STAT3 and neoplasm: IL-6 can increase the activity of HIF-1α in tumor cells via STAT3 signaling, and HIF-1α may activate GLUT-1 via the Phosphatidylinositol-3-kinase (PI3K) pathway (39–41), which shifts glucose metabolism from oxidative phosphorylation to anaerobic processes (the Warburg effect) (42–44).