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. Author manuscript; available in PMC: 2009 Jul 1.
Published in final edited form as: Mol Cancer Ther. 2008 Jul;7(7):1846–1850. doi: 10.1158/1535-7163.MCT-08-0168

Figure 3.

Figure 3

HER2 knockdown leads to lapatinib resistance in HER2-overexpressing cells. A, BT-474 and SK-BR-3 breast cancer cell lines were treated with control siRNA or HER2 siRNA for 48 h. Western blot analysis was done to determine the expression level of HER2 after siRNA knockdown. β-actin was used as a loading control. The relative intensity of HER2 was quantified with the NIH Image program. Ratios were calculated to compare the densities of HER2 expression in HER2 siRNA–transfected cells versus control siRNA–treated cells. B, at 48 h after siRNA knockdown, the cells were treated with the indicated concentrations of lapatinib for another 72 h. Growth-inhibitory effects of lapatinib on BT-474 and SK-BR-3 cells were studied by WST-1 assay. Viability of HER2 knockdown cells was compared with that of control siRNA knockdown cells. P values are indicated. Each experiment was repeated thrice independently.

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