IDDF2023-ABS-0255 Ace2 deficiency promotes colorectal cancer by remodeling gut microbiota

Background

Ace2 expression is critical for maintaining microbial homeostasis in the gut. Here, we aimed to investigate whether ACE2-dependent changes in intestinal flora promote colorectal cancer (CRC).

Methods

Intestinal conditional knockout mice were generated by crossing Ace2^Fl/Fl to Villin-Cre mice. CRC mouse models were established by azoxymethane (AOM) plus dextran sulfate sodium (DSS), with or without antibiotics cocktail treatment. Fecal Microbiota and metabolites of mice were determined by metagenomic sequencing and high-performance liquid chromatography-mass spectrometry. Semi-quantitative PCR was employed to validate differential bacteria in mice stools. Gut permeability was evaluated by gavaging 4 kd Fluorescein Isothiocyanate (FITC)-Dextran and detecting tight junction protein.

Results

Ace2 deficiency in mice promoted colorectal tumorigenesis in AOM/DSS induced CRC mouse model compared to wild-type mice, including colon tumor number (3.25 ± 1.24 vs 6.55 ± 1.07, P = 0.015) and tumor burden (22.50 ± 7.95 vs 85.16 ± 21.27 mm³, P = 0.005). Gut microbiota depletion with antibiotics significantly decreased colon tumor formation in Ace2 knockout mice (P < 0.0001). Ace2 knockout accelerates intestinal epithelium proliferation in AOM/DSS-treated mice (P = 0.028). Metagenomic analyses revealed the distinguishing microbiota composition difference between Ace2 knockout and wild-type mice by beta diversity analyses (R = 0.374, P = 0.006). The gut dysbiosis in Ace2 knockout mice includes increased pathogenic bacteria Enterorhabdus caecimuris and Eggerthella lenta and decreased probiotic bacteria Eubacterium rectale CAG 36. Semi-quantitative PCR confirmed that Enterorhabdus caecimuris was enriched in Ace2 knockout mice. Moreover, the Metagenomic sequence identified that detrimental metabolites, such as sphingosine, are elevated in Ace2 knockout group. Moreover, impaired gut barrier function was observed in Ace knockout mice compared to WT mice by intestinal permeability test (16.38 ± 0.86 vs 22.12 ± 2.52 μg/ml, P = 0.015) and downregulated expression of E-cadherin (P = 0.016) and occludin (P =0.004).

Conclusions

Ace2 deficiency drives microbiota dysbiosis and relevant toxic metabolites to prompt colorectal tumorigenesis by impairing gut barrier integrity.