UNLABELLED

The gut microbiome's role in the pathogenesis of hematologic malignancies is actively being explored; yet studies on chronic lymphocytic leukemia (CLL) are limited. Using the Eμ-TCL1 murine model of CLL, we identify a unique and dysbiotic disease-associated gut microbiome that develops in mice over time. Leukemic mice show an increase in abundance of pathogenic bacteria, specifically members of the Proteobacteria phylum. We found that this dysbiotic microenvironment is associated with CLL involvement within the intestinal tract and high levels of markers indicative of altered tight junction permeability (e.g., claudin-2, soluble CD14, and zonulin). Moreover, utilizing the syngeneic model of CLL in tandem with an antibiotic-mediated microflora ablation approach, we found that leukemic mice receiving microflora-ablating antibiotics show marked changes to the gut microbiome and a delayed disease onset compared with mice receiving antibiotic-free water. Immunophenotyping of murine spleens showed that this delay in disease was accompanied by more tumor-reactive CD8+ T cells that coexpressed fewer inhibitory receptors (e.g., PD-1, LAG-3, and TIM-3). These findings confirm that a dysbiotic gut microbiome develops during CLL disease and demonstrate unique intestinal involvement and potential immune dysregulation occurring during CLL progression that may be influencing the overall microbial signature.

SIGNIFICANCE

There is a growing appreciation for the gut microbiome's role in hematologic malignancies. Despite this, its role in CLL remains obscure. This study demonstrates a dysbiotic microbiome within CLL that may contribute to further intestinal and immune dysregulation present during CLL progression.