Therapeutic efficacy of dendritic cell vaccination in a novel syngeneic mouse model of diffuse hemispheric glioma, H3 G34-mutant

The prognosis for pediatric high-grade gliomas associated with mutations in the H3-3A gene is very poor. To investigate whether tumor lysate-pulsed dendritic cells (DC) together with checkpoint blockade might be a potential treatment modality for diffuse hemispheric glioma H3 G34-mutant (DHG), we have developed a novel syngeneic mouse model. We used the RCAS/tv-A system to target the expression of H3G34R and PDGFβ and knock out p53 in neural progenitors in C57BL/6 neonatal mice. Three independent cell lines were obtained that expressed transcripts associated with oligodendrocyte and interneuron lineages. Lethal tumor developed following intracranial injection. Two cycles of DC vaccination with PD-1 blockade decreased tumor burden and increased survival. In treatment resistant tumors we found higher expression of several genes involved in remodeling the extracellular matrix compared with tumors from untreated animals, suggesting a causal link to resistance to immunotherapy in this tumor model. Immunotherapy involving autologous dendritic cells pulsed with tumor lysate and combined with anti-PD-1 antibody might be an effective treatment for DHG. Treatment failure in our tumor model is associated with increased expression of genes implicated in remodeling extracellular matrix in the tumor microenvironment.