Abstract 48: Cellular dynamics and heterogeneity of active Kras induced-gastric pre-neoplasia in mouse

Cellular heterogeneity in cancer development is considered as a source of cancer cell generation and drug resistance. However, cellular heterogeneity has not been fully eluciated during metaplasia progression to gastric pre-neoplasia and neoplasia in gastric carcinogenesis. Recent investigations have suggested that Ras activation, rather than Ras mutation, may promote the gastric carcinogenesis. We have recently established several in vitro metaplastic/pre-neoplastic organoid lines; Meta3-metaplasia and Meta4-pre-neoplasia, derived from mouse stomachs induced active Kras expression in chief cells and investigated cellular heterogeneity and plasticity that may lead to the progression of metaplasia to gastric neoplasia. While both Meta3 and Meta4 initially formed spherical or spheroidal structures and generated complicated budding or cyst-like structures between 2 and 4 weeks, Meta4 cells displayed more disorganized structures and aggressive behaviors than Meta3. We also examined altered cellular behaviors, structural changes and survival of Meta4 organoids after MEK inhibition which is a downstream mediator of Kras signaling pathway. The Meta4 treated with Selumetinib for 3 days died or did not show an increase in size at various concentrations. However, some Meta4 organoids showed an ability to survive and retained a spheroidal structure despite the Selumetinib treatment. Single cell-RNA sequencing (scRNA-seq) data analysis demonstrated distinct characteristics of Meta4 cells as pre-neoplastic cells and a signature of presence and heterogeneity of pre-neoplasia stem cell (PNSC) populations. The scRNA-seq data analysis also revealed that cellular behavior and dynamics of pre-neoplastic cells can be controlled by MEK inhibition, but the PNSC populations still maintain the niche for stem-like cells in gastric pre-neoplasia. The isolated two PNSC populations showed functional differences and the stemness of the PNSCs in pre-neoplastic stage through high-throughput functional analysis. Therefore, our study concludes that putative gastric cancer stem cells in gastric pre-neoplasia might be the source for maintenance of heterogeneity and contribute to the progression of gastric pre-neoplasia to cancer. Citation Format: Eunyoung Choi, Paige N. Vega, Jimin Min, Amy C. Engevik, janice A. Williams, Qing Yang, Loraine M. Patterson, Alan J. Simmons, Ken S. Lau, Scott T. Magness, James R. Goldenring. Cellular dynamics and heterogeneity of active Kras induced-gastric pre