Reasons cancer increases with age are not obvious - Cancer

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
  DeGregori J. 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.