SCIENTISTS FIND `IDEAL CANCER TARGET' - AN ENZYME THAT'S RARELY IN NORMAL CELLS

Scientists have found a long sought "ideal cancer target" - that is, a substance occurring in all cancer cells but in almost no normal ones. Then doctors could home in on tumors with powerful, specific diagnostic tools and treatments.

Such a universal cancer target may be an enzyme, called tel-omer-ase, that was recently discovered to be active in about 85 percent of cancers. A report in the current issue of the Journal of the National Cancer Institute says that researchers in Texas and Japan found telomerase in most cells taken from lung tumors but in few cells in surrounding normal tissue.Telomerase has a very specific function - to repair the ends of chromosomes, which shorten as cells divide and reproduce. Normally, cells go through a certain number of rounds of reproduction and then die, in part because they don't have active telomerase to maintain the length of chromosomes.

An exception is cells in the testes and ovaries, which have active telomerase because reproductive cells must keep dividing.

The other type of cell in which telomerase is active is the cancer cell, which divides and grows abnormally.

Writing in the NCI journal, molecular biologist Gregg B. Morin of the University of California at Davis said:

"Telomerase fulfills many of the criteria for an ideal cancer target. While . . . finding a specific telomerase inhibitor remains daunting, the present optimism appears justified."

- Richard Saltus