Scientists discover role of cell proteins in cancer

May 14, 1999
Web posted at: 10:15 AM EDT (1415 GMT)

BOSTON (Reuters) - In a discovery researchers hope leads to new treatments for cancer, scientists have found that the proteins capping the ends of chromosomes in a cell may also play a role in cancer, according to two studies in Friday's issue of the journal Cell.

Although the research is preliminary, it helps scientists better understand the process that turns normal cells into malignant cells.

The caps, known as telomeres, keep a cell's genetic material from unraveling, just as an elastic band keeps braided hair in place. When the telomeres become too short, the aging cell stops dividing and begins to die.

In special cases where a mutation lets the cell continue to divide anyway, the telomeres deteriorate even further. The genetic material in the cell unravels and becomes so scrambled that the cell reaches a "crisis" stage and commits suicide.

To see whether the crisis stage helps prevent cancers, a team led by Dr. Lynda Chin of the Dana-Farber Cancer Institute created a breed of mice that is unable to rebuild its telomeres as they shorten from normal wear and tear.

Chin and her colleagues discovered that, with each generation of mice, cancer rates declined, from 64 percent in the first generation to 31 percent by the fifth generation.

Chin said the finding "represents the first proof that telomere shortening during crisis inhibits the growth and creation of tumors. Without intact telomeres, cells have a harder time dividing and proliferating."

Uncontrolled cell growth is the hallmark of a tumor.

A tumor suppressor gene, known as p53, was the subject of a separate experiment, which showed that when telomeres stop doing their job, the p53 protein orders the cell to commit suicide, the journal said.

But when that order is not carried out properly, the cell can turn cancerous.

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