The study found that Lactobacillus plantarum IMB19 enhances anti-tumor immunity by activating macrophages and regulating iron availability. The bacterium's capsule isopolysaccharide is the main effector molecule, prompting macrophages to transition to an active phenotype and triggering "vegetative immunity", thereby inhibiting tumor growth in mice. This study offers new strategies for cancer treatment, emphasizing the link between diet and health.
01
Anti-tumor immunity is the body's natural defense mechanism against cancer. Macrophages, as part of the immune system, are able to play an important role in the tumor microenvironment. Iron is a key element in cell growth and proliferation, and by regulating iron availability, it can affect the survival of tumor cells.
Recently, a new study published in Nature Immunology revealed how a symbiotic bacterium in kimchi boosts anti-tumor immunity by activating macrophages. The study, conducted by South Korean scientists, not only provides new perspectives on cancer treatment, but also new clues to our understanding of the complex relationship between food and health.
02
The research team found that Lactobacillus plantarum IMB19 (LpIMB19) can significantly enhance anti-tumor immunity in mouse allogeneic and xenograft tumor models. The capsule isopolysaccharide (CPS) of LpIMB19 is the primary effector molecule and acts by acting as a ligand for TLR2. This molecule works in two ways:
First, it induces a transition of tumor-associated macrophages to a classically active phenotype, eliciting a sustained CD8+ T cell response.
Second, it triggers the "nutritional immunity" of macrophages by deploying the high-affinity ferroporter lipocalin-2 (LCN2), which captures and sequesters iron in the tumor microenvironment, inducing tumor cell death.
LpIMB19 induces inflammatory macrophage aggregation
Key findings include:
1. LpIMB19 inhibits tumor growth in mice, and this effect is dependent on CD8+ T cells.
2. LpIMB19-treated mice showed no significant differences in the relative abundance and diversity of gut microbiomes in different phyla and families, and were not colonized in vivo.
3. Heat-inactivated LpIMB19 was also able to induce inflammatory responses, suggesting that the heat-stabilizing component was at work.
4. Single-cell RNA sequencing (scRNA-seq) analysis revealed an increase in effector and memory CD8+ T cells in LpIMB19-treated tumors.
03
This study offers a novel strategy to enhance the body's anti-tumor immune response through food symbionts. Although the study was conducted in a mouse model, the results suggest that microbes in the daily diet may have a profound impact on health.
This study highlights the link between diet and health, especially the potential role of microbes in regulating host immune responses. Although these findings are in their early stages, they provide valuable information for the development of new cancer treatment strategies.
reference
Sharma, G., Sharma, A., Kim, I. et al. A dietary commensal microbe enhances antitumor immunity by activating tumor macrophages to sequester iron. Nat Immunol 25, 790–801 (2024).