Fig. 4: Breast cancer cells expressing G309A, S310Y, and P523S induce intrinsic resistance to HER2-personalized medicines.

A Graph showing proliferation rate measured at every 24 h for 5 days in ZR-75-1 cells overexpressing wild-type HER2 (H2-WT) and its dimerization domain mutations (DDMs). The error bars represent 5 replicates per timepoint for each mutation. Graphs showing the long-term clonogenic survival potential of H2-WT and its DDMs expressing ZR-5-1 cells (B) and AU-565 cells (E) in the presence or absence of trastuzumab. The error bars represent 4 replicates per timepoint for each mutation. C Graph showing the 3D anchorage-independent growth of ZR-75-1 cells expressing H2-WT and its DDMs in the presence of trastuzumab. The error bars represent 3 replicates per timepoint for each mutation (D) Graph showing proliferation of H2-WT and its DDMs expressing cells. The error bars represent 10 fields per timepoint for each mutation. Representative photomicrographs and green fluorescence images depict proliferation of H2-WT and P523S expressing AU-565 cells at days 1, 3, and 5. F Graphs showing percentage of early and late apoptosis in ZR-75-1 cells expressing H2-WT or other DDM studied after trastuzumab treatment. The graph is representative of 3 replicates. Western blots of p-HER2, pan-HER2, cleaved PARP, and α-tubulin performed after treatment with high doses of trastuzumab (G) and neratinib (H) using AU-565 cells stably expressing H2-WT or DDMs. Error bars for all experiments represent ± standard deviation; *P < 0.05; **P < 0.01; ***P < 0.001 ****P < 0.0001; ns non-significant.