Regulatory T-cell and neutrophil extracellular trap interaction contributes to carcinogenesis in non-alcoholic steatohepatitis

Abstract

Background & aims: Regulatory T-cells (Tregs) impair cancer immunosurveillance by creating an immunosuppressive environment that fosters tumor cell survival. Our previous findings demonstrated that neutrophil extracellular traps (NETs), which are involved both in innate and adaptive immunity, are abundant in livers affected by non-alcoholic steatohepatitis (NASH). However, how NETs interact with Tregs in the development of NASH-associated hepatocellular carcinoma (NASH-HCC) is not known.

Methods: A choline-deficient, high-fat diet+diethylnitrosamine mouse model and the stelic animal model were utilized for NASH-HCC and a western diet mouse model was used for NASH development. Treg depletion was achieved using FoxP3-DTR mice. RNA sequencing was used to explore the mechanism by which NETs could regulate Treg differentiation. Bioenergetic analyses of naïve CD4⁺ T-cells were assessed by Seahorse.

Results: Although the absolute number of CD4⁺ T-cells is lower in NASH livers, the Treg subpopulation is selectively increased. Depleting Tregs dramatically inhibits HCC initiation and progression in NASH. There is a positive correlation between increased NET and hepatic Treg levels. RNA sequencing data reveals that NETs impact gene expression profiles in naïve CD4⁺ T-cells, with the most differentially expressed genes being those involved in mitochondrial oxidative phosphorylation. By facilitating mitochondrial respiration, NETs can promote Treg differentiation. Metabolic reprogramming of naïve CD4⁺ T-cells by NETs requires toll-like receptor 4. Blockade of NETs in vivo using Pad4^-/- mice or DNase I treatment reduces the activity of Tregs.

Conclusions: Tregs can suppress immunosurveillance in the premalignant stages of NASH. NETs facilitate the crosstalk between innate and adaptive immunity in NASH by promoting Treg activity through metabolic reprogramming. Therapies targeting NETs and Treg interactions could offer a potential strategy for preventing HCC in patients with NASH.

Lay summary: Regulatory T-cells (Tregs) can promote tumor development by suppressing cancer immunosurveillance, but their role in carcinogenesis during non-alcoholic steatohepatitis (NASH) progression is unknown. Herein, we discovered that selectively increased intrahepatic Tregs can promote an immunosuppressive environment in NASH livers. Neutrophil extracellular traps (NETs) link innate and adaptive immunity by promoting Treg differentiation via metabolic reprogramming of naïve CD4⁺ T-cells. This mechanism could be targeted to prevent liver cancer in patients with NASH.

Keywords: Carcinogenesis; Hepatocellular carcinoma (HCC); Metabolic reprogramming; Neutrophil extracellular traps (NETs); Nonalcoholic steatohepatitis (NASH); Oxidative phosphorylation (OXPHOS); Regulatory T-cell (Treg).