6-phosphofructo-2-kinase/fructose-2,6-biphosphatase 4 is essential for p53-null cancer cells

The bifunctional enzyme 6-phosphofructo-2-kinase/fructose-2,6-biphosphatase-4 (PFKFB4) controls metabolic flux through allosteric regulation of glycolysis. Here we show that p53 regulates the expression of PFKFB4 and that p53-deficient cancer cells are highly dependent on the function of this enzyme. We found that p53 down-regulates PFKFB4 expression by binding to its promoter and mediating transcriptional repression via histone deacetylases. Depletion of PFKFB4 from p53 deficient cancer cells increased levels of the allosteric regulator fructose 2,6-bisphophate, leading to increased glycolytic activity but decreased routing of metabolites through the oxidative arm of the pentose phosphate pathway. PFKFB4 was also required to support the synthesis and regeneration of nicotinamide adenine dinucleotide phosphate (NADPH) in p53 deficient cancer cells. Moreover, depletion of PFKFB4 attenuated cellular biosynthetic activity and resulted in the accumulation of reactive oxygen species and cell death in the absence of p53. Finally, silencing of PFKFB4 induced apoptosis in p53 deficient cancer cells in vivo and interfered with tumour growth. These results demonstrate that PFKFB4 is essential to support anabolic metabolism in p53-deficient cancer cells and suggest that inhibition of PFKFB4 could be an effective strategy for cancer treatment.

双功能酶6-磷酸果糖-2-激酶/果糖-2,6-二磷酸酶4（PFKFB4）可通过别构调控糖酵解过程，进而控制细胞代谢流。本研究证实，p53能够调控PFKFB4的表达，且p53缺陷型癌细胞高度依赖该酶的生物学功能。研究发现，p53可结合PFKFB4的启动子区域，并通过招募组蛋白去乙酰化酶介导转录抑制，从而下调PFKFB4的表达水平。在p53缺陷型癌细胞中敲除PFKFB4，会升高别构调节剂果糖-2,6-二磷酸的含量，进而增强糖酵解活性，但同时会减少代谢物经磷酸戊糖途径氧化分支的流通量。此外，PFKFB4对于p53缺陷型癌细胞中烟酰胺腺嘌呤二核苷酸磷酸（NADPH）的合成与再生不可或缺。进一步实验表明，敲除PFKFB4会削弱细胞的合成代谢活性，并在p53缺失的条件下诱导活性氧积累与细胞死亡。最后，体内实验证实，沉默PFKFB4可诱导p53缺陷型癌细胞发生凋亡，并显著抑制肿瘤生长。上述研究结果表明，PFKFB4是维持p53缺陷型癌细胞合成代谢的关键因子，提示靶向抑制PFKFB4或可成为有效的癌症治疗策略。