BACKGROUND: Pyruvate kinase M2 (PKM2) is highly expressed in multiple cancer types and contributes to the Warburg effect. METHODS: We have used various approaches including animal studies, human GBM specimen analyses, and biochemical studies, to understand the cellular functions of PKM2. RESULTS: We have uncovered the mechanisms underlying the upregulation of PKM2, nuclear translocation of PKM2, and metabolic and non-metabolic functions of PKM2 in promoting cancer cell metabolism, proliferation, and cell cycle progression. CONCLUSIONS: We have concluded that the nuclear function of PKM2 is essential for the Warburg effect and brain tumor development. SECONDARY CATEGORY: n/a.