NASA Astronauts' Blood Shows Signs of DNA Mutation After Returning From Space
Affected genes include those involved in cancer.
A new study found that astronauts have a higher level of DNA mutations after space travel, and that could be a sign of an increased risk of cancer. The main concern is about radiation, which occurs at higher levels above earth's atmosphere. Exposure to excessive radiation is one of the known risk factors for cancer. Read on to find out what the study found, which cancer processes might be involved, and what is recommended for astronauts from now on.
Fourteen astronauts from the space shuttle program participated in the study. They flew on shuttle missions averaging 12 days in length between 1998 and 2001. The median age of the astronauts was 44. Researchers collected whole blood samples from the astronauts twice—ten days before flight and on the day of landing—and white blood cells that were collected just once, three days after landing. Those samples were frozen at 112 degrees below zero for 20 years.
The researchers discovered the astronauts were more likely to have somatic mutations in their genes, compared to people who haven't been to space. Somatic mutations occur in DNA after conception and involve cells other than sperm or egg cells, meaning they're not passed down to offspring. The mutations identified found in the astronauts resulted in the overrepresentation of blood cells derived from a single clone, a process called clonal hematopoiesis. That process is at the root of several types of blood cancer, including chronic myeloid leukemia.
"Astronauts work in an extreme environment where many factors can result in somatic mutations, most importantly space radiation, which means there is a risk that these mutations could develop into clonal hematopoiesis," said David Goukassian, the study's lead author and a professor of cardiology at Icahn Mount Sinai in New York, in a statement. He added: "Given the growing interest in both commercial spaceflights and deep space exploration, and the potential health risks of exposure to various harmful factors that are associated with repeated or long-duration exploration space missions, such as a trip to Mars, we decided to explore, retrospectively, somatic mutation."
Using DNA sequencing and bioinformatics analysis, researchers identified 34 mutations in 17 genes in the astronauts. The most common mutations were in TP3, a gene that produces a tumor-suppressing protein, and DNMT3A, one of the genes most likely to mutate in acute myeloid leukemia. Although these mutations were elevated, they didn't exceed two percent, an official threshold of concern. But the researchers had recommendations for NASA going forward. "The presence of these mutations does not necessarily mean that the astronauts will develop cardiovascular disease or cancer, but there is the risk that, over time, this could happen through ongoing and prolonged exposure to the extreme environment of deep space," said Goukassian.
The researchers said NASA and its medical teams should screen astronauts for somatic mutations and clonal changes every three to five years, even after they retire. "What is important now is to conduct longitudinal retrospective and well-controlled prospective studies involving a large number of astronauts to see how that risk evolves based on continued exposure and then compare that data against their clinical symptoms, imaging, and lab results," said Goukassian. "That will enable us to make informed predictions as to which individuals are more likely to develop disease based on the phenomena we are seeing and open the door to individualized precision medicine approaches to early intervention and prevention."
Other studies have focused on astronauts' cancer risk. A 2019 study that looked at more than 300 U.S. astronauts and more than 100 Russian cosmonauts found no increase in relative cancer risk compared to the general population—in fact, their cancer risk was lower than expected.