Spermine oxidase promotes Helicobacter pylori-mediated gastric carcinogenesis through acrolein production

Helicobacter pylori is the primary cause of gastric cancer, and there is a need to discover new molecular targets for therapeutic intervention in H. pylori disease progression. We have previously shown that spermine oxidase (SMOX), the enzyme that catabolizes the back-conversion of the polyamine spermine to spermidine, is upregulated during infection and is associated with increased cancer risk in humans. We sought to determine the direct role of SMOX in gastric carcinogenesis during H. pylori infection. In this study, we demonstrate that transgenic FVB/N insulin-gastrin (INS-GAS) mice that develop gastric carcinoma with H. pylori infection were protected from cancer development with Smox deletion. RNA sequencing revealed that genes associated with the immune system and cancer were downregulated in the infected Smox^-/- mice. Furthermore, there was a decrease in cell proliferation and DNA damage in infected Smox^-/- animals. There was significant generation of adducts of the highly reactive electrophile acrolein, a byproduct of SMOX activity, in gastric tissues from H. pylori-infected humans and wild-type, but not Smox^-/- mice. Genetic deletion of Smox in murine organoids or chemical inhibition of SMOX in human gastric epithelial cells significantly reduced generation of acrolein induced by H. pylori. Additionally, acrolein-induced DNA damage in gastric epithelial cells was ablated with the electrophile scavenger 2-hydroxybenzylamine (2-HOBA). Gastric acrolein adduct levels were attenuated in infected INS-GAS mice treated with 2-HOBA, which exhibit reduced gastric carcinoma. These findings implicate SMOX and acrolein in H. pylori-induced carcinogenesis, thus indicating their potential as therapeutic targets.