Figure 3. Trastuzumab treatment increases the interaction between ErbB2 and CHK in BT474 cells. (A) BT474 cells were electroporated with either empty pCMV6-entry vector or pCMV-entry vector encoding DDK-tagged CHK. After transfection, cells were grown in the serum-containing media to recover for 24 h, and then were serum-starved overnight. Immunoprecipitation was performed as indicated and the immunoprecipitates were run in parallel with WCL from the indicated reactions to detect CHK and ErbB2 expression by western blot analysis. (B) BT474 cells were plated, serum-starved, fixed, and permeabilized. Following permeabilization, Duolink proximity ligation assay was performed according to the manufacturer’s instructions as indicated in the Materials and Methods. Representative images of samples incubated with anti-ErbB2 and anti-CHK antibodies (top row), and negative control samples (no primary antibodies, middle; anti-ErbB2 antibody only, bottom row).