Cancers are age-related, much more frequent in the old than in the young. A University of Colorado Cancer Center review published today in the journal Oncogene argues against the conventional wisdom that the accumulation of cancer-causing mutations leads to more cancer in older people, instead positing that it is the changing features of tissue in old age that promote higher cancer rates in the elderly.
"If you look at Mick Jagger in 1960 compared to Mick Jagger today, it's obvious that his tissue landscape has changed," says James DeGregori, PhD, investigator at the University of Colorado Cancer Center and professor of molecular biology at the University of Colorado School of Medicine. "And it's this change, not the accumulation of cancer-causing mutations, that drives cancer rates higher as we grow older."
For evidence, DeGregori points first to the fact that by the time we stop growing in our late teens, we've already accumulated a large fraction of the mutations we will have in our lifetimes. "There's a mismatch between the mutation curve and the cancer curve," DeGregori says, meaning that if cancer were due to reaching a tipping point of, say, five or six mutations, we should see higher cancer rates in 20-year-olds, as this is when mutation rate is highest.
Second, DeGregori points out that even healthy tissues are full of oncogenic mutations. "These mutations are many times more common than the cancers associated with them," DeGregori says. Simply, more mutations doesn't equal more cancer not across the aging population and not even in specific tissues.
DeGregori's final two points come from evolution. As we've evolved from one-celled, short-lived life forms into multicellular, long-lived humans, we've had to develop complicated machinery to maintain our tissues and avoid disease.
"But we're no better at preventing mutations than our yeast or bacteria cousins," DeGregori says. "You'd think if avoiding
|Contact: Garth Sundem|
University of Colorado Denver