Physics of the Future: How Science Will Shape Human Destiny and Our Daily Lives by the Year 2100

patients show that their immune cells did indeed incorporate the new gene, as planned, hence activating their immune systems.
    But there have been setbacks. In 1999, at the University of Pennsylvania, one patient died in a gene therapy trial, causing soul-searching within the medical community. It was the first death among the 1,100 patients undergoing this type of gene therapy. And by 2007, four of the ten patients who had been cured of one particular form of SCID developed a severe side effect, leukemia. Research in gene therapy for SCID is now focused on curing the disease without accidentally triggering a gene that can cause cancer. To date, seventeen patients who suffered from a different variety of SCID are free of both SCID and cancer, making it one of the few successes in this field.
    One target for gene therapy is actually cancer. Almost 50 percent of all common cancers are linked to a damaged gene, p53. The p53 gene is long and complex; this makes it more probable that it will be damaged by environmental and chemical factors. So many gene therapy experiments are being conducted to insert a healthy p53 gene into patients. For example, cigarette smoke often causes characteristic mutations in three well-known sites within the p53 gene. Thus gene therapy, by replacing the damaged p53 gene, may one day be able to cure certain forms of lung cancer.
    Progress has been slow but steady. In 2006, scientists at the National Institutes of Health in Maryland were able to successfully treat metastatic melanoma, a form of skin cancer, by altering killer T cells so that they specifically targeted cancer cells. This is the first study to show that gene therapy can be successfully used against some form of cancer. And in 2007, doctors at the University College and Moorfields Eye Hospital in London were able to use gene therapy to treat a certain form of inherited retinal disease (caused by mutations in the RPE65 gene).
    Meanwhile, some couples are not waiting for gene therapy but are taking their genetic heritage into their own hands. A couple can create several fertilized embryos using in vitro fertilization. Each embryo can be tested for a specific genetic disease, and the couple can select the embryo free of the genetic disease to implant in the mother. In this way, genetic diseases can gradually be eliminated without using expensive gene therapy techniques. This process is currently being done with some Orthodox Jews in Brooklyn who have a high risk of Tay-Sachs disease.
    One disease, however, will probably remain deadly throughout this century—cancer.
    COEXISTING WITH CANCER
    Back in 1971, President Richard Nixon, amid great fanfare and publicity, solemnly announced a war on cancer. By throwing money at cancer, he believed a cure would soon be at hand. But forty years (and $200 billion) later, cancer is the second-leading cause of death in the United States, responsible for 25 percent of all deaths. The death rate from cancer has dropped only 5 percent from 1950 to 2005 (adjusting for age and other factors). It is estimated that cancer will claim the lives of 562,000 Americans this year alone, or more than 1,000 people per day. Cancer rates have fallen for a few types of the disease but have remained stubbornly flat in others. And the treatment for cancer, involving poisoning, slicing, and zapping human tissue, leaves a trail of tears for the patients, who often wonder which is worse, the disease or the treatment.
    In hindsight, we can see what went wrong. Back in 1971, before the revolution in genetic engineering, the causes of cancer were a total mystery.
    Now scientists realize that cancer is basically a disease of our genes.Whether caused by a virus, chemical exposure, radiation, or chance, cancer fundamentally involves mutations in four or more of our genes, in which a normal cell “forgets how to die.” The cell loses control over its reproduction and reproduces without limit, eventually killing the patient. The fact that it takes a sequence of four or more defective genes to cause cancer probably explains why it often kills decades after an original incident. For example, you might have a severe sunburn as a child. Many decades later, you might develop skin cancer at that same site. This means it probably took that long for the other mutations to occur and finally tip the cell into a cancerous mode.
    There are at least two major types of these cancer genes, oncogenes and tumor suppressors, which function like