Abstract 5312: Murine syngeneic tumor model characterization by ultrahigh-plexed immunofluorescence imaging

Abstract Murine syngeneic tumor models are widely used tools to demonstrate efficacy and the mechanism of novel anticancer immunotherapies. Each model is likely to have a unique tumor microenvironment (TME) with immune cells, fibroblasts, endothelial cells and extracellular matrix that may reflect a variety of TME profiles in humans. Baseline characterization of tumor TME features of each model paired with therapy-based mechanistic studies can confirm pharmacodynamic (PD) biomarker hypotheses and inform combination strategies. However, a comprehensive dataset of TME compositions and spatial information is unavailable. PhenoCycler is an ultrahigh-plexed spatial biology imaging platform that can detect up to 100 markers on formalin fixed paraffin embedded (FFPE) sections at a single cell resolution using cyclic detection of DNA-conjugated antibodies. Very few publications have used Phenocycler technology to image murine FFPE tissues. In this study, we constructed a FFPE tissue microarray (TMA) block that includes 12 commonly used preclinical murine models of breast, colon, lung, pancreatic ductal, renal and bladder carcinomas with duplicate cores, and built a 29-marker panel to characterize the complexity of the TME of these models. Our data showed distinct TMEs in the different models and cell-cell interactions that differed depending on the tumor type examined. For instance, Py2T and Pan02 are cancer associated fibroblast (CAF) and macrophage enriched tumors whereas MC-38 tumors have low levels of CAF and T cell infiltration. Based on these analyses, the EMT6 tumor model, an immunocompetent triple negative mammary carcinoma with adequate extracellular matrix, was selected for an in vivo pharmacology study for a novel anti-stroma immunotherapy. Evaluation of whole tissue tumor samples from the study revealed significant increases in CD8+ T cell infiltration and a reduction of COL1A1 expression in treated tumors compared to vehicle group tumors consistent with antitumor efficacy. Our study demonstrated that ultrahigh-plexed immunofluorescence imaging is a powerful technology that can efficiently assist in vivo model selection and support biomarker discovery, especially in combination with a TMA section that can include multiple tumor models. Citation Format: Jaimee Wong, Ngan Doan, Andrew Woolley, Anandi Sawant, Shilpa Keerthivasan, Sunitha Bachawal, Jennifer Sahni, Nicholas Wilson, Amanda Mikels Vigdal, Xiaoyun Liao. Murine syngeneic tumor model characterization by ultrahigh-plexed immunofluorescence imaging [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2025; Part 1 (Regular Abstracts); 2025 Apr 25-30; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2025;85(8_Suppl_1):Abstract nr 5312.