Abstract 5335: Immune cell population variations in the livers of commonly used mouse strains
Authors: Rodriguez-Matos Francisco J. , Huang Patrick , Trehan Rajiv , Ruf Benjamin , Ma Chi , Greten Tim F. 
Published: March 2024

Abstract
Previous studies have shown that the distribution of major immune cell populations differ across mouse strains in peripheral blood and hematopoietic organs at baseline. Additionally, variations in immune responses exist between mouse strains in Leishmania spp. and Melanoma models, but these studies in the context of liver diseases including Non Alcoholic Fatty Liver Disease (NAFLD) and Hepatocellular Carcinoma (HCC) have not been carried out. With the effort to state if these variations exist within the liver, we performed comprehensive spectral flow cytometry analysis on the liver and spleens of three female mouse strains commonly used in cancer research (BALB/c, C57BL/6, and FVBN). NAFLD was induced by providing mice with a methionine choline deficient diet. To promote HCC, a single genotype (myc/p53+/-) was induced by administering transposon-based vectors to overexpress Myc-Luc and CRISPR/Cas-9 vectors to knock down p53 via hydrodynamic tail-vein injection. To confirm vector integration and monitor tumor growth (luciferase activity), in vivo imaging was performed at different time points. As a result, we confirm throughout this study that differences exist within immune cell populations of the liver and spleen at baseline. Moreover, we depict differences in the shift of immune cell populations across mouse strains in the pathologic states included. In NAFLD, there is an increase of dendritic cells (DCs), macrophages, NK cells, ILC1s, T regulatory cells (Tregs), TH1, and TH2, and a decrease of CD4+ T cells, B cells, γδ-T cells, and NKT cells in the liver across all mouse strains, when compared to controls. However, the population of neutrophils in BALB/c decreases, and the population of CD8+ T cells increases in C57BL/6 mice, which differs from the patterns of change seen in the other mouse strains. Moreover, in spleens, NAFLD promotes an increase of TH1 and NK cells, and a decrease of TH2 and NKT Cells across the mouse strains included in the study, whereas the patterns of change differ between mouse strains among the remaining immune cell types. When evaluating liver immune cell population shifts on our HCC model, BALB/c mice showed a decrease in macrophages and ILC1s, C57BL/6 mice showed a decrease in γδ-T cells, prominent shifts across Neutrophils, TH1, and NKT cells, and null changes in TH2 and CD4+ T cell shifts, and FVBN mice had a less prominent decrease of B cells, which differed from the shifts observed in the mouse strains used for comparison. Immune cell populations in the spleens of our HCC mouse model also presented with differences across the mouse strains studied. In conclusion, we highlight that key differences in immune profiles exist across commonly used mouse strains for cancer research in the presence of liver pathology including HCC, suggesting that mouse strains could be possible confounders in the study of immune oncology of HCC.
Citation Format: Francisco J. Rodriguez-Matos, Patrick Huang, Rajiv Trehan, Benjamin Ruf, Chi Ma, Tim F. Greten. Immune cell population variations in the livers of commonly used mouse strains [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 5335.