Figure 6. Cdc25A-mediated PKM2 pS37 dephosphorylation promotes the EGF-induced Warburg effect and tumorigenesis.

(a,b,d,e) Cdc25A-depleted U87/EGFR cells with the reconstituted expression of rCdc25A WT or rCdc25A Y59F or PKM2-depleted U87/EGFR cells with the reconstituted expression of rPKM2 WT or rPKM2 S37D were incubated with no serum DMEM in the presence or absence of EGF (100 ng ml⁻¹) for 20 h. The media were collected for analysis of glucose consumption (a,d) or lactate production (b,e), which was normalized by cell numbers (per 10⁶). Data represent the means±s.d. of three independent experiments. *P<0.05: statistically significant value in relation to the corresponding cells without EGF treatment. (c,f) A total number of 2 × 10⁴ Cdc25A-depleted U87/EGFR cells with the reconstituted expression of rCdc25A WT or rCdc25A Y59F or PKM2-depleted U87/EGFR cells with the reconstituted expression of rPKM2 WT or rPKM2 S37D were plated and counted 7 days after seeding in DMEM with 0.5% bovine calf serum in the presence or absence of EGF (100 ng ml⁻¹). Data represent the means±s.d. of three independent experiments. *P<0.05: statistically significant value in relation to the corresponding cells without EGF treatment. (g,h) A total number of 5 × 10⁵ Cdc25A-depleted U87/EGFRvIII cells with the reconstituted expression of rCdc25A WT or rCdc25A Y59F (g), or PKM2-depleted U87/EGFRvIII cells with the reconstituted expression of rPKM2 WT or rPKM2 S37D (h) were intracranially injected into randomized athymic nude mice. After 2 weeks, the mice were euthanized and tumour growth was examined. Hematoxylin and eosin-stained coronal brain sections show representative tumour xenografts (top panel). Tumor volumes were calculated (bottom panel). Data represent the means±s.d. of seven mice.