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Fig. 6 | Molecular Cancer

Fig. 6

From: SALL1 functions as a tumor suppressor in breast cancer by regulating cancer cell senescence and metastasis through the NuRD complex

Fig. 6

MAPK p38 and ERK1/2, and mTOR signaling pathways control the molecular process of SALL1-induced breast cancer cell senescence. a Transfection of wild type SALL1 but not mutated SALL1 in MCF-7 and E0771 cells induced phosphorylation of ERK and p38 in senescent tumor cells. Transfected breast cancer cells were cultured for different time points and cell lysates were prepared for western blot analyses. Results from western blot analyses of phosphorylated activation of ERK and p38 were shown in the upper panel. Phosphorylated ERK and p38 protein levels shown in the lower histogram were analyzed quantitatively and compared against the GAPDH expression level with a densitometer. Results shown in the histogram were means±SD from 3 independent experiments. *p<0.05 and **p<0.01 compared with the mutated SALL1 transfected group. b Inhibition of ERK1/2 or p38 signaling pathways by specific pharmacological inhibitors significantly prevented breast cancer cell senescence induced by SALL1, resulting in decreased SA-β-Gal expression. SALL1-transfected MCF-7 and E0771 cancer cells were cultured in the presence or absence of inhibitors U0126 or SB203580 (10μM) for 5 days. The treated tumor cells were analyzed for SA-β-Gal expression. Data shown are mean ± SD from three independent experiments with similar results. **p < 0.01, compared with the SALL1-transfected group but not treated with inhibitor. c Knockdown of ERK1/2 and p38 genes by shRNAs in MCF-7 and E0771 cells dramatically blocked SALL1-induced tumor cell senescence. Breast cancer cells were infected with lenti-shRNAs specific for ERK1/2 or p38 molecules. Transduced (GFP+) cancer cells were purified by FACS sorting and then transfected with SALL1 and cultured for 5 days. The SA-β-Gal+ cancer cells were determined. **p < 0.01, compared with the group transduced with the control shRNA. Data shown are representative of three independent experiments with similar results. d Phosphorylation and subsequent activation of mTOR signaling in breast cancer cells transfected with SALL1 but not mSALL1. Transfected MCF-7 and E0771 cells cultured for different times, and then were collected for western blot analyses of total and phosphorylated mTOR, p70S6K, and 4E-BP1 protein levels. e Rapamycin markedly inhibited the SALL1-mediated breast cancer cell senescence. SALL1-transfected MCF-7 and E0771 cancer cells were cultured in the presence or absence of mTOR inhibitor rapamycin (5 μM) for 5 days. The treated tumor cells were stained for SA-β-Gal expression. Data shown are mean ± SD from three independent experiments with similar results. **p < 0.01, compared with the SALL1-transfected group but not treated with inhibitor. f Knockdown of mTOR by shRNA in MCF-7 and E0771 cells significantly blocked SALL1-induced tumor cell senescence. Transfection procedure was identical to (c) and SA-β-Gal+ cancer cells were determined. **p < 0.01, compared with the group transduced with the control shRNA. Data shown are representative of three independent experiments with similar results

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