mTOR inhibition potentiates cytotoxicity of Vγ4 γδ T cells via up-regulating NKG2D and TNF-α

J Leukoc Biol. 2016 Nov;100(5):1181-1189. doi: 10.1189/jlb.5A0116-053RR. Epub 2016 Jun 2.


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.

Keywords: STAT5; cytotoxicity; rapamycin.

MeSH terms

  • Animals
  • Cell Line, Tumor
  • Coculture Techniques
  • Cytotoxicity, Immunologic
  • Gene Expression Regulation / drug effects
  • Immunotherapy, Adoptive
  • Melanoma, Experimental / immunology*
  • Melanoma, Experimental / pathology
  • Melanoma, Experimental / therapy
  • Mice
  • Mice, Knockout
  • NK Cell Lectin-Like Receptor Subfamily K / biosynthesis*
  • NK Cell Lectin-Like Receptor Subfamily K / genetics
  • RNA Interference
  • RNA, Small Interfering / genetics
  • Receptors, Antigen, T-Cell, gamma-delta* / deficiency
  • Receptors, Antigen, T-Cell, gamma-delta* / genetics
  • STAT5 Transcription Factor / antagonists & inhibitors
  • STAT5 Transcription Factor / genetics
  • STAT5 Transcription Factor / physiology
  • Sirolimus / pharmacology
  • Specific Pathogen-Free Organisms
  • T-Lymphocyte Subsets / drug effects
  • T-Lymphocyte Subsets / immunology*
  • T-Lymphocytes, Cytotoxic / drug effects
  • T-Lymphocytes, Cytotoxic / immunology*
  • TOR Serine-Threonine Kinases / antagonists & inhibitors*
  • TOR Serine-Threonine Kinases / physiology
  • Tumor Necrosis Factor-alpha / biosynthesis*
  • Tumor Necrosis Factor-alpha / genetics
  • Up-Regulation / drug effects


  • Klrk1 protein, mouse
  • NK Cell Lectin-Like Receptor Subfamily K
  • RNA, Small Interfering
  • Receptors, Antigen, T-Cell, gamma-delta
  • STAT5 Transcription Factor
  • Stat5a protein, mouse
  • Tumor Necrosis Factor-alpha
  • mTOR protein, mouse
  • TOR Serine-Threonine Kinases
  • Sirolimus