Introduction: While Helicobacter pylori infection is largely recognised in gastric cancer (GC) aetiology, only 1-3% of infected individuals will develop this inflammatory disease. Inheritable mutations in Toll-like receptor 4 (TLR4) deregulate responsiveness to H. pylori and may influence clinical outcomes. This study delineates the effect of the novel TLR4 rs11536889 (G>C) mutation in the host response during H. pylori-related gastric carcinogenesis.
Methods: The relationship between this mutation, H. pylori infection and GC aetiology was evaluated in a multiethnic (Australian Caucasian, Colombian Mestizo, Han Chinese and Iranian) case-control study encompassing 315 GC cases, 372 gastric precancerous lesion cases and 1043 controls. Host gene expression changes using RNA-seq on gastric biopsies and systemic inflammation levels using multiplex ELISAs on sera were performed in a subset of subjects, and correlated with carriage of TLR4 rs11536889. Inflammation and bacterial clearance were further examined in H. pylori-challenged models of CRISPR/Cas9-edited mutant gastric epithelial (AGS) and macrophage (THP-1) cell lines.
Results: We show that carriage of TLR4 rs11536889 offers a reduced susceptibility to H. pylori infection. Meanwhile, harbouring this mutation independently increases the risk of GC, which is greatly intensified by its joint presence with H. pylori. Further, RNA-seq of gastric tissue revealed TLR4 rs11536889 carriage was correlated with gene expression changes linked to diverse roles in controlling tumour suppression, mucosal antimicrobial defence and inflammatory signalling, of all which may contribute to carcinogenesis. The influence of TLR4 rs11536889 on these cellular processes was echoed at the protein level, with abnormal circulating cytokine levels conducive of a pro-inflammatory signature. At the cellular level, the effects of TLR4 rs11536889 led to opposing responses in gastric epithelial cells and macrophages for H. pylori clearance – while mutant epithelial cells showed diminished bacterial survival, H. pylori survival was augmented in mutant macrophages.
Conclusion: Understanding the role of TLR4 rs11536889 offers appreciable insight into the host immune responses to H. pylori, and provide the basis for a novel biomarker for GC screening programs. These findings hint at a possible race- and disease status-specific effect incurred this mutation, and could confer the opposite phenotypic outcomes observed between high- and low-risk populations.