ERBB2 and breast cancer: The results from flow cytometry demonstrated that the SKBR3 cells efficiently bound to the trastuzumab reference standard (NIBSC-19/108), exhibiting an MFI of 4224.5 as compared to other HER2-positive breast cancer cell lines BT474 with an MFI of 1961.5, MDA-MB-453 with an MFI of 740.5, and MDA-MB-175 with an MFI of 514 (Figure 1c).