Gene Found For Key Protein in Cancer Growth

WASHINGTON (August 14, 1997 4:40 p.m. EDT) -- A gene has been identified that makes a protein key to the uncontrolled growth of cancer cells, a discovery that could lead to new anti-cancer drugs, researchers report.

A team led by Nobel laureate Thomas Cech of the University of Colorado, Boulder, reports the new-found gene makes a protein that is an essential part of telomerase, an enzyme that allows cancer cells to grow without restraint.

"Telomerase takes one of the brakes off of cell division," said Cech. "That's why this enzyme may be important in cancer."

He said the discovery also provides new directions for studying the aging process, which is directly affected by the death of individual cells.

A report on the study is to be published Friday in the journal Science.

Another research team, led by Dr. Robert A. Weinberg of the Whitehead Institute for Biomedical Research, also has isolated the telomerase gene. That work will be published next week in the journal Cell.

The telomerase enzyme blocks a process that limits the lifetime of most cells. It does this by acting on the tips of chromosomes, a part called the telomere.

In normal cells, the telomere shortens each time the cell divides. Eventually, the telomere becomes so short that the cell can no longer divide and will die. In effect, the telomere acts as a molecular clock that controls cell aging.

Most cancer cells, however, avoid this life-shortening process by making telomerase. The enzyme permits the telomere to maintain its length through unlimited cell divisions, thus allowing cancer to spread without restraint.

Cech said in an interview that the new discovery may make it possible to find drugs that would block the action of telomerase and limit the lifetime of cancer cells.

"This gives us a whole new thing to look for in cancer," said Cech. "This will allow us to create telomerase inhibitors which then could be tested for their anti-cancer activity."

He said telomerase is active in up to 95 percent of all human cancers.

In a statement released by the Whitehead Institute, Weinberg said the telomerase discovery will enable drug companies to more rapidly test compounds that may inhibit telomerase.

Ron Eastman, president of the Geron Corp., a California pharmaceutical company, said drug-makers will use the telomerase discovery to fine-tune the search for new cancer chemotherapies.

"It's difficult to think of a better target (for drug development) since telomerase is active in most cancers," he said.

However, Eastman said that it will take years to develop a drug that can be tested in humans.

Cech also cautioned that whether or not a telomerase inhibitor will work against cancer is only theoretical at this point.

"Experience has shown that many drugs that look promising in the test tube may be very different in humans," he said.

-- By PAUL RECER, AP Science Writer