By the age of 60, we all have at least 100 billion cells with at least one cancerous mutation in our body. Fortunately, not all of them mean cancer.
Our cells renew and change. Sometimes, this natural phenomenon creates mutations that can cause cancer. But how many of these cells are there in our body? A research team from the University of Colorado has made an estimate. The results of their work have been published in the scientific journal Aging and Cancer. The researchers estimate that, from the age of 60, a person has at least 100 billion cells with at least one cancerous mutation in his or her body.
“We knew that many mutations in humans are associated with cancer, but we didn’t know how many,” says Edward J. Evans, lead author of the study. When you have billions of cells and they survive up to a century, they accumulate mutations,” adds coauthor James DeGregori. It’s not surprising that we have mutations.
The team compiled data sets from scientists who had previously investigated mutations in normal human tissue. Edward J. Evans learned to code to create an algorithm that could extract the necessary data and then create blocks to classify mutations according to genes, tissues, and age of individuals. To understand the origin of cancer, we have to look at normal tissues,” explains the researcher. When cancer occurs, all the mutations are already present and we don’t always know which ones actually contribute to the disease.
A large number of cancer-related cells
The analysis showed that a person over 60 years old has at least 100 billion cells with oncogenic mutations. We have about three trillion cell nuclei in our body, so, to put it in perspective, 100 billion cells with oncogenic mutations are not the majority of our total cell count,” says Edward J. Evans. But it’s a surprisingly high number when you consider that it only takes one cell to cause cancer.” The researchers wonder about the implications of these mutations since individuals can have billions of cells with these oncogenic mutations without developing cancer.
How should these results be interpreted?
The authors of this research found that oncogenic mutations are extremely common in certain tissue types: skin, colon, and the esophagus. These mutations can be more dominant in some of the tissues. “For example, if you look at the esophagus, half of the tissue is filled with NOTCH1 mutations, which rarely contribute to cancer in nonsmokers,” says James DeGregori. It’s not very useful to test for this mutation if most of us have it and it rarely leads to cancer. For the researchers, looking for oncogenic mutations is unnecessary and time-consuming, since everyone has them and they don’t necessarily mean cancer. “How these oncogenic mutations interact with the tissue environment will tell us a lot more about risk,” the researcher adds. Future work will be devoted to looking at tissues to understand why some tissues have a high frequency of oncogenic mutations with no associated cancer risk.