ERBB2 and neoplasm: Titration of the anti-HER2 FACS antibody on ice using MDA-MB-453 tumor cells against increasing trastuzumab concentration (0–10 μg/mL) did not impede HER2 staining (Figure 1E), suggesting that there was no steric hindrance of trastuzumab and the anti-HER2 detection antibody but possibly enhanced internalization of HER2 by trastuzumab [31].