A molecule produced from vitamin A may help protect against some cases of bowel cancer, according to US research.
The study, published in the journal Immunity, hints at a possible way to treat some bowel cancers caused by damage to the gut.
The research found that mice with bowel cancer caused by damage to the gut were found to have lower-than-normal levels of retinoic acid, which is made in the body from vitamin A, in their intestines. But when the team boosted retinoic acid levels in the animals’ gut, tumour growth was slowed.
The researchers also found that tissue samples from bowel cancer patients had high levels of a molecule that breaks down retinoic acid, and that those who had the highest levels tended to have poorer survival.
Some of the bowel tumour samples in the study came from patients whose disease was linked to an inflammatory bowel condition called ulcerative colitis.
Professor Edgar Engleman, from Stanford University School of Medicine and who led the study, said there is a “clear link” in humans between inflammatory bowel conditions, such as ulcerative colitis, and the development of bowel cancer.
“Retinoic acid has been known for years to be involved in suppressing inflammation in the intestine,” he said. “We wanted to connect the dots and learn whether and how retinoic acid levels directly affect cancer development.”
Professor Alastair Watson, a Cancer Research UK expert in bowel cancer, said the findings were “interesting” and that further studies would need to confirm the link in people.
“The next challenge is establish whether giving vitamin A to people with ulcerative colitis could reduce their risk of developing bowel cancer,” he said.
“Less than one in 10 cases of bowel cancer are caused by ulcerative colitis, so a further challenge is to determine whether vitamin A also has a role to play in more common cases of the disease.”
Retinoic acid plays a variety of important roles in cell growth, development and immune system function. It also helps to reduce inflammation in the gut.
Bacteria found in the gut can also lead to damage to the bowel, and the researchers found that in mice this process can lead to changes in retinoic acid levels.
Dr Oliver Maddocks, a Cancer Research UK expert in cancer metabolism, said: “This study found that bacteria in the gut may contribute to the development of bowel cancer by changing how immune cells react to tissue damage that can cause the disease.
“Crucially, if confirmed in further studies, the results suggest that therapies designed to boost the activity of the immune system could help prevent or treat some bowel cancers.”
Bhattacharya, N. et al. (2016). Normalizing Microbiota-Induced Retinoic Acid Deficiency Stimulates Protective CD8+ T Cell-Mediated Immunity in Colorectal Cancer. Immunity. DOI:10.1016/j.immuni.2016.08.008