Figure 3

MTDH manipulation regulated trastuzumab resistance by influencing PTEN and pAkt expression in HER2 positive breast cancer cells. A. Western blot analysis revealed that MTDH-shRNA blocked MTDH expression accompanied by increased PTEN and reduced p-Akt in SK-BR-3/R cells. Up-regulation of MTDH in SK-BR-3 cells was also realized accompanied with downregulated PTEN and elevated p-Akt; B. MTT assay indicated that MTDH-shRNA significantly reduced trastuzumab resistance in SK-BR-3/R cells, while MTDH up-regulation led to the resistance of trastuzumab (5 μg/ml, 72 h) in SK-BR-3 cells (*P < 0.05). MTDH was overexpressed in SK-BR-3 cells and knocked down in SK-BR-3/R cells; C. 5-ethynyl-2′-deoxyuridine (EdU) incorporation assay demonstrated trastuzumab resistance in MTDH-SK-BR-3 cells but not in engineered SK-BR-3/R cells (*P < 0.05); D. and E. Results of TUNEL assay denoted higher apoptosis rate in SK-BR-3/R cells interfered by MTDH-shRNA (magnification at 200×, *P < 0.05).