High-fat diet increases incidence of colorectal cancer, study finds

A high-fat diet increases the incidence of colorectal cancer, according to a new study in mice published in the journal Cell Stem Cell.

According to the study, fat disrupts the relationship between intestinal cells and the immune cells that patrol them looking for emerging tumors. Reconfiguring the gut microbiome may be a way to heal the relationship, the researchers said.

The immune system patrols tissues looking for and eliminating threats. Certain immune cells look for tags that distinguish between normal and abnormal cells. One tag, called MHC-II, helps target cells for destruction. Cell-surface MHC-II activates the immune system to destroy that cell, whether it is just worn out or about to become cancerous, according to the study.

The researchers found that when mice ate diets high in fat, MHC-II levels were suppressed in intestinal cells. Cells with reduced levels of these tags were not recognized as abnormal and thus could grow into tumors.

Additionally, the researchers found that a high-fat diet changed the mouse’s intestinal microbiome. Several bacteria, including Helicobacter, increase MHC-II, which may help immune cells locate abnormal cells. The team did a “dirty roommate” experiment where mice without these bacteria were housed with ones that had it. The “clean” mice became infected with the Helicobacter bacteria and produced more of the MHC-II tag.

The findings suggest a new way to boost current immunotherapy treatments against cancer. Increasing the production of this MHC-II tag, either by diet, drugs, or changing the microbes in the body, can help the immune system recognize and eliminate cancer cells.