Great fleas have little fleas upon their backs to bite 'em / And little fleas have lesser fleas, and so ad infinitum.
August 6, 2008 6:40 PM   Subscribe

All cancers are parasitical, but most cancers aren't contagious. But some evolve to be. Most viruses parasite cells, but some then make their own "cells", and othr viruses evolve to parasite those. Evolution is stupidly clevererer.

The couplet that forms this post's title is from the great British mathematician Augustus De Morgan, who (lesser bug-like) adapted it from the Anglo-Irish satirist, essayist and author Jonathan Swift.
posted by orthogonality (19 comments total) 8 users marked this as a favorite
Stupid science. Discovering all this weird shit, making the world scary. Back to the humors I say!
posted by Science! at 6:46 PM on August 6, 2008 [2 favorites]

Also with a whole hell of a lot of simplification, I've spent the last year, without success, trying to mutate a virus to carry another virus. Stupid evolution, doing things better than me.
posted by Science! at 6:49 PM on August 6, 2008

Super Cancer is said to be at least 6 inches taller than the normal cancer, he rides a flying motorcycle and has a jar of marmelade that forces people to commit adultery.
posted by qvantamon at 7:00 PM on August 6, 2008 [1 favorite]

The virus/algae connection kind of depressed me. Just because most people seem to take a perverse pleasure in settling for the simplest everyday metaphors for nature and never bothering to enjoy, or be wary of, its complexity.

But now I'm digging this Tasmanian devil thing, which I'd heard of but forgotten to follow up on.

Both fascinating, though. Great fpp. Many thanks.
posted by Durn Bronzefist at 7:07 PM on August 6, 2008

Interesting post; both articles stretch a couple definitions and concepts to a point where you have to question the way you previously looked at things. To regard all cancers as parasitical seems odd to me; I have never regarded cancer as being a different organism than the affected host, and it's not something I have commonly heard in the cancer research institute where I work. Cancer is usually thought of as a disease where your own body turns against you, not something else that enters your body. Yet in the cases of Devil tumor and CTVT, the cancer clearly is a parasite as it may be only distantly related to the host.
The second article demonstrates how blurred the boundary between life and non-life can be. It's fascinating that big viruses can carry little viruses, but I've never previously heard that "the ability to be infected by viruses" was the key distinction between a life-form and a whatever-it-is-that-viruses-are-if-they-are-not-alive. The sound-bites in the Telegraph article do not persuade me that there is any logic in this view.
posted by nowonmai at 7:09 PM on August 6, 2008

For those thinking "this post title is useless without pictures."
posted by agentofselection at 7:14 PM on August 6, 2008 [2 favorites]

I find the idea of contagious cancers terrifying.
posted by Caduceus at 7:31 PM on August 6, 2008


The definition of life is very hard. I wonder if, in the end, it's even a meaningful thing to talk about - maybe there will turn out to be no good way to deny that a rock is a form of life that's just very bad at reproducing. (I believe viruses are life. Not sure about prions. I believe these cancers are a life form, though I see them as multiple individuals or colonies, not as a single dispersed individual. I'm not sure if that makes regular cancer also a life form.)
posted by TheOnlyCoolTim at 7:43 PM on August 6, 2008

While I agree that the definitions get stretched, I think that it shows the importance of not getting tied into definitions. Medically, cancer is not considered parasitic or a different organism, but it still leaches blood from its host, doesn't respond to signals to control proliferation, and can undergo rapid evolution to escape and circumvent the host's efforts to control it. Natural selection works just as well at the cellular level as it does at the population level, after all, which is why the body has so many safeguards against allowing somatic evolution. Likewise, the fact that "the ability to be infected by viruses" is not a key distinction between true life and the self-replicating non-metabolic springs that viruses emphasizes which aspects of life are important and which are circumstantial. It reminds one that, especially in biology, categories can only be extended so far.
posted by Schismatic at 7:56 PM on August 6, 2008 [2 favorites]

Maybe the upside of this is that somehow, Cancer can catch a virus.
posted by Devils Rancher at 8:07 PM on August 6, 2008 [1 favorite]

The Tasmanian devil "contagious" cancer doesn't sound fundamentally different from regular cancers - it's been known for years that you could inject cancer cells from one animal into another and the recipient would often develop a tumor. (Sometimes the recipient's immune system saves the day, sometimes not.) It sounds to me like the devils are just unusual because they bite and scratch each other so much, giving cancer cells a ready route of entry into a new host.

