mTOR Inhibition Potentiates Cytotoxicity of Vγ4 γδ T Cells via Pp-regulating NKG2D and TNF-α.

γδ T cells play a critical role in early anti-tumor immunity and perform cytotoxicity via NKG2D for recognition and multiple cytotoxic factors for tumor killing. Recent studies have demonstrated pivotal roles of mTOR-mediated metabolism in the maturation, differentiation, and effector function of diverse immune cells, including DCs, NK cells, CD4+ T cell subsets, and CD8+ T cells, but the role of mTOR signaling in γδ T cells is barely known. Here, we showed that suppressing mTOR signaling in in vitro-expanded Vγ4 γδ T cells via the mechanistic inhibitor rapamycin enhanced their cytotoxicity against multiple tumor cell lines, and these cells performed better tumor-suppressing effects upon adoptive therapy. Further investigation revealed that elevated cytotoxicity was a result of up-regulation of NKG2D and TNF-α. Moreover, rapamycin treatment significantly decreased the expression of CISH and increased pSTAT5. The inhibition of STAT5 pathways via siRNA interference or a specific inhibitor eliminated the up-regulation of NKG2D and TNF-α in rapamycin-treated Vγ4 γδ T cells. These results uncovered an important role of mTOR signaling in the cytotoxic effector function of γδ T cells and provided a potential strategy to improve γδ T cell-based cancer immunotherapy.

γδ T细胞在早期抗肿瘤免疫中起关键作用，通过NKG2D识别并借助多种细胞毒性因子发挥细胞毒性以杀伤肿瘤。近期研究表明，mTOR介导的代谢在多种免疫细胞（包括树突状细胞、自然杀伤细胞、CD4 + T细胞亚群和CD8 + T细胞）的成熟、分化和效应功能中具有关键作用，但mTOR信号在γδ T细胞中的作用鲜为人知。在此，我们发现通过机制性抑制剂雷帕霉素抑制体外扩增的Vγ4 γδ T细胞中的mTOR信号，可增强其对多种肿瘤细胞系的细胞毒性，并且这些细胞在过继性治疗中具有更好的肿瘤抑制效果。进一步研究表明，细胞毒性升高是NKG2D和肿瘤坏死因子 -α上调的结果。此外，雷帕霉素处理显著降低了细胞因子信号抑制因子（CISH）的表达并增加了磷酸化信号转导及转录激活因子5（pSTAT5）。通过小干扰RNA干扰或特异性抑制剂抑制STAT5通路，消除了雷帕霉素处理的Vγ4 γδ T细胞中NKG2D和肿瘤坏死因子 -α的上调。这些结果揭示了mTOR信号在γδ T细胞的细胞毒性效应功能中的重要作用，并为改进基于γδ T细胞的癌症免疫治疗提供了一种潜在策略。