Regulation of the double-stranded RNA (dsRNA) response in gastric metaplasia and dysplasia

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PROJECT SUMMARY/ABSTRACT Gastric metaplasia represents a critical pre-neoplastic event in the progression to gastric cancer, one of the leading causes of cancer-related deaths worldwide. The extent of gastric metaplasia is a significant indicator of gastric cancer incidence. While we recognize that metaplastic epithelium is characterized by the loss of acid-secreting parietal cells and a reprogramming of zymogenic chief cells to a proliferative phenotype, we still lack a mechanistic understanding of how gastric epithelium regulates cellular stress during metaplasia and what signaling pathways determine the progression to cancer. My preliminary findings identified the response to double-stranded RNA (dsRNA) as the most highly upregulated pathway across two distinct metaplasia-inducing models in mice, suggesting that dsRNA signaling represents a conserved, metaplastic pathway. In addition, my independent analysis found that the dsRNA response was one of the most significantly downregulated pathways in human gastric cancer. Though the dsRNA response has often been studied in the context of viral infection, these findings would suggest that the epithelial regulation of the dsRNA response is crucial to gastric metaplasia and tumorigenesis. This application proposes to define how the regulation of the dsRNA response affects the establishment of gastric metaplasia and the progression to dysplasia. As part of my first Aim, I will determine the necessity and sufficiency of dsRNA signaling in gastric metaplasia, using established gastric organoid and in vivo models. More specifically, I will characterize how the dysregulation of the dsRNA response in chief cells, an epithelial lineage critical to the metaplastic response, affects the development of gastric metaplasia in vivo. This will rely on a newly developed murine model where a key regulator of dsRNA signaling, ADAR1, can be conditionally and specifically deleted from chief cells. Along those lines, a similar mouse model that I developed found that specific deletion of ADAR1 from parietal cells resulted in gastric dysplasia, implying lineage-specific effects of dsRNA signaling in gastric tumorigenesis. My second Aim will examine the role of dsRNA signaling in parietal cell fate by transcriptionally characterizing Adar1-deficient parietal cells at distinct stages of parietal cell development. In addition, this Aim will define the role of Tnfrsf11b, one of the most highly upregulated genes in my murine model of gastric dysplasia and a gene found to be upregulated in human gastric cancer, in promoting the dysplastic milieu. The experiments proposed in this application are informed by some of the objectives from my K08 award, but they will investigate new experimental approaches that will complement and expand on these hypotheses. More importantly, these findings will offer new mechanistic insight into the contribution of dsRNA signaling to gastric tumorigenesis and potentially lead to new diagnostic and therapeutic alternatives.