STAT3 and cancer: Nuclear PKM2 displays intriguing non-glycolytic functions including phosphorylating some nuclear proteins such as histone H3 [2, 23], signal transducer and activator of transcription 3 (stat3) [24], Bub3 [25], and myosin light chain 2 (MLC2) [26], for which PKM2 uses the high-energy phosphate from PEP but not ATP as a phosphate donor, proposing that PKM2 in cancer cells presents protein kinase activity.