Thursday, November 22, 2007

Premature Stem Cell Celebration
[. . .]

So if you ask when doctors and patients will see new treatments, scientists can only hedge.

"I just can't tell you dates," says James Thomson of the University of Wisconsin-Madison, one of the scientists in the U.S. and Japan who announced the breakthrough on Tuesday.

[. . .]

Paul Berg, a Stanford University Nobel laureate who helped establish federal guidelines for human research on genetically manipulated cells, said the celebration over this week's announcement is premature.

"I'm amazed at the ethicists" saying the problem of needing embryos has been solved, Berg said. "We're not in the clear - this is a first step."

So what are the next steps?

The first basic question to solve is how similar iPS cells are in behavior and potential to the embryonic cells that scientists have studied for nearly a decade.

"My guess is that we'll find that there are significant differences," said Dr. Robert Lanza of Advanced Cell Technology, which has been trying to produce stem cells from cloned human embryos. "I'd be surprised if these cells can do all the same tricks as well as stem cells derived from embryos."

Another big question is how to make iPS cells in a different way. The breakthrough technique treats skin cells by using viruses to carry in a quartet of genes. Those viruses disrupt the DNA of the skin cells. When that happens, there's a risk of cancer.

That's show-stopper when it comes to creating tissue to transplant into people. So scientists have to figure out a way to make iPS cells without those DNA-disrupting viruses.

Scientists should be able to find other ways to slip the genes into the skin cells, Thomson said. Other scientists suggest that a purely chemical treatment, not inserting genes at all, might be able to get the same result.

The cancer-risk problem should be solved quickly, maybe within a year or so, said Doug Melton, co-director of the Harvard Stem Cell Institute.

Before then, iPS cells could be used in lab studies to study the early roots of genetic disease or to screen drugs. But of course, it's anybody's guess when a useful treatment would result from that.

Even with the cancer problem solved for transplant uses, there's another big hurdle:

The whole idea of using embryonic stem cells or iPS cells for treating people with conditions like diabetes and Parkinson's disease via transplant is itself far from proven. Scientists will need to learn how to turn iPS cells into the right kind of tissue, and how to use that tissue in a way that will treat a person's disease.

Such studies, in the lab, animals and finally people, will take years.

As far as that obstacle goes, Thomson said, the breakthrough announced this week changes nothing.

"We have a lot of work to do."

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