OUR FRIEND, THE ZEBRAFISH

The Patchy-Kitty, World's most beautiful cat

Linda loved her

If you are a cancer scientist and want to test a new idea, you do not just visit the nearest cancer ward and start injecting.  Oh, no – that would get you at least fired, and just possibly jailed to boot.  No, you try out your idea on some innocent animal and then, if it seems to work you may progress to human cancer cells in a Petrie dish.  Then, and only then, do you screw up your courage and approach the NIH or some equally august body for permission to deal with real human beings.

There are all sorts of “animal models” in play at any one time.  They range from nematode worms and fruitflies (not much like us, but cheap) through mice (genetically a surprisingly close match, but much more expensive) to dogs, chickens and, finally, apes.  (However, currently it is illegal to experiment with chimps – even if they give written permission.)  A surprisingly useful animal model is the zebrafish.

A zebrafish is an ordinary looking fish from SE Asia, about two inches long; apparently it is a favorite of people who keep fish tanks.  The overwhelming advantage of zebrafish in cancer research is that they are transparent, at least when young.  You can see right through the little creatures and observe what your drug is doing to their organs, without cutting them open (and thereby ending the experiment.) 

Well, zebrafish figure hugely in the story I am about to tell you.  It comes from the NYTimes (courtesy of Joanne Ingwall.)  If you want to read it, click here:

http://www.nytimes.com/2016/01/29/health/how-skin-cancer-develops-melanoma-zebra-fish.html?smprod=nytcore-ipad&smid=nytcore-ipad-share&_r=0

Apparently cancer researchers have long known and puzzled over the fact that cells can have all the mutations necessary to go cancerous (e.g., mutated oncogenes such as our old friend BRAF, together with a defective tumor suppressor gene – p53, say –) and still not go cancerous. Working with melanoma, and zebrafish, people at Boston Children’s Hospital have shown that more than a “cancerized field” is needed to kick-start the development of cancer.  What is needed is a functional gene named “crestin”, which normally is active only in the embryonic state.  These Children’s Hospital docs first “cancerized” (with melanoma) every pigmented skin cell in a bunch of poor, long-suffering zebrafish – and then watched for cancers.  Instead of explosive development they observed that only a few cells went bad – and these all contained active crestin genes. 

Why the crestin genes – supposedly inactive since the gastrula stage of embryogenesis – arose from the dead in these few cells is an object of intense curiosity and, one hopes, diligent research.  If these observations apply to other kinds of cancer, and if we can discover how to prevent resurrection the crestin gene , we will have a powerful weapon.  Let it be so.

Thank you, little transparent fish.



Linda and sleeping kitten