Utility of a bacterial infection model to study epithelial–mesenchymal transition, mesenchymal–epithelial transition or tumorigenesis

Abstract

DCLK1 and Lgr5 have recently been identified as markers of quiescent and cycling stem cells in the small intestinal crypts, respectively. Epithelial–mesenchymal transition (EMT) is a key development program that is often activated during cancer invasion and metastasis, and also imparts a self-renewal capability to disseminating cancer cells. Utilizing the Citrobacter rodentium (CR)-induced transmissible murine colonic hyperplasia (TMCH) model, we observed a relative decrease in DCLK1 expression in the colonic crypts, with significant shift towards stromal staining at peak (12 days post infection) hyperplasia, whereas staining for Lgr5 and Msi-1 increased several fold. When hyperplasia was regressing (days 20–34), an expansion of DCLK1 +ve cells in the CR-infected crypts compared with that seen in uninfected control was recorded. Purified colonic crypt cells exhibiting epigenetic modulation of the transforming growth factor-β (TGFβ), Wnt and Notch pathways on 12 or 34 days post infection formed monolayers in vitro, and underwent trans-differentiation into fibroblast-like cells that stained positive for vimentin, fibronectin and DCLK1. These cells when trypsinized and regrown in soft agar, formed colonospheres/organoids that developed into crypt-like structures (colonoids) in Matrigel and stained positive for DCLK1. Mice exhibiting 12 or 34 days of TMCH were given azoxymethane once for 8 h (Gp1) or weekly for 3 weeks (Gp2), and subjected to crypt isolation. Crypt cells from Gp1 animals formed monolayers as well as colonospheres in soft agar and nodules/tumors in nude mice. Crypt cells isolated from Gp2 animals failed to form the monolayers, but developed into colonospheres in soft agar and nodules/tumors in nude mice. Thus, both hyperplasia and increased presence of DCLK1 +ve cells promote cellular transformation in response to a second hit. The TMCH model, therefore, provides an excellent template to study how alterations in intestinal stem cells promote trans-differentiation, crypt regeneration or colon carcinogenesis following bacterial infection.

Prolonged and repetitive exposure to Porphyromonas gingivalis increases aggressiveness of oral cancer cells by promoting acquisition of cancer stem cell properties

“…Recent studies have demonstrated that microbial pathogens, including Epstein-Barr virus, hepatitis B and C virus, and Citrobacter rodentium, can play a role in the induction of EMT, just as H. pylori, a well-established EMT inducer in gastric epithelial cells [33][34][35][36][37][38]. In contrast, there is no study to define the role of P. gingivalis in EMT induction.…”

Human Enteroids/Colonoids and Intestinal Organoids Functionally Recapitulate Normal Intestinal Physiology and Pathophysiology

“…Further studies of infections of human enteroids are expected to lead to identification of novel mechanisms of human response to infection with a wide spectrum of human commensals as well as bacterial, viral, and parasitic pathogens, many of which currently lack animal models. New models of chronic infection, including those that may lead to understanding intestinal development and tumor biology, are also possible, with evidence already being reported for a bacterial infection model to study epithelial-mesenchymal transition or tumorigenesis (42).…”

Human Fecal Microbiome–Based Biomarkers for Colorectal Cancer

“…Commensal bacterial like lactobacilli, bifidobacteria, and those belonging to the Clostridium genera are able to counteract the intestinal inflammation via the activation of T-regulatory cells causing an immunosuppressive niche in the intestine that can further affect tumor development. Apart from inflammasome activation leading to colorectal cancer, certain bacteria (specifically Citrobacter rodentium) are also able to induce epithelial-mesenchymal transition in the dedifferentiation of intestinal cells forming colonosphere in the in vitro culture models with murine colon cell lines (25). This group has established the tumormediated colonic hyperplasia murine models and studied the PI3K/AKT signaling leading to colorectal cancer via WNT-b-catenin and TLR-4-based NF-kB activation pathways stimulated by C. rodentium (26).…”