Abstract 3382: Unveiling gastric premalignancy: A comprehensive study of tumor initiation and evolution using organoid models

Abstract Tumor initiation and evolution is still a poorly characterized process. Organoid models recapitulate three-dimensional tissue structure, differentiation, and disease pathogenesis. These models can help to better characterize pre-neoplastic processes and tumor evolution, with implications for early cancer detection and personalized therapeutic strategies for patients with gastric cancer (GC). In our research, we performed whole exome sequencing (WES) on 24 GC patient tumors, uncovering distinct mutation frequencies in well-known tumor suppressor genes -APC, TP53, and ARID1A (18.75%, 37.5%, 43.75%, respectively) -compared to The Cancer Genome Atlas (TCGA) PanCancer Altas Cohort (n=440) (13.48%, 50.56%, 22.47% respectively). To gain a deeper understanding of how these mutated genes promote gastric premalignancy, we generated multiple isogenic gastric organoid lines with mutant APC (AT-dmut) or ARID1A (ArT-dmut) on a TP53 mutant background as well as TP53 mutant-only lines (T-mut) using our established CRISPR/Cas9 genome-editing platform and two HLA patient-derived normal gastric organoid lines (HL-PDOs). After confirmation of functional gene knockouts, we focused on elucidating carcinogenic changes via a two-pronged approach: (1) a comparative analysis of growth and morphology between these mutant organoid models and the parental normal gastric organoids and (2) an in-depth examination of mutational and transcriptional changes in our edited AT-mut, ArT-mut and T-mut organoid models. We cultured each edited organoid line for up to 350 days and collected histological and molecular data at multiple time points. Preliminary analysis shows an increased growth rate of all edited cell lines compared to parental normal lines. The ArT-mut and AT-mut cell lines exhibit distinct morphological and 3D structural alterations, while T-mut cell lines do not. We expect to find additional mutation gains in these cells’ lines compared to the parental normal gastric organoids that promote gastric phenotype with the greatest gain of alternations at the 350-day timepoint. These additional mutations and transcriptional changes will help us gain insights into the pathways altered in gastric cancer initiation and early progression that may be specific to HLAs. Our overall goal is to enhance our understanding of the molecular mechanisms underlying gastric premalignancy among HLAs, ultimately contributing to advancements in early detection and tailored therapeutic interventions for HLA patients with GC and advancing cancer health equity. Citation Format: Alexa Morales Arana, Nicole B. Halmai, Hongyong Zhang, Paul Lott, Ana Estrada, University of California Minority Patient-DerivedXenograft Development and Trial (UCaMP) Center, Luis Carvajal-Carmona. Unveiling gastric premalignancy: A comprehensive study of tumor initiation and evolution using organoid models [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 3382.