Mystery of the environmental triggers for cancer deepens
- CamWAMS Team
- Oct 31, 2021
- 2 min read
Behind the Headlines
Mystery of the environmental triggers for cancer deepens
Cancer biologists like to trace the intellectual basis of their field back to the work of Darwin and Mendel. The former established how natural selection and ‘modification’ (what we would know today as mutation) can cause changes in phenotype over time, while the latter introduced genetics, which is now central to our understanding of these processes. Cancer can be conceptually considered as a result of these processes working at the cellular level. One or more genetic mutations confer an advantage on the cell possessing them, allowing it to divide much faster than neighbouring cells do. Eventually, it displaces neighbouring normal tissues and starts invading other tissues and organs.
Occasionally, some cancers arise almost entirely due to inherited mutations that a patient is born with. In most cases however, at least some of these mutations develop due to interactions between the organism’s genome and environmental factors such as radiation, viruses, toxins, and the like.
The question, then, is which environmental factors are important causative factors for a particular type of cancer? Environmental factors can be linked to particular patterns of genetic mutations (or mutational signatures). So, the answer is to sequence many cancer samples and look for mutations they have in common that can be linked to environmental factors. Of course, when doing this we would want to be sequencing the genomes of cancers which we already think are due to environmental factors.
It thus made sense for the brilliant scientists at the Sanger Institute to try this technique on oesophageal squamous cell carcinoma (OSCC), a type of oesophageal cancer. As the article points out, the incidence of this cancer varies greatly across the world, being particularly high in countries including Kenya, China, Iran, and Turkey. If all these countries were from a single region, we could say that there is probably some hereditary genetic factor at work here. However, these countries are quite distant from each other, so it seems quite likely (theoretically, at least) that there are some common environmental factors underlying their high rates of OSCC.
Unfortunately, this effort turned out to be unsuccessful, and no mutational patterns indicative of any environmental factor were found. For now, there seem to be many possibilities which may explain the outcome of this study. Perhaps the environmental factors are affecting cells at the epigenetic or RNA level, instead of directly causing mutations. Or maybe the high incidence rate in these countries is not due to environmental factors at all. Ultimately, we must remember that a study with negative results is never useless, so long as we ask the right questions afterwards.
The paper itself can be found here:
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