STAT3 and neoplasm: Besides, the nucleus-accumulated pyruvate kinase M2 isoform (PKM2) can directly bind to β-catenin, hypoxia-inducible factor 1α (HIF1α), and CtBP-interacting protein (CtIP) and phosphorylate signal transducer and activator of transcription 3 (STAT3) to regulate downstream gene expression and then facilitate tumor development32–35.