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Transcriptomic analysis of KDM4B-mediated genes in AGS cells

ABSTRACT: KDM4B, an important epigenetic regulator of cell proliferation, metastasis and genome stability, is often overexpressed in gastric cancer. Notably, elevated expression of KDM4B is associated with a poor clinical outcome. A global transcriptomic analysis between KDM4B control and KDM4B-knockdown AGS cells without or with Helicobacter pylori challenge reveals differentially expressed genes involved in response to virus, multi-organism process, and response to stimulus, suggesting KDM4B as an inducible epigenetic factor under H. pylori challenge.

ORGANISM(S): Homo sapiens

PROVIDER: GSE107703 | GEO | 2019/02/05

REPOSITORIES: GEO

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Project description:Background: Helicobacter pylori is an important human pathogen that infects the human gastric mucosa leading to chronic inflammation which is responsible for severe gastroduodenal diseases. The Outer Inflammatory Protein A (OipA) of H. pylori is an important virulence factor. However, the role of OipA in gastric cancer and ulcer development is still not well-established. Phase variation within a CT dinucleotide repeat motif of oipA switches its expression “on” and “off”. This study aims to elucidate the role of OipA in H. pylori infection using oipA “on” and “off” clinical strains and oipA deletion mutant. Methods: Proteomics analysis was performed on AGS human gastric epithelial cell line post-infection with oipA “on” and “off” H. pylori using liquid chromatography / mass spectrometry (LC/MS). In addition, AGS apoptosis and cell cycle assays were performed. To confirm the findings, oipA deletion mutant (ΔoipA) was generated and expression of VacA was detected using Western blotting. Result: Expression of AGS proteins involve in human disease was suppressed / down-regulated post-infection with oipA “off” strains, as well as oipA mutant, compared to oipA “on” strains. Furthermore, oipA “off” strains and oipA mutant resulted in a higher level of apoptosis and G0/G1 cell-cycle arrest in AGS cells than oipA “on” strains. Interestingly, deletion of oipA was found to increase VacA production by the bacterium. Discussion: The capability of oipA “off” strains to induce apoptosis and suppress proteins having roles in human disease may suggest that these H. pylori may be less virulent or may even be protective against carcinogenesis compared to its oipA “on” counterparts. This may potentially explain the higher incidence of gastric cancer among East Asian which oipA “on” strains predominates. Conclusions: Data from this study strengthened our understanding of the role of H. pylori OipA as a virulence factor in chronic inflammation, metastasis and carcinogenesis.

Project description:Helicobacter pylori infection promotes chronic inflammation and plethora of DNA damages including strand breaks, base alterations, point mutations, microsatellite instability and epigenetic alterations. The gastric epitheliaI cells, in order to prevent genomic instability, require an integrous DNA damage repair (DDR) machinery which, however, has been reported to be modulated by the infection. CagA is a major Hp virulence factor that deregulates host cell functions such as proliferation, apoptosis and chromosomal integrity. Its pathogenic activity is partly regulated by tyrosine phosphorylation on repeated EPIYA-motifs. Our aim was to identify putative effects of H. pylori infection and CagA protein on DDR machinery, investigating the transcriptome of AGS cells, infected with P12 H. pylori wild-type strain, as well as, its corresponding CagA knock-out and the CagA phosphorylation-defective mutant following tyrosine (EPIYA) substitution by phenylalanine (EPIFA) in the EPIYA-C motifs. Upon RNA-Sequencing on polyA-selected transcripts we performed Differential Expression Analysis, Pathway Enrichment Analysis and visualization on KEGG Pathway Maps per DDR mechanism. Key DDR components that were observed to be downregulated in a CagA-related manner were validated via Western Blot utilizing AGS and the non-cancerous GES1 cell lines. Transcriptome analysis revealed that a notable number of DDR genes were downregulated during H. pylori infection resulting to potential modulation of Base Excision Repair, Mismatch Repair and a more intricate deregulation of Nucleotide Excision Repair, Homologous Recombination and Non-Homologous End-Joining. CagA contributes to MUTYH, FEN1, APE1, POLD1 and LIG1 downregulation and those observations were verified on the protein expression level, with the exception of APE1 that was on contrary observed to be upregulated. Our study accentuates the role of CagA, as a significant contributor of the H. pylori infection-mediated DDR modulation, disrupting the balance between DNA damage introduction and repair thus favoring genomic instability and potentially contributing to gastric carcinogenesis.

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Transcriptomic analysis of KDM4B-mediated genes in AGS cells

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