By age 60, the probability of eventually developing cancer is nearly one in two for men and one in three for women. The challenge of cancer is likely to increase as more people live longer and the Baby Boom generation becomes elderly.
So why don't we all just take telomerase — an enzyme that rebuilds telomeres — and avoid cell senescence? It's not that simple. As DePinho explains, there is one category of cells containing high levels of telomerase that is worthy of note: the cancerous ones. In abnormal cells, telomerase enables cancer cells to keep dividing long past the usual limits of growth.
In addition, DePinho and K. Lenhard Rudolph, M.D., have shown that telomeres may not have a direct effect on aging at all. Mice bred with short telomeres do not age any more quickly than a normal group of mice, the DFCI researchers reported in early 1999. Rather, DePinho says, telomeres may have an indirect effect on aging and cancer because they protect the rest of the genome from damage.
"Telomeres are not the clock," he says, "but they probably do enable cells to proliferate properly and respond to acute and chronic stresses often associated with aging."
Keeping DNA protected from damage and endowing cells with proliferative potential may provide a means to slow some aspects of aging, as well as lessening cancer risk. Epidemiological studies indicate that simple practices, such as avoiding tobacco, sunlight, and other environmental cancer-causing agents; moderating weight, exercising, and eating lots of fresh fruits and vegetables could reduce the incidence of cancer by as much as two-thirds nationally.
The American Cancer Society estimates that 187,000 deaths, or about one-third of the total deaths from cancer in 1999, were related to nutrition; another 173,000 were attributed to tobacco use. And thousands more were the result of too much sun, too little exercise, excessive alcohol use, and unprotected exposure to sexually transmitted, cancer-causing viruses.
Time marches on, but a better understanding of how aging and cancer are linked may help us remain healthier as we grow older.
Bruce Ames, Ph.D., who has been studying the mechanisms of cancer and aging at the University of California, Berkeley, since the late '60s, argues strongly that eating fruits and vegetables daily restores some 40 micronutrients that can protect DNA against the kind of damage that promotes genetic instability, aging, and cancer. Even if you can't or won't eat fruits and vegetables, Ames recommends taking a daily multivitamin containing folic acid; vitamins B12, B6, C, and E; as well as iron, zinc, and niacin.
People Joe Alessi's age may think they're past the point where lifestyle changes can still make a difference in whether they get cancer. But research indicates that living smarter at any age can repair some cellular damage. And further understanding of how aging is linked to cancer may allow us to stay healthier as we get older so we can keep doing what we like to do. There's no doubt that Alessi is still determined to leave driving on his "to-do" list. John F. Lauerman is co-author of Living to 100: Lessons in Living to Your Maximum Potential at Any Age, with Thomas T. Perls, M.D., M.P.H., and Margery Hutter Silver, Ed.D.
