Glioblastoma is the most common form of primary brain tumour in adults. For more than a decade, conventional treatment has produced a relatively modest improvement in the overall survival of glioblastoma patients. Chimeric antigen receptor (CAR)-T cell therapy has been highly successful in haematological malignancies, but its efficacy is not reproduced in solid cancer settings. This is due to restricted trafficking and infiltration, as well as functional exhaustion. In this study, we aimed to improve the phenotype of GD2-specific CAR-T cells targeting glioblastoma tumour.
We compared two CAR-T manufacturing protocols previously published by our laboratory. Generated CAR-T cells were analysed for their killing potency through impedance-based cytotoxicity assay and in vitro tumour rechallenge assay. Using cellular indexing of transcriptomes and epitopes by sequencing (CITE-seq), we evaluated CAR-T cell memory phenotype and chemokine receptor expression. Patient-derived glioblastoma explants were used as 3D systems to model CAR-T cell immunotherapy.
Our results showed both original protocol CAR-T cells and modified protocol CAR-T cells were capable of killing GD2+ glioblastoma tumour cells. However, original protocol CAR-T cells have an effector memory phenotype that likely contributed to higher proliferation rate, albeit lower cell persistence with repeated stimulation. We have also uncovered differences between the two CAR-T cell products in terms of their chemokine receptor expression, which could have contributed to the increase in infiltrating original protocol CAR-T cells within patient-derived glioblastoma explants.
Overall, refining the qualities of CAR-T cell products in the context of glioblastoma could potentially yield greater understanding of CAR-T cell biology and opportunities for the success of future glioblastoma CAR-T cell therapy.