The Role of Telomeres in Aging and CancerThis article describes telomeres -- small stretches of DNA at each end of every chromosome that shorten with each replication until the chromosome is unable to replicate further. This may be a cause of aging, since cells with chromosomes whose telomeres are depleted will not be able to replicate to replace dying cells. In cancer, a chemical called telomerase helps rebuild the telomeres, allowing the cells to reproduce out of control. One approach to fighting cancer may be to stop telomerase from functioning, allowing the cancer cells to age and die. But telomerase occurs naturally in the body, and interfering with it may have unwanted side effects, such as damaging fertility, the healing process, blood cell production and immune system cells. It is not known if shortened telomeres cause aging or are mearly a side effect, but shortened telomeres and age go hand-in-hand. Just as some people age faster than others, some have shorter telomeres than others. Geneticist Richard Cawthon and colleagues at the University of Utah found shorter telomeres are associated with shorter lives. Among people older than 60, those with shorter telomeres were three times more likely to die from heart disease and eight times more likely to die from infectious disease. So we wonder, could lifespan be extended by exposing cells to more telomerase? Or would that cause cancer? Laboratory studies have shown that human cells exposed to telomerase kept dividing well beyond their normal limit, and no cancer developed. But that is a far cry from testing in the human body, where things are much more complex. Perhaps telomerase would cause pre-cancerous cells normally kept in check by the body's immune system to develop into cancer. Or maybe not -- human testing is needed, but would that be ethical? Probably not before we learn more about how telomeres and telomerase function. |
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