Preclinical platforms to study therapeutic efficacy of human γδ T cells

摘要

Background: Gamma delta (gamma delta) T lymphocytes are promising candidate for adoptive T cell therapy, however, their treatment efficacy is not satisfactory. V delta 2 T cells are unique to primates and few suitable models are available to assay their anti-tumour function. @@@ Methods: We tested human gamma delta T cell activation, tumour infiltration, and tumour-killing in four three-dimensional (3D) models, including unicellular, bicellular and multicellular melanoma spheroids, and patient-derived melanoma organoids. We studied the effects of checkpoint inhibitors on gamma delta T cells and performed a small molecule screen using these platforms. @@@ Results: gamma delta T cells rapidly responded to melanoma cells and infiltrated melanoma spheroids better than alpha beta T cells in PBMCs. Cancer-associated fibroblasts (CAFs) in bicellular spheroids, stroma cells in multicellular melanoma spheroids and inhibitory immune cells in organoids significantly inhibited immune cell infiltrates including gamma delta T cells and lessened their cytotoxicity to tumour cells. Tumour-infiltrating gamma delta T cells showed exhausted immunophenotypes with high checkpoints expression (CTLA-4, PD-1 and PD-L1). Immune checkpoint inhibitors increased gamma delta T cell infiltration of 3D models and killing of melanoma cells in all four 3D models. Our small molecule screen assay and subsequent mechanistic studies demonstrated that epigenetic modifiers enhanced the chemotaxis and cytotoxicity of gamma delta T cells through upregulating MICA/B, inhibiting HDAC6/7 pathway and downregulating the levels of PD-L1 and PD-L2 in CAFs and tumour cells. These compounds increased CXCR4 and CD107a expression, IFN-gamma production and decreased PD-1 expression of gamma delta T cells. @@@ Conclusions: Tumour-infiltrating gamma delta T cells show exhausted immunophenotypes and limited anti-tumour capacity in melanoma 3D models. Checkpoint inhibitors and epigenetic modifiers enhance anti-tumour functions of gamma delta T cells. These four 3D models provided valuable preclinical platforms to test gamma delta T cell functions for immunotherapy.

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