Role of PFKFB3 and PFKFB4 in Cancer: Genetic Basis, Impact on Disease Development/Progression, and Potential as Therapeutic Targets

Glycolysis is a crucial metabolic process in rapidly proliferating cells such as cancer cells. Phosphofructokinase-1 (PFK-1) is a key rate-limiting enzyme of glycolysis. Its efficiency is allosterically regulated by numerous substances occurring in the cytoplasm. However, the most potent regulator of PFK-1 is fructose-2,6-bisphosphate (F-2,6-BP), the level of which is strongly associated with 6-phosphofructo-2-kinase/fructose-2,6-bisphosphatase activity (PFK-2/FBPase-2, PFKFB). PFK-2/FBPase-2 is a bifunctional enzyme responsible for F-2,6-BP synthesis and degradation. Four isozymes of PFKFB (PFKFB1, PFKFB2, PFKFB3, and PFKFB4) have been identified. Alterations in the levels of all PFK-2/FBPase-2 isozymes have been reported in different diseases. However, most recent studies have focused on an increased expression of PFKFB3 and PFKFB4 in cancer tissues and their role in carcinogenesis. In this review, we summarize our current knowledge on all PFKFB genes and protein structures, and emphasize important differences between the isoenzymes, which likely affect their kinase/phosphatase activities. The main focus is on the latest reports in this field of cancer research, and in particular the impact of PFKFB3 and PFKFB4 on tumor progression, metastasis, angiogenesis, and autophagy. We also present the most recent achievements in the development of new drugs targeting these isozymes. Finally, we discuss potential combination therapies using PFKFB3 inhibitors, which may represent important future cancer treatment options.

Synergistic Effect of Colistin Combined with PFK-158 against Colistin-Resistant Enterobacteriaceae

As increasing numbers of colistin-resistant bacteria emerge, new therapies are urgently needed to treat infections caused by these pathogens. The discovery of new combination therapies is one important way to solve such problems. Here, we report that the antitumor drug PFK-158 and its analogs PFK-015 and 3PO can exert synergistic effects with colistin against colistin-resistant Enterobacteriaceae, including mcr-1-positive or high-level-colistin-resistant (HLCR) isolates, as shown by a checkerboard assay. The results of a time-kill assay revealed that colistin combined with PFK-158 continuously eliminated colistin-resistant Escherichia coli 13-43, Klebsiella pneumoniae H04, and Enterobacter cloacae D01 in 24 h. Images from scanning electron microscopy (SEM) at 5 h postinoculation confirmed the killing effect of the combination. Finally, in vivo treatment showed that PFK-158 had a better synergistic effect than its analogs. Compared to the corresponding rates after colistin monotherapy, the survival rates of systemically infected mice were significantly increased 30% or 60% when the mice received an intravenous injection of colistin in combination with 15 mg/kg of body weight PFK-158. These results have important implications for repurposing PFK-158 to combat colistin resistance.