Divergent immune landscapes of primary and syngeneic Kras-driven mouse tumor models

Abstract

Immune cells play critical functions in cancer, and mice with intact immune systems are vital to understanding tumor immunology. Both genetically engineered mouse models (GEMMs) and syngeneic cell transplant approaches use immunocompetent mice to define immune-dependent events in tumor development and progression. Due to their rapid and reproducible nature, there is expanded interest in developing new syngeneic tools from established primary tumor models. However, few studies have examined the extent that syngeneic tumors reflect the immune profile of their originating primary models. Here, we describe comprehensive immunophenotyping of two well-established GEMMs and four new syngeneic models derived from these parental primary tumors. To our knowledge, this is the first systematic analysis comparing immune landscapes between primary and orthotopic syngeneic tumors. These models all use the same well-defined human-relevant driver mutations, arise at identical orthotopic locations, and are generated in mice of the same background strain. This allows for a direct and focused comparison of tumor immune landscapes in carefully controlled mouse models. We identify key differences between the immune infiltrate of GEMM models and their corresponding syngeneic tumors. Most notable is the divergence of T cell populations, with different proportions of CD8+ T cells and regulatory T cells across several models. We also observe immune variation across syngeneic tumors derived from the same primary model. These findings highlight the importance of immune variance across mouse modeling approaches, which has strong implications for the design of rigorous and reproducible translational studies.

The KrasG12D;Trp53fl/fl murine model of undifferentiated pleomorphic sarcoma is macrophage dense, lymphocyte poor, and resistant to immune checkpoint blockade

“…Consistent with other studies in this field [ 56 , 57 ], the TIME of transplanted KP tumours was more inflamed than spontaneous UPS, showing a 2-fold and 3-fold increase in CD4+ and CD8+ lymphocytes. These finding were also observed on a transcriptomic level as the NanoString® immunological profiling also demonstrated a trend towards higher T cell, adaptive immunity and NK pathways scores in the transplanted model, however these differences were not statistically significant.…”

“…These finding were also observed on a transcriptomic level as the NanoString® immunological profiling also demonstrated a trend towards higher T cell, adaptive immunity and NK pathways scores in the transplanted model, however these differences were not statistically significant. In a recent study by Gutierrez et al [ 57 ], examining spontaneous and transplanted Trp53/Kras models of UPS and ERMS, a 2–3 fold increase in CD4 and CD8 lymphocytes were also observed in both models. Similar results have been reported by Riddell et al, showing that spontaneous cre-induced Trp53;Kras KP lung cancer tumours are less immunogenic than transplanted KP lung models [ 58 ].…”

“…Across multiple immune competent murine sarcoma models, macrophages are the most common immune cell of the TIME [ 56 , 57 , 59 ]. These findings are also observed in human sarcomas [ 20 , 25 , 29 , 56 , 60 ], although how this dominant myeloid compartment within sarcomas influences tumour immunobiology remains unclear.…”

Tumor-educated Tregs drive organ-specific metastasis in breast cancer by impairing NK cells in the lymph node niche

“…Furthermore, syngeneic cell lines like 4T1 poorly reflect the immunogenicity of human tumors of the same origin (Zhong et al, 2020). Recent research has shown that syngeneic cell lines derived from genetically Cell Reports 38, 110447, March 1, 2022 13 Article ll engineered mouse models (GEMMs) show key differences in their immune landscape, with increased frequencies of T regs , CD8 + T cells, and NK cells, compared with primary tumors in GEMMs (Gutierrez et al, 2021). These differences in immune landscape may critically affect the outcome of immunological studies, and thereby reduce their clinical value compared with GEMM-based models such as the KEP model.…”

Emerging mechanisms of immunotherapy resistance in sarcomas

“…However, another study performed similar experiments in the KP model, with conditional Kras G12D mutation plus Tp53 deletion, comparing the immune infiltrates and response to checkpoint blockade in primary tumors to those transplanted into naïve C57Bl/6 mice. Interestingly, in the setting of a low mutational burden tumor, there was no improvement in immunogenicity despite the transplantation, and despite an increase in immune cell infiltration, there was no improvement in response to checkpoint blockade [18] . Finally, a third paper summarized divergent immune landscapes with transplantation of primary KP UPS and rhabdomyosarcoma models into syngeneic recipient mice.…”