A high-salt diet may induce effective tumor immunity-II
So, how do NK cells influence tumor growth when a high-salt diet is consumed? Researchers continued their work.
Previous research has shown that a high-salt diet can regulate the gut microbiota in an autoimmune background, and that gut microbiota modulation is linked to tumor growth. Researchers utilized antibiotics to deplete the microbiota of mice to establish an AIMD (antibiotic-induced microbiome depletion) mouse model and a control group that was fed a high-salt diet separately to study the role of the gut microbiota in high-salt diet-mediated tumor immunity. Tumor growth was not inhibited in AIMD mice, although tumor growth was inhibited in control mice. It can be concluded that the loss of tumor immunity induced by the high-salt diet is caused by gut microbiota ablation, implying that the high-salt diet induces tumor immunity via modulating the gut microbiota.
How does the gut microbiota interact with natural killer cells (NK cells)?
The frequency of NK cells rose in the control group mice fed a high-salt diet, while the frequency of NK cells in AIMD mice did not change, according to flow cytometry analysis of tumor infiltrating immune cells. In the control group mice, a rise in the activation marker (CD107a) and a decrease in the inhibitory marker (CD96) were observed at the same time. The AIMD mice showed no signs of this alteration. The mice’s feces were then examined, and it was shown that the number of bifidobacteria in the tumor animals fed a high-salt diet grew considerably. As a result, the researchers hypothesized that when a high-salt diet is consumed, bifidobacteria in the intestinal microbiota increases, activating NK cells and exerting immunological effects.
To verify their hypothesis, the researchers used oral gavage (FMT) to transfer the feces of mice on a high-salt diet to AIMD mice. Compared with AIMD mice that received FMT from mice feces from a normal diet, the tumor volume and mass of the former had subsided, and the survival rate was improved. Furthermore, the number of NK cells in tumor-infiltrating immune cells increased considerably.
The researchers examined the feces of two groups of mice, and the results showed a significant increase in bifidobacteria in AIMD mice receiving fecal FMT from mice on a high-salt diet. This suggests that the regulation of the intestinal microbiota by the high salt diet enriched bifidobacteria, which in turn increased NK cell frequency and promoted tumor immunity.
In conclusion, this research demonstrates that a high-salt diet increases the amount of bifidobacteria in the gut microbiota, which boosts the frequency of NK cells and enhances tumor immunity in vivo. According to the findings, bifidobacteria are critical mediators of enhanced NK cell activity and tumor immunity, and the researchers indicated that the gut microbiota maintained on a simulated high-salt diet may have intriguing anticancer translational potential based on this finding.