High dietary fiber can improve the immunotherapy effect of cancer patients
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Science: High dietary fiber can improve the immunotherapy effect of cancer patients.
In recent years, the rapid development of tumor immunotherapy represented by PD-1/PD-L1 immune checkpoint inhibitors has significantly changed the pattern of human cancer treatment.
But this therapy is only effective for a small number of cancers.
Immunotherapy uses the body’s own immune system to attack cancer, but most tumors create a highly immunosuppressive environment that inactivates T cells.
However, immune checkpoint therapy works by rejuvenating T cells, thereby destroying tumors.
December 24, 2021, researchers from MD Anderson Cancer Center, University of Texas and the US National Institutes of Health published a research paper, entitled: Dietary Fiber and Probiotics Influence at The Gut microbiome and the Response melanoma Immunotherapy .
Research on melanoma patients receiving immune checkpoint blocking therapy found that higher dietary fiber is associated with significantly improved progression-free survival.
Studies in mouse models have shown that high dietary fiber can help improve tumor immunotherapy.
The development of tumor immunotherapy has brought a revolutionary effect in the treatment of melanoma, which can improve the life span of some patients with advanced stages, and sometimes even extend it by several years.
However, for many patients, immune checkpoint inhibitors cannot prevent tumor growth. Early research suggests that the composition of gut bacteria may affect the response to immunotherapy.
One study pointed out that some melanoma patients who initially did not respond to immune checkpoint blockers did respond after receiving stool transplants from patients who responded to the drug.
However, dietary fiber intake and the use of probiotic supplements have also been shown to affect the composition of gut bacteria, but it is not clear how fiber intake and how probiotics change the flora and immunotherapy response.
In this study, the researchers analyzed the effects of human and mouse gut microbiota, dietary habits, and probiotic usage on immune checkpoint blockers in the treatment of advanced melanoma.
First, the researchers analyzed 128 melanoma patients with known dietary fiber intake. The researchers defined 20 grams of dietary fiber as a sufficient amount.
Among all participants, 91 participants had insufficient fiber intake and 37 had adequate intake.
During the 13-month follow-up, patients with adequate fiber intake had improved progression-free survival compared with patients with insufficient fiber intake.
In addition, every 5 grams increase in daily fiber intake reduces the risk of cancer progression or death by 30%.
In the mouse model, in order to simulate the different diets of melanoma patients, the researchers fed the mice a diet rich in fiber or low-fiber, injected the mice with melanoma cells, and then treated the mice with anti-PD-1 therapy.
It was found that compared with mice on a low-fiber diet, mice on a fiber-rich diet delayed tumor growth after anti-PD-1 treatment.
Subsequently, the researchers repeated the experiment on mice without bacteria in their intestines. In sterile mice, the diet had no effect on the immunotherapy response.
The researchers pointed out that this suggests that diet is affecting the response to immune checkpoint treatment by changing the composition of the gut microbiota.
One possible mechanism for dietary fiber to exert its beneficial effects is by increasing the types of bacteria in the intestines, such as Rumenococcus, which produce high levels of certain short-chain fatty acids with anti-tumor effects.
Research model
Further experiments found that in mice fed a high-fiber diet, a short-chain fatty acid propionic acid content was found to increase.
In addition, compared with cancer patients who did not respond to immunotherapy, the gut microbiota of cancer patients who responded to immunotherapy contained more Rumenococcus bacteria.
Finally, the researchers also analyzed the effects of probiotics on intestinal bacteria in a mouse model of melanoma.
In the mouse model, mice fed probiotics had a reduced response to anti-PD-L1 drug treatment and developed larger tumors than control mice.
Further analysis showed that mice fed probiotics had lower levels of tumor-killing immune cells.
This is also true in humans, indicating that the use of probiotics alone has nothing to do with progression-free survival or the chance of immunotherapy response.
In summary, the study shows that cancer patients undergoing immunotherapy respond better to immunotherapy when their diet is rich in fiber.
The data also shows that cancer patients undergoing immunotherapy are best not to use probiotics.
References:
https://www.science.org/doi/10.1126/science.aaz7015
High dietary fiber can improve the immunotherapy effect of cancer patients
(source:internet, reference only)
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