Aryl hydrocarbon receptor nuclear translocator limits the recruitment and function of regulatory neutrophils against colorectal cancer by regulating the gut microbiota

Although the role and mechanism of neutrophils in tumors have been widely studied, the precise effects of aryl hydrocarbon receptor nuclear translocator (ARNT) on neutrophils remain unclear. In this study, we investigated the roles of ARNT in the function of CD11b Gr1 neutrophils in colitis-associated colorectal cancer. Wild-type (WT), ARNT myeloid-specific deficient mice and a colitis-associated colorectal cancer mouse model were used in this study. The level and functions of CD11b Gr1 cells were evaluated by flow cytometry and confocal microscopy. We found that ARNT deficiency drives neutrophils recruitment, neutrophil extracellular trap (NET) development, inflammatory cytokine secretion and suppressive activities when cells enter the periphery from bone marrow upon colorectal tumorigenesis. ARNT deficiency displays similar effects to aryl hydrocarbon receptor (AHR) deficiency in neutrophils. CXCR2 is required for NET development, cytokine production and recruitment of neutrophils but not the suppressive activities induced by Arnt in colorectal cancer. The gut microbiota is essential for functional alterations in Arnt neutrophils to promote colorectal cancer growth. The colorectal cancer effects of Arnt neutrophils were significantly restored by mouse cohousing or antibiotic treatment. Intragastric administration of the feces of Arnt mice phenocopied their colorectal cancer effects. Our results defined a new role for the transcription factor ARNT in regulating neutrophils recruitment and function and the gut microbiota with implications for the future combination of gut microbiota and immunotherapy approaches in colorectal cancer.