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Science Forum Index » Medicine - Cancer Forum » Stem Cell - Medical history suggests it may be wise not to b
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 Posted: Wed Nov 29, 2006 8:12 am |
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http://www.timesonline.co.uk/article/0,,8122-2442876,00.html
November 08, 2006
It is a therapy that holds promise, but it is not without numerous risks
Commentary by Nigel Hawkes
Stem cells are the cutting edge of medical research, but there are two
schools of thought about how to proceed.
All agree that the potential is huge. Stem cells have the capacity to
develop into any of the specialised cells of the body, thus offering for
the first time a means of repairing damage caused by injury, accident or
disease.
But the issue is whether we should plunge ahead with clinical trials while
stem cells are only partly understood, or hold back and do years of
careful scientific study first.
The new trial belongs — with no offence to anybody involved — to the
“quick and dirty” school. Medical history is full of examples of
treatments that have worked before they were fully understood, from
Jenner’s vaccination against smallpox onwards, so there is good precedent
for this approach.
Although described as a stem-cell trial, nobody really knows if the
material to be injected actually contains stem cells able to develop into
muscle cells. Earlier work suggests that there is a benefit from the
treatment, but it is hard to prove that this is how it occurs.
An alternative possibility is that the bone marrow cells contain growth
factors that encourage the development of new blood vessels in the heart,
or even that sticking the needles into the heart produces a beneficial
mechanical effect. Frankly, nobody really knows.
To some, this is a call for caution. They argue that the stem cells could
develop undesirably, into immune system cells triggering inflammation, for
example, or even into tumour cells.
It is true that the German trials give no indication this will happen, but
we have not had enough time to be absolutely sure.
Among those arguing for more research is Roger Pedersen, of the University
of Cambridge.
Professor Pedersen has said that we know little about what triggers cells
to differentiate, and that “simple alchemy” will not work: “We’re going to
have to do some science.”
On the other side of the argument, Anthony Mathur, senior lecturer and
consultant cardiologist at Bart’s, argues: “If we were to wait for the
mechanisms of every drug to be worked out, we would be withholding a lot
of wonderful treatments that are already in use.”
There are other approaches, such as taking immature muscle cells from the
leg and injecting them into the heart. Tony Gershlick, a consultant
cardiologist from Leicester, is trying this method, reasoning that cells
already differentiated into muscle are more likely to behave as muscle.
The risk of holding back is that people will lose enthusiasm — while the
risk of plunging on is that something nasty will happen and stop the field
in its tracks.
Gene therapy, greeted a decade or more ago with all the same enthusiasm as
stem-cell therapy today, is now under a cloud. It did not work and one
patient in the US died as a side-effect of using a virus as a vector to
carry the right gene to his lungs.
It would be wonderful if the London trial did produce an easy way to limit
the damage done by heart attacks. Medical history suggests it may be wise
not to be overoptimistic. |
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