Host-microbiome interactions in leukemia: mechanisms, treatment response, and clinical implications

Host-microbiome interactions regulate immune function, epithelial barrier integrity, and hematopoietic homeostasis. Intestinal microbial communities show consistent disruption in leukemia, particularly during intensive chemotherapy and hematopoietic stem cell transplantation. Reduced microbial diversity, depletion of short-chain fatty acid (SCFA)-producing commensals, and expansion of opportunistic taxa are recurrent findings across cohorts. Such patterns correlate with inflammatory signaling, impaired barrier function, and shifts in immune responses affecting treatment tolerance and hematopoietic recovery. Clinical associations show greater consistency for treatment-related outcomes, including infection risk, mucosal injury, and delayed immune reconstitution, than for leukemogenesis. Evidence supporting a direct causal role of specific microbial taxa in disease initiation remains limited. This review examines microbiome composition, microbial taxa, and mechanistic pathways in leukemia, with emphasis on how microbiome alterations may influence leukemia biology, disease progression, treatment response, and clinical outcomes, while acknowledging that most human evidence remains associative.