Sporadic colorectal cancer (CRC) is a result of complex interactions between the host and its environment. Environmental stressors act by causing host cell DNA alterations implicated in the onset of cancer. Here we investigate the stressor ability of CRC-associated gut dysbiosis as causal agent of host DNA alterations. The epigenetic nature of these alterations was investigated in humans and in mice. Germ-free mice receiving fecal samples from subjects with normal colonoscopy or from CRC patients were monitored for 7 or 14 wk. Aberrant crypt foci, luminal microbiota, and DNA alterations (colonic exome sequencing and methylation patterns) were monitored following human feces transfer. CRC-associated microbiota induced higher numbers of hypermethylated genes in murine colonic mucosa (vs. healthy controls’ microbiota recipients). Several gene promoters including SFRP1,2,3, PENK, NPY, ALX4, SEPT9, and WIF1 promoters were found hypermethylated in CRC but not in normal tissues or effluents from fecal donors. In a pilot study ( n = 266), the blood methylation levels of 3 genes ( Wif1 , PENK , and NPY ) were shown closely associated with CRC dysbiosis. In a validation study ( n = 1,000), the cumulative methylation index (CMI) of these genes was significantly higher in CRCs than in controls. Further, CMI appeared as an independent risk factor for CRC diagnosis as shown by multivariate analysis that included fecal immunochemical blood test. Consequently, fecal bacterial species in individuals with higher CMI in blood were identified by whole metagenomic analysis. Thus, CRC-related dysbiosis induces methylation of host genes, and corresponding CMIs together with associated bacteria are potential biomarkers for CRC.

Courtship behavior plays a critical role in attracting females and reproduction success. However, the effects of exposure to a ubiquitous contaminant di(2-ethylhexyl) phthalate (DEHP) on these behaviors and, in particular, on courtship vocalizations have not been examined. The effects of adult exposure to DEHP on courtship and mating behaviors and gonadotropic axis and neural mechanisms involved in DEHP-induced effects were analyzed in male mice. Adult C57BL/6J males were orally exposed to DEHP (0, 0.5, 5, and 50μg/kg/d) for 4 wk. Olfactory preference, ultrasonic vocalizations (USVs), partner preference and mating, as well as locomotor activity and motor coordination, were measured. The kisspeptin system and testosterone levels were analyzed. Proteomic and molecular studies were conducted on the hypothalamic preoptic nucleus, the key region involved in sexual motivation to vocalize and mate. DEHP at 50μg/kg/d reduced the emission of USVs, whereas lower doses changed the ratio of syllable categories. This was associated with diminished sexual interest of female partners toward males exposed to 5 or 50μg/kg/d and increased latency to mate, despite normal olfactory preference. The kisspeptin system and circulating testosterone levels were unaffected. In DEHP-exposed males, proteomic analysis of the preoptic nucleus identified differentially expressed proteins connected to the androgen receptor (AR). Indeed, exposure to 5 or 50μg/kg/d of DEHP induced selective AR downregulation in this nucleus and upstream chemosensory regions. The involvement of AR changes in the observed alterations was further supported by the reduced emission of courtship vocalizations in males with disrupted neural AR expression. These data demonstrate the critical role of neural AR in courtship vocalizations and raises the possibility that the vulnerability of this signaling pathway to exposure to endocrine disrupters may be detrimental for courtship communication and mating in several species. https://doi.org/10.1289/EHP1443.

Summary: Recently, an intestinal dysbiotic microbiota with enrichment in oral cavity bacteria has been described in colorectal cancer (CRC) patients. Here we characterized and investigated one of these oral pathobionts, the Gram-positive anaerobic coccus Parvimonas micra. We identified two phylotypes (A and B) exhibiting different phenotypes and adhesion capabilities. We observed a strong association of phylotype A with CRC, with its higher abundance in feces and in tumoral tissue compared with the normal homologous colonic mucosa, which was associated with a distinct methylation status of patients. By developing an in vitro hypoxic co-culture system of human primary colonic cells with anaerobic bacteria, we showed that P. micra phylotype A alters the DNA methylation profile promoters of key tumor-suppressor genes, oncogenes, and genes involved in epithelial-mesenchymal transition. In colonic mucosa of CRC patients carrying P. micra phylotype A, we found similar DNA methylations alterations, together with significant enrichment of differentially expressed genes in pathways involved in inflammation, cell adhesion, and regulation of actin cytoskeleton, providing evidence of P. micra possible role in the carcinogenic process.

The gastrointestinal tract is abundantly colonized by microbes, yet the translocation of oral species to the intestine is considered a rare aberrant event, and a hallmark of disease. By studying salivary and fecal microbial strain populations of 310 species in 470 individuals from five countries, we found that transmission to, and subsequent colonization of, the large intestine by oral microbes is common and extensive among healthy individuals. We found evidence for a vast majority of oral species to be transferable, with increased levels of transmission in colorectal cancer and rheumatoid arthritis patients and, more generally, for species described as opportunistic pathogens. This establishes the oral cavity as an endogenous reservoir for gut microbial strains, and oral-fecal transmission as an important process that shapes the gastrointestinal microbiome in health and disease.

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 .

SUMMARY: Mechanistic insights are essential to understand how gut microbiota pathobionts contribute to tumorigenesis, given the mounting evidence linking them to colorectal cancer. We report a higher prevalence of the Rho GTPases-targeting cnf1 toxin gene from Escherichia coli in the microbiota of early-stage, proximal colorectal cancer. Comparative gene set enrichment analysis reveals a concordant serrated pathway signature between colorectal cancer tissue of patients colonized with cnf1 ⁺ bacteria and CNF1-treated mouse intestinal organoids. RNA sequencing of organoids shows that CNF1 induces a fetal-like transcriptional reprogramming. Using integrated approaches, we demonstrate that CNF1 reprograms Lgr5⁺ stem cells into a Ly6a/Sca-1⁺ fetal-like state, that exhibits enhanced stemness potential. This reprogramming is preceded by a Yap/Taz-driven early transcriptional program and nuclear translocation of Yap. Functional analyses identify a RhoA/Rock–Yap/Taz–dependent transition to Ly6a/Sca-1⁺ stem cells, highlighting a mechanistic link between bacterial effectors and stem cell plasticity in colorectal tumorigenesis.