Researchers led by Hiroshi Ohno at the RIKEN Center for Integrative Medical Sciences in Japan have unveiled a groundbreaking discovery: food antigens, such as those found in milk proteins, possess the unique ability to halt the growth of tumours in our small intestines. Their study, published on September 18 in the journal Frontiers in Immunology, sheds light on how these proteins activate the intestinal immune system to effectively prevent the formation of new tumours.
Food antigens often receive negative attention because they trigger allergic reactions to common foods like peanuts, shellfish, bread, eggs, and milk. Despite not always causing allergies, these antigens and those found in various plants and beans are still recognised by the immune system as foreign entities requiring surveillance. Ohno’s team has previously demonstrated that food antigens activate immune cells within the small intestines rather than the large intestines. Moreover, it is known that specific immune cells stimulated by gut bacteria play a role in suppressing tumours within the gut. In their latest research, the team at RIKEN IMS merged these two concepts to explore whether food antigens could suppress tumours in the small intestines.
The initial phase of their research utilised a specific breed of mice that carried a mutation in a gene responsible for tumour suppression. Like humans with familial adenomatous polyposis—a condition where malfunctioning genes lead to widespread tumour development in the intestines—these mice developed tumours in both the small and large intestines. In a simple experiment, the researchers fed these mice either regular food containing antigens or a special antigen-free diet. They observed that mice consuming regular food exhibited fewer tumours in the small intestines, though the number in the large intestines remained unchanged.
To delve deeper, they introduced a common antigen, albumin (typically found in meat and absent from the regular diet), to the antigen-free diet. They adjusted the protein levels to match those in the regular diet. Remarkably, the presence of this antigen in the diet led to a suppression of tumours in the small intestine comparable to that observed with the regular diet. This finding indicated that tumour suppression was directly linked to the presence of antigens rather than the nutritional content or any specific antigen.
Furthermore, the research team noted significant differences in the presence of immune cells, specifically T cells, in the small intestines of the mice, depending on their diet. Mice on the plain antigen-free diet showed a marked reduction in T cells compared to those fed either regular or modified antigen-free diets. Subsequent experiments shed light on the biological mechanisms enabling this process.
The implications of these findings are significant, particularly for clinical practice. While clinical elemental diets, which are simpler in composition and primarily consist of basic amino acids instead of whole proteins, are often prescribed for severe gastrointestinal conditions like Crohn’s disease or irritable bowel syndrome, Ohno strongly advises caution in their use. This is especially true for patients with familial adenomatous polyposis, who face a higher risk of small intestinal tumours compared to more common colon tumours.
It’s important to note that elemental diets are not only used by individuals with severe gastrointestinal issues, but also by those seeking to lose weight or alleviate bloating and inflammation. This new research underscores the potential risks associated with such practices and highlights the crucial need for medical supervision when considering these diets.
More information: Takaharu Sasaki et al, Food antigens suppress small intestinal tumorigenesis, Frontiers in Immunology. DOI: 10.3389/fimmu.2024.1373766
Journal information: Frontiers in Immunology Provided by Riken Research institute
