Oral Presentation Australian Society for Microbiology Annual Scientific Meeting 2019

Role of IRGM polymorphism in Helicobacter pylori related Gastric cancer. (#8)

Apeksha B Goswami 1 , Hazel M Mitchell 1 , Natalia Castaño-Rodríguez 1
  1. UNSW Sydney, Matraville, NSW, Australia

Introduction: Globally, gastric cancer (GC) is the 5th most common malignancy. As a multifactorial disease, Helicobacter pylori infection and host genetics are crucial for GC development. Autophagy, a protective cellular mechanism that is triggered upon pathogen invasion, is regulated by the Human Immunity-related GTPase M (IRGM) gene. The current study aimed to investigate the role of IRGM rs4958847 in H. pylori-induced inflammation and GC in ethnically diverse populations.

Methods: This case-control study comprised 1246 subjects from high-risk Ethnic Chinese (N=304) and Colombian (N=587) populations, and one low-risk Caucasian population (N=304). IRGM rs4958847 was genotyped by MADLI-TOF mass spectrometry. Using CRISPR/Cas9, a knock-in gastric epithelial cell line (AGS) was generated. Infection assays (2hr and 24hr) were conducted, and gene and protein expression levels of pro-inflammatory cytokines (IL8 and IFN-) were analysed using qPCR and ELISA, respectively. H. pylori infection status as well as the presence of the virulence factors CagA and VacA were determined using the Helico Blot 2.1 kit. Statistical analyses included bivariate, multivariate and joint analyses.

Results: Multivariate analyses suggest that IRGM rs4958847 AA genotype increases GC risk in Chinese (A>G, OR:0.28, p-value:0.01) and Colombians (G>A, OR:2.63, p-value:0.15), but decreases risk in Caucasians (G>A, OR:0.17, p-value:0.09). Consistent with previous literature, male gender was found to be a risk factor in Ethnic Chinese (OR:2.01, p-value:0.01) and Colombians (OR:2.01, p-value:0.004). Joint analysis showed that Ethnic Chinese and Caucasians harbouring this polymorphism and infected with H. pylori, experience a significant increased GC risk of 2.5-fold. Inflammation is decreased in edited infected cells as compared with wild-type infected cells (IL8, Fold change:0.42, p-value:0.10), a result corroborated at the protein level (p-value:0.004).

Conclusions: IRGM rs4958847 is a risk factor for GC in high-risk populations; importantly, a synergistic relationship was established between H. pylori infection and this polymorphism. In vitro preliminary analysis suggests that this polymorphism plays a relevant role in H. pylori-related inflammation and thus, GC.