ERBB2 and breast carcinoma: To further test the correlation between ERRF expression and lapatinib sensitivity, we analyzed ERRF expression and sensitivities of breast cancer cell lines to ERBB2 drugs including lapatinib in a published study [45] and the CCLE, and found that lapatinib sensitive cell lines expressed significantly higher levels of ERRF than lapatinib resistant cell lines (Figure 1E).