PKM and cancer: The main mechanism that allows cancer cells to maintain a high glycolytic flux is the overexpression of some glycolytic enzymes such as PFK, ENO-3, PKM2 and LDH, and one of the isoforms of the bifunctional enzyme 6-phosphofructo-2-kinase/fructose-2,6-bisphosphatase (also known as PFK-2) that produces F-2,6-BP, the potent activator of the glycolytic PFK [404] (figure 3a).