Scientists Show Stem Cells Don't Cause Cancer
02.14.08, 12:00 AM ET
THURSDAY, Feb. 14 (HealthDay News) -- A major concern with using stem
cells to treat disease has been the possibility that the retrovirus
used to implant the cells might cause cancer, but now a group of
scientists appears to have solved that problem.
In November, two groups of researchers -- one in Japan and one in the
United States -- showed that adult human and mouse skin cells could
be reprogrammed into stem cells similar to embryonic stem cells,
which can be made into any type of cell. These cells, called induced
pluripotent stem cells (iPS), could be the key to using stem cells to
cure a variety of diseases.
In this latest study, published in the Feb. 14 issue of Science, the
Japanese researchers prove these stem cells are made from normal
mature adult cells, and they show that these stem cells can be
implanted using a retrovirus without fear of causing cancer.
"This is a real nice follow-up and confirmation of the previous
papers that looked at inducing normal cells to become stem cells,"
said Dr. Hugh Taylor, an associate professor at Yale University
School of Medicine.
"The question that still existed from the previous paper was whether
these stem cells were some sort of adult stem cells," Taylor
said. "This paper shows that these stem cells are fully
differentiated adult cells, that they can be reprogrammed into stem
cells," he added. "You can probably take almost any adult cell and
turn it into a stem cell."
In addition, there has been a fear that using a retrovirus to implant
stem cells results in an increased risk of cancer. This study showed
that doesn't happen, Taylor said. "It proves, without a doubt, that
these cells are safe for human use," he noted.
However, Taylor thinks the cells need to be studied over a longer
period to ensure they don't have an elevated cancer risk.
"It will still take years of basic research before we become able to
use iPS cells to treat patients," said lead researcher Dr. Shinya
Yamanaka, from Kyoto University in Japan. "We are doing our best to
bring it to clinics as quick as possible."
In experiments with mice, Yamanaka's team reprogrammed adult mouse
liver and stomach lining cells into iPS cells. Using a retrovirus,
the scientists were able to transplant these cells into mice.
Moreover, Yamanaka's team found that these reprogrammed cells avoided
sites that are known to trigger tumors. In fact, mice that received
the iPS remained tumor-free for six months.
Creating embryonic-like stem cells from adult cells may resolve an
ethical dilemma, but whether these cells will act like real embryonic
stem cells is yet to be determined.
"Using adult cells to create what appeared to be embryonic stem cells
solves the ethical dilemma that some people have in creating or
destroying embryos to create stem cells," Taylor said.
"The one thing we can't say yet is that whether these stem cells
generated in this way will have the full potential that embryonic
stem cells have," Taylor said. "They probably won't. But exactly
where that line will be drawn isn't known. If they do almost
everything that embryonic stem cells do, that'll be wonderful. If
they don't, we may still need to consider using embryonic stem cells."
Another expert thinks this is an important step forward, but it's
going to take a long time before cells generated this way can be used
to treat people.
"They're one step closer to solving the problem," said Paul Sanberg,
director of the University of South Florida Center for Aging and
Brain Repair in Tampa. "Now they're going to have to grow the cells,
implant them in animals, and show that they work for diseases," he
said. "There's a lot of experiments to do between making these cells
and putting them in people."
More information
For more about stem cells, visit the International Society for Stem
Cell Research.
http://www.forbes.
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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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