We studied the tumor suppressor function of the Krüppel-like factor 4 (KLF4) in pediatric leukemia because we identified that KLF4 inhibits T cell proliferation during homeostasis, and it is expressed at low levels in lymphoblasts from children with T-ALL, especially in the poor prognoses of ETP-ALL and TLX groups and the inhibitory role in T cell proliferation (50–52). The gene discussed is KLF4; the disease is leukemia.