Re: [asa] Embryonic Stem Cells in Mice with No Embryos and No Cloning

From: Rich Blinne <>
Date: Thu Jun 07 2007 - 17:37:38 EDT

On 6/7/07, Thomas Robey <> wrote:

The one-sentence summary that I (as a scientist who
> works with human embryonic stem cells) can offer is a
> quote by Rudy Jaenisch indicating his perspective on
> when this will be used in humans.
> "This is really dangerous. We would never transplant
> these into a patient." In his view, research into
> embryonic stem cells made by cloning remains
> "absolutely essential."

Science addresses these dangers in more detail:

But the Yamanaka study showed a big downside to the strategy. The only
> author to study the offspring of the chimeras after birth, he observed that
> 20% of the 121 mice developed tumors. That finding, Yamanaka notes, shows
> the danger of using retroviral vectors, which can turn on cancer-causing
> genes.
> This highlights what Jaenisch calls "major, major problems which need to
> be resolved" if this work is to be applied to humans. Once the appropriate
> human transcription factors are identified, scientists will have to find
> ways to introduce the factors without retroviruses or to safely activate the
> relevant genes within the cell.
A likely alternative would be the use of small molecules to penetrate cell
> walls and turn on production of the necessary transcription factors. "Now
> that we know there's a mechanism by which this [reprogramming] can happen,
> there will be an aggressive search to find small molecules that can activate
> these pathways," predicts Duncan. "It will take a lot of work, but the fact
> that the pathways exist gives you a [place] to start. This is huge."
> It's still a long road to potential therapies with reprogrammed adult
> cells. But Cowan is optimistic: "The most amazing thing about these papers
> is you now take this whole idea of reprogramming out of the hands of cloning
> specialists and put it into the hands of anyone who can do molecular and
> cell biology." In some ways, he says, "it's a much simpler system than we
> thought." As a result, he predicts, "we're really going to see this process
> accelerate."

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Received on Thu Jun 7 17:38:27 2007

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