γδ T cells are a rare but potent subset of T cells with pleiotropic functions. They commonly reside within tumors but the response of γδ T cells to tyrosine kinase inhibition is unknown. To address this, we studied a genetically engineered mouse model of gastrointestinal stromal tumor (GIST) driven by oncogenic Kit signaling that responds to the Kit inhibitor imatinib. At baseline, γδ T cells were antitumoral, as blockade of either γδ T-cell receptor or IL17A increased tumor weight and decreased antitumor immunity. However, imatinib therapy further stimulated intratumoral γδ T cells, as determined by flow cytometry and single-cell RNA sequencing (scRNA-seq). Imatinib expanded a highly activated γδ T-cell subset with increased IL17A production and higher expression of immune checkpoints and cytolytic effector molecules. Consistent with the mouse model, γδ T cells produced IL17A in fresh human GIST specimens, and imatinib treatment increased γδ T-cell gene signatures, as measured by bulk tumor RNA-seq. Furthermore, tumor γδ T cells correlated with survival in patients with GIST. Our findings highlight the interplay between tumor cell oncogene signaling and antitumor immune responses and identify γδ T cells as targets for immunotherapy in GIST.

Supplemental Figure S1. (A) Alternate gating strategy for identifying γδ T cells in KitV558Δ/+ tumors by flow cytometry (B) Prevalence of γδ T cells as a percentage of T cells in KitV558Δ/+ mice across multiple anatomic compartments. (C) Percent of cells positive for IFNγ in KitV558Δ/+ tumor by flow cytometry after intracellular cytokine stimulation. (D) Histograms of flow cytometry staining for the transcription factors T-bet and EOMES in T cells from KitV558Δ/+ tumors. (E) Vγ2 expression in tumor and spleen γδ T cells from KitV558Δ/+ mice. Representative of 4 mice. Data represent mean ± SEM; p values were calculated using a two-sided Student’s t test; *, P < 0.05.

Supplemental Figure S2. Relative expression on a per cell basis in KitV558Δ/+ tumors of (A) Trdv4 and (B) multiple genes known to be members of the SCART1+ γδ T cell phenotype. Dot plots represent scRNAseq data of γδ T cells from 6 mice as detailed in the methods section.