ERBB2 and breast cancer: The data revealed that the efficacy of neratinib was correlated with expression level of phosphorylated HER2 (pHER2; R2 = 0.5056, p = 0.0480) but not HER2 (R2 = 0.3396, p = 0.1295) across the HER2+ breast cancer cell lines tested (Figure 1B and Supplementary Figure S1C).