Magazine article Science News

Cancer Linked to Aging DNA Repair Ability

Magazine article Science News

Cancer Linked to Aging DNA Repair Ability

Article excerpt

Despite decades of progress in learning how chemicals, sunlight, and other environmental factors can increase one's risk of developing cancer, the reasons that some people develop tumors and others do not remain mysterious.

Now, researchers studying people with skin cancer have found new evidence that individuals differ not just in their susceptibility to these factors, but also in their ability to fix damaged genes. In addition, adults lose about 1 percent of their capacity to repair DNA each year, says Lawrence Grossman, a molecular biologist at Johns Hopkins University in Baltimore.

This loss may help explain why aging is a risk factor for cancer, adds Qingyi Wei, a molecular epidemiologist at Johns Hopkins.

Wei, Grossman, and their colleagues studied 88 people with basal cell carcinoma, an easily observed and readily treated cancer. The researchers also looked at DNA repair in 135 individuals with mild skin problems but not skin cancer. All study participants were Caucasians between the ages of 20 and 60. Researchers took blood samples and medical histories from them and asked questions about the number of severe sunburns they had had and the incidence of cancer in their families. Dermatologists evaluated the participants' skin condition.

The researchers then take an unusual approach to assessing an individual's ability to fix broken genes, Grossman says. They inject a small piece of genetic material into white blood cells extracted from each participant. The genetic material contains a mutant bacterial gene that normally codes for an enzyme the white blood cells never make. If the cells fix the gene, the gene then causes the cells to produce the enzyme. Forty hours later, the researchers measure the activity of that enzyme, which signals how well the cells have mended the gene.

The study revealed that young people with this skin cancer had the repair capacity of someone 30 years older. …

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