Enterotoxigenic Bacteroides fragilis induces the stemness in colorectal cancer via upregulating histone demethylase JMJD2B

Abstract

The enrichment of Enterotoxigenic Bacteroides fragilis (ETBF) has been identified in CRC patients and associated with worse prognosis. Cancer stem cells (CSCs) play essential roles in CRC development. However, whether ETBF is involved in CSCs regulation is unknown. To clarify the role of ETBF in CSCs properties, we performed extreme limited dilution assays (ELDA) in nude mice injected with ETBFtreated or untreated CRC cells subcutaneously, tumor organoids culture in azoxymethane (AOM) mouse model after gavaging with or without ETBF, and cell sphere formation assay after incubating CRC cell lines with or without ETBF. The results indicated that ETBF increased the stemness of CRC cells in vivo and in vitro. Furthermore, ETBF enhanced the expression of core stemness transcription factors Nanog homeobox (NANOG) and sex determining region Y-box 2 (SOX2). Histone H3 Lysine 9 trimethylation (H3K9me3) is critical in regulating CSCs properties. As an epigenetic and transcriptional regulator, JmjC-domain containing histone demethylase 2B (JMJD2B) is essential for embryonic stem cell (ESC) transformation and H3K9me3 demethylation. Mechanistically, ETBF infection significantly upregulated JMJD2B levels in CRC cell lines and nude mice xenograft model. JMJD2B epigenetically upregulated NANOG expression via demethylating its promoter H3K9me3, to mediate ETBF-induced stemness of CRC cells. Subsequently, we found that the Toll-like receptor 4 (TLR4) pathway, activated by ETBF, contributed to the enhanced expression of JMJD2B via nuclear transcription factor nuclear factor of activated T cells 5 (NFAT5). Finally, in human CRC samples, the amount of ETBF positively correlated with nuclear NFAT5, JMJD2B, and NANOG expression levels. In summary, ETBF upregulated JMJD2B levels in a TLR4-NFAT5-dependent pathway, and played an important role in stemness regulation, which promoted colorectal carcinogenesis.

Gut microbiota composition in colorectal cancer patients is genetically regulated

“…Bacteroides comprises pathogenic species with proinflammatory and invasive properties; they are able to colonize epithelial cells and their abundance is increased in CRC [6,34,35]. Bacteroides fragilis has a known role in colon carcinogenesis [36,37]. We observed germline variants in 5 genes predisposing to a more efficient barrier and lower inflammation that would hinder Bacteroides expansion.…”

Microbiome and cancer

“…Furthermore, Wnt/b-catenin and NF-kB signaling (Wu et al, 2003(Wu et al, , 2004, as well as Th17 adaptive immunity, are activated in this process (Cheng et al, 2020;Kim et al, 2008). Mechanistically, ETBF infection may play an important role in stemness regulation via upregulation of epigenetic and transcriptional regulator levels in a toll-like receptor (TLR4)-dependent pathway, which promotes colorectal carcinogenesis both in vitro and in vivo (Liu et al, 2020).…”

Colorectal cancer: the facts in the case of the microbiota

“…Nanog homeobox (NANOG), an important transcription factor for stemness (63,64). Besides epigenetic modifications, BFT elicits generation of reactive oxygen species, inducing DNA damage and activating histone γ-H2AX, which is indicative of DNA repair (56).…”