When foreign invaders like bacteria end up in the intestines, the immune system gears up to squelch them. Oftentimes, inflammation — the release of chemicals from injured cells that leads to swelling — results. And this inflammation is a key risk factor in some cancers, including colorectal cancer.
Researchers have long-known that retinoic acid, a byproduct of vitamin A, can tamp down this inflammation. But now, a team of Stanford and University of California, Berkeley researchers have connected low levels of retinoic acid with colorectal cancer in both mice and humans. Our press release explains:
Mice with the cancer have lower-than-normal levels of the metabolite [retinoic acid] in their gut, the researchers found. Furthermore, colorectal cancer patients whose intestinal tissues express high levels of a protein that degrades retinoic acid tend to fare more poorly than their peers.
The research is the first to unravel a complicated dance between retinoic acid levels, immune-related inflammation and gut microorganisms. It may suggest new ways to prevent or treat colorectal cancer in humans.
The research took advantage of a snazzy technique to measure the levels of retinoic acid in mice intestines, allowing the scientists to track the relationship between colorectal cancer and decreased, or increased, amounts of the metabolite.
The findings, which appear today in Immunity, have raised additional questions for investigation, senior author Edgar Engleman, MD, a professor of pathology and of medicine, said in the release:
It’s become very clear through many studies that chronic, smoldering inflammation is a very important risk factor for many types of cancer... Now that we’ve shown a role for retinoic acid deficiency in colorectal cancer, we’d like to identify the specific microorganisms that initiate these changes in humans. Ultimately we hope to determine whether our findings could be useful for the prevention or treatment of colorectal cancer.
Here's to that. But an important caveat: This doesn't mean it's time to gobble a handful of vitamin A pills, or to munch through an entire bunch of carrots (or a seal liver!). Excess levels of vitamin A can be toxic.
Previously: Researchers prime immune system's T cells with foreign antibodies to target cancer cell, Cancer-causing gene also helps tumors dodge immune system and The Big Bang model of human colon cancer
Image by Sebastian Kaulitzki/Shutterstock