In 1513, Ponce de Léon set off in search of the legendary Fountain of Youth. Instead, he found Florida. Nearly 500 years later, scientists at three universities discovered a substance called telomerase deep within some of our cells. Telomerase enables cells to reproduce infinitely, in a way, to become immortal. Most human cells, however, are limited to 30-50 divisions. Scientists are now studying whether turning off telomerase activity can prevent cancer, and whether telomerase, properly controlled, can be a kind of cellular "fountain of youth," which might one day prevent the ravages of aging on our blood, skin, tissues and organs.

Telomerase is not found in most normal cells, but is nearly ubiquitous in cancer cells. Scientists, therefore, have been asking whether measuring telomerase levels in the body might be a useful way to make an early diagnosis of cancer, perhaps before a tumor has grown too large to be cured.

For example, a group of Japanese researchers studied lung fluid obtained from patients with respiratory disease. Nearly half of the samples from patients who had lung cancer showed telomerase activity, while less than 6% of those without known lung cancer had telomerase activity. A few of the patients without known lung cancer who had telomerase activity also had evidence of early signs of cancer.

These results suggest that increased telomerase activity may someday be useful in identifying patients with lung cancer. One might also ask whether those patients with telomerase activity, but no known cancer are in the process of developing a very early cancer. Like Pap smears and other blood tests, telomerase screens, therefore, could well prove to be a potent tool in the early diagnosis of cancer.