3). uptake (3). High expression of Glut1 was correlated with poor prognosis Metergoline in several cancer types, including breast cancer (4, 5). There are five distinct subtypes of breast cancer with different clinical outcomes: luminal A, luminal B, HER2-positive, basal-like, and normal-like (6, 7). Basal-like breast cancers generally lack hormone receptors and HER2, and the majority of these cancers are also called triple-negative breast cancer (TNBC) (8). It was previously demonstrated that expression Metergoline of Glut1 is significantly associated with high histologic grade, ER negativity, PR negativity, CK5/6 negativity, EGFR expression, and high p53 expression (9). Although Glut1 is expressed in TNBCs at Metergoline a high level (9), the signaling pathways regulated by Glut1 remain poorly understood. In this study we investigated the effects of Glut1 silencing in two TNBC cell lines, MDA-MB-231 and Hs578T, using a short hairpin RNA (shRNA) system. Glut1 knockdown (Glut1 shRNA) cells were compared with control knockdown (Control shRNA) cells with respect to cell proliferation, colony formation, cell-cycle distribution, glycolytic phenotypes, wound-healing ability, migration, and invasion. We also showed that Glut1 regulated expression of EGFR and integrin 1, and modulated the EGFR/mitogen-activated protein kinase (MAPK) signaling pathway and integrin 1/Src/focal adhesion kinase (FAK) signaling pathway in TNBC cell lines. RESULTS Effects of Glut1 silencing on IL2RA proliferation, colony formation, and cell-cycle distribution To investigate the role of Glut1 in TNBC cells, we silenced Glut1 in TNBC cells using a shRNA system. Glut1 silencing was verified by Western blot analysis and Metergoline qRT-PCR (Fig. 1A and 1B). First, we compared the proliferation rates of Glut1 shRNA cells (MDA-MB-231 Glut1 sh and Hs578T Glut1 sh) and Control shRNA cells (MDA-MB-231 Cont sh and Hs578T Cont sh). The growth rate of Glut1 shRNA cells was lower than that of Control shRNA cells (Fig. 1C). Moreover, silencing of Glut1 significantly decreased the rate of colony formation (Fig. 1D). To identify the mechanisms responsible for the reduced cell proliferation in Glut1 shRNA cells, we analyzed the cell-cycle distribution by flow cytometry. Glut1 shRNA cells displayed accumulation of cells in G1 phase with a decrease in the S phase fraction (Fig. 1E). Open in a separate window Fig. 1 Effects of Glut1 silencing on proliferation, colony formation, and cell-cycle distribution. (A) Glut1 silencing was verified by Western blot analysis using anti-Glut1 antibody in MDA-MB-231 and Hs578T breast cancer cell lines. -tubulin was used as a loading control. (B) Ablation of Glut1 was confirmed by qRT-PCR using Glut1-specific primers. The values were normalized to GAPDH mRNA (***P < 0.0005). (C) Cont shRNA (Cont sh) cells and Glut1 shRNA (Glut1 sh) cells were seeded at 1 104 cells/well in 12-well plates and counted with a hemocytometer over 4 days (*P < 0.05, **P < 0.005). (D) Cells were seeded at 200 cells/well in 6-well plates. The number of colonies (> 20 m diameter) was counted at 12 days (**P < 0.005, ***P < 0.0005). (E) Cells were seeded at 1 106 cells/100-mm dish. After 24 h, cells were harvested, fixed in methanol, and incubated in PBS containing 40 g/ml propidium iodide and 100 g/ml RNase A. Propidium iodide-labeled nuclei were analyzed by flow cytometry. Reduction of glycolytic phenotypes by Glut1 knockdown Next, we examined metabolic.