Fig. 3

The effects of trastuzumab on HER2 homodimerization in CHO-K6 cells as revealed by crosslinking. Following trastuzumab treatment as indicated, CHO-K6 cells were treated with BS³ and the homodimerization of HER2 was revealed by immunoblotting as described in Materials and Methods. a CHO-K6 cells were treated with trastuzumab at various concentrations ranging from 0.1–10 μg/ml for 1 h. b Quantification of the data in (a). c CHO-K6 cells were treated with 10 μg/ml trastuzumab for various time period as indicated. Cells treated with normal human IgG were used as control. d Quantification of the data in (b). The level of HER2 homodimerization were quantitated by densitometry and expressed as the ratio of dimer/total HER2. Each value is the average of at least three experiments and the error bar is standard error. **: p < 0.01, ***: p < 0.001