STEM CELLS are about to have a big impact on medicine, says Irving Weissman
of Stanford University Medical School. He has been working on haematopoietic
stem cells鈥攖he stem cells that give rise to all the cells of the blood
system鈥攆or the past 30 years. Now he sees basic research turning into
possible treatments for cancer, autoimmune diseases and conditions such as
Parkinson鈥檚 disease.
Research into improving cancer therapy is most advanced. Conventional
therapies decimate blood stem cells as well as killing cancer cells. So before
treatment, doctors take a special blood sample containing stem cells, so that
they can re-infuse them afterwards. But in many patients, cancer cells
contaminate the sample and allow the cancer to re-establish itself later.
Now Systemix, a company Weissman co-founded, may have cracked the problem
with a technique for isolating stem cells. The first clinical results due to be
published later this year by his colleague Richard Nigrim, are encouraging. 鈥淣ot
one sample contained detectable breast cancer cells,鈥� says Weissman.
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Other uses for stem cells are less developed but have tremendous potential.
Weissman and Judy Shizuru have found that they can be transplanted between
genetically different mice without rejection. That property has enabled the
researchers to tackle one autoimmune disease, type I diabetes, in which the
body鈥檚 own T cells attack the insulin-producing islet cells in the pancreas.
The researchers took mice that were developing diabetes and destroyed all
their T cells, then injected them with stem cells from a healthy animal. The
animals grew new T cells, and no more of their islet cells were destroyed.
Even more exciting, Shizuru has found that in mice with another form of
diabetes it is possible to transplant both stem cells and new islet cells. For
reasons that aren鈥檛 yet clear, stem cells help the mouse tolerate the transplant
of the foreign islet cells. 鈥淵ou can induce tolerance and you can reverse an
autoimmune state,鈥� exclaims Weissman. Other autoimmune diseases now in
Weissman鈥檚 sights include multiple sclerosis and rheumatoid arthritis.
That鈥檚 not the end of the story. Five years ago, Weissman had the radical
idea that 鈥渙rgan systems besides blood might have their own stem cells that are
needed during fetal life for their generation and during adult life for their
continued regeneration鈥�. Weissman formed a company to pursue the idea, and this
year one of its researchers, Nobuko Uchida, isolated prospective brain stem
cells from human fetuses. These cells appear to be able to develop into many
kinds of neural cells, and could eventually be used to treat disorders such as
Parkinson鈥檚 disease.