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Say 'Aaah' | Media Mix / Nick Owchar

Cancer's Essential and Evolutionary Role in Genes

CANCER: The Evolutionary Legacy; By Mel Greaves; Oxford University Press; 276 pages, $27.50.

September 25, 2000|NICK OWCHAR

Mutation is a fact of nature, not an exception to the rule, observes Mel Greaves in "Cancer: The Evolutionary Legacy." Even those single-celled creatures floating in the primordial soup--our distant ancestors--had to experience mutations to evolve into the bone, blood, flesh, organs and everything else that makes us human. And cancer, Greaves explains, has always played an essential part in this process.

"No changes in genes = no cancer," he writes. "No changes in genes = no evolution = no us." Follow this simple formula and you arrive at what seems stunning, if not unbelievable: No cancer = no us. But Greaves, with a deft pen and chatty colloquial manner, helps lay readers understand why this is so.

A cellular biologist and leukemia researcher, Greaves takes readers on a tour of history, from Egyptian mummies with bone cancer to the tumors that killed a 15th century king of Naples and possibly Napoleon Bonaparte, all to remind us of cancer's abiding presence on this planet. He challenges the paradox that today's healthier society has more cancer incidence by pointing out that there isn't a paradox--medical breakthroughs have only reduced "the competing causes of death," leaving cancer terrifyingly conspicuous on the playing field.

But his book's greatest contribution to the body of cancer literature is in its discussion of cancer's genetic mechanism and the role of DNA. Greaves isn't the first to write about cancer cells and their mutated DNA--the latest bestsellers by Martin Katahn or the American Cancer Society certainly acknowledge that the DNA in cancerous cells is different from other cells. But what they don't explain, and what Greaves shows, is how this difference works to a cancer cell's advantage, making it "deaf" to the body's regulatory chemical commands, and how this supposed defect, following a remarkable chain of events obeying the Darwinian rules of natural selection, enables it to survive and multiply stealthily.

Readers are given an extraordinary glimpse of the human body on the microscopic level: how genetic and chemical commands organize cells and maintain boundaries among tissues with the delicacy and harmony of a symphony orchestra. An enormous amount of cloning takes place daily in this environment, from cell growth for healing to the 100,000 million new red cells flooding the blood supply. Such a vast assembly line, Greaves points out, isn't error-free: Cells with miscopied DNA get cloned all the time. And, if their mutated DNA enables them to ignore what the rest of the orchestra is playing, these cells may expand, invade and eventually threaten other tissues--all in the name of survival. And though many families struck by cancer rage against it in the most personal of terms--it's "a curse," "a destroyer," "pure evil"--Greaves points out that cancer development obeys the random nature of evolution. "Evolution has no malign intent," he writes. "It's just the way it works, blindfolded to consequences."

This doesn't mean that cancer is caused by genes alone and that other factors, like diet and smoking, are off the hook. In fact, the book's second half describes how modern lifestyles, and cultural attitudes dating back centuries, have increased the stress on that cellular assembly line, as well as the risk that a cell with the right mutations will arise and begin its deadly journey. Greaves also makes an interesting case that society's preference for sex as a form of recreation, not procreation, may be contributing to a higher incidence of breast and prostate cancers.

The last section of the book looks at the search for better cancer therapies, such as the creation of "smart bombs" (engineered viruses that seek and destroy malignant cells by zeroing in on their lack of the protein p53) and efforts to bind proteins to cancer cell surfaces to make them more stable for therapy. Greaves' descriptions help readers understand exactly why the mapping of the human genome earlier this year excited so many cancer researchers. He also discusses clinical trials involving thalidomide and endostatin to stop blood vessel growth to tumors, called angiogenesis, and he calls this "probably the best new therapeutic card we have to play."

Will cancer patients benefit from reading this book? Greaves certainly supplies them with enough technical information to keep up with any oncologist. But there is an even more basic consolation here: that cancer has long been a part of human development, it isn't "bad luck or an act of God" that has singled out any individual, Greaves assures us. Whenever science can be used to rescue patients from blaming themselves for their condition, there is reason to celebrate.

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