In recent years, immunotherapy has shined in the field of oncology. Under normal circumstances, the immune system can recognize and clear tumor cells, but tumor cells will take "small means" to avoid the pursuit of the immune system in order to survive and grow, and the immunotherapy of tumors is to activate the immune system so that it can accurately identify tumor cells that want to escape, thereby controlling and clearing tumors.
Immune checkpoint inhibitors PD-(L)1 inhibitors, therapeutic antibodies and small molecule inhibitors are all immunotherapy, and have also demonstrated strong anti-tumor activity in the treatment of multiple tumor species, such as melanoma, non-small cell lung cancer, kidney cancer and prostate cancer.
But for some patients, immunotherapy also fails to stop tumor growth in their bodies. A recent study by the National Cancer Institute (NCI) found that eating a high-fiber diet may improve the efficacy of immunotherapy in melanoma patients.
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A paper published by NCI in Science, Dietary Fiber and Probiotics influence the gut microbiome and melanoma immunotherapy response, mentions: In advanced melanoma populations receiving immunotherapy, Patients who consumed at least 20 g of dietary fiber per day survived the longest.
Giorgio Trinchieri, director of NCI's Integrated Cancer Immunology Laboratory, said: "The data suggest that foods rich in dietary fiber may improve the efficacy of immunotherapy in patients with melanoma by influencing the gut microbiota. ”
The study compared the progression of cancer over the course of the experiment by comparing the daily dietary fiber intake of 128 patients with different daily dietary fiber intakes, and found that patients who consumed at least 20 g of dietary fiber per day had a longer survival period than those who consumed less dietary fiber, and there was no progression in the course of the disease during this time.
The researchers further conducted simulation trials in mice, where they studied the effects of dietary fiber on drug therapy for PD-1 inhibitors in a mouse model of melanoma. To mimic the different diets of melanoma patients, the researchers fed mice dietary fiber-rich or low-fiber foods and injected the mice with melanoma cells, followed by a PD-1 inhibitor on the mice. The results found that mice that consumed dietary fiber rich in dietary fiber delayed tumor growth after treatment with PD-1 inhibitors.
The researchers also conducted experiments on germ-free mice.
"In germ-free mice, diet was exempt from the efficacy of immunotherapy. This suggests that dietary fiber intake is affecting the efficacy of immunotherapy by altering the composition of the intestinal flora. ”
Intestinal flora
Giorgio Trinchieri says the mechanism by which dietary fiber works may be by increasing the types of bacteria in the gut, such as rumen cocci.
A 2017 Science paper, Gut microbiome modulates response to anti–PD-1 immunotherapy in melanoma patients, mentions significant differences in the diversity and composition of the intestinal flora of PD-1 immunotherapy responders (R) and respondents (NR). Through the analysis of patient fecal microorganisms, R has a significantly higher diversity and a relative abundance of rumen cocci bacteria.
Giorgio Trinchieri said: "In mice fed a high-fiber diet, we saw an increase in a certain short-chain fatty acid propionic acid. "Rumen cocci bacteria produce high levels of certain short-chain fatty acids that have anti-tumor effects.
Prior to this study on the gut microbiota, researchers also tried to introduce different gut microbiota into patients through fecal transplantation, which also made some patients who initially did not respond to PD-1 inhibitor therapy effective.
In addition to dietary fiber, the researchers also studied the effects of probiotics on the gut microbiota of mice with melanoma. Mice fed probiotics were treated with PD-1 inhibitors less effectively, and mice that consumed probiotics developed larger tumors than the control group.
Both dietary fiber and probiotics can alter the gut microbiome, and many cancer patients are taking probiotics to improve their gut health.
Although from the data of this study, probiotics have a negative impact on cancer patients who are receiving immunotherapy, the impact of dietary fiber and probiotics on the intestinal flora is only a small part of the internal environment changes, and there are many factors that will affect the ability of melanoma patients to respond to immunotherapy.
Edit: Allen
Photo: Network, arranged by Zhou Luyuan