Abstract
Chronic Helicobacter pylori (HP) infection is the leading risk factor for gastric cancer (GC); however, decreasing HP prevalence has led to implication of autoimmunity as a factor for increasing early-onset GC. We sought to identify early gene expression and protein changes that occur in pre-malignancy in autoimmunity-driven GC. Using a mouse model mimicking human CTLA4 insufficiency and its risk of autoimmunity-driven GC, CTLA4KD, at pre-malignancy (young) and malignancy (old) we conducted scRNAseq analysis of the gastric mucosa and detected increased Embigin (EMB) in CTLA4KD young mice. Flow cytometry confirmed EMB protein increases in gastric epithelial cells from CTLA4KD mice. Gastric epithelial cells positive for CD133, a cancer stem cell marker, and EMB were up in CTLA4KD young and old mice, indicating a potential role of EMB in stemness. We identified EMB, a potential biomarker for autoimmunity driven GC, to be upregulated in pre-malignancy.
As autoimmunity increases, HP and gastric autoimmunity are likely to converge; a second aim of this dissertation was to examine how combinatorial HP infection and autoimmunity affect tumorigenesis and the immune landscape. CTLA4KD mice were infected with HP (PMSS1). Tumorigenesis was histologically assed. Cell suspensions were analyzed by 40-color spectral flow cytometry. Human PBMCs were co-cultured with HP, followed by flow cytometry and qRT-PCR of sorted PBMC subsets. HP infection, even short exposure, caused long-lasting effects in the context of autoimmunity. The combination exacerbated dysplasia and loss of tumor suppressors, E-Cadherin and DMBT1, in the gastric mucosa. In addition, the combinatorial environment led to systemic downregulation of innate immunity, increased tertiary lymphoid structures in the gastric mucosa and upregulation of Helios in CD4+Foxp3- cells. Helios+ CD4 cells co-expressed inhibitory markers PD-1, CD200 and CD39. Autoimmunity and HP infection cooperatively elicited suppression of innate and adaptive immunity while promoting epithelial tumorigenic differentiation in the stomach.