Combine this with an unfortunately virulent strain of cancer cells, and the poor devils are in a world of hurt. But again, cancer cells in the lab come in a range of virulences - some are easy to maintain and propagate (HeLa, I'm looking at you), others are more finicky, and the devils happen to have developed their own analog of the nearly unstoppable HeLa cells. Unlucky devils indeed, but I don't think there's some evil new freakish phenomenon afoot here.
posted by Quietgal at 8:20 PM on August 6, 2008

Likewise, the fact that "the ability to be infected by viruses" is not a key distinction between true life and the self-replicating non-metabolic springs that viruses emphasizes which aspects of life are important and which are circumstantial.

I don't think that "can be infected by viruses" is key, but neither do I think that "is made of cells" and "has metabolism" are good choices either. I think self-perpetuation and evolution are more interesting bases.
posted by TheOnlyCoolTim at 8:29 PM on August 6, 2008

Wow, those mimiviruses are badass.

"The size and complexity of the Mimivirus genetic code - which is 1.2 million "letters" long, at least 10 times larger than the code of a typical virus - "challenges the established frontier between viruses and parasitic cellular organisms", they report today in the journal Science.

One of the defining characteristics of a virus is that it is unable to make proteins independently, instead relying on the cells it infects to manufacture its proteins and thus reproduce. But the Mimivirus contains a number of genes for protein translation.

It also contains genes for DNA repair enzymes and other proteins, all typically thought to be trademarks of cellular organisms."
posted by afu at 10:58 PM on August 6, 2008

Prions and contagious cancers are both just mindblowingly horrifying to me. I too, have been following the Tasmanian Devil facial tumor story with a sort of macabre fascination.

I hope that the study of their ailment provides us with new insights into cancers and that that whole isolation / cull thing works out saving them. But alas, the details are in the Devils . . .
posted by mizjana2u at 3:18 AM on August 7, 2008

Ice-9 made of meat.
posted by ryanrs at 6:46 AM on August 7, 2008 [3 favorites]

Every time I read about cancer, viruses, DNA, cell replication, and the like - I am reminded of how many religions have this idea of the fatal intrinsic flaw in the universe or in humanity. It's interesting in cancer that the fundamental chaotic condition that establishes a dynamic state is also responsible for something that can destroy what it has helped to create. It's as if creation and destruction are simply opposite sides of the same coin. Which brings us back to religion and philosophy.

It's ironic, and of course, as I have said before, the universe was created to generate irony as mana for its creator.
posted by Xoebe at 7:49 AM on August 7, 2008

Would viruses that produce cancers be selected for in some circumstances?

I think so; viruses often are able to infect only cells of a particular type in a higher organism and then kill the cells that they are able to infect; plus, the immune system does its best to kill virus infected cells before the viruses can reproduce.

But somatic cells (which are almost all cells) in higher organisms can divide only a limited number of times (the Hayflick limit), so the virus can run out of new cells to infect unless it can transform some of the cells it infects into cancers, the cells of which can divide indefinitely in many cases.

Yet in order for that to work as a reproductive strategy, the virus must put off killing the cells it has transformed and reproduce in them later or some such thing. Perhaps instead it infects stem cells, transforms them into cancers and then reproduces only in daughter cells.
posted by jamjam at 2:17 PM on August 8, 2008

Thanks for the link to Quammen's cancer article.

(Also, just noting my earlier post to the blue on Devil Facial Tumor Disease.)
posted by parudox at 8:07 PM on August 9, 2008

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