Different Regulation of Glut1 Expression and Glucose Uptake during the Induction and Chronic Stages of TGFβ1-Induced EMT in Breast Cancer Cells

Transforming growth factor beta 1 (TGF-beta 1) is associated with epithelial-mesenchymal transition (EMT), lymph metastasis, and poor prognosis in breast cancer. Paradoxically, TGF-beta 1 is also a potent inhibitor of cell proliferation. TGF-beta 1-induced EMT involves activation of several pathways including AKT, which also regulates glucose uptake. Recent data show that prolonged TGF-beta 1 exposure leads to a more stable EMT phenotype in breast cancer cells. However, whether this is linked to changes in glucose metabolism is not clear. Here, we used a model of TGF-beta 1-induced EMT in mammary epithelial cells to study the regulation of Glut1 and EMT markers during the induction compared to a prolonged phase of EMT by western blot, immunofluorescence and qPCR analysis. We also measured cell proliferation and uptake of the glucose analogue 2-NDBG. We found that EMT induction was associated with decreased Glut1 expression and glucose uptake. These effects were linked to reduced cell proliferation rather than EMT. Knockdown of Glut1 resulted in growth inhibition and less induction of vimentin during TGF-beta 1-induced EMT. Intriguingly, Glut1 levels, glucose uptake and cell proliferation were restored during prolonged EMT. The results link Glut1 repression to the anti-proliferative response of TGF-beta 1 and indicate that re-expression of Glut1 during chronic TGF-beta 1 exposure allows breast cancer cells to develop stable EMT and proliferate, in parallel.