By GINA KOLATA Full story, NYTimes Health (requires free registration), December 27, 2005

Also online at Detnews.com. Excerpt:

In other genetic diseases, gene alterations disable cells. In cancer, genetic changes give cells a sort of superpower.

At first, as scientists grew to appreciate the complexity of cancer genetics, they despaired. “If there are 100 genetic abnormalities, that’s 100 things you need to fix to cure cancer,” said Dr. Todd Golub, the director of the Cancer Program at the Broad Institute of Harvard and M.I.T. in Cambridge, Mass., and an oncologist at the Dana-Farber Cancer Institute in Boston. “That’s a horrifying thought.”

Making matters more complicated, scientists discovered that the genetic changes in one patient’s tumor were different from those in another patient with the same type of cancer. That led to new questioning. Was every patient going to be a unique case? Would researchers need to discover new drugs for every single patient?

“People said, ‘It’s hopelessly intractable and too complicated a problem to ever figure out,’ ” Dr. Golub recalled.

But to their own amazement, scientists are now finding that untangling the genetics of cancer is not impossible. In fact, they say, what looked like an impenetrable shield protecting cancer cells turns out to be flimsy. And those seemingly impervious cancer cells, Dr. Golub said, “are very much poised to die.”

In the end, all those altered genes may end up being the downfall of cancer cells, researchers say.

“Cancer cells have many Achilles’ heels,” Dr. Golub says. “It may take a couple of dozen mutations to cause a cancer, all of which are required for the maintenance and survival of the cancer cell.”

Gleevec, researchers say, was the first test of this idea. The drug knocks out a gene product, abl kinase, that is overly abundant in chronic myelogenous leukemia. The first clinical trial, which began seven years ago, seemed like a long shot.