FOXO4 and neoplasm: Forkhead box O (FoxO) transcription factors, including FoxO1, FoxO3a, FoxO4 and FoxO6, are important family of proteins that exhibit tumor suppression functions by regulating expressions of genes participated in apoptosis, cell cycle progression, angiogenesis, DNA repair, oxidative stress resistance and other cellular functions19, 20, 21.