Send in the Clones

Ronald Bailey from the June 1998 issue

Remaking Eden: Cloning and Beyond in a Brave New World, by Lee Silver, New York: Avon Books, 317 pages, $25.00

Clone: The Road to Dolly and the Path Ahead, by Gina Kolata, New York: William Morrow & Co., 276 pages, $23.00

Cloning human cells could one day save your life and the lives of the people you love. Yet Congress seems hellbent on stopping the medical advances that cloning can make possible. Congress is responding to polls that show most Americans are opposed to the cloning of human beings. But carelessly crafted legislation would restrict not only research leading to the birth of cloned people but research that could find cures for cancer, genetic diseases such as cystic fibrosis, and damaged hearts, livers, and brains.

Now readers interested in this topic have two good, complementary introductions to the science, morality, politics, and future of animal and human cloning. Gina Kolata, who works for The New York Times, is one of the best science reporters in America. Lee Silver is a professor in the departments of molecular biology, ecology, and evolutionary biology and the program in neuroscience at Princeton University. Kolata does a particularly good job of describing the science that led up to Dolly, while Silver explores the futuristic medical and reproductive techniques that cloning makes possible.

In February 1997, the Roslin Institute in Scotland, an obscure farm animal research facility, announced that it had succeeded in cloning a sheep from an adult, differentiated cell. The cloned sheep, Dolly, made headlines around the world and launched a fierce debate over the potential uses for this new technology. The breakthrough showed for the first time that genetic information encoded in the DNA of an adult cell could be "reset" and made young again. Once reset, the cells with rejuvenated DNA could produce all of the cells needed to grow a complete organism. "[S]uperficially, it's a step toward immortality," explained Ronald James, whose company, PPL Therapeutics, paid for the cloning research. "And if you take a step toward immortality, everybody stops and takes notice."

Since Dolly, much has happened. President Clinton imposed a ban on federally funded cloning research, and Pope John Paul II declared that each human being has a "right to a unique human genome." UNESCO has issued a Universal Declaration on the Human Genome and Human Rights declaring, "Practices which are contrary to human dignity, such as reproductive cloning of human beings, shall not be permitted." The European Union has also adopted a ban.

In the United States, the National Bioethics Advisory Commission issued a report last June calling for federal legislation to ban human cloning for three to five years. "Freelance" physicist Richard Seed created a mini media firestorm in December when he said he was looking for investors to open a cloning clinic. Congressional hearings have been held, and in February the U.S. Senate debated a bill that would ban cloning research on human embryos. Throughout it all, bioethicists have been offering grim warnings about the moral dangers of human cloning.

As Kolata shows, the science of cloning is fascinating. The achievement of Ian Wilmut and his colleagues at the Roslin Institute was the culmination of decades of research on eggs, embryos, and in vitro fertilization. The researchers inserted the nucleus of an adult udder cell into a sheep egg cell whose nucleus had been removed, a technique called "somatic cell nuclear transfer." Once the egg with its new nucleus began to divide, Wilmut implanted the developing embryo into the uterus of another sheep, the surrogate mother who gave birth to Dolly.

If it can be done with sheep, there appears to be no biological reason it cannot be done with human beings. Putting that possibility aside, however, cloning techniques could be the basis for a variety of life-saving medical treatments. Cloning probably will first be used to create animals that excrete important therapeutic human proteins, such as insulin or interferons, in their milk. This is what Wilmut was trying to do.

Another exciting possibility is that doctors, using somatic cell nuclear transfer, could create embryonic stem (ES) cells, the self-renewing precursors to blood, skin, heart, and nerve cells.

The treatment for leukemia, a cancer in which the bone marrow overproduces white blood cells, could be revolutionized. Today, one of the more successful treatments involves the destruction of a patient's bone marrow through chemotherapy and the transplantation of healthy marrow cells taken from a closely matched donor. The problem is that many leukemia patients die because they can't find appropriate donors. With cloning, healthy marrow cells that are perfect genetic matches for a leukemia patient could be created from the patient's own cells. Doctors could take a skin cell nucleus and implant it in an enucleated human egg, resetting the cell's DNA. Once reset, the cell could become an embryonic stem cell. After the ES cells began to divide, they could be treated with hormones that would cause them to develop into marrow cells, which could then be returned to the patient.

Similarly, islet cells could be created from the skin cells of a diabetic and returned to the patient's pancreas, where they would produce insulin. Eventually, ES cells could be turned into healthy heart or liver cells that could be used to repair tissue damaged by heart attacks or hepatitis.

Congress is considering several bills, sponsored mainly by Republicans, that would ban the research that could lead to these new treatments. Stampeded by the anti-abortion lobby, congressional Republicans want to treat ES cells like human embryos, even though their ultimate form depends entirely on the intentions of the patients and doctors who create them.

Silver highlights the important distinction between growth and development. ES cells can grow and divide into millions of identical cells, but they do not develop into any particular kind of cell until told to do so through biochemical signals. In a sense, the creation of ES cells in vitro would be like enhancing the natural production of ES cells in vivo. ES cells created from a patient's skin to treat disease are no more ethically problematic than veins taken from his legs to be used in a heart bypass operation. Both are the patient's cells, and both are being used for purposes different from their original function.

Down the road, it may be possible to reset cells without using enucleated human ova. Scientists in Wisconsin are doing some promising work using cow eggs to rejuvenate DNA taken from other species. But right now, researchers need to use human eggs in order to learn about the process of resetting cells. Such knowledge could lead to cures for cancer by teaching doctors how to turn off the uncontrolled growth of cancer cells, avoiding the relatively crude radiation and chemotherapy treatments used today. If research using human ova is blocked, the development of new treatments will be delayed, and many people who might have lived will die.