Friday, June 04, 2010

Life


As I noted here not long ago (May 18-20), I have been trying to understand the significance of the journals my father kept as he was dying of cancer at age 64. Which means cancer has been much on my mind -- not a particularly cheerful train of thought. But take a look at this cover of the May 21 issue of Science. Not only is it pretty, it conveys a bit of cheerful news.

The therapeutic effect of many anticancer drugs is limited by their ability to penetrate tumor tissue. A group of researchers in California found a way to channel the drugs deep into a tumor, as illustrated schematically on the Science cover (click to enlarge). Along with the drugs (green), the researchers administered the peptide iRGD (multicolored ring), which binds to integrin receptors (blue and yellow) in tumor blood vessels, and is subsequently cleaved (open rings). The cleaved peptide then binds to neuropilin-1 receptors (purple), activating a transport system that carries the drugs deeper into tumor tissue.

All this is going on deep inside a mouse's body in a space smaller than the period at the end of this sentence.

Now I don't know what you make of this, but it makes my head spin. What's a peptide? From the Greek, "a little digestible," a little protein, if you will. A short chain of those ubiquitous molecules in the Tinker Toy set of life called amino acids, of which twenty will do nicely, thank you. We think of life as rather like the cover above, all pink and meaty and chunky -- a fatty dish of flesh and blood and bone. But it's all chemistry. It's all Cs and O and Hs and Ns. Hooking up. Making chains. Twisting and folding. Binding and releasing. We think of living as pumping and breathing, coughing and wheezing, eating and sleeping, burping and excreting, with that angelic sprite called "Me" operating the machine. But down there it's all those utterly indistinguishable Cs and Os and Hs and Ns doing what they have been endowed to do since the dawn of time.

So pop in those peptides, let them cleave and bind and pump through pores. Oh Lord, if only we could see it, feel it, that unceasing stir of molecules that just goes and goes and goes in every cell of our bodies.

Until it doesn't.

(Cover image: Peter Allen/University of California, Santa Barbara.)