Gut Microbiome Modulation in Hepatocellular Carcinoma: Preventive Role in NAFLD/NASH Progression and Potential Applications in Immunotherapy-Based Strategies

Abstract

Hepatocellular carcinoma (HCC) is a heterogeneous tumor associated with several risk factors, with non-alcoholic fatty liver disease (NAFLD) emerging as an important cause of liver tumorigenesis. Due to the obesity epidemics, the occurrence of NAFLD has significantly increased with nearly 30% prevalence worldwide. HCC often arises in the background of chronic liver disease (CLD), such as nonalcoholic steatohepatitis (NASH) and cirrhosis. Gut microbiome (GM) alterations have been linked to NAFLD progression and HCC development, with several investigations reporting a crucial role for the gut-liver axis and microbial metabolites in promoting CLD. Moreover, the GM affects liver homeostasis, energy status, and the immune microenvironment, influencing the response to immunotherapy with interesting therapeutic implications. In this review, we summarize the main changes in the GM and derived metabolites (e.g., short-chain fatty acids and bile acids) occurring in HCC patients and influencing NAFLD progression, emphasizing their potential as early diagnostic biomarkers and prognostic tools. We discuss the weight loss effects of diet-based interventions and healthy lifestyles for the treatment of NAFLD patients, highlighting their impact on the restoration of the intestinal barrier and GM structure. We also describe encouraging preclinical findings on the modulation of GM to improve liver functions in CLD, boost the antitumor immune response (e.g., probiotic supplementations or anti-hypercholesterolemic drug treatment), and ultimately delay NAFLD progression to HCC. The development of safe and effective strategies that target the gut-liver axis holds promise for liver cancer prevention and treatment, especially if personalized options will be considered.

Keywords: HCC; NAFLD; immunotherapy; microbiome.

Figure 1

Mechanisms by which the gut microbiome promotes or hinders the progression of HCC. On the left, the mechanisms associated with HCC suppression are characterized by the presence of an eubiotic gut microbiome (GM) profile, enriched in beneficial microbes and capable of producing short-chain fatty acids (SCFAs), which enhance intestinal epithelial integrity and promote apoptosis of tumor cells via reactive oxygen species (ROS), as well as reduced levels of tumor-promoting metabolites such as secondary bile acids and microbe-associated molecular patterns (MAMPs), leading to reduced hepatic inflammation and fibrosis. This environment is characterized by a decrease in inflammatory macrophages and an increase in effector CD8+ T cells, fostering an anti-tumor immune response. On the right, the mechanisms that promote HCC progression are summarized. Gut dysbiosis, reduced ability to produce SCFAs, and increased intestinal permeability (“leaky gut”) may lead to increased generation and translocation of tumor-promoting metabolites, such as secondary bile acids. Dysbiosis also heightens hepatic exposure to gut-derived MAMPs and pathogen-associated molecular patterns (PAMPs), which drive hepatic inflammation, fibrosis, and cell proliferation. This pro-tumor environment is further characterized by an increase in macrophages, monocytic myeloid-derived suppressor cells, and a reduction in CD8+ T cells, contributing to immune evasion. “The figure was partly generated using Servier Medical Art provided by Servier, licensed under a Creative Commons Attribution 4.0 unported license”.

Figure 2

Healthy lifestyles and gut microbiome modulation concur to reduce NAFLD progression to NASH by reducing steatosis and improving markers of hepatic damage. HFC: hepatic fat content; BAs: bile acids; SCFA: short-chain fatty acids; MD: Mediterranean diet; ZO-1: zonulin-1; PUFA: polyunsaturated fatty acids; FMT: fecal microbiota transplantation. Numbers preceded by “#” indicate the reference article.

Figure 3

Modulating gut microbiome by probiotics and postbiotics or Atorvastatin reduces NAFLD progression to HCC in animal models of NAFLD/NASH-HCC. STZ: streptozotocin; HFD: high-fat diet; IL-6: interleukin 6; TNF-α: tumor necrosis factor α; NKT cells: natural killer T cells; HDAC: histone deacetylase; DEN: diethyl nitrosamine; HFHC: high-fat high-cholesterol; CD-HFD: choline-deficient high fat diet; JAK1: Janus kinase 1; STAT3: signal transducer and activator of transcription 3; FMT: fecal microbiota transplantation. Numbers preceded by “#” indicate the reference article.

Figure 4

Akkermansia muciniphila reduces HCC progression and improves ICI treatment response in HCC patients and mouse models. ALT: alanine transaminase; AST: aspartate transferase; TGF- β: transforming growth factor β; Col1a1: Collagen type I alpha 1 chain; Mcp1: Monocyte chemoattractant protein-1; Tlr4: Toll-like receptor 4; NEMO^Δhepa: steatohepatitis-HCC mouse model with NEMO gene deletion; ICI: immune checkpoint inhibitors; PD-L1: programmed cell death ligand 1; INF-γ: interferon γ; BAs: bile acids; PD1: programmed cell death protein 1. Numbers preceded by “#” indicate the reference article.