PFKFB3 and neoplasm: Fru-2,6-P2 concentration is significantly higher in tumor cells than in normal cells (56, 73, 74) and is regulated by different bifunctional isoenzymes called 6-phosphofructo-2-kinases/fructose 2,6-bisphosphatases (PFK-2/FBPase-2), which catalyze the synthesis and degradation of this metabolite (68–71, 75).