Abstract 643: Correlations of dietary fiber with intestinal microbiome and outcomes in allogeneic hematopoietic cell transplantation

Abstract Background: Allogeneic hematopoietic cell transplantation (allo-HCT) can be a curative therapy for patients with hematological malignancies. However, allo-HCT poses a significant risk for post-transplant mortality due to graft-versus-host disease (GVHD), which is associated with loss of beneficial intestinal microbiota and decrease of microbial metabolites. In addition, dietary fiber can modulate the intestinal microbiome and the production of short-chain fatty acids (SCFAs), which are microbial metabolites associated with intestinal homeostasis. Therefore, we hypothesized that a high-fiber diet is associated with an increase of beneficial commensals, higher concentrations of SCFAs, and decreased risk of GVHD. Methods: We collected dietary data and fecal samples from 73 allo-HCT patients (GVHD n=45, No-GVHD n=28) at Memorial Sloan Kettering Cancer Center, collected longitudinally throughout the allo-HCT course, and performed 16s rRNA, shotgun metagenomic sequencing, and gas chromatography mass spectrometry (n=311). We assessed the α-diversity, microbiome composition, and concentrations of fecal SCFAs in response to fiber intake. We also tested different concentrations of dietary fiber (0%, 6%, 12% and 40%) in a preclinical GVHD model (C57BL/6J into BALB/c, n=30 per group, n=180 total) and assessed GVHD lethality and fecal microbial composition. Results: We found that in allo-HCT patients, fiber intake significantly correlated with microbial α-diversity (R=0.3, p=0.01) and patients with a higher fiber diet had a significantly higher microbial α-diversity when compared to the low fiber cohort (p<0.001). Remarkably, the decrease in dietary fiber post-allo-HCT correlated with a significant reduction in the fecal concentrations of SCFAs in the GVHD group (n=14), butyrate (p=0.003), propionate (p=0.01), and acetate (p=0.004), that was not significant in the No-GVHD cohort (n=28), indicating that low dietary fiber could lead to lower production of bacterial metabolites in GVHD. In addition, mice receiving a fiber-rich diet (12%) had a significant reduction in GVHD lethality (p=0.02) compared to mice receiving lower or higher fiber (0%, 6%, 40%). A 12% fiber diet also resulted in higher microbial α-diversity (p=0.02) and a significant decrease in Enterococcus faecalis (p=0.05), a pathogen associated with worse GVHD mortality in mice and humans. Conclusions: Our study demonstrates that a) higher fiber intake in patients after allo-HCT is associated with an increase in α-diversity and SCFA concentrations, and b) optimal fiber consumption in pre-clinical GVHD models leads to an increase in α-diversity, a decrease in pathogen mono-domination, and more importantly, a decrease in GVHD lethality. These results suggest that dietary fiber could be used in the prevention of GVHD. Citation Format: Jenny Paredes, Peter Adintori, Anqi Dai, Ruben J. Faustino Ramos, Teng Fei, Harold Elias, Marina Burgos da Silva, Romina Ghale, Charlotte Pohl, Justin Cross, Oriana Miltiadous, Marcel van den Brink. Correlations of dietary fiber with intestinal microbiome and outcomes in allogeneic hematopoietic cell transplantation [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 643.