Sept. 25, 2003 -- When people hit middle age, the cells within their body may have a midlife crisis of their own that could cause cancer.
A new study suggests that this midlife cellular breakdown might help explain why growing older is the single biggest risk factor for cancer and nearly 80% of cancers are diagnosed after age 55.
And the keys to understanding this process might already be in your kitchen.
Researchers found that human cells are a lot like baker's yeast when it comes to the aging process. They both become highly unstable as they approach middle age.
"While yeast don't get cancer, they do have one of the major hallmarks of malignancy, which is genetic instability," says researcher Daniel Gottschling, PhD, of the Fred Hutchinson Cancer Research Center in Seattle, in a news release. "We found a similar thing in yeast that has been seen in humans: Genetic instability shoots up dramatically in the middle to late stage of life."
Cancer Clues in Yeast
Although age is widely accepted as a potent risk factor for cancer, researchers say no one knows exactly why.
In the study, published in the Sept. 26 issue of the journal Science, researchers examined whether yeast cells might serve as a model to help explain the abrupt surge in cancer risk that occurs when humans hit late middle age.
Researchers discovered that yeast cells consistently experience a sudden, 200-fold surge in the production of genetic changes as they reach the human equivalent of late-middle age. They say this finding makes yeast cells ideal for understanding the genetic changes that occur in human cells during the aging process that might cause cancer.
"Yeast gives us, for the first time, the potential for not only understanding the principles of what's going on mechanistically but also which molecules might be relevant to the process of age-related cancer development," says Gottschling.
Researchers found that the genetic instability associated with causing cancer wasn't related to how close the cells were to death, but it was how far they were from birth that mattered.
Age Isn't Everything
But researchers say that doesn't mean that cancer is a necessary by-product of the aging process. They say people should still lead a healthy lifestyle to help reduce their risk of cancer because these interventions may actually delay the cellular midlife breakdown.
"Our yeast were on a diet equivalent to steak and potatoes. We had the mother cells growing in a very rich, nutrient-dense environment. They were, in essence, pigging out the whole time," says Gottschling. "We'd like to do similar experiments in which we put the yeast on a 'lean and mean' diet to see if we could delay the switch that triggers the genetic instability."
"Yeast promises to be an excellent model system for testing various environmental factors, such as caloric restriction, to get at the mechanisms of cancer initiation," says Gottschling.