STAT3 and gastric cancer: Moreover, Lin et al. claimed that CSF-2 promoted the M2 macrophage-mediated C-X-C Motif Chemokine Ligand 8 (CXCL8) secretion, leading to upregulated expression of PD-L1 and activation of signal transducer and activator of transcription 3 (STAT3) pathway, which further downregulated tumor-infiltrating CD8+ T cells as well as promoted functional exhaustion of T cells, exhibiting unfavorable prognosis in GC patients (Lin et al., 2019).