Effect of acute and chronic ATF6 activation on gene expression in the colonic epithelium, in specific pathogen-free and germ-free mice.

The induction of endoplasmic reticulum unfolded protein responses (UPRER) contributes to cancer development and progression. We recently linked microbiota-related triggers to the tumor-promoting role of signal transducer activating transcription factor 6 (ATF6) in the colon. Here we substantiate the clinical relevance of ATF6 and related bacterial genera in colorectal cancer patient cohorts. Spatial and longitudinal bacterial profiling in ATF6 transgenic mice (nATF6IEC) identified tumor-initiating and tumor-progressing shifts in the mucosa-associated microbiota. Transcriptional analysis in intestinal epithelial cells (IEC) of germ-free and specific pathogen-free nATF6IEC mice defined bacteria-specific changes in cellular metabolism enriched for fatty acid biosynthesis. Untargeted metabolomics, isotope-labeling in intestinal organoids and FASN inhibition confirmed ATF6-mediated involvement of long-chain fatty acids in tumorigenesis. Multi-omics data integration identified a bacteria-lipid network characterized by fatty acid efflux, catabolism and detoxification. We postulate chronic ATF6 signaling to drive a clinically relevant pathologic response altering lipid metabolism to select for a tumor-promoting microbiota. To identify the transcriptional response to ATF6 activation, we performed intestinal epithelial cell isolation from colonic tissue of mice. Gene expression profiling analysis was performed on six mice per group were used for the following experimental groups: 5 week-old fl/fl SPF, 5 week-old tg/tg SPF, 5 week-old fl/fl GF, 5 week-old tg/tg GF, fl/fl after 4d of ATF6 induction, tg/tg after 4d of ATF6 induction.