This post and the next have been bubbling in the pipeline for some months now, and were finally prodded to the open by this post by Carl Zimmer about the facial tumour disease wiping out Tasmanian Devils.
So what’s the deal with the face-cancer first up? (Sidenote: You’d be surprised how many people have found my post about Cordyceps by searching face fungus. I hope you googlers don’t have face fungus, that makes me sad.) Anyhoo, Tassie Devils are the world’s largest carnivorous marsupials and are only found in Tasmania, this makes them very special little critters. They are also violent and bitey mofos, and they’re pretty ugly to boot. Here’s one.
Okay, that one’s actually cute. Try this one.
Like big teethy rats.
Tasmania ain’t a big place, so if a male meets a sexy female devil and she’s not a sister, she’s probably a cousin. That means there’s not much genetic diversity between individuals. Enter the cancer. The cancer infects the face, and Tasmanian Devils have a nasty habit of biting each other on the face, which passes on the cancer. It’s an infectious tumour! This is very VERY rare, the only other one I know is Stickers Sarcoma which infects dogs, we people don’t catch tumours from each other. Cancer researchers need to be super-sterile in teh lab to protect the cancer cells, not themselves.
In the Tassie’s case, their DNA is so much the same,
I bet if you asked them if they wanted icecream they’d both say yes the cancer cells feel at home in a new host, and their inbred immune system doesn’t notice them. Cancer cells do, after all, survive the immune system by looking like a normal cell.
It’s all bad news for the Tasmanian Devils. Cancer is a hard disease to cure for the same reason it evades the immune system – it looks like a normal cell. Killing it often involves collateral damage, and it’s a shaky balance to kill the cancerous cells faster than the rest of the body. Treatments are tailored and expensive – and it’s damn hard to give radiotherapy or chemotherapy to a wild animal. On the other hand, all these devils have the same cancer cells, if we COULD find a way to target them specifically we would cure them all. It might be an easier cancer to treat than the human varieties.
An intriguing question – is this a new lifeform? The cancer cells are genetically different to the Tasmanian Devil cells, they have the ability to evolve, grow, move between hosts. Are they a single-celled parasite, an infectious microbe in their own right? Where do we draw line between a mutated cell and a new species?
Will it infect us too?
Not sure about you (each to their own), but I don’t make a habit of biting people’s faces. Plus we are a pretty spread-out species with plenty of laws and morals against inbreeding. So I think we’re safe.
But we do have something that causes cancer, and it is VERY infectious. It’s a virus called HPV, and you’ve probably already been infected by it. You probably wouldn’t even know it.
That’s the topic for tomorrow. Check out part two.