Fig. 3.

Changes in ErbB2 levels in EBP1-silenced and overexpressing cells and relationship to response to lapatinib. a Expression of ErbB2 in EBP1-silenced or overexpressing cells. Lysates of logarithmically growing C13 or A16 cells, C81 vector control or EBP1-overexpressing cells and C4-2B vector (C4V) or EBP1-transfected (C4E) cells were immunoblotted for ErbB2 or GAPDH as indicated. Representative of 3 experiments. The numbers below the blots indicate the relative densities of ErbB2 and AR normalized to GAPDH. b Effects of ErbB2 levels on the response to lapatinib. A16 cells were transfected with ErbB2. Growth was assessed 4 days later using a Promega Cell Proliferation assay as described in the “Materials and Methods” section. Each data point represents the Mean ± SD of 6 wells. Representative of two experiments. Inset Western blot for ErbB2 expression. c, d A16 and C13 (c) and C81V and C81E (d) cells were grown in androgen-depleted media for 3 days. R1881 (10⁻⁹) M and lapatinib (1 μM) were added as indicated 24 h prior to harvesting cells. Western blotting was performed for ErbB2 and GAPDH as shown. Representative of 3 experiments. The numbers below the blots indicate the relative densities of ErbB2 normalized to GAPDH. The value of each untreated cell line was set at 1