C-Src Promotes Tumorigenesis And Tumor Progression By Phosphorylating And Activating PFKFB3

Metabolic reprogramming of tumor cells plays an important role in tumorigenesis and progression.Warburg effect,the observation that cancer cells tend to favor metabolism via glycolysis rather than the much more efficient oxidative phosphorylation pathway even in aerobic conditions,is one of the most prominent metabolic features of various tumors.A previous investigation in our laboratory indicates that the famous non-receptor tyrosine kinase c-Src can promote hexokinase activity to enhance Warburg effect and tumorigenesis.It has been well understood that some intermediates of glycolysis are important raw materials for biosynthesis pathways such as the pentose phosphate pathway(PPP)and the de novo synthesis of serine.However,it is unclear whether and how c-Src regulates the distribution of glycolytic intermediates in these anabolic pathways,thereby promotes tumorigenesis and tumor progression.Based on this concern,we discorvered that c-Src interacted with and activated 6-phosphate fructose 2-kinase/fructose-2,6bisphosphatase 3(PFKFB3)by phosphorylating its tyrosine 194 site.PFKFB3 functions to catalyze the conversion of fructose-6-phosphate to fructose-2,6-bisphosphate which is an allosteric activator of PFK1,a rate-limiting enzyme of glycolysis.Therefore,c-Src stimulates glycolysis flux by indirectly activating PFK1.As PFK1 is a key hub determining the distribution of glycolytic flux into glycolysis and oxidative PPP,c-Src activation of PFK1 increases glycolysis flux and relatively reduces oxidative PPP flux.Increased glycolysis intermediates replenish the non-oxidized pentose phosphate pathway(PPP)and serine de novo synthesis pathway required for biosynthesis of tumor cells.PFKFB3 knockout cells and its counterpart reconstituted with PFKFB3-Y194F mutant showed impaired abilities for cell proliferation,migration,and xenograft formation.Furthermore,PFKFB3-Y194F knock-in mice showed impaired glycolysis,and mating of these mice with APCmin/+ mice significantly attenuated spontaneous colon cancer formation in APCmin/+mice.In addition,phosphorylation level of PFKFB3-Tyr194 is highly correlated with c-Src activity in clinical tumor samples.Taken together,these results prove that c-Src phosphorylation of PFKFB3 Tyr194 plays an important role in tumorigenesis and tumor progression.In summary,we identified a novel mechanism by which c-Src enhances glycolysis and biosynthesis pathways through stimulating PFKFB3,a key activator of glycolysis to maximumly meet the cancer cell proliferation.Our investigation thus provides evidence for PFKFB3 as a novel target for tumor therapy and phosphorylation level of PFKFB3 Tyr194 as a potential evaluation for tumor prognosis...