PD-L1 Restrains the PD-1hiNrp1loTGFb+ Treg to block IL6+ Neutrophil tumor infiltration to Suppress Inflammation-driven Colorectal Cancer

PD-L1 functions as a suppressor of T cell activation and colonic inflammation. The consequence of and mechanism underlying these opposite functions of PD-L1 in colorectal cancer remains unknown. We report that global Cd274 deletion promotes inflammation-driven colorectal tumorigenesis. 16S rRNA and shotgun metagenomic sequencing revealed that loss of host PD-L1 leads to expansion of gut Ligilactobacillus murinus and activation of the AhR pathway in tumor-bearing mice. scRNA-seq analysis revealed that PD-L1 regulates PD-189Nrp11215 Treg, IL6+ neutrophils, and B cells in colorectal tumor. Treg expresses high level of TGF{beta} to recruit IL6+ neutrophils. IL6 inhibits activation of B and T cells. IL6 blockade or B cell activation via CD40 agonist increases CTL activation and suppresses colon tumor growth in vivo. Our findings determine that PD-L1 functions as a tumor suppressor in the context of inflammation-driven colorectal cancer and the PD-L1/L. murius/PD-189Nrp11215TGF{beta}+ Treg/IL6+ neutrophils pathway controls host cancer immunosurveillance and colorectal tumorigenesis. Key pointsGlobal deletion of Cd274 promotes inflammation-driven colorectal tumorigenesis. Loss of PD-L1 increases gut L. murinus and activates AhR pathway in colorectal tumor. PD-1hiTGF{beta}+Nrp1lo Treg recruits IL6+ neutrophils to inhibit B and T cell function in colorectal tumor. L. murinus and tryptophan metabolites connect PD-L1 and colorectal tumor immunosurveillance. Graphic summary O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=164 SRC="FIGDIR/small/562132v1_ufig1.gif" ALT="Figure 1"> View larger version (50K): org.highwire.dtl.DTLVardef@2d23bcorg.highwire.dtl.DTLVardef@1852c8eorg.highwire.dtl.DTLVardef@304978org.highwire.dtl.DTLVardef@278c5b_HPS_FORMAT_FIGEXP M_FIG C_FIG