STAT4 and neoplasm: Th1-secreted interferon gamma (IFN-γ) not only induces the activation of signal transducer and activator of transcription (STAT)1 and STAT4 to promote the differentiation of more Th1 cells but also recruits CD8+ T cells, NK cells, and other immune cells to enhance anti-tumor immunity, while Th2 cells with tumor-promoting effects mainly depend on the induction of IL-4 for differentiation (17).