Gastric coinfection with thiopeptide-positive Cutibacterium acnes decreases FOXM1 and pro-inflammatory biomarker expression in a murine model of Helicobacter pylori-induced gastric cancer

ABSTRACT Helicobacter pylori (H. pylori) causes a cascade from gastritis to gastric neoplasia. During the chronic stages, the oncogenic transcription factor forkhead box protein M1 (FOXM1) becomes increasingly expressed. Given certain strains of the gastric commensal Cutibacterium acnes (C. acnes) produce thiopeptides that directly inhibit FOXM1, we hypothesized that coinfection with thiopeptide-positive C. acnes would decrease Foxm1 expression and alter H. pylori-induced pathogenesis. C. acnes was isolated from 31% of gastric biopsies from Nicaraguan patients, and thiopeptide-positive strains were identified by whole genome sequencing. Germ-free INS-GAS mice were inoculated with thiopeptide-positive C. acnes, H. pylori SS1, H. pylori 1 week before C. acnes, C. acnes 2 weeks before H. pylori, or no bacteria. At 17 weeks post-infection, males dosed with C. acnes followed by H. pylori exhibited increased inflammation scores by histopathology; however, males dosed with H. pylori followed by C. acnes exhibited reduced gastric Foxm1, pro-inflammatory cytokine (Il-1β, Ifn-γ, Tnf-α, Il-17a, and iNOS), regulatory cytokine (Foxp3) gene expression, pro-inflammatory IgG2a antibodies, and gastric lymph node RORγT expression compared to H. pylori-monoinfected mice. Male mice coinfected with C. acnes followed by H. pylori exhibited reduced gastric inflammatory markers (IL-17, IL-10, GM-CSF, M-CSF, MCP-1, MIP-1α, MIP-2, RANTES, and VEGF) by cytokine array analysis and reduced H. pylori gastric colonization. These data show that thiopeptide-positive C. acnes exhibited anti-inflammatory and anti-FOXM1 properties in the context of H. pylori gastritis. IMPORTANCE H. pylori infects half of the world population and is the leading cause of gastric cancer. We previously demonstrated that gastric cancer risk is associated with gastric microbiota. Specifically, gastric urease-positive Staphylococcus epidermidis and Streptococcus salivarius had contrasting effects on H. pylori-associated gastric pathology and immune responses in germ-free INS-GAS mice. As gastritis progresses to gastric cancer, the oncogenic transcription factor Foxm1 becomes increasingly expressed. In this study, we evaluated the gastric commensal C. acnes, certain strains of which produce thiopeptides that directly inhibit FOXM1. Thiopeptide-positive C. acnes was isolated from Nicaraguan patient gastric biopsies and inoculated into germ-free INS-GAS mice with H. pylori. We, therefore, asked whether coinfection with C. acnes expressing thiopeptide and H. pylori would decrease gastric Foxm1 expression and pro-inflammatory cytokine mRNA and protein levels. Our study supports the growing literature that specific non-H. pylori gastric bacteria affect inflammatory and cancer biomarkers in H. pylori pathogenesis.