Intestinal dysbacteriosis activates tumor-associated macrophages to promote epithelial-mesenchymal transition of colorectal cancer

Abstract

In this study we investigated the association between intestinal dysbacteriosis with colorectal cancer progress and the underlying molecular mechanisms. Tumor progression was evaluated using xenograft mice model. The epithelial-mesenchymal transition (EMT) markers were quantified by both real-time PCR and immunoblotting. The serum content of IL-6 and TNF-α were measured with ELISA kits. Cell proliferation was determined by the Cell Counting Kit-8. Intestinal dysbacteriosis was successfully simulated by the administration of a large dose of antibiotics and was demonstrated to promote xenograft tumor growth and induce EMT. Accordingly, the serum concentrations of cytokines IL-6 and TNF-α were significantly increased. Furthermore, the production and secretion of IL-6 and TNF-α were remarkably elevated in macrophages isolated from intestinal dysbiotic mice in comparison with the normal counterparts, and conditioned medium from these was shown to significantly stimulate EMT process in HT29 cells in vitro. Macrophage depletion completely abrogated the pro-tumor effect of intestinal dysbacteriosis. Our results suggest that intestinal dysbacteriosis stimulates macrophage activation and subsequently induces EMT process via secreted pro-inflammatory cytokines IL-6 and TNF-α.

Effect of heat-inactivated <i>Lactobacillus paracasei</i> N1115 on microbiota and gut-brain axis related molecules

“…On the other hand, the antibiotics used did not influence the serum TNF-α levels of the mice. These results agree with those of previous studies in which antibiotic use also increased serum IL-6 in mice suffering from microbiota dysbiosis induced by antibiotics [ 38 ]. Heat-inactivated Lactobacillus rhamnosus GG and Lactobacillus delbrueckii subsp.…”

Interplay between the Gut Microbiota and Inflammatory Mediators in the Development of Colorectal Cancer

“…Dual [28] ↑ [29,30] ↓ in tumor under immunotherapy [33] ↑ in serum [74] ↓ by FMT under DSS [27] NF-κB Promote [ ↑ [134] ↓ in colon [94] ↑ by FMT [27,94,95] IL-17 Promote [106,135] ↑ [114,135] ↓ in CD4 + T cell [113] ↓ in colon [94] ↓ by FMT under DSS [75] IFNs Suppress (α, β) [122] Controversial (γ) [124,129,130] ↓ IFNAR1 [122] ↓ α, β in ileum under viral infection [131] ↓ γ in T cells under viral infection [132] ↓ β, γ in SI under T. gondii infection [60] ↑ γ by L. delbrueckii, S. thermophilus under DMH-induced CRC [133] ↓ γ by FMT under DSS [75] ↑, up-regulated; ↓, down-regulated; CRC, colorectal cancer; GF, germ-free; ABX, antibiotics cocktail; TNF, tumor-necrosis factor; FMT, fecal microbiota transplantation; DSS, dextran sulfate sodium; NF-κB, nuclear factor kappa B; P. anaerobius, Peptostreptococcus anaerobius; IL-1, interleukin-1; LP, lamina propria; SI, small intestine; T. gondii, Toxoplasma gondii; VSL#3, probiotic mixture; CD, Crohn's disease; IL-6, interleukin-6; UC, ulcerative colitis; LPS, lipopolysaccharide; IL-10, interleukin-10; IL-17, interleukin-17; IFNs, interferons; IFNAR, interferon-α/β receptor; L. delbrueckii, Lactobacillus delbrueckii; S. thermophilus, Streptococcus thermophilus; DMH, 1,2-dimethylhydrazine.…”

“…It was found that LPS-induced IL-6 secretion was inhibited in the group treated with the bacterial mixture compared to that in the control [ 73 ]. ABX treatment upregulated the serum concentration and macrophage expression of IL-6 compared to the values in control mice with HT29 CRC xenografts [ 74 ]. Burrello et al evaluated the effects of FMT in chronic intestinal colitis induced via three cycles of 7-day DSS treatment.…”

The Macrophages-Microbiota Interplay in Colorectal Cancer (CRC)-Related Inflammation: Prognostic and Therapeutic Significance

“…Multiple lines of evidence indicate the existence of a tight relationship between enteric bacteriome, macrophages, and tumor promotion [ 96 ]. Macrophages of mice with intestinal dysbacteriosis release pro-tumorigenic cytokines (e.g., IL-6 and TNF) and stimulate in vivo the growth of tumor xenografts, while promoting colon cancer cell proliferation and EMT in vitro [ 101 ]. Notably, depletion of macrophages totally abrogates the pro-tumor effect of intestinal dysbacteriosis, indicating that bacteria require macrophages to exert pro-tumor activities [ 101 , 102 ].…”

“…Macrophages of mice with intestinal dysbacteriosis release pro-tumorigenic cytokines (e.g., IL-6 and TNF) and stimulate in vivo the growth of tumor xenografts, while promoting colon cancer cell proliferation and EMT in vitro [ 101 ]. Notably, depletion of macrophages totally abrogates the pro-tumor effect of intestinal dysbacteriosis, indicating that bacteria require macrophages to exert pro-tumor activities [ 101 , 102 ]. Moreover, macrophages can drive alterations of the microbial profile associated with CRC promotion.…”