ERBB2 and breast cancer: Considering that ERRF enhances lapatinib-induced apoptosis (Figure 5), ERRF expression inversely correlates with ERBB2 status [41], and MCL1 is not only an anti-apoptotic gene that mediates lapatinib resistance in HCT116 cells [50] but also an upstream regulator of ERBB2 [51], we evaluated whether ERBB2 and MCL1 are related to ERRF in any way in breast cancer cells.