But telomerase also has a dark side: When active in cancer cells, it enables unlimited growth, a hallmark of cancer.

It had been thought that telomerase only works on the shortest telomeres in a cell, but in the new study, the UT Southwestern researchers found that telomerase rebuilds most or all of the telomeres in a cell for each division, not just the shortest ones, as had been thought.

"Understanding ways to inhibit this telomerase mechanism might lead to novel anticancer therapies," said Dr. Jerry Shay, professor of cell biology and co-senior author of the paper.

Clinical trials using a drug that blocks telomerase are already under way at UT Southwestern for lung cancer and chronic lymphocytic leukemia.

The new study was possible because the researchers developed a way to examine the very ends of telomeres after a single cell division. Previous research in the field required multiple cell divisions to detect such changes.

"Now that we can look at what telomerase is doing in a single cell-division cycle, there is potential for a tremendous number of follow-up studies," Dr. Wright said.

Source: UT Southwestern Medical Center