H. PYLORI INFECTION INDUCES SOX9 THROUGH CAP-DEPENDENT TRANSLATION MEDIATED BY AURKA-EIF4E AXIS

Background In gastrointestinal cancers, Aurora kinase A (AURKA) is amplified. Stomach stem cells can be identified by SOX9 which plays a role in gastric tumorigenesis. The primary risk factor for gastric cancer is infection with H. pylori. In our study, we focused on examining how AURKA regulates SOX9 in response to H. pylori infection, shedding light on an intricate mechanism that can be involved in gastric tumorigenesis.
Methods In this study, we used gastric cancer cell lines and spheroids, patient-derived organoids, in vivo mouse models, as well as the analysis of publicly available TCGA and GEO datasets. The molecular assays utilized, western blotting, qRT-PCR, immunohistochemistry, luciferase reporter assays, immunoprecipitation, and polysome fractionation.
Results Using GSEA, we successfully identified a strong association and elevated expression of AURKA and SOX9 in gastric cancer tissue samples. Upon H. pylori infection, we observed a notable increase in the protein levels of AURKA and SOX9 in gastric cancer cell lines and mouse gastric tissues. Furthermore, our findings demonstrated the increase in SOX9 protein levels, following H. pylori infection, was dependent on AURKA. This was evident in cell lines, spheroids, and human gastric organoids. We also observed an AURKA-dependent enhancement in the transcriptional activity of SOX9, as indicated by the pGF1–4eCOL2A1-Luc reporter assay. These significant changes in SOX9 protein levels and activity were facilitated by an upregulation of cap-dependent translation, as confirmed by the pcDNA3-rLuc-PolioIRES-fLuc reporter assay, polysome fractionation assay, and analysis of SOX9 polysomal RNA. Mechanistically, our study revealed that AURKA interacts with EIF4E, suppressing its ubiquitination and promoting EIF4E-dependent translation. In vivo analysis, using AURKA conditional knockout mice (Krt19^Cre/AURKA^flox/flox), demonstrated reduced baseline levels of SOX9 protein with diminished induction following H. pylori infection in the gastric glands of the AURKA knockout mice. Immunohistochemistry analysis of de-identified human tissues shows weak immunostaining of AURKA and SOX9 in normal gastric mucosa, whereas moderate to strong immunostainings were significantly more prevalent in gastric cancer tissues. Additionally, Spearman's correlation analysis revealed a significant correlation between AURKA and SOX9 in gastric cancer tissue samples, further supporting their potential functional relationship in gastric tumorigenesis.
Conclusion We identified a novel mechanism by which AURKA regulates the levels of SOX9. These findings establish a novel connection between AURKA and the activation of SOX9, which plays a crucial role in promoting stem-like properties and enhancing the survival of gastric cells in response to H. pylori infection during gastric tumorigenesis.