HUMAN cloning is finally here. But while the Korean team has overcome some technical obstacles, the political barriers to realising cloning鈥檚 medical potential remain. Many people object to the idea of any human cloning research, even for medical reasons, claiming it will inevitably open the door to reproductive cloning or, more generally, that experimenting with embryos is immoral. I believe the opposite: cloning promises such great benefits that it would be immoral not to do it.
That is why a number of UK labs, including my own, plan to apply to the relevant authorities for permission to study human cloning here in the UK. And while I remain implacably opposed to reproductive cloning per se, I do envisage that producing cloned babies would be desirable under certain circumstances, such as preventing genetic disease.
The therapeutic promise of human cloning lies in embryonic stem cells, or ES cells. Derived from 6-day-old embryos, ES cells can form any cell type in the body, such as nerve or blood cells. It is possible to extract such cells from spare IVF embryos. But this has a drawback. Researchers have no control over the genetic make-up of the cells in these embryos. This presents a problem if such stem cells are used to regenerate tissue destroyed by accident or disease: if they don鈥檛 genetically match the patient, they could trigger an immune response.
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Cloning, however, could overcome this problem and provide patients with tissue-matched stem cells. Although critics often claim therapeutic cloning would be too expensive and impractical, I think many of the problems can be tackled. But even if therapeutic cloning doesn鈥檛 make it to the clinic, there are other compelling reasons why we need to develop human cloning technology.
The most imminent development is likely to be using cloning to study disease, particularly inherited conditions. At present, it is often impossible to safely take samples of affected cells from living patients, especially those suffering from genetic diseases that affect the brain and heart such as Parkinson鈥檚 disease or inherited heart arrhythmias. What鈥檚 more, by the time a patient develops symptoms, their disease has been progressing for some time. This makes it hard to find out whether the changes we see in their cells are directly related to the cause of that disease, or whether they are merely secondary effects. Ideally, we would like to be able to monitor the progress of the disease as it develops inside the cells, so that we can home in on its cause.
Cloning would allow us to recreate these diseased cells, with the same genetic make-up, outside the patient鈥檚 body, and watch them develop from scratch. In principle, we could take, say, a skin cell, make a cloned embryo and then use its stem cells to create cultures of any cell type we wanted. These cell cultures would give us the power to do the kind of sophisticated genetics that we can often only do in animals.
Our team plans to start cloning ES cells from people with the neurodegenerative condition ALS, or Lou Gehrig鈥檚 disease. This progressive and fatal paralysis strikes people in middle age, robbing them of their ability to move, speak or breathe unaided. It is incurable and most victims die within five years of being diagnosed.
The disease affects nerve cells called motor neurons, which are found in the brain and spine. Owing to their location, it is impossible to remove living motor neurons for study. Partly because of this, we have little idea of what causes ALS. We do know that about 10 per cent of cases are inherited and that a fifth of these are caused by mutations in a gene called SOD1. But the cause of the majority of cases is a mystery.
Using cloning to create cultures of motor neurons from such patients would help us to track down the causes of the disease. What damages these cells? Does the damage come from within, or from faulty interactions with other cells? What鈥檚 more, being able to study which genes are switched on or off in such cells could tell us what might be going wrong in the 90 per cent of ALS patients who did not inherit their condition. Cloning might even give us the chance to test new therapies.
For all these reasons, my colleagues and I are preparing to apply for a licence to clone cells from ALS patients in the UK. As well as benefiting ALS research, we hope our techniques could be adapted for research into other neurodegenerative diseases, such as Parkinson鈥檚 and Alzheimer鈥檚.
Human cloning also has the potential to revolutionise other areas of biomedical research. One key area is developing and testing new drugs. It is a surprising fact that bad reactions to prescription drugs, even when those drugs are used correctly, kill thousands of people every year. At the moment, drug companies have no reliable way of predicting who will react badly.
In most cases, the variation from person to person is due to differences in the genes that code for the liver enzymes that break down drugs. Human cloning could help in a number of ways. Researchers could clone and create cultures of liver cells from families who had suffered bad reactions to drugs. Such reactions often involve many different enzymes, and being able to study gene activity in the liver cells of susceptible people would let researchers identify variations in the key enzymes.
Findings from such research could allow drug companies to test their new drugs more safely and effectively by letting them screen out susceptible individuals from their trials. Such patients could also be warned that certain drugs are not suitable for them. Drug companies currently use post-mortem liver samples as part of their extensive preclinical drug safety tests. However, these samples are often pooled, and the drug sensitivities of the donors are unknown.
Although research is likely to be the first beneficiary of human cloning, the most exciting developments will come as 鈥渢herapeutic鈥� cloning: ways to repair or cure diseased organs or repair genetic defects. Transplants of stem cells that are genetically identical to their recipients promise new treatments, such as repairing damaged heart muscle following a heart attack.
Of course, this is still some way off. We have technical problems to solve, such as how to get human ES cells to reliably form different cell types. There are safety aspects, too: we need to know these cells won鈥檛 cause problems such as cancer. Lastly, human eggs are in short supply and this threatens to limit the use of therapeutic cloning. However, these problems can be addressed.
It is true that therapeutic cloning is unlikely to be practical for routine use. But not all diseases are equal in terms of expense, and treatments could be targeted to maximise benefit. An older person with heart disease, for example, could be treated with stem cells that are not a genetic match, take drugs to suppress their immune system for the rest of their life, and live with the side-effects. A younger person might benefit more from stem cells that match exactly.
What鈥檚 more, therapies are likely to become cheaper and easier to use as the technology progresses. One way of overcoming the human egg shortage could be to use cow eggs, strictly for making stem cells. I personally wouldn鈥檛 have an issue with it from a moral point of view because essentially, you can just see eggs as bags of proteins. But you would have to be even more careful about the safety aspect.
The most radical use of human cloning technology is to treat inherited disease 鈥� particularly those affecting whole organs that can鈥檛 be replaced by stem cells, such as the lungs. It would also solve many of the problems that have recently plagued gene therapy, such as the risk of causing cancer.
At the moment, people carrying certain genetic diseases can try to avoid passing them on by undergoing IVF and having the embryos tested so that only healthy ones are implanted. But if none of the embryos created is suitable, the couple face another round of invasive treatment to create more.
There is another way. In March 2003, Thomas Zwaka and James Thomson at the University of Wisconsin in Madison reported that they had found a way of precisely replacing faulty genes in ES cells with healthy copies. This precision means there is little chance of a gene landing in the wrong place and causing problems. But how can the therapeutic gene be sent to every cell in the body?
This is where cloning could help. First, you would create an ordinary embryo using IVF. Then you would take the ES cells from it and correct the diseased gene with genetic engineering. However, ES cells by themselves cannot be used to reconstitute the embryo they came from. To do this, you would take the nucleus from one of these corrected ES cells and transfer it into an egg. The resulting embryo would be the identical twin of the original embryo, but with the diseased gene corrected in every one of its cells. This embryo could then be implanted in its mother鈥檚 womb to develop into a baby. Although such a child would be a human clone, it would be a clone of a new individual, not a clone of one of its parents. This form of cloning would not create the same ethical and social problems as reproductive cloning.
Of course the question of safety still applies. For now, we still know far too little about what happens to the genes in a nucleus during cloning to consider creating a child in this way. But that should not hold us back from developing a technology that has such great potential to help so many people. Human cloning must not be banned. It could save many thousands of lives.