Figure 6. CagA-mediated MGMT hypermethylation and subsequent protein decrease by upregulating DNMT1 via PDK1/AKT-NFκB pathway is recapitulated in vivo.

(A and B) RUT and Giemsa staining validates the successful HP colonization in C57BL/6 mice. (C) IHC staining of gastric tissues from mice infected with different HP strains. A marked DNMT1 elevation occurs in CagA+ HP infected tissues compared with control group. (D) WB analysis of related protein expression in mouse gastric tissues infected with different HP strains. A notable MGMT loss paralleled with a significant increase in P-PDK1/P-AKT/P-NFκB/DNMT1 expression is observed in CagA+ HP infected tissues compared with control groups. (E) MSP analysis MGMT methylation in gastric tissues from mice infected with different HP strains. A significant increase in MGMT methylation is observed in CagA+ HP infected tissues compared with control groups, which is consistent with what has been confirmed in vitro. (F) Signal pathway schematic diagram. CagA is delivered into the cytoplasm by a type IV secretion system of the adhered HP. CagA then causes an increase in AKT phosphorylation by activating PDK1, subsequently, activated P-AKT translocates into the nucleus where it upregulates DNMT1 by activating NFκB. The upregulated DNMT1 further promotes MGMT hypermethylation, which leads to MGMT loss. The graph represents densitometric analysis of the bands obtained for each signal. Results are expressed as relative expression compared with control cells (*p < 0.05). Each value is the mean ± SD of three experiments.