The movie Trading Places was an ’80s classic about two wealthy commodity brokers who make a bet. They wager on whether a homeless street hustler, played by Eddie Murphy, can become a successful commodity trader on Wall Street. One broker takes the side that nature is stronger and Mr. Murphy will fail, while the other believes that in his new nurturing environment, Mr. Murphy will be successful. These commodity brokers also seem to be well-versed in experimental testing, and reverse the scenario by taking a current commodity broker (played by Dan Aykroyd) and removing all his wealth. In the end, Mr. Murphy and Mr. Aykroyd find out about this bet and get their revenge for being unwilling participants in this nature vs. nurture experiment. This fascination with Nature vs. Nurture has enough interest to make a fairly successful movie about it, but what is nature and nurture, and what does it have to do with cancer?
Within our cells lies one of the most famous molecules, DNA. DNA serves as an instruction book for our cells and represents the “nature” part of the debate. It is the DNA that represents a code telling the cells which type of cell to be- a kidney, heart, or brain cell, as well as how to behave like a good cell. When the DNA code is correct, things go well but when broken, the cell itself (or even group of cells) will function poorly or perhaps not function at all. Cancer serves as a prime example of this. Cancer is in part caused by changes in the DNA that allow it to misbehave and grow without constraints, move around more, and resist dying.
But the DNA code is not the whole story. The environment the cell lives in is important and since cells are your body, then your environment is the cell’s environment. For instance, if you walk into a smoky bar, the cells in your lungs get bathed in that smoke, and if you consume too much alcohol, the cells too are consuming the alcohol. Fortunately for all of us, we (our cells) have evolved strategies to adapt to different environments on a short-term basis. But over the longer term, perhaps many years or decades, multiple exposures to a bad environment can cause problems. The most notorious example is smoking, whereby repeated exposure to cigarette smoke damages the cell’s environment and DNA.
Nature and Nurture Impacts the Risk of Cancer
So is it nature (your DNA) or nurture (your environment) that impacts the probability of getting cancer? In cancer, as in most cases, it is likely not nature OR nurture but rather nature AND nurture that impacts cancer risk. Let’s use skin cancer as an example. In general, people whose DNA encodes them with fair skin are at a higher risk of getting skin cancer. These individuals have a choice to make. They can be diligent by reducing sun exposure and applying sunblock, thereby decreasing their cancer risk, or they can never apply sunblock, lay on tanning beds, and spend long periods in the sun, increasing their cancer risk. In either case, it is both their nature (skin tone) AND their nurture (sun exposure) that impacts their cancer risk.
The map below shows state-by-state restrictions on tanning beds published by the American Cancer Society (CPED Facts and Figures, 2014). Using this data, it would be incorrect to conclude that all states with lax regulations have increased skin cancer incidence, since nature plus nurture would say that there are many factors that go into developing skin cancer. Nevertheless, allowing children under 18 to be irradiated with UV light can increase their risk of developing skin cancer over their lifetime.
Understanding the biology of cancer has taught us that nature vs nurture is not the right question to ask. We must not pit them against each other but instead figure out how they cooperate. Any scientist will tell you that this is a tricky business, and separating nature and nurture in the lab is an important challenge. We probably can’t turn to Hollywood or Mr. Murphy for any more insight on this, but down the road expect to see new advances in predicting and preventing cancer.
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