A new link between cancer and aging?
A new study in 2022 reveals a stimulating relationship between how long animals live and how quickly their genetic code mutates.
Cancer is a product of time and mutations, so researchers studied its onset and impact in 16 unique mammals. A new perspective on DNA mutation expands our understanding of aging and cancer development and how we may be able to control it.
Mutations, aging and cancer: an introduction
Cancer is the uncontrolled growth of cells. It is not a pathogen that infects the body, but a normal bodily process gone wrong.
Cells are dividing and multiplying in our body all the time. Sometimes during DNA replication, tiny errors (called mutations) appear randomly in the genetic code. Our body has mechanisms to correct these errors, and for much of our youth, we stay strong and healthy thanks to these corrective measures.
However, these protections weaken with age. The development of cancer becomes more likely as mutations escape our defenses and continue to multiply. The longer we live, the more mutations we carry and the likelihood of them manifesting as cancer increases.
A biological enigma
Since mutations can occur randomly, biologists expect larger life forms (those with more cells) to have a higher chance of developing cancer than smaller life forms.
Curiously, no association exists.
It’s one of the biggest mysteries in biology as to why massive creatures like whales or elephants rarely seem to get cancer. It’s called Peto’s paradox. Even weirder: some smaller creatures, like the naked mole rat, are completely resistant to cancer.
This phenomenon motivates researchers to look into the genetics of naked mole rats and whales. And while we’ve found that special genetic bonuses (like extra tumor-suppressing genes) benefit these creatures, a pattern of cancer rates in all other species is still poorly understood.
Cancer may be closely associated with lifespan
Researchers at the Wellcome Sanger Institute report the first study to compare mutation rates with the lifespan of animals.
Mutation rates are simply the rate at which species breed mutations. Mammals with shorter lifespans have very fast average mutation rates. A mouse undergoes nearly 800 mutations in each of its four short years on Earth. Mammals with longer lifespans have much slower average mutation rates. In humans (average lifespan of about 84 years), there are less than 50 mutations per year.
The study also compares the number of mutations at the time of death with other traits, such as body mass and lifespan. For example, a giraffe has about 40,000 times more cells than a mouse. Or a human lives 90 times longer than a mouse. What surprised the researchers was that the number of mutations at the time of death only differed by a factor of three.
Such weak differentiation suggests that there may be a total number of mutations that a species can collect before it dies. Since mammals reached this number at different speeds, finding ways to control the rate of mutations can help curb the development of cancer, delay aging and prolong life.
The future of cancer research
The results of this study raise new questions for understanding cancer.
Confirming that mutation rate and lifespan are strongly correlated requires comparison with non-mammalian life forms, such as fish, birds, and even plants.
It will also be necessary to understand what factors control mutation rates. The answer to this probably lies in the complexities of DNA. Geneticists and oncologists continue to study genetic curiosities such as tumor suppressor genes and their impact on mutation rates.
Aging is likely to be a confluence of many issues, such as epigenetic changes or telomere shortening, but if mutations are involved there may be hopes of slowing genetic damage or even reversing it.
Although only a first step, linking mutation rates to lifespan is reframing our understanding of cancer development, and it may open the door to new strategies and therapies to treat cancer or tame the number of health problems associated with aging.