ERBB2 and breast cancer: The ERBB2-negative MDA-MB-468 breast cancer cell line was used as a negative control (MDA-MB-468, MFI 1.2 ± 0.2, n = 3), while the MDA-MB-453 breast cancer cell line served as a positive control (MDA-MB-453, MFI 138.1 ± 26.3, n = 3).