The year is 2040. 71 years after the Apollo 11 has landed on the moon, the United States has finally made technological advancement for the first ever manned mission to Mars. This mission is very crucial to help people determine the livability of Mars. A group of astronauts have applied to participate in this important mission. However, they must go through a series of physical tests before they could be selected to go through a 20-month training to obtain the essential skills needed to travel to Mars.
Traveling to Mars is not an easy task. There are many challenges this human mission must overcome. One of the challenges is the physical harm of exposure to high-energy cosmic rays and other ionizing radiation might pose to the astronauts. Some people have a certain genomic profile that contains a mutation in a gene called p53 that makes them more susceptible to radiation-induced damage. Astronauts with such a genomic profile will be counseled about the special risks of going on this mission. During the training session, the astronauts who are physically qualified will learn about what kind of radiation will penetrate the spaceship and how exposure to the radiation might affect them.
Luna and Orion both are young astronauts who have applied to the program. The two of them have very different lifestyles and grew up in different environments. Luna is a healthy eater and runs regularly. Orion, on the other hand, likes to eat fried food even though he is still fit. They both have 20/20 vision and are qualified for the mission in terms of their height, blood pressure and education. The genomic test is the only thing left for both Luna and Orion before they become crew members of this Mars mission.
In order to construct Luna and Orion’s genomic profile, both of them were sent a kit by NASA to collect their DNA. The kit had the words “Buccal Swab” written on it and contained a pair of latex gloves, a small plastic tube, a long cotton swab, a return envelope, and a set of instructions. The collection process was pretty simple. All they had to do was swab the inside of their cheek with the cotton swab and then put the cotton tip inside the plastic tube (Figure 1). After the two had returned their buccal samples to NASA, they were called to go to the local medical center for a consultation with a genetic counselor.
At the genetic counselor’s office, Luna and Orion were both excited to hear their results. First, they were asked to fill out a questionnaire regarding their family medical history. Luna’s father was diagnosed with pancreatic cancer several months ago, and her paternal grand-father died of colon cancer a couple of years ago. After filling out the forms, the counselor started to inform Luna and Orion about how the genetic testing was done. The test was only for common mutations in the tumor suppressor p53 gene, which encodes the tumor suppressor p53 protein that normally helps cells to die when they are damaged, a process called apoptosis. Some people carry a mutated p53 gene that makes them more susceptible to getting cancer when they are exposed to a carcinogen.
It turns out that Luna tested positive for a p53 mutation. The counselor explains that having a p53 mutation can increase the risk of developing cancer, especially after exposure to carcinogens, or substances in the environment such as tobacco, alcohol, and a lot of high fat foods.
More importantly, exposure to ionizing radiation, such as that encountered by astronauts in outer space, would greatly increase one’s chance of developing cancer—regardless of whether (s)he has a mutation in their p53 gene. And back here on earth, exposure to ultraviolet (UV) radiation from the sun (or tanning beds!) increases our risk of skin cancer. Luckily for many people, we have a protective mechanism against UV-induced skin cancer. We get some protection from a brown pigment in our skin called melanin, which increases when we are exposed to UV light, to help block the harmful radiation from penetrating the skin. Another protective strategy is the use of sunscreen—and sunblock is even better!
Now that you know a little background about p53 and radiation, your mission is to assess how radiation exposure to astronauts in space impacts their risk of developing cancer. You are especially interested in how to minimize the risk.