With increasing urbanization and industrialization, the prevalence of inflammatory bowel diseases (IBDs) has steadily been rising over the past two decades. IBD involves flares of gastrointestinal (GI) inflammation accompanied by microbiota perturbations. However, microbial mechanisms that trigger such flares remain elusive. Here, we analyzed the association of the emerging pathogen atypical enteropathogenic
E. coli
(aEPEC) with IBD disease activity. The presence of diarrheagenic
E. coli
was assessed in stool samples from 630 IBD patients and 234 age- and sex-matched controls without GI symptoms. Microbiota was analyzed with 16S ribosomal RNA gene amplicon sequencing, and 57 clinical aEPEC isolates were subjected to whole-genome sequencing and in vitro pathogenicity experiments including biofilm formation, epithelial barrier function and the ability to induce pro-inflammatory signaling. The presence of aEPEC correlated with laboratory, clinical and endoscopic disease activity in ulcerative colitis (UC), as well as microbiota dysbiosis. In vitro, aEPEC strains induce epithelial p21-activated kinases, disrupt the epithelial barrier and display potent biofilm formation. The effector proteins
espV
and
espG2
distinguish aEPEC cultured from UC and Crohn’s disease patients, respectively. EspV-positive aEPEC harbor more virulence factors and have a higher pro-inflammatory potential, which is counteracted by 5-ASA. aEPEC may tip a fragile immune–microbiota homeostasis and thereby contribute to flares in UC. aEPEC isolates from UC patients display properties to disrupt the epithelial barrier and to induce pro-inflammatory signaling in vitro.
Background Under certain stress conditions, such as oxidative stress or nutrient deprivation, specific RNA-binding proteins aggregate with actively translated mRNAs to facilitate translational reprogramming and cell survival. 1 High levels or deregulated activity of these RNA-binding proteins, which include Ras GTPase-activating protein-binding protein 1 (G3BP1) or Y-box-binding protein 1 (YB-1) contribute to tumour progression and metastasis. 2 Inhibition of stress granule (SG) formation may therefore exert a synergistic effect with cytotoxic chemotherapy. Materials and Methods Formalin-fixed paraffin-embedded sections from neoadjuvant-treated colorectal cancer (CRC) liver metastasis patients (n=33) were immunohistochemically (IHC) stained for YB-1. CRC cell-lines as well as organoids and tissue slice cultures from surgical specimen were treated with oxaliplatin/5-fluorouracil alone or in combination with the histone deacetylase inhibitor (HDACi) MS-275. Incubation with arsenic acid served as positive control for SG aggregation. Immunofluorescence co-staining of YB-1 and G3BP1 was used to detect SG formation. Cell viability and apoptosis induction were analysed using viability (cellular adenosine triphosphate) and cytotoxicity (lactate-dehydrogenase release) assays, flowcytometry (active caspase 3, viability dye) and IHC (haematoxylin & eosin, active caspase 3, Ki-67). Results In the cohort of CRC liver metastasis patients, YB-1 protein expression was a negative predictor for overall survival. Oxaliplatin-based chemotherapy induced SG formation in CRC cell-lines and primary tumour tissue culture. Pre-treatment with the HDACi MS-275 prevented stress-granule aggregation and increased the sensitivity of CRC cell lines to oxaliplatin. Conclusions Clinical data and CRC cell-line or primary tissue cultures identify SG formation as a resistance factor for chemotherapy and as a therapeutic target in CRC.
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