Dietary suppression of MHC-II expression in intestinal epithelial cells enhances intestinal tumorigenesis

Little is known about how interactions between diet, intestinal stem cells (ISCs) and immune cells impact the early steps of intestinal tumorigenesis. Here, we show that a high fat diet (HFD) reduces the expression of the major histocompatibility complex II (MHC-II) genes in intestinal epithelial cells including ISCs. This decline in epithelial MHC-II expression in a HFD correlates with reduced diversity of the intestinal microbiome and is recapitulated in antibiotic treated and germ-free mice on a control diet. Mechanistically, pattern recognition receptor (PRR) and IFN g signaling regulate epithelial MHC-II expression where genetic ablation of these signaling pathways dampen MHC-II epithelial expression. Interestingly, upon loss of the tumor suppressor gene Apc in a HFD, MHC-II- ISCs harbor greater in vivo tumor-initiating capacity than their MHC-II+ counterparts when transplanted into immune-component hosts but not immune-deficient hosts, thus implicating a role for epithelial MHC-II-mediated immune surveillance in suppressing tumorigenesis. Finally, ISC-specific genetic ablation of MHC-II in engineered Apc-mediated intestinal tumor models increases tumor burden in a cell autonomous manner. These findings highlight how a HFD perturbs a microbiome – stem cell – immune cell crosstalk in the intestine and contributes to tumor initiation through the dampening of MHC-II expression in pre-malignant ISCs. single-cell RNA-seq of Lgr5+ intestinal stem cells derived from control or HFD mice