Cancer risk cut in new method for embryo-free stem cells
Sunday, December 2, 2007
San Francisco -- Scientists eliminated a gene known to trigger cancer
from a process that turns skin cells into multipurpose stem cells,
solving a flaw that may have kept the technique from becoming a
useful therapy.
Researchers led by Shinya Yamanaka of Kyoto University announced Nov.
20 that by inserting four genes into skin cells they
could "reprogram" them to an embryonic-like state able to turn into
any other cell in the body. In follow-up research published Friday in
the journal Nature Biotechnology, the team omitted a tumor-causing
gene, c-Myc, and achieved the same effect.
The original advance may allow development of powerful stem cells
without harvesting human eggs or destroying embryos. Scientists
working to refine the technique can now try to eliminate the
remaining genes, as well as the viruses used to shuttle them into the
skin cells, since they may spur disease in the transformed cell.
"The race is now on for replacing each of these genes," said Bruce
Conklin, director of the stem cell core laboratory at Gladstone
Institute for Cardiovascular Disease in San Francisco, in a telephone
interview today. "That was the most important one to get rid of, but
we want to get rid of all the genes and replace them with other ways"
of transforming the skin cells.
Conklin collaborates closely with Yamanaka, who in August was
appointed the L.K. Whittier Foundation Investigator in Stem Cell
Biology at Gladstone.
In the newest study, Yamanaka and his team tweaked the process they
used to grow, select and manipulate the cells. They worked first in
mice and were able to make mouse skin cells called fibroblasts revert
to an embryo-like state using the three-gene technique, without c-Myc.
They then transplanted these cells into a mouse embryo and implanted
that into a female mouse. The resulting mouse pups were genetically
related to the mouse that provided the skin cells.
When Yamanaka and his colleagues used this process in mice two years
ago, using all four genes, six of the 37 mice that were born
developed cancer. This time, without c-Myc, none of the 26 mice they
created sprouted tumors.
Employing the same process in humans, the team took a skin cell from
a 36-year-old woman, applied the three genes and created what
Yamanaka calls "induced pluripotent cells." Those cells showed many
signs of having embryonic cell-like properties.
Though the process was less efficient -- fewer of the skin cells were
reprogrammed -- the fact that they were able to do it is a key
achievement, Conklin said.
"Eventually, we'll be able to do this without using genes," he said.
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StemCells subscribers may also be interested in these sites:
Children's Neurobiological Solutions
http://www.CNSfoundation.org/
Cord Blood Registry
http://www.CordBlood.com/at.cgi?a=150123
The CNS Healing Group
http://groups.yahoo.com/group/CNS_Healing
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