Immune tolerance to colon cancer is mediated by colon dysbiosis: Human results and experimental In Vivo validation.

Abstract

e16062 Background: Lynch syndrome (Ly) but not Sporadic (Sp) CRC patients are responsive to immunotherapies. We have shown micorbiota from CRC patients induces precancerous colonic lesions in germ-free mice. The aim was to investigate microbiota linked compromised anti tumor immune response. Methods: We compared 1) Whole metagenomic fecal microbiotas of CRC patients [Sp, n = 53+Ly, n = 19] to controls (n = 90) or being first degree relatives of Ly patients (n = 14), respectively; 2) Tumoral to normal mucosa-adherent microbiota (16sRNA sequences); 3) Normal to tumoral tissues’ mRNA RT-PCRs of IL1b, IL4, IL6, IL8, IL17, TNFa, TGFb, FasL, Granzyme A&B, Thy1; 4) CD3, CD4, CD8, Granzym, KL1, FoxP3, RORgT, MastCell, cells in tumor tissues quantified by immunohistochemistry (IHC), between subgroups. Associations between bacteria, tissue immune cell infiltrates and clinical data (3-yrs follow up or death) were established by using unsupervised Systems Biology and Bioinformatics analyses (Institut Pasteur Shaman platform and Qlucor program). Anti tumoral immune response links with bacteria were based on differences between Ly and Sp CRC patients. Tumor tolerance links with bacteria were identified using germ-free mice (n = 185) who orally received microbiota (9 Sp CRC patients vs 9 controls) with colonic mucosa examined 3 months after human fecal transfer (whole exome sequencing, methylchips, IHC for CD3, CD11b, FoxP3, RORgT, ILC3). Results: Enrichment in Peptostreptococcus, Thermodesulfovibrio and diminution in Ruminococcus, Eubacterium, Coprococcus were linked with FoxP3 and IL-17 over expressions in tumor tissues. Enrichment in Escherichia, Enterobacter, Thioalkalimicrobium, and diminution in Eubacterium, Faecalibacterium and Butyrovibrio were associated with higher FoxP3, FasL, Granzyms A&B, Perforin, Thy1 mRNAs/mRNACD3. Diminution of Eubacterium, Dorea, Faecalibacterium genera and enrichment in Fusobacterium, E. Coli/Shigella were associated with higher CD3, FoxP3, GranzymA and B and FOXP3-RORgT cells in tumor tissues. Higher fecal enrichments in oral bacteria (parvimonas micra) and lack of Thermodesulfovibrio enrichment were associated with higher FoxP3-RORgt cells and short survival; in mice ILC3 and FoxP3-RORgT cells were linked with Sp CRC dysbiosis. Species linked with immunotolerance are identified. Conclusions: Fecal and tissue microbiota can impact failure of anti tumoral immune response in sporadic CRC patients by enhancing overexpression of IL-17 and reducing cytotoxic T-cell infiltration in tumors. Clinical trial information: NCT01270360 .