Fig. 4

The effects of trastuzumab on HER2 phosphorylation in CHO-K6 cells by immunoblotting. a CHO-K6 cells were treated with trastuzumab at various concentrations for 1 h. The phosphorylation of HER2 at Y1005, Y1127, Y1139, Y1196, and Y1248 were then examined by immunoblotting as described in Materials and Methods. Cells treated with normal human IgG or EGF were used as controls. b Quantification of the results in (a). The phosphorylation level of each HER2 pY residue was normalized against the expression level of tubulin. Each value is the average of at least three experiments and the error bar is standard error. **: p < 0.01. c Time course experiments. CHO-K6 cells were treated with trastuzumab (10 μg/ml) for various time as indicated. The phosphorylation of various HER2 pY residues were examined by immunoblotting