Impact of Helicobacter pylori Infection and Its Major Virulence Factor CagA on DNA Damage Repair.

Eleftherios Kontizas,Dionyssios N Sgouras,Panagoula Kollia,Timokratis Karamitros,Artemis G Hatzigeorgiou,Spyros Tastsoglou,Yiannis Karayiannis

doi:10.3390/microorganisms8122007

Abstract

Helicobacter pylori infection induces a plethora of DNA damages. Gastric epithelial cells, in order to maintain genomic integrity, require an integrous DNA damage repair (DDR) machinery, which, however, is reported to be modulated by the infection. CagA is a major H. pylori virulence factor, associated with increased risk for gastric carcinogenesis. Its pathogenic activity is partly regulated by phosphorylation on EPIYA motifs. Our aim was to identify effects of H. pylori infection and CagA on DDR, investigating the transcriptome of AGS cells, infected with wild-type, ΔCagA and EPIYA-phosphorylation-defective strains. Upon RNA-Seq-based transcriptomic analysis, we observed that a notable number of DDR genes were found deregulated during the infection, potentially resulting to base excision repair and mismatch repair compromise and an intricate deregulation of nucleotide excision repair, homologous recombination and non-homologous end-joining. Transcriptome observations were further investigated on the protein expression level, utilizing infections of AGS and GES-1 cells. We observed that CagA contributed to the downregulation of Nth Like DNA Glycosylase 1 (NTHL1), MutY DNA Glycosylase (MUTYH), Flap Structure-Specific Endonuclease 1 (FEN1), RAD51 Recombinase, DNA Polymerase Delta Catalytic Subunit (POLD1), and DNA Ligase 1 (LIG1) and, contrary to transcriptome results, Apurinic/Apyrimidinic Endodeoxyribonuclease 1 (APE1) upregulation. Our study accentuates the role of CagA as a significant contributor of H. pylori infection-mediated DDR modulation, potentially disrupting the balance between DNA damage and repair, thus favoring genomic instability and carcinogenesis.

Highlights

Gastric cancer is the fifth most common type of cancer and the third most prevalent cause of cancer death worldwide [1]
Apyrimidinic Endodeoxyribonuclease 1 (APE1) protein levels were found to be increased, potentially due to CagA expression. These results suggest that CagA can act as a significant compromising factor of DNA damage repair (DDR), which could favor genomic instability in gastric epithelial cells, via putative disruption of the equilibrium between DNA damage introduction and repair, increasing the risk for gastric cancer development
Pathway enrichment analysis indicated that H. pylori infection can potentially affect every major DDR mechanism and CagA protein can be a significant contributor to the deregulation of Base excision repair (BER), nucleotide excision repair (NER), MMR, and homologous recombination (HR)

Summary

Introduction

Gastric cancer is the fifth most common type of cancer and the third most prevalent cause of cancer death worldwide [1]. The risk of gastric cancer development is determined by specific interactions between H. pylori and the host, which in turn are dependent on the expression of strain-specific bacterial virulence factors [9], inducing a variable inflammatory response governed by host genetic predisposition, as well as environmental factors [10,11]. Upon its delivery to the cytoplasm, CagA can interact, in an EPIYA-phosphorylation-dependent or -independent manner, with several host proteins, deregulating crucial cellular functions such as proliferation, apoptosis, inflammation, and genomic integrity [16,17,18]. Infection with CagA-positive strains has been reported to augment inflammation in the gastric mucosa, triggering oxidative stress and DNA damage, favoring genomic instability and increasing the risk for gastric cancer development [19,20,21]

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