Role of Gut Microbiota in Hepatocarcinogenesis

Abstract

Hepatocellular carcinoma (HCC), one of the leading causes of death worldwide, has a causal nexus with liver injury, inflammation, and regeneration that accumulates over decades. Observations from recent studies have accounted for the involvement of the gut-liver axis in the pathophysiological mechanism responsible for HCC. The human intestine nurtures a diversified colony of microorganisms residing in the host ecosystem. The intestinal barrier is critical for conserving the normal physiology of the gut microbiome. Therefore, a rupture of this barrier or dysbiosis can cause the intestinal microbiome to serve as the main source of portal-vein endotoxins, such as lipopolysaccharide, in the progression of hepatic diseases. Indeed, increased bacterial translocation is a key sign of HCC. Considering the limited number of clinical studies on HCC with respect to the microbiome, we focus on clinical as well as animal studies involving the gut microbiota, with the current understandings of the mechanism by which the intestinal dysbiosis promotes hepatocarcinogenesis. Future research might offer mechanistic insights into the specific phyla targeting the leaky gut, as well as microbial dysbiosis, and their metabolites, which represent key pathways that drive HCC-promoting microbiome-mediated liver inflammation and fibrosis, thereby restoring the gut barrier function.

Keywords: gut microbiota; gut–liver axis; hepatocellular carcinoma; intestinal dysbiosis.

Figure 1

Mechanisms associated with the pathophysiology of hepatocellular carcinoma. Diet, alcohol, obesity, and genetic factors lead to prominent changes in microbiota which induce intestinal bacterial overgrowth, dysbiosis, intestinal permeability, bacterial translocation, and endotoxemia, resulting in the development of HCC. HCC, hepatocellular carcinoma; HBV, hepatitis B virus; HCV, hepatitis C virus; HSC, hepatic stellate cell; ROS, reactive oxygen species; TLR, Toll-like receptor; IR, insulin resistance; LPS, lipopolysaccharide; TNF, tumor necrosis factor; SCFA, short-chain fatty acid; DAMPs, damage-associated molecular patterns; PAMPs, pathogen-associated molecular patterns; TMA, trimethylamine.