By examining the DNA of some 70,000 people, researchers have highlighted the possible genetic basis of the link between the consumption of red or processed meat and the risk of colorectal cancer.
- We know that excessive consumption of red meat or processed meat is a risk factor for colorectal cancer, one of the most common in France with more than 47,000 cases per year. But why ? A new study suggests it could be linked to genetic causes.
- By studying gene-environment interactions using DNA samples from around 70,000 people, the researchers found that, among those who ate a lot of meat, some were, due to their DNA, facing an even higher risk of colorectal cancer compared to others who ate as much.
- This is the case for people with variations in the SMAD7 gene, which regulates hepcidin, a protein linked to iron metabolism. Because red and processed meats contain high levels of iron, researchers hypothesize that different variants of SMAD7 may increase cancer risk by changing how the body processes iron.
We know, thanks to various studies, that excessive consumption of red or processed meat is a risk factor for colorectal cancer, one of the most common in France with more than 47,000 cases per year. If the underlying biological mechanisms were until now poorly understood, a new study, published in the journal Cancer Epidemiology, Biomarkers & Preventionsuggests that this could be linked to genetic causes.
Meat consumption linked to increased risk of colorectal cancer
As part of their work, researchers from the Keck School of Medicine at the University of Southern California, in the United States, analyzed data from 27 studies including nearly 30,000 people with colon cancer and of the rectum, and nearly 40,000 others without cancer. After examining their consumption of red meat (beef, pork and lamb) and processed meat (bacon, sausages, cold cuts, etc.), they found that participants who ate the most red or processed meat were faced, respectively, with at a 30 or 40% increased risk of colorectal cancer. So far, nothing really new.
To go further, the researchers then analyzed, using a statistical method, the gene-environment interactions using DNA samples from the volunteers. In particular, they looked at the most common type of genetic variation – single nucleotide polymorphisms – to see if a genetic variant could change the risk of colorectal cancer in people who ate more meat. In other words: are certain individuals, due to their DNA, faced with an even higher risk if they consume it?
Colorectal cancer and meat: a possible link with iron metabolism
The team of scientists identified two genes, HAS2 and SMAD7, that altered colorectal cancer risk levels based on levels of red or processed meat consumption. Thus, participants with a common variant of the HAS2 gene (found in 66% of the population) had a 38% greater chance of developing this type of cancer if they ate a lot of meat, while those with another rarer variant of the same gene did not have an increased risk, even though they consumed as much meat.
For their part, people showing variations in the SMAD7 gene were exposed to an increased risk (from 18 to 46% depending on the variant) of colorectal cancer if they were very carnivorous. This gene is known to regulate hepcidin, a protein linked to iron metabolism. Because red and processed meats contain high levels of heme iron (i.e., well-absorbed by the body), researchers hypothesize that different variants of SMAD7 may increase cancer risk by changing the how the body processes iron. “When hepcidin is dysregulated, it can lead to increased iron absorption and even iron overload inside cells”says Professor Mariana C. Stern, lead author of the study, in a communicated.
The team of researchers plans to conduct further experimental studies to more precisely examine the potential role of dysregulation of iron metabolism in the development of colorectal cancer.
