Identification of Immunological Targets for Brain Cancer Immunotherapy

Abstract: Background Cancer immunotherapy has yielded many successes. Yet to some hard-to-treat brain tumors, such as glioblastoma multiforme (GBM) and diffuse intrinsic pontine glioma (DIPG), it still lacks substantial improvement. Neoantigens resulting from mutations in malignant cells are the key targets for employing adoptive cell therapies. A novel therapeutical strategy may be developed based on the identification of T cell receptors (TCRs) targeting specific neoantigens. Methods Previous work had been done to provide essential materials, including candidate neoantigen peptides, human leukocyte antigen (HLA) genotypes, and peripheral blood mononuclear cell (PBMCs) from patients and healthy donors (HDs). Autologous antigen-presenting cells (APCs) and T cells were isolated from PBMCs for in vitro assays. The activation of T cells against peptides was evaluated by the upregulation of 41BB utilizing flow cytometry (FACS). The cell populations with positive signals were sorted through FACS for TCR sequencing directly or after rapid cell expansion. Results T cells and APCs from 12 HDs were isolated. T cells from 10 HDs were analyzed after in vitro stimulation. T cells from HD30 showed reactions to several public neoantigens; while T cells from HD49 and HD53 showed reactions also to private neoantigens restricted in GBM patient C6. Conclusion The upregulation of 41BB indicated the activation of T cells and the existence of reactive TCRs against either public or private neoantigens in some HDs. Those reactive TCRs and their encoding sequences were the fundamentals of future works. Due to practical reasons, TCR sequencing cannot be done within this project. In future works, wildtype peptides will be included to further validate the results, ensuring identified TCRs recognize neoantigens specifically. Furthermore, the identified TCRs will be cloned and transferred to freshly isolated T cells to confirm their functionality. Keywords Cancer immunotherapy, brain cancer, neoantigen, MHC/HLA, TCR