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Immune Cells in Cancer · Journal article
Cancer Discovery · August 17, 2026
Encouraging direction, but not yet definitive.
This preclinical mechanistic study demonstrates that high-fat diet-induced enrichment of Lactobacillus johnsonii and production of the bacterial metabolite desaminotyrosine enhance immunotherapy efficacy in mice independently of obesity-related metabolic dysfunction. A related metabolite was elevated in human ICI responders, and fecal microbiota transplant from high-BMI donors restored ICI response in mice, suggesting a potential dietary intervention strategy.
Preclinical mechanistic study with human translational biomarker validation. Mice bearing lung cancer xenografts or models; human lung cancer patients for biomarker analysis. Intervention: High fat diet, Lactobacillus johnsonii, desaminotyrosine (DAT) administration, and fecal microbiota transplant from high-BMI donors. Compared with: Low fat diet, other Western dietary patterns, antibiotic treatment, and fecal microbiota transplant from low-BMI donors.
High fat diet mice showed enrichment of Lactobacillus and highest ICI efficacy in lung cancer models, independent of body weight or metabolic status Switching nonresponsive mice to high fat diet conferred treatment sensitivity; switching responsive mice away reversed the effect Antibiotic treatment eliminated the ICI benefit, confirming gut bacteria were required for the effect
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If validated in clinical trials, dietary manipulation to promote specific gut microbiota could offer a non-pharmacological strategy to enhance immunotherapy response. The dissociation of the obesity paradox from metabolic dysfunction suggests that microbiome-targeted interventions might benefit patients regardless of BMI.
Mechanistic mouse study with human biomarker validation identifying a diet-microbiome pathway affecting ICI efficacy, but efficacy outcomes are limited to preclinical models and surrogate endpoints in human patients.
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Quoted from the source exactly as published.
If validated in clinical trials, dietary manipulation to promote specific gut microbiota could offer a non-pharmacological strategy to enhance immunotherapy response. The dissociation of the obesity paradox from metabolic dysfunction suggests that microbiome-targeted interventions might benefit patients regardless of BMI.
Graded across the dimensions that decide whether you should act, each from what the source actually supports. There is no single score, and where a dimension was not assessed it says so.
Patients with high body mass index (BMI) often respond better to immune checkpoint inhibitors (ICI) in several cancers, including lung cancer, a paradox given obesity's association with metabolic dysfunction and gut dysbiosis. To isolate the contributing mechanism, Desharnais and colleagues systematically modeled a diverse range of 12 diets in mice that reflect variation in human dietary patterns, spanning high fat, low fat, Mediterranean, Japanese, and other Western patterns, and assessed immune changes across models. Obesogenic diets were associated with fewer T cells and more monocytes in the blood, with a higher proportion of PD-1+ T cells. In a lung cancer mouse model, this systemic pattern did not predict outcome: obesity had no effect on tumor growth, and ICI efficacy was highest in mice fed high fat diets, independent of body weight or metabolic status. This suggested that the immune changes associated with obesity and the mechanism driving ICI response were independent. High fat diet mice shared a distinct gut microbial signature, particularly enrichment of Lactobacillus, previously linked to favorable ICI response. Switching nonresponsive mice to a high fat diet conferred treatment sensitivity, while switching responsive mice away from this diet reversed the effect. Antibiotic treatment eliminated the benefit, confirming gut bacteria, rather than diet or metabolic status, were required for this effect. Lactobacillus johnsonii were identified as a key species, and its effect was traced to a bacterial metabolite, desaminotyrosine (DAT), produced during microbial breakdown of tyrosine—an unexpected role for this bacteria that may be diet- or context-specific. Administering DAT to nonresponsive mice restored ICI sensitivity. In human lung cancer patients, a related metabolite was elevated among ICI responders, and transplanting gut bacteria from high, but not low, BMI donors restored ICI response in mice. Collectively, these findings identify a diet-driven microbial pathway, separate from obesity's metabolic effects, as the basis of the obesity paradox in ICI response, suggesting dietary intervention as a potential therapeutic strategy.Desharnais L, Swaby A, Messaoudene M, Doré S, Yu MW, Fiset B, et al. Diet–microbiome synergy underlies obesity-associated immunotherapy efficacy. Nature 2026 Jul 8 [Epub ahead of print].Note: Research Watch is written by Cancer Discovery editorial staff. Readers are encouraged to consult the original articles for full details. For more Research Watch, visit Cancer Discovery online at https://aacrjournals.org/cdnews.
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