Smoking-induced gut microbial dysbiosis mediates cancer progression through modulation of anti-tumor immune response.

Cigarette smoke exposure (CSE) increases the risk for a plethora of cancers. Recent evidence indicates that the gut microbiome can influence cancer progression by immune system modulation. Since CSE alters the gut microbiome, we hypothesized that the gut microbiome serves as a causative link between smoking and cancer growth. Through a combination of syngeneic animal models and fecal microbiota transplantation studies, we established an essential role for smoke-induced dysbiosis in cancer growth. 16s rRNA sequencing and liquid chromatography-mass spectrometry indicated a unique CSE-associated microbial and metabolomic signature. Immunophenotyping of tumor specimens and experiments in Rag1-KO and CD8-KO demonstrated that smoke-induced tumor growth requires functional adaptive immunity. Finally, utilizing gut microbial ablation strategies with broad- and narrow-spectrum antibiotics, we demonstrated the reversal of phenotypic effects of CSE. Our study provides evidence for gut microbiome as an actionable target to mitigate CSE-induced tumor promotion.