T cell receptor dynamic and transcriptional determinants of T cell expansion in glioma-infiltrating T cells.

BACKGROUND

Glioblastoma (GBM) is characterized by low numbers of glioma-infiltrating lymphocytes (GIL) with a dysfunctional phenotype. Whether this dysfunctional phenotype is fixed or can be reversed upon culturing is poorly understood. The aim of this study was to assess T cell receptor (TCR)-dynamics and -specificities as well as determinants of GIL expansion by sequencing-based technologies and functional assays to explore the use of GIL for cell therapy.

METHODS

By means of flow cytometry, T cell functionality in GIL cultures was assessed from 9 GBM patients. TCR beta sequencing (TCRB-seq) was used for TCR repertoire profiling before and after expansion. Microarrays or RNA sequencing (RNA-seq) were performed from 6 micro-dissected GBM tissues and healthy brain RNA to assess the individual expression of GBM-associated antigens (GAA). GIL reactivity against predicted tumor-associated antigens (TAA) and patient-individual GAA was assessed by ELISpot assay. Combined single cell (sc)TCR-/RNA-seq and post-expansion TCRB-seq were used to evaluate transcriptional signatures that determine GIL expansion.

RESULTS

Human GIL regains cellular fitness upon expansion. Profound TCR dynamics were observed during expansion and only in one of six GIL cultures, reactivity against GAA was observed. Paired scTCR/RNA-seq and TCRB-seq revealed predictive transcriptional signatures that determine GIL expansion.

CONCLUSIONS

Profound TCR repertoire dynamics occur during GIL expansion. transcriptional T cell states determine expansion capacity in gliomas. Our observation has important implications for the use of GIL for cell therapy including genetic manipulation to maintain both antigen specificity and expansion capacity.