ABSTRACT Gastric cancer (GC), the third leading cause of cancer death worldwide, is characterized both by histologic and molecular criteria. The two most common forms include Diffuse GC (DGC) and Intestinal GC (IGC). Each class of GC is associated with early inactivation of a distinct tumor suppressor, CDH1 (encoding E-cadherin) for DGC and p53 for IGC. Beyond genetic changes, gastric cancer development is promoted by environmental factors, specifically Helicobacter infection and exposure to dietary nitrates. We posit that addressing two fundamental questions in the gastric cancer field: defining the cells-of-origin and defining the distinct mediators of progression, should be addressed together given their interconnectedness. We will evaluate the interplay of genetic and environmental precipitants to gastric cancer using novel engineered mouse models where we can selectively target key tumor suppressors in the gastric epithelium in concert with relevant exposures. We will then deeply interrogate tissues with the combination of multi-omic single cell technologies enabling dual analysis of gene expression and chromatin accessibility in individual cells and the subsequent use of spatial transcriptomic tools allowing us to map features of individual cell types spatially to refine the cellular origins of these altered cell types. In concert to defining cellular origins of the two primary classes of gastric cancer, our integrated multi-omic and spatial analyses will be evaluated to define changes in cellular programs and candidate mediators of these altered phenotypes. In addition, we will explore how coevolving changes in the gastric microenvironment may accompany or promote the cell’s precancerous transformation. We will better define the interaction of environmental exposures in gastric tumorigenesis and investigate interactions of resulting early mutations with environmental factors, testing our hypothesis that this interaction modulates both gastric cells and microenvironment. Utilizing our cellular and spatial profiling, we will generate a map of the microenvironment showing the development of the disease in its spatial context, which will also be a resource for future studies. To generalize our findings in the mouse to human, we will perform single cell multi-ome analysis of human and mouse derived organoids and expand our existing single cell atlas of the human GI tract. Subsequently, we will perform functional validation of candidate mediators of progression, evaluating both features intrinsic to gastric epithelial cells and those emerging from the microenvironment. These studies will both address longstanding debates over origins of gastric cancers as well as define new targets to prevent cancer development.

PROJECT NARRATIVE To address fundamental questions regarding the cell-of-origin of distinct classes of gastric cancer, we will integrate novel mouse models, organotypic cultures of human and mouse cells using state- of-the-art single cell profiling and spatial transcriptional analyses. We will also explore the related issue of disease development by defining key transcriptional mediators of the progression to gastric cancer and then perform experimental validation. Taken together, our studies will address and resolve longstanding debates over the origins of gastric cancer while also defining possible targets to prevent cancer initiation.