Dietary fiber improves the effectiveness of cancer immunotherapy

One study shows that consumption of dietary fiber is associated with better survival in patients with metastatic melanoma treated with immunotherapy.

Immune awakening

As its name suggests, cancer immunotherapy is based on destroying tumors by stimulating the immune system. It has long been known that in some types of tumors, cancer cells create an immunosuppressive climate that paralyzes killer lymphocytes (white blood cells) and prevents them from attacking.

The discovery that some antibodies can eliminate this paralysis and thus awaken immune cells to enable them to eliminate cancer cells, thus represented a major breakthrough in the effective treatment of some types of cancer, a discovery which was also rewarded with The Nobel Prize in Medicine, awarded in 2018 to Dr. James Allison and Tasuku Honjo. A fully deserved distinction because immunotherapy has made it possible to achieve a dramatic increase in the survival of certain patients with highly aggressive and advanced cancers which were previously considered incurable, particularly metastatic melanomas.1.

Involvement of the intestinal microbiome

Despite the tremendous success of immunotherapy, it was quickly realized that the therapeutic efficacy of this approach could vary considerably from patient to patient. Numerous studies that have examined this question have shown that the intestinal microbiome (hundreds of billions of commensal bacteria present in the gut) plays a major role in these interpersonal variations.2.

This microbiome contribution is biologically reliable, as it has been well established that a diversified microbiome generates several components (for example, short-chain fatty acids) that improve the effectiveness of the immune system.

Since the composition of the microbiome is strongly influenced by lifestyle-related factors, in particular the nature of the diet, it would be possible to optimize the effectiveness of immunotherapy by adopting a diet that promotes the implantation of friendly bacteria, which exert a positive effect. impact on immunity.

Fiber in the menu

Dietary fiber is a key ingredient of nutritional origin capable of modifying the microbiome and, consequently, immunity: the fermentation of these fibers by intestinal bacteria allows the creation of a diverse bacterial flora, composed of species that produce anti-inflammatory compounds that affect immune system. systems.

This fiber-related immune modulation appears to affect the effectiveness of immunotherapy: by comparing the fiber intake of patients with metastatic melanoma who have been treated with immune checkpoint inhibitors (the most common form of immunotherapy), US researchers put note that those who consumed a minimum of 20 g of fiber per day responded better to treatment (longer progression-free survival) than those who consumed less3.

Importantly, however, this improvement in efficacy is not seen in patients taking probiotic supplements, a strategy often used by cancer patients to improve bowel health: on the contrary, the study shows that these supplements impair the effectiveness of immunotherapy and reduce the survival of patient. .

This suggests that the large diversity of bacterial populations (several hundred) created by the varied diet is greater than the growth of a single bacterial population, caused by supplementation.

These observations were confirmed using animal models of metastatic melanoma treated with immunotherapy: here again, the lack of fiber or administration of probiotic supplements reduced the response to therapy as well as longevity. , possibly due to a lower recruitment of killer T cells into the tumor microenvironment.

Overall, these results suggest that higher fiber intake is associated with the creation of a more diverse intestinal microbiome and improved tumor response to immunotherapy. Although this link remains to be better characterized, a diet rich in dietary fiber (vegetables, whole grains, legumes) seems to represent a very interesting strategy for patients treated with these drugs and seeking to increase their probability of survived. However, the use of probiotic supplements can not be advised, as they do not appear to offer any improvement in survival and may even interfere with treatments.

♦ 1. Ribas A and JD Wolchok. Cancer immunotherapy using checkpoint blockade. science 2018; 359: 1350-1355.

♦ 2. Gopalakrishnan V etj. The intestinal microbiome modulates the response to anti-PD-1 immunotherapy in patients with melanoma. science 2018; 359: 97-103.

♦ 3. Spencer CN etc. Dietary fiber and probiotics affect the intestinal microbiome and the response to melanoma immunotherapy. science 2021; 374: 1632-1640.

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