Stem-cell sentry sounds the alarm to maintain balance between cancer and aging, U-M resear...( ANN ARBOR Mich.---Like a sentry guar...),Health

ANN ARBOR, Mich.---Like a sentry guarding the castle walls, a molecular messenger inside adult stem cells sounds the alarm when it senses hazards that could allow the invasion of an insidious enemy: Cancer.

The alarm bell halts the process of cell division in its tracks, preventing an error that could lead to runaway cell division and eventually, tumor formation.

"Our work suggests that to be able to prevent abnormal cell proliferation, which could lead to cancer, stem cells developed this self-checking system, what we're calling a checkpoint," said Yukiko Yamashita of the University of Michigan's Life Sciences Institute.

"And if it looks like the cell is going to divide in the wrong way, the checkpoint senses there's a problem and sends the signal: 'Don't divide! Don't divide!'" said Yamashita, a research assistant professor of life sciences and an assistant professor of cell and developmental biology at the U-M Medical School.

If everything looks OK, the checkpoint allows adult stem-cell division to proceed, providing new cells to replace damaged and worn-out tissues.

Yamashita and her colleagues have not yet identified the molecules that form the checkpoint mechanism. But they've seen it at work in adult stem cells of the fruit-fly testes, so-called germ-line stem cells.

"Aging is too few divisions and cancer is too many divisions, and people have long speculated that some process controls the balance between them," Yamashita said. "We may have found the mechanism that maintains the delicate balance between over-proliferation---which can lead to cancer---and aging."

The team's findings will be published Oct. 15 in the online version of the journal Nature.

If humans possess a similar checkpoint system and if researchers could someday harness it, they could fine-tune the rate of cellular division to control tumor development as well as tissue aging. But Yamashita stressed that no
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