Helicobacter pylori (Hp) is a gram-negative bacterium which causes chronic gastritis and
peptic ulcer disease, while being the primary risk factor for the development of gastric
neoplasia. CagA protein is a major Hp virulence factor, which upon infection is delivered into
gastric epithelial cells by the type-IV secretion system and exhibits pleiotropic activity,
related to apoptosis, cell proliferation and inflammatory response. Recently, Hp infection at
the cellular level has been shown to be associated with cholesterol glycosylation and
cholesterol scavenging from the cell membranes of infected gastric epithelial cells. The aim
of our study was to identify putatively CagA-dependent deregulated biological processes
related to cholesterol biosynthesis and homeostasis of gastric epithelial cells during Hp
infection. To this end, we studied the transcriptome of human gastric adenocarcinoma cells
(AGS) infected with isogenic Hp strains expressing or not the CagA protein. PolyA-isolated
RNA was analyzed by hybridization on human Gene Chip Transcriptome array 2.0
microarrays (Affymetrix), as well as, RNA-seq analysis on the Ion Proton platform.
Bioinformatics analysis by DAVID was applied on differentially expressed transcripts which
fulfilled statistical significance for microarray and RNA-seq data at the significance level of pvalue≤0.05, log2FoldChange≥0.9. DAVID-GO-term analysis of RNA-seq data suggested that
cholesterol biosynthesis, homeostasis efflux and metabolism were deregulated strongly
during the infection. Relating to cholesterol biosynthesis, microarray analysis highlighted
HMGCS1, INSIG1, MVK as strongly deregulated genes, whereas RNA-seq highlighted 8
deregulated genes including DHCR7, INSIG1 and MSMO, all in a CagA-dependent manner.
Concerning cholesterol homeostasis, the RNA-seq analysis indicated 15 deregulated genes
including SOAT1, ABCA1 and SIRT, as a result of Hp-infection. Key deregulated cholesterol
components INSIG1 and DHCR24 were further studied at the translational protein level.
Interestingly, a CagA-dependent upregulation of INSIG1 gene, encoding an important
protein-regulator of lipid metabolism and cholesterol homeostasis, was verified on the
protein expression level. In contrast, DHCR24, a reductase involved in terminal cholesterol
synthesis, which was observed to be downregulated at the transcriptional level, was found
to be overexpressed at the protein level. Furthermore, we studied the effect of the
cholesterol biosynthesis inhibitor fluvastatin on AGS epithelial cells and its ability to induce
an elongation and scattering phenotype resembling to the epithelial-to-mesenchymaltransition phenotype. The combination of fluvastatin and H. pylori on AGS cells was found to
induce a stronger deregulating elongation and scattering phenotype, leading to complete
disruption of epithelial continuum.