6-phosphofructo-2-kinase/fructose-2,6-bisphospatase (PFKFB) family of enzymes are responsible for the conversion of fructose-6-phosphate (F6P) to fructose-2,6-bisphosphate (F2,6BP) and vice versa. F2,6BP is an allosteric glycolytic activator. Among the four identified PFKFB isozymes (PFKFB1-4), PFKFB2 is the least studied isozyme in human cancers.
mRNA expressions were analysed by RT-PCR and real-time qPCR, protein quantities were analysed by Western blotting. Glycolysis analyses were carried with radiactive glucose isotopes. F26BP levels were analysed by spectrophotometry. Intracellular localization of ectopically expressed PFKFB2 was determined by confocal microscopy.
First, PFKFB2 expressions in cancer cell lines were investigated and we observed that both PFKFB2 variants are expressed in cancer cells. The endogenously expressed PFKFB2 protein partially localizes to the nuclei in HeLa, HCT116 and Panc1 cells, as determined by Western blotting. When over-expressed ectopically, IF-IC imaging revealed more prominent nuclear localization of P2-v1 compared to P2-v2. Then effects of variants on glycolytic phenotype of cells was compared. Over-expression of both PFKFB2 variants increased F26BP concentration in MIA PaCa-2 cells, but only P2-v2 over-expression resulted with increased glucose uptake. On the other hand, in Panc1 cells, only over-expression of P2-v2 increased F26BP concentration and glucose uptake. siRNA-mediated knockdown of PFKFB2 in Panc1 and BxPC-3 cells reduced F26BP concentrations (40% and 60%). Additionally, knockdown of PFKFB2 in BxPC-3 cells reduced cell proliferation (44,89% p
Taken together, these results suggest both PFKFB2 variants is expressed and functional in cancer cells. When evaluated individually, P2-v1 seems to be important in nucleus, while prominantly cytoplasmic P2-v2 increases glycolysis. Also increased sensitivity of cells to gemcitabine treatment with PFKFB2 knockdown suggests drugs targeting PFKFB2 could be used with gemcitabine in further clinical trials.
Clinical trial identification
Legal entity responsible for the study
Uludag University, Bursa, Turkey
The Scientific and Technological Research Council of Turkey
All authors have declared no conflicts of interest.