EXTH-49. DEVELOPMENTAL ANTIGENS CAN TARGET EMBRYONAL PEDIATRIC BRAIN CANCERS IN ADOPTIVE CELLULAR THERAPY

Mutations in tumor neoantigens have shown promise in immunotherapies for many cancers, yet pediatric brain tumors, which typically have a lower mutational burden, offer fewer opportunities to capitalize on these targeted therapies. Studies indicate that medulloblastoma (MB) and brain stem gliomas (BSG) originate from abnormal reactivation of post-natal developmental processes. This led us to investigate whether proteins expressed during the early post-natal development of the mouse cerebellum and brainstem could be powerful antigens to fight MB and BSG, respectively. We performed both in vitro and in vivo studies in mice with the RNA of developmental antigens from the brain stem and cerebellum in an adoptive cellular therapy (ACT) platform. We evaluated the reactivity and therapeutic efficacy of these treatments as sustainable antigenic targets against BSG and MBs. We demonstrate that T cells activated towards these non-mutated, tissue-specific developmental antigens can recognize distinct subtypes of MB and BSG, and activate specifically without cross-reacting to the normal brain. This conferred a survival benefit in established orthotopic models of these pediatric brain tumor types. Our research exhibits the value developmental antigens can offer when serving as tumor rejection antigens in MB and BSG.