Evidence has been rising over the past few years that the gut microbiome can significantly influence how well cancer treatments work, especially immunotherapies. But the underlying mechanism has remained unclear. Now, a new study reveals how bacteria in the gut can help determine whether the amino acid asparagine (obtained from diet) will increase tumor growth or activate immune cells against the cancer. The findings, published in Cell Microbe and Host in the paper, “Microbiota utilization of intestinal amino acids modulates cancer progression and anticancer immunity,” could lead to a novel cancer treatment approach and monitoring strategy; instead of targeting tumors directly, clinicians may one day be able to reshape the gut microbiome or diet to starve tumors while supercharging immune cells. “Our study suggests that we need to think about how the interplay of diet, gut microbiota and tumor-infiltrating immune cells could affect cancer growth and response to therapy. We can’t overlook this key level regulation,” said Chunjun Guo, PhD, associate professor of immunology at Weill Cornell. The researchers first established that some bacteria could deplete amino acids and affect tumor progression in mouse models with human gut microbiota. Both cancer cells in the nutrient-poor environment inside tumors and CD8+ T cells, the cytotoxic immune cells that directly attack and destroy tumor cells, require asparagine to be active. The team worked with Bacteroides ovatus, a common gut bacterium. When the bo‑ansB gene—which encodes an enzyme that breaks down asparagine—was present, B. ovatus consumes more asparagine in the gut, so less of it is absorbed into…
