“Therapeutic” Cloning Lags Behind Adult Stem Cell Success

Date: 03/08/2002

A report today in the journal Cell, announced by the Associated Press, purports to use “therapeutic” cloning to partially correct a genetic based immune system defect in mice. However, this report comes years after “remedied” adult stem cells – not embryonic stem cells–were used to cure human infants of severe combined immunodeficiency syndrome, in the first successful clinical trials in human gene therapy. In the cloning experiments, performed by researchers at the Whitehead Institute (W.M. Rideout et al., “Correction of a genetic defect by nuclear transplantation and combined cell and gene therapy,” Cell Immediate Early Publication, published online March 8, 2002) mice with an immune defect causing some white blood cells to be missing were cloned, and the cloned mouse embryos were destroyed for their stem cells. Since the embryonic stem cells were genetically identical to the mice (supposedly to prevent transplant rejection), they carried the same genetic defect. The researchers used gene therapy to fix the defective gene in the embryonic stem cells. Several different attempts were then made to correct the immune defect in the mice using these stem cells. In one experiment, the “repaired” embryonic stem cells were differentiated in culture into blood-forming cells and these were transplanted into the defective mice. The authors note that this showed little to no success (though the data are not shown in the paper). Next they tried reducing the number of those cells in the recipient mice that were blocking successful transplant. Again, this approach was essentially negative (again, the data are not shown in the paper). Finally, the researchers transplanted the “repaired” blood-forming cells into a different mutant mouse that had the same genetic defect, but also lacked the cells that had been destroying the transplanted cells. This situation resulted in a modest restoration of the missing blood cells, but at less than one-tenth the amounts in normal mice. However, the researchers were able to restore normal levels of the missing blood cells by first using the “repaired” embryonic stem cells to grow born mice, then using the bone marrow stem cells or blood stem cells (similar to umbilical cord blood) of those born mice for the transplant. In other words, the researchers were most successful when they resorted to using adult stem cells. The published scientific paper actually shows that the “repaired” embryonic stem cells from cloned embryos were unsuccessful in treating the gene defect in the mice that provided the donor cells for cloning. The authors note: “Our results raise the provocative possibility that even genetically matched cells derived by therapeutic cloning may still face barriers to effective transplantation for some disorders.” This study also bears out the enormous global risk to women’s health entailed in the speculative idea of “therapeutic cloning” to treat diseases in humans. Only 1 embryonic stem cell line was successfully cultured, starting with 202 cloning attempts. Even if the experiment had been successful, the number of human eggs needed for such treatments would translate to 303 million human eggs needed to treat the 1.5 million Parkinson’s patients in the U.S., and over 3.2 billion human eggs needed to treat the 16 million diabetes patients in the U.S. Far from being a step forward, this report shows that cloning is years behind the far more successful advances using adult stem cells, including their use to reverse immune deficiencies in humans. As reported in April 2000 in the journal Science, French scientists restored the immune systems of 3 infants with severe combined immunodeficiency (the “bubble boy syndrome”) using gene therapy with the patients’ own bone marrow stem cells. Researchers removed stem cells from the infants’ bone marrow, added a working copy of the gene to the cells’ DNA, and injected the repaired stem cells back into the infants. Since the procedure used the patients’ own cells, there was no problem of transplant rejection. After treatment, the numbers and function of the patients’ immune cells were restored to normal levels, and the children were living at home and developing normally with no further treatment (M. Cavazzana-Calvo, et al., “Gene Therapy of Human Severe Combined Immunodeficiency (SCID)-X1 Disease,” Science 288, 669-672, April 28, 2000). Far from showing the supposedly superior benefits of stem cells from cloned embryos, the new study shows that this approach continues to lag behind adult stem cell advances – even in mice, where embryonic stem cell research has been pursued for over twenty years. Adult stem cells are successfully treating real human children with serious diseases.

Do No Harm: The Coalition of Americans for Research Ethics is a national coalition of researchers, health care professionals, bioethicists, legal professionals, and others dedicated to the promotion of scientific research and health care which does no harm to human life. Do No Harm rejects the course of action taken by the National Institutes of Health, to support destructive human embryo stem cell research. Instead, our government should promote adult stem cell research which protects the inviolability of all individuals, rejects harming some for the potential benefit of others, and holds as much, if not more promise, for medical progress.