The single-cell transcriptome defines an effector Vd1 gd T cell-dependent anti-tumor immunity in human gastrointestinal stromal tumor (GIST)

Gamma-delta (gd) T cells bridge innate and adaptive immunity and have the ability to recognize diverse tumor-associated antigens. However, the function of gd T cells in human gastrointestinal stromal tumor (GIST), the most common type of human sarcoma, is unknown. Here, we combined single-cell RNA-seq (scRNA-seq), immunophenotyping, and next-generation T-cell receptor (TCR) sequencing of sorted human circulating and intratumoral gd T cells to query their impact on tumor immunity in GIST. We identified major subtypes of Vd1 and Vd2 cells, which were more differentiated in tumors. The effector Vd1 subset exhibited higher expression of cytotoxicity-related transcription and exhaustion molecules, and highly expressed the key transcription factors TBX21 and EOMES. Tyrosine kinase inhibitor (TKI) treatment induced the tumor-enriched Vd1 cells to undergo profound phenotype differentiation, alternative clonal expansion, and TCR diversity. Upon antigen exposure, the Vd1 subset maintained enhanced cytotoxicity properties through an innate-effector phenotype and adaptive-like activation. In a genetically engineered murine GIST model, combination therapy of imatinib with a checkpoint inhibitor increased the adaptive immune response of gd T cell subsets in GIST. Collectively, our findings highlight the importance of Vd1-dependent anti-tumor immunity and open the possibility of specific targeting of gd T subsets based on V gene usage for immunotherapy of GIST.