As far as anyone has ever been able to tell, naked mole rats don’t get cancer. Scientists have observed large colonies of these freaky-looking rodents over their relatively long lives (about 30 years) and never seen one with a tumor or other symptoms of cancer. This week, researchers from Rochester University announced that they’ve found one of the mole rat’s tricks for cancer resistance. Science writer Ed Yong has what’s maybe the best intro into the story.
The problem with writing about the naked mole rat is the long list of bizarre traits that you don’t have space to talk about. For this post, let’s forget that they look like a wrinkled finger with teeth. Put aside their inability to feel pain in their skin, their tolerance for chokingly low oxygen levels, their bizarrely rubbish sperm or their poor temperature control. Don’t even think about how they live in ant-like colonies, complete with queens and workers. Ignore their ability to live for more than 30 years—an exceptional lifespan for a rodent of their size.
Instead, let’s talk about the cancer angle.
They don’t get it.
While the researchers were trying to grow mole rat cells in a flask, the liquid that held the cells kept getting thick and syrupy.
This was because the cells secreted a sugar called hyaluronan, which was thickening the liquid. Hyaluronan is common in the skin, cartilage and other connective tissues of mammals. Like mortar in a wall, it’s one of many molecules that fill the spaces between cells and provide them with support. The naked mole rat makes an exceptionally large version of the sugar that’s over five times bigger than ours. And it has a lot of it.
…Andrei Seluanov, who led the study, suspects that the larger hyaluronan physically cages potential cancer cells, preventing them from breaking free and growing into tumours. But it also allows cells to stop each other from growing if they become too crowded. This is called ‘contact inhibition’—it’s why healthy cells form a flat layer if they’re grown in a dish but cancerous ones pile on top of each other.
The overgrown sugars probably aren’t the be-all, end-all of for the rats’ cancer dodge, though, but one part of a suite of defenses.
Not so fast, cautions Rochelle Buffenstein from the University of Texas Health Science Center, who discovered the naked mole rats’ cancer resistance. “This is now the third study to provide a potential mechanism,” she says. “Clearly there are multiple anti-cancer defenses employed in the naked mole rat.” Others might include mass suicide of overgrowing cells, and a tolerance for DNA-damaging oxygen molecules. [Not Exactly Rocket Science]