We have all been through the ups and downs of “scientific
promise.” The war on cancer officially began in 1971, yet
many of us are still losing loved ones. Gene therapy was the
revolution of the ’90s but has yet to cure diseases. Now the
topic of hope and hype is stem cells. But what are stem cells, and
how can they truly help humans? What about the political, moral and
ethical debate?
First, we need to clear up a little confusion as to the nature
of stem cells. During the development of an organism there are many
complex, highly orchestrated processes involving stem cells. These
cells have the capability of producing copies of themselves when
they divide and also to give rise to different cell types.
There are also many different “kinds” of stem cells.
For example, some stem cells give rise to a particular organ,
others to bone marrow. Not only do these cells play important roles
during normal development; they also can serve as reservoirs to
replace cells that are lost through disease or injury.
One can imagine a whole range of therapies to take advantage of
stem cells. For example, one might transplant stem cells to replace
neurons ““ which can’t be replaced normally ““ lost
in Alzheimer’s or Parkinson’s diseases. Not only can
stem cells be used to replace lost cells throughout the body; they
can also be used to ferry genes and proteins into
difficult-to-reach organs such as the brain. The list of potential
uses for stem cells is limited only by scientists’
imaginations.
Embryonic stem cells are a very special kinds of stem cells.
They are found within the inner cell mass of an egg a few days
after it has been fertilized. Under the right circumstances,
embryonic stem cells are unique in that they can become any cell in
the body ““ including other types of stem cells. So the
embryonic stem cell could be a “magic bullet” cell that
could be manipulated and used in therapies to replace almost any
other cell.
So why aren’t stem cells being used to treat any number of
disorders right now? Well, the answer is that things are much more
complicated than we previously believed. We just don’t know
enough to implement stem cell therapy on a broad scale. We need to
learn more about how to tame stem cells ““ how to get them to
do what we want them to do in the living body. We need to know more
about the potential dangers of stem cell therapy.
We don’t know, for instance, whether implanted stem cells
““ because of their inherent ability to proliferate ““
could form tumors under some circumstances. Work from my laboratory
and several others around the world has documented that some cancer
cells are very similar to normal stem cells. We also need to deal
with the issue of rejection ““ biological, not emotional.
Plus, there are issues of potential infection, disruption of the
normal host environment, and many others. In short, there is a lot
of work to be done prior to the institution of large-scale clinical
trials.
Finally, we must consider the ethical debate. Where are we going
to get the cells from? Tissue-specific stem cells can be obtained
either from a patient’s own tissues, from banked cells (such
as umbilical cord blood) or from aborted fetuses. The use of
fetuses, while generally legal and acceptable, has been challenged
from the standpoint of a general opposition to abortion.
Though embryonic stem cells are a seemingly ideal source of all
kinds of cells, many have raised ethical questions regarding their
use. The current sources of these cells are usually the extra
fertilized eggs that are not used following in vitro fertilization.
Some people are worried that unethical scientists will encourage
more test tube fertilization procedures in order to garner more
stem cells.
Another source of embryonic stem cells could result from the
process of “somatic cell transfer,” a form of cloning.
But another nightmarish moral dilemma could result from this
““ the cloning of a human being. Though successful cloning of
animals has occurred, such is not the case for humans. No rational
scientist or physician would condone such a process, and there is
reason to believe that it would not be successful, resulting in
ill, malformed, non-viable offspring.
Because of ethical and moral concerns, in August 2001 the
president issued an executive order placing limits on the use of
federal funds for stem cell research. This order states that the
only human embryonic stem cell research that can be federally
funded is a limited set of lines that were established prior to the
executive order. Though these lines are only available through
government application, their availability has certainly allowed
for significant scientific progress in human stem cell biology.
Still, the restrictions place a significant impediment to the
development of these cells for therapy. First, very few cell lines
are actually broadly available. Second, the process of application
is cumbersome. Most importantly, the existing stem cell lines do
not represent the diversity of human genetics and do not allow for
us to determine whether effects in one line will be similar to
others.
Due to the restrictions on federally funded stem cell research,
several companies and private institutions are developing
additional embryonic stem cell lines. While this is a positive
development for stem cell research, practically speaking it will
still be difficult for any federally funded scientist to make use
of them because it requires separate facilities with no mixing of
federal and private funds.
On the other hand, companies and private individuals will be
able to continue embryonic stem cell research without federal
oversight of both scientific and ethical practices. I view this as
the most negative outcome of the executive order.
This is where California’s Proposition 71 comes into play.
This measure would create a bond initiative for the funding of stem
cell research. It would earmark funds for building stem cell
research infrastructure and would support scientific endeavors that
are not likely to be funded by the federal government.
It would still not allow the unauthorized use of federal funds
for research, but the way the proposition is written and intended
would allow for a much easier separation of funds by allowing for
the construction of separate facilities for embryonic stem cell
research at California universities.
It will also allow for the creation of a more streamlined
process for getting funds into the hands of stem cell researchers.
Currently, it takes about a year from the submission of a grant
application to the delivery of funds. This is too long, given the
rapid pace of scientific progress.
The university and its employees acting on behalf of the
university cannot by law endorse the measure. But many of us as
private individuals have offered our support for this proposition.
The voters will have to explore their own value systems and decide
whether stem cells’ promise for cures is worth the
considerable investment.
Kornblum is a professor of molecular and medical
pharmacology and pediatrics.