Reasons cancer increases with age are not obvious - Printz - 2012 - Cancer - Wiley Online Library
Researchers at
the University of Colorado Cancer Center in Denver have argued against
the traditional belief that older people develop cancer because they
accumulate more cancer-causing mutations. Instead, they argue that it is
due to changing features of tissue as people age.
Their review, published in Oncogene,
notes that by the time people stop growing in their teens, they have
already developed many of the mutations they will acquire during their
lives.1 Lead author James DeGregori, PhD, a professor of molecular
biology at the University of Colorado, says there is a mismatch between
the mutation curve and the cancer curve. If cancer were to develop based
on 5 or 6 mutations, cancer rates would be much higher in those aged 20
years, when the mutation rate is highest, but that is not the case, he
says.
Dr. DeGregori adds that even healthy
tissues are full of oncogenic mutations, which are much more common
than the cancers associated with them. Furthermore, he points out that
introducing oncogenes into mice stem cells theoretically should help
rather than hurt the cells' survival; however, the cells that harbor
oncogenes tend to get weeded out.
Rather
than gathering mutations that cause cancer, what happens as people age
is that the mechanisms that help young adults fight cancer begin to
deteriorate. Healthy cells are optimized for the conditions of young,
healthy tissue. Those cells are able to tackle those cells with
cancerous mutations but, as the tissue ages, mutations can help a cancer
cell adapt in ways that a healthy cell can not, he says.
Reference
- 1. Challenging the axiom: does the occurrence of oncogenic mutations truly limit cancer development with age? [published online ahead of print July 2, 2012]. Oncogene. doi: 10.1038/onc.2012.281.
