Researchers seeking a common biological target for a cancer cure are hopeful about an enzyme present in 85 percent or more of all tumors. This common component is "telomerase," an enzyme that can rebuild the end segments of chromosomes, called telomeres. "Telomerase is most likely the solution to the end replication problem of chromosomes in immortal cells, so it is probably a good target for studies of cancer," says Gregg Morin, the UC Davis molecular biologist who first found telomerase activity in human cells in 1989. Telomeres slowly break down as most cells replicate, eventually causing death, but in cancer cells telomerase allows the cells to replicate forever. In an editorial from the June issue of the Journal of the National Cancer Institute, Morin is optimistic about research findings that strongly support the telomere hypothesis in cancers. "What remains is to show that tumors require telomerase for growth and that loss of telomere function would be clinically useful," Morin says. By learning more details about how the enzyme functions, researchers like Morin may find ways to reduce telomerase activity only in cancer cells, since telomerase also has been found in some non-cancerous cells that continually divide. Morin's work also helps in designing better tests for finding drugs that could halt the enzyme's activity.