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. 2018 Jan 24;12(3):305–321. doi: 10.1002/1878-0261.12162

Figure 4.

Figure 4

Erk/Sp1 signaling pathway is involved in TGF‐β‐induced EGFR upregulation. (A) Inhibition of Sp1 by MTM weakens TGF‐β‐induced upregulation of EGFR mRNA in breast cancer cells. Two breast cancer cells were pretreated with Sp1‐nonspecific inhibitor MTM overnight and then treated with TGF‐β for 24 h. EGFR mRNA levels were determined by quantitative PCR analysis. Statistical analysis was performed by one‐way ANOVA (*P < 0.05). (B) MTM significantly inhibited the TGF‐β‐induced increase in the protein expression levels of EGFR. (C) Knockdown of Sp1 inhibits TGF‐β‐induced upregulation of EGFR mRNA. Two breast cancer cells were transfected with control or Sp1‐specific siRNA, then treated with TGF‐β for 24 h; the expression level of EGFR mRNA was determined by quantitative PCR analysis. Statistical analysis was carried out by two‐way ANOVA (*P < 0.05; **P < 0.01; ***P < 0.001). (D) Western blot analysis of the effect of Sp1 knockdown on TGF‐β‐induced upregulation of EGFR protein level. (E) Quantitative PCR analysis of the expression level of Sp1 mRNA in two breast cancer cells treated with TGF‐β for indicated times. Statistical analysis was carried out by one‐way ANOVA (*P < 0.05; **P < 0.01). (F) Western blot analysis of the expression level of Sp1 protein in two breast cancer cells treated with TGF‐β for the indicated times. (G) Inhibition of Erk1/2 signaling by PD98059 weakens TGF‐β‐induced upregulation of EGFR mRNA in two breast cancer cells. (H) Western blot analysis of the expression level of EGFR, Sp1, total and phosphorylated Erk1/2 proteins in cell lysates from two breast cancer cells pretreated with PD98059 and then stimulated with TGF‐β for the indicated times. Statistical analysis was carried out by two‐way ANOVA (***P < 0.001).