Constitutively active Stat3 in mouse embryonic fibroblasts (MEFs). Mus musculus

Signal Transducer and Activator of Transcription 3 (STAT3) is considered as an oncogene being constitutively activated in a wide variety of primary human tumours, which often become addicted to its activity. Using primary fibroblasts derived from a knock-in mouse expressing only the constitutively active form STAT3-C as well as STAT3-dependent tumor cell lines MDA-MB468, DU145 and SKBR3, we provide evidence that STAT3 can act as a central regulator of cell metabolism. STAT3C/C MEFs are resistant to apoptosis and senescence and they show reduced mitochondrial activity but activate aerobic glycolysis, as shown by enhanced expression of master regulators of glycolysis such as PDK-1 and HIF-1α, and by increased lactate production, glucose avidity and sensitivity to glycolysis inhibitors. HIF-1α is up-regulated in the STAT3C/C MEFs and is responsible for the glycolytic phenotype. Moreover, inhibition of STAT3 activity in STAT3-addicted tumour cell lines restores mitochondrial activity and down-regulates glycolytic metabolism, preceding the induction of massive apoptosis. Thus, the essential role observed for STAT3 in so many different cancer cell types may be partly explained by its ability to act as a molecular switch of cellular metabolism triggering abnormal cell survival/proliferation. Overall design: Three biological replicates of MEFs from mice with constitutively active Stat3 are compared to three biological replicates of wild-type MEFs.