Cancer: A balance between genes and exposures?


What causes cancer? This single question crosses many people’s minds over their course of their life, especially researchers who dedicate their life to trying to understand cancer. With the development of new scientific technologies developed over the last 30 years, scientists continue to pinpoint certain genes and cellular pathways involved in the development of cancer. This has led to the development of a vast array of new, targeted drugs to treat patients. Furthermore, studying populations of people have allowed researchers to see which cancers are more common in certain populations. Scientists can then try to find the factors these populations are exposed to that increase their risk of cancer. To date, it looks like we have a pretty good idea of where cancer comes from.


But cancer is more complicated than it seems. There is still ongoing research to determine whether everyday things such as eating red meat or using cell phones “cause” cancer. The fact is the risk of getting cancer is influenced by many factors over the course of one’s lifetime. This could be referred to as an exposome, which is the complete set of internal and external exposures of that individual, including his/her genome.


But what does that mean? An internal exposome could include a person’s hormones, their metabolism, and even the bacteria that resides in their gut – all of which have the potential to contribute to cancer development. The external exposome includes lifestyle choices (such as diet, smoking, drinking alcohol), as well as other factors, such as exposures to viruses (HPV for example) as well as exposure to UV radiation and certain chemicals. It can also include one’s social, economic and psychological circumstances.


How are researchers nowadays studying these variable exposures in relation to the risk of disease and cancer? Almost one third of all cancers can be prevented by eating well, being active and maintaining a healthy body weight. But new research also indicates that an individual’s health can be affected before conception in the mother’s womb. In fact, the exposomes of both parents can be predictive of the risk for future diseases, though this is still being studied. While it is more obvious that the mother’s eating habits can affect her baby’s health, how can the father’s eating habits be of influence?


A McGill study in mice led by Dr Sarah Kimmins suggests that paternal diet is equally crucial. Her research group found that when male mice were fed a diet deficient of folate, also known as vitamin B9, their sperm’s epigenome was altered compared to that of mice fed a normal folate-sufficient diet. This led to birth defects, and an increased risk of chronic disease and cancer of the offspring. An epigenome is the collection of chemical “markers” on DNA that dictates which genes are expressed or not, and these markers are passed on to the DNA of the offspring. Therefore, in this case, the sperm carried a “snapshot” of the father’s lifestyle choices (a low folate diet) that ultimately affected the development of his children. These findings show that environmental risk factors sometimes go beyond one’s control, but, the “you are what your father eats” claim is only one of the uncountable number of factors that may contribute to cancer and other diseases. Despite this interesting finding, more research still needs to be done to confirm this type of finding in people. And research needs to be done to see if a child can “change” these effects over time.


Lifestyle choices, hereditary genetics, and aging can play a big role in cancer development, and some of these risks are inevitable. Now according to new research, there is the possibility that parents can affect their children’s future health. The best advice in light of these new findings is that it’s never a bad idea be more conscientious of our everyday choices and habits. Of course, there are some things that can’t be easily changed, but it’s doable when it comes to deciding between fries or a salad.

References

  1. Wild, C. P., Scalbert, A., & Herceg, Z. (2013). Measuring the exposome: a powerful basis for evaluating environmental exposures and cancer risk. Environmental and molecular mutagenesis, 54(7), 480-499.

  2. Lambrot, R., Xu, C., Saint-Phar, S., Chountalos, G., Cohen, T., Paquet, M., ... & Kimmins, S. (2013). Low paternal dietary folate alters the mouse sperm epigenome and is associated with negative pregnancy outcomes. Nature communications, 4.

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