Contagious cancer

The April issue of Harper's had a fascinating article about the evolution of contagious cancer. The story, now readable online, begins in Tasmania where cancer appeared to be passing between Sarcophilus harrisii, commonly known as Tasmanian devils. As it turns out, "Devil Tumor" isn't the only contagious cancer. From Harper's:

Under ordinary circumstances, cancer is an individuated phenomenon. Its onset is determined partly by genetics, partly by environment, partly by entropy, partly by the remorseless tick-tock of time, and (almost) never by the transmission of some tumorous essence. It arises from within (usually) rather than being imposed from without. It pinpoints single victims (usually) rather than spreading through populations. Cancer might be triggered by a carcinogenic chemical, but it isn’t itself poisoning. It might be triggered by a virus, but it isn’t fundamentally viral. Cancer differs also from heart disease and cirrhosis and the other lethal forms of physiological breakdown; uncontrolled cell reproduction, not organ dilapidation, is the problem.

Such uncontrolled reproduction begins when a single cell accumulates enough mutations to activate certain growth-promoting genes (scientists call them oncogenes) and to inactivate certain protections (tumor suppressor genes) that are built into the genetic program of every animal and plant. The cell ignores instructions to limit its self-replication, and soon it becomes many cells, all of them similarly demented, all bent on self-replication, all heedless of duty and proportion and the larger weal of the organism. That first cell is (almost always) a cell of the victim’s own body. So cancer is reinvented from scratch on a case-by-case basis, and this individuation, this personalization, may be one of the reasons that it seems so frightening and solitary. But what makes it even more solitary for its victims is the idea, secretly comforting to others, that cancer is never contagious. That idea is axiomatic, at least in the popular consciousness. Cancer is not an infectious disease. And the axiom is (usually) correct. But there are exceptions. Those exceptions point toward a broader reality that scientists have begun to explore: Cancers, like species, evolve. And one way they can evolve is toward the capacity to be transmitted between individuals.

Contagious cancer (Harper's, thanks Vann Hall!)

• [Joe]

  No, the oldest genetic material on the planet is the stuff that codes for some of the basic processes of life, the biochemistry that works the same way in your body as it does in a yeast cell or a bacterium. Some of that might be a billion years old.

  Even if you point out that the genes are formed by copying, remember that bacteria reproduce by splitting.

• [PacoBell]

  Thus began the genesis of the Descolada…

• [trimeta]

  Speaking of unicellular human life: HeLa cells, derived from one woman’s cancer in 1951, persist today in laboratory cultures and are surprisingly difficult to kill.

• [arlisssimo]

  Anthropometaphors has been following this topic and has posted a summary to a follow-up study recently covered in the Proceedings of the National Academy of Sciences (PNAS).

  http://morethangray.wordpress.com/2008/07/15/genetic-retalliation/

• [ill lich]

  Thanks. Thanks a lot. I was already scared sh!tless of mad cow disease, ebola, hanta, Marburg, bird flu, cooties. . . to say nothing of terrorism and totalitarianism.

  Add it to the list and pour another drink.

• [ophite]

  Incidentally, this is the same reason that Bush’s stem-cell research compromise isn’t a compromise at all: stem-cell cultures invariably turn cancerous. The evolutionary incentives for unicellular life are wildly different from those for multicellular life.

  In culture, stem cells lose any evolutionary incentive to respond to apoptosis signals. They lose any incentive to put the brakes on their own reproduction. They become unicellular human life.

  – ACS

  * Incidentally, for the creepiest thing that can potentially happen during a pregnancy, look up ‘choriocarcinoma.’

• [Robotech_Master]

  I seem to recall reading somewhere—I think it may have been right here on BoingBoing—that contagious feline cancers can contain some of the oldest still-living genetic material on the planet, since they still contain within them genetic material from their Patient Zero. (A google doesn’t turn it up on boingboing, though, so maybe it wasn’t.)

• [Neuron]

  Human cervical cancer is an infectious disease. There’s a vaccine for it.

• [zuzu]

  Can you get PML from a dog cytomegalovirus?
  

  What are canine transmissible venereal tumours? In this episode, the NorBAC team speculates that canine CMV had spread among some of the dogs in Iron River through a type of cancer they all had. Dogs can indeed spread cancer cells to each other: Canine transmissible venereal tumours are usually passed from dog to dog by sexual contact, but can also be spread to a dog’s mouth by licking. This disease is very unique, because the cancer cells themselves – not a virus or other pathogen – are transferred between dogs. Only dogs can be infected by this type of cancer – it’s not a threat to humans.

  The cells probably originated from a wolf several hundred years ago. How did the first dog or wolf get this type of cancer? Scientists believe that it might originally have been caused by a virus, in the same way that humans can get cervical cancer from the Human Papilloma Virus, but there isn’t currently an active virus in canine transmissible venereal tumours.