Fig. 2

Pyrotinib promotes HER2 degradation via the ubiquitin–proteasome pathway. (a) HER2 mRNA expression in SK-BR-3 and JIMT-1 cells treated with pyrotinib (0.5µM) or lapatinib (1µM) as assessed using RT-qPCR. (b–d) SK-BR-3 and JIMT-1 cells were treated with the lysosomal inhibitor Baf-A1 (20nM) or proteasome inhibitors Velcade (0.5 µM) or MG-132 (10µM) for 0.5 h, with DMSO as the control, followed by the addition of pyrotinib (0.5µM) for 0, 2, and 4 h. (e–f) Cells were subjected to MG132 (10 µM) treatment for 0.5 h or DMSO as the control, followed by the addition of pyrotinib (0.5 µM) for 0, 2, and 4 h. HER2 was immunoprecipitated from the lysates, and the samples were analyzed by immunoblotting with an anti-ubiquitin, anti-HER2, and anti-HSP70 antibodies. GAPDH served as the loading control. Results are representative of 3 independent replicates.