25 April 2012

Dear Americans for Medical Progress

Dear Americans for Medical Progress,

As a pro-research, pro-science advocacy group, I'd like to think you take facts seriously.

On your FAQ, on the very first question justifying animal research, you write:

For instance, sharks are immune to cancer. By studying their biological system, scientists hope to understand what mechanism prohibits shark cells from mutating into cancer cells, and from this information, create a medicine that mimics that mechanism to prevent cancerous cells from forming in humans and animals.

Let’s look at those two sentences in turn.

“Sharks are immune to cancer.”

This is a myth. Christie Wilcox wrote a fantastic blog post debunking this. The title says it all: “Sharks DO get cancer!” Here’s the key quote (my emphasis):

(I)n 2004, Dr Gary Ostrander and his colleagues from the University of Hawaii published a survey of the Registry for Tumors in Lower Animals. Already in collection, they found 42 tumors in Chondrichthyes species (the class of cartilaginous fish that includes sharks, skates and rays). These included at least 12 malignant tumors and tumors throughout the body. Two sharks had multiple tumors, suggesting they were genetically susceptible or exposed to extremely high levels of carcinogens. There were even tumors found in shark's cartilage! Ostrander hoped that this information would finally put to rest the myth that sharks are somehow magically cancer-free. 

The second sentence claims that there are researchers who are actively studying cancer in sharks. That sharks do get cancer does not mean that there would be no researchers on them, so this is a completely separate claim. This is also not true, as far as I have been able to find.

A PubMed search for “cancer” and “shark” reveals a fifteen articles with those words in the title. None reveal any researchers using sharks to study cancer. Most of those papers bemoan the use of shark cartilage as quackery, and a few test the shark cartilage treatment (it failed). Another search for “tumor” and “shark” finds a few papers that are testing shark derived products on cancer. But testing a shark product for anti-cancer properties is not the same as studying sharks.

I can find nobody doing the type of research you describe in your answer: studying the cellular biology of sharks. I may be wrong on this, and would like to knowing what researchers are actively studying tumorigenesis in sharks.

The combination of these two claims may give people the false impression that there is something the quack science concerning treatment of cancers using shark cartilage. This is also not true, and contributes to severe overfishing of sharks (also addressed in Christie Wilcox’s post).

Beside, using sharks as an example misses the point that concerns most people. Most people are concerned about the use of mammals in research. You should address that directly and use mammals in answering the question.

One alternative would be to naked mole rats in the example. There is ongoing research on tumorigenesis in this species; references are below. Frankly, an example of information gained from a more common lab animal, like a mouse, would be even more convincing.

I hope you will consider changing your FAQ. As a researcher, I am very concerned about issues surrounding animal care. Errors like this can damage the credibility of everyone who has to use animals in research.

Yours truly,

Zen Faulkes

Additional: I emailed this to AMP this morning, and received an email back from them in about five hours. They plan on reviewing their FAQ and should have a revised version up soon.


Update, 26 November 2013:  I had cause to revisit this post because David Shiffman tweeted a new picture of a shark with a tumour from this scientific paper. I hopped over to the Americans for Medical Progress FAQ, and saw (my emphasis):

The differences exhibited in a research model can also provide great insights.  For instance, sharks rarely get cancer, cockroaches can regenerate damaged nerves, and some amphibians can regrow lost limbs.

This is not a great revision. It still perpetuates the idea that somehow sharks are at least resistant to cancer, and that there is active research on this. Many other species have low rates of cancer, like whales, crustaceans, and naked mole rats. Naked mole rats probably have the most research on their inherent cancer resistance.


Seluanov A, Hine C, Azpurua J, Feigenson M, Bozzella M, Mao Z, Catania K, Gorbunova, V. 2009. Hypersensitivity to contact inhibition provides a clue to cancer resistance of naked mole-rat. Proceedings of the National Academy of Sciences 106(46): 19352-19357. DOI: 10.1073/pnas.0905252106

Liang S, Mele J, Wu Y, Buffenstein R, Hornsby P. 2010. Resistance to experimental tumorigenesis in cells of a long-lived mammal, the naked mole-rat (Heterocephalus glaber). Aging Cell 9(4): 626-635. DOI: 10.1111/j.1474-9726.2010.00588.x

Shark picture by PacificKlaus on Flickr; used under Creative Commons license.


Kyle said...

I have heard the same comment made about the American bison (Bison bison bison) and never believed it.

Indeed, a quick search finds that cancer HAS been reported in Bison, but it does appear to be somewhere rare, or just underreported:



Michael said...

As I understand it, species that are evolutionarily stable (successful form in long-stable microenvironments) have better DNA repair, fewer persistent mutations, and one would assume, less cancer, but that wouldn't apply to all sharks as a group. It might apply to pelagic sharks, though, and those would be unlikely to be studied - almost impossible to house.