Just last year, Josh Shifman, a children's cancer doctor in Utah, discovered why. By gathering samples of blood from the elephants at Utah’s Hogle Zoo, he discovered that these enormous pachyderms have extra copies of tumour suppressor gene called P53, known as the ‘guardian of the genome’ that helps to stop cells turning cancerous when they damage their DNA, but they’re still not completely immune to the disease.
Sadly for sharks, elephants and those wrinkly Naked mole-rats, like the superpowers of comic book heros, the idea that they’re completely invincible, at least to cancer, is just as fictional.