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. 2013 Nov;27(11):4444–4454. doi: 10.1096/fj.12-224907

Figure 2.

Figure 2.

TGFβ stimulates ErbB ligand expression via ErbB autoinduction. A) RT-PCR analyses of ErbB ligand expression in HB-EGF-treated AKR-2B cells. Activation of ErbB induces expression of its own ligands. B) RT-PCR analyses of ErbB ligands and Western blot analysis of ErbB1 phosphorylation (15 h post-treatment) following cell stimulation with TGFβ1 in the presence of the ErbB1/ErbB2 inhibitor, lapatinib. The lack of effect on Smad3 phosphorylation (3 h) confirms the specificity of lapatinib. Stimulation of ErbB ligand expression by TGFβ requires ErbB autoinduction. C) RT-PCR analyses of ErbB ligands (12 h post-treatment) in response to TGFβ1 stimulation of cells stably expressing shRNA targeting ErbB1, ErbB2, or both (shE1+shE2). Western blot analyses (1 h) show efficient knockdown of ErbB1 and ErbB2 and uniform activation of Smad3. Results further support the role of ErbB autoinduction in ErbB ligand up-regulation by TGFβ.