Abstract
Background
The lack of murine glioblastoma models that mimic the immunobiology of human disease has impeded basic and translational immunology research. We therefore developed murine glioblastoma stem cell lines derived from
Nestin-CreERT2QkL/L; Trp53L/L; PtenL/L (QPP) mice driven by clinically relevant genetic mutations common in human glioblastoma. This study aims to determine the immune sensitivities of these QPP lines in immunocompetent hosts and underlying mechanisms.
Methods
The differential responsiveness of QPP lines was assessed in the brain and flank in untreat ed, anti-PD-1, or anti-CTLA-4 treated mice. The impact of genomic landscape on responsiveness of each tumor was measured through whole exome sequencing. The immune microenvironments of sensitive (QPP7) versus resistant (QPP8) lines were compared in the brain using flow cytometry. Drivers of flank sensitivity versus brain resistance were also measured for QPP8.
Results
QPP lines are syngeneic to C57BL/6J mice and demonstrate varied sensitivities to T cell immune checkpoint blockade ranging from curative responses to complete resistance. Infiltrating tumor immune analysis of QPP8 reveals improved T cell fitness and augmented effector to suppressor ratios when implanted subcutaneously (sensitive), which are absent upon implantation in the brain (resistant). Upregulation of PD-L1 across the myeloid stroma acts to establish this state of immune privilege in the brain. In contrast, QPP7 responds to checkpoint immunotherapy even in the brain likely resulting from its elevated neoa ntigen burden.
Conclusions
These syngeneic QPP models of glioblastoma demonstrate clinically-relevant profiles of immunotherapeutic sensitivity and potential utility for both mechanistic discovery and evaluation of immune therapies.
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