Fig. 2

Protumor effects of γδT cells. γδT cells are activated and recruited to tumor sites under stimulation by commensal bacteria. Signal transducer and activator of transcription 3 (STAT3) and orphan nuclear receptor gamma t (RORγt) are essential transcription factors for γδT17 cells. a γδT17 cells express antiapoptotic genes, such as Bcl-2, McL-1 and Survivin, promoting the growth of cells with tumorigenic potential and imparting the possibility for tumor initiation. b γδT17 cells increase the concentration of vascular endothelial growth factor (VEGF), which promotes tumor angiogenesis. c Secretion of IL-17 is accompanied by production of granulocyte–macrophage colony-stimulating factor (GM-CSF), leading to accumulation of polymorphonuclear myeloid-derived suppressor cells (PMN-MDSCs) and tumor-associated neutrophils (TANs), which is conducive to tumor metastasis. PMN-MDSCs can also sense heat shock proteins (HSPs) released by cancer cells and play a further immunosuppressive role. d In addition, γδTregs can inhibit the secretion of interferon γ (INF-γ) from γδTh1 cells by increasing the amount of adenosine in the tumor microenvironment, resulting in excessive tumor proliferation