Some biotechnology companies claim that a ban on producing human embryos through cloning would stall important research in generating "stem cells" to cure a variety of diseases [Cong. Record, 2/5/98, S425]. To put this claim in perspective:
- Cloning is desired as a source of "customized stem cell lines" which would be an exact genetic match to each individual patient with a given disease. But this would require each individual patient to undergo somatic cell nuclear transfer to produce one or many living human embryos who genetically are the patient's identical twin sisters or brothers. These embryos would then be destroyed to provide embryonic stem cells.
Two methods of obtaining the cells have been described. In one, the embryo is allowed to develop normally for a week or two to the blastocyst stage, at or after the usual time of implantation in the mother's womb; then this embryo, consisting of hundreds of cells, is dissected for its stem cells. The other method is to introduce molecular signals into the embryo's environment to "trick" its cells into departing from normal development and instead producing "a mass of undifferentiated tissue," which can then be reprogrammed into various kinds of cells [Lee Silver, Remaking Eden: Cloning and Beyond in a Brave New World (Avon Books 1997), p. 128]. In either case, the living embryo is destroyed.
- This avenue for providing medical benefits has been described even by supporters as "largely conjectural" (J. Kassirer and N. Rosenthal, in New England Journal of Medicine, March 26, 1998, p. 905). President Clinton's National Bioethics Advisory Commission called it "a rather expensive and far-fetched scenario." The Commission observed: "Because of ethical and moral concerns raised by the use of embryos for research purposes it would be far more desirable to explore the direct use of human cells of adult origin to produce specialized cells or tissues for transplantation into patients."
The Commission outlined three alternative avenues for promising research using stem cells that do not involve human cloning, two of which do not use human embryos at all (Cloning Human Beings: Report and Recommendations of the National Bioethics Advisory Commission, June 1997, pp. 30-31).
- The Commission's Alternatives
- Generating "a few, widely used and well characterized human embryonic stem cell lines, genetically altered to prevent graft rejection in all possible recipients." This would raise its own ethical objections because it may involve producing and destroying some human embryos at the outset; but it does not require somatic cell nuclear transfer, or the creating and destroying of genetically related embryos for each individual patient.
- Stimulating "proliferation and differentiation of the quiescent stem cells which are known to exist in many adult tissues, including even the nervous system." Such stem cells could be "customized" to each individual patient and would not be from embryonic sources.
- Identifying "methods by which somatic cells could be 'de-differentiated' and then 're-differentiated' along a particular path." This would permit "the growth of specialized cells compatible with a specific individual person for transplantation." While at present this option is considered speculative, its feasibility is now enhanced by the central finding of the research that produced "Dolly" the sheep: An adult body cell can be "de-differentiated" surprisingly easily and regressed all the way back to a stage at which it can provide the nucleus for a new developing embryo. The question is: Can this regression be done to a point short of this, so an adult cell becomes the basis for cells that are like embryonic stem cells but never came from an embryo?
Other Alternatives (not explicitly cited by the Commission)
- There are other promising sources of pluripotent (not embryonic) stem cells for treatment of disease. One example is hematopoietic (blood cell producing) stem cells from bone marrow or even from the umbilical cord blood in live births. These cells are already widely used in cancer treatment and in research on treating leukemia and other blood diseases. Their versatility was recently found to be even greater than once thought. For example, given the right environment bone marrow cells can be used to regenerate muscle tissue, opening up "a whole avenue of potential therapies that didn't exist before" for muscular dystrophies ("Bone Marrow Cells May Provide Muscle Power," Science, 6 March 1998, p. 1456).
- An enormously promising new source of stem cells is fetal bone marrow, which is "23 times more effective than adult marrow and eight times better than umbilical cord blood." Recent studies show that "miscarriages can provide enough cells for transplantation if we would collect them effectively and store them in banking" ("Fetal marrow transplants promising against disease," Detroit News, May 4, 1997). A stem cell line from such sources could provide a continuous supply of stem cells for research. It seems fetal bone marrow cells do not provoke the same immune reactions as adult or even newborn infant cells. This is true whether the unborn child is the donor or the recipient -- that is, fetal cells can be used to treat adults, or adult bone marrow cells can be used to treat a child in the womb, without harmful immune reactions (see Jack Goldberg, "Fetal stem cell therapy," in Jauniaux et al. (eds.) Embryonic Medicine and Therapy [Oxford U. Press 1997], pp. 474-80).
- Other approaches to tissue regeneration involve the growth factors (activators and inhibitors of cell division and growth) responsible for the development of various cell types and tissues. These factors may be used to manipulate the cells of a tissue along the spectrum of differentiation, without the need to create stem cells first. Use of these factors has already shown promise in the clinical setting, as a vascular growth factor has been successful in saving the legs of three patients who had potentially lethal blood clots requiring amputation: Application of the growth factor allowed new vessels to grow around the clots and restore circulation to the legs (see Circulation, 3/31/97, pp. 1114 ff.). Now such factors have been used to generate new blood vessels to human hearts in 20 patients ("Drug Stimulates Growth of Heart Blood Vessels," Washington Post Health, Feb. 24, 1998, p. 5).
- Cells of different kinds are now being genetically engineered to repair damaged organs, especially by injecting them with an "oncogene" (a type of gene that causes cancer cells to reproduce rapidly). Heart cells produced with this gene can "survive and beat like normal heart muscle cells" when transferred to a damaged heart ("Study: Cells Repair Heart Damage," Associated Press, March 17, 1998).
- Methods are being developed for growing entire replacement organs, to treat children before or after birth. Cells of the needed variety are extracted from the child and cultured, then grown into organs in the laboratory using biodegradable scaffolds. The researchers say they hope to receive FDA approval for routine use of the technology within five years. They add that "there are no ethical concerns doing this treatment, as there are about some other procedures [such as human cloning]" ("Doctors grow animal organs," Washington Times, July 23, 1997, pp. A1, A18; also see Ben Bova, "Lost a lung? Grow your own," in USA Today, Feb. 24, 1998).
- Promising avenues have been opened up in research on cancer and diseases of aging by studies of telomerase, dubbed by some "the immortality enzyme." It protects and rebuilds telomeres, the protective caps on the ends of chromosomes which deteriorate as we age. It is now believed that telomerase activity is required for the uncontrolled growth of most cancerous tumors. Mastering this enzyme may enable researchers to (a) inhibit its activity in cancer cells and reduce or stop tumor growth, and (b) to use telomerase itself in a controlled way to help rejuvenate and regenerate damaged tissues and organs. (J. Madeleine Nash, "The Immortality Enzyme," Time, Sept. 1, 1997)
The alternatives outlined by President Clinton's Commission are as follows:
In short: The claim that human embryo cloning is needed to advance promising medical research in cancer, degenerative diseases, etc. is simply false.
Even if the use of somatic cell nuclear transfer to create and cannibalize human embryos were to enable more rapid development of some limited branches of research (a proposition for which there is no firm evidence), the words of Professor Patricia King, co-chair of the NIH Human Embryo Research Panel, would remain valid:
"The fertilization of human oocytes for research purposes is unnerving because human life is being created solely for human use.... In particular, the public should be assured that embryos will not be created because such creation is the most convenient means of answering important scientific questions that can be answered -- perhaps more slowly -- in other ways." [Final Report of the Human Embryo Research Panel (NIH, Sept. 27, 1994), p. 97]