The effect of pertuzumab on HER2 homodimerization. (A) Immunoblot expression of monomer (185 kDa) and dimer (360–380 kDa) HER2 and quantified dimer/monomer ratios in CHO-K6 cells treated with 0.1, 1 and 10 μg/mL pertuzumab, 10 μg/mL trastuzumab or their combination for 60 min (dose-course treatment). (B) Time-course treatment of CHO-K6 with 10 μg/mL pertuzumab for 15, 30, 60 and 120 min. Ten μg/mL human IgG and 20 μM CP-724714 were used as mock and HER2 inhibitor controls. CP-724714 reduced dimer HER2. Trastuzumab increased dimer HER2 and pertuzumab had no significant effect on HER2 homodimerization. * p < 0.05, ** p < 0.01, *** p < 0.001.