Host and <i>Helicobacter pylori</i> HtrA protease variants converge on Wnt/β-catenin signaling to drive stomach adenocarcinoma

Helicobacter pylori-associated stomach adenocarcinoma (STAD) represents a highly severe malady, with up to 1 million new cases annually. Here, we examined novel human and bacterial risk determinants as well as related signal transduction events associated with STAD development. H. pylori serine protease HtrA cleaves the junctional protein E-cadherin, which results in the disruption of epithelial cell connections, the release and nuclear accumulation of β-catenin, and the onset of epithelial-mesenchymal transition (EMT), a hallmark of many tumors. In addition, the injection of H. pylori oncoprotein CagA into host epithelial cells targets β-catenin-mediated cell proliferation and other cancer signaling pathways. By analyzing over 2,000 H. pylori genomes, we identified single-nucleotide polymorphism (SNP) variants of HtrA and CagA that are associated with STAD progression. In addition, we investigated the role of the human serine proteases HTRA1, HTRA2, HTRA3, and HTRA4 in STAD progression and linked the genetic and expression data with specific signaling pathways. Elevated HTRA1, HTRA2, and HTRA3 expression in STAD patients correlated with upregulated extracellular matrix (ECM) receptor interactions and signaling that are critical for EMT. Moreover, H. pylori-positive STAD patients exhibited increased epithelial cell signaling, chronic inflammation, transcription factor Wnt/β-catenin signaling, ECM damage and metastasis, and single-cell analyses showed a strong association between HTRA1, the receptor Wnt, β-catenin, and oncogene MYC expression. Analyses of mutations in human HTRA1 and H. pylori HtrA revealed a role in the up- or downregulation of STAD progression. Together, our data show that SNPs in human and H. pylori serine protease HtrA and CagA modulate cancer signaling in complex Wnt-/β-catenin and ECM signaling networks, and that the protein variants can be causative or protective factors. A signaling model is proposed that highlights the complex interplay of human and bacterial factors in critical tumor signaling events, which could serve as predictive STAD biomarkers in patients.