Research Highlights Gut Microbiome's Role in Cancer Defense Mechanisms

The research, published on January 2 in Cell Host & Microbe, focuses on asparagine, an amino acid found in many foods. Asparagine supports protein production and cell survival and is needed by both cancer cells and immune cells called CD8+ T cells, which attack tumors. The study shows that gut bacteria can control how much asparagine reaches tumors, shaping whether it benefits cancer cells or immune defenses.

Using mouse models with human gut bacteria, researchers studied Bacteroides ovatus, a common gut microbe. Some strains of this bacterium carry a gene called bo-ansB, which allows them to break down asparagine in the intestine. When this gene was present, bacteria consumed more asparagine, reducing the amount absorbed into the bloodstream and delivered to tumors.

When the gene was removed, more asparagine entered the circulation and reached tumors. Surprisingly, this extra asparagine did not fuel cancer growth. Instead, it was taken up by CD8+ T cells, pushing them into a powerful “stem-like” state linked to long-lasting anti-tumor immunity. These immune cells became better at multiplying and killing cancer cells.

The study also found that higher asparagine levels increased the activity of a key transporter protein, SLC1A5, on immune cells. Blocking this transporter erased the immune benefits, showing its importance in the process.

The findings suggest that future cancer treatments may go beyond targeting tumors directly. Instead, doctors could combine immunotherapy with personalized diets or microbiome-based strategies—such as tailored probiotics—to starve tumors while strengthening immune responses.

REFERENCE: Qiao, S., et al. (2026). Microbiota utilization of intestinal amino acids modulates cancer progression and anticancer immunity. Cell Host & Microbe. doi: 10.1016/j.chom.2025.12.003. https://www.cell.com/cell-host-microbe/fulltext/S1931-3128(25)00522-0