Figure 2From: Engagement of immune effector cells by trastuzumab induces HER2/ERBB2 downregulation in cancer cells through STAT1 activationEngagement of FcγRs on immune cells with trastuzumab Fc is required for HER2 downregulation. (A) WB detection of HER2 in BT474 breast cancer cells with or without co-culture with PBMCs in the presence of trastuzumab, scIgG-T, N297A-T, or F(ab’)2-T for 48 h as labeled on the top of each panel. The same amount of protein lysates was loaded on each lane and β-actin was used as a loading control. (B) WB detection of HER2 in BT474 cancer cells after co-culture with NK cells, monocytes, T cells and PBMCs as labeled on each panel in the presence and absence of trastuzumab for 48 h. (C) PBMCs were pretreated with isotype IgG (10 μg/ml) for 1 h to block FcγRs before conducting co-culture with BT474 cancer cells in the presence or absence of trastuzumab (5 μg/ml) for 48 h. HER2 expression was detected by WB. (D) WB detection of HER2 downregulation in cancer cells after co-culture in transwell chambers with PBMC (the right two lanes) in the presence and absence of trastuzumab. Cancer cells co-cultured with PBMCs without the transwell chamber (the left two lanes) were used as controls. Fab, fragment, antigen binding; Fc, fragment, crystallizable; FcγR, Fc gamma receptor; HER2, human epidermal growth factor receptor 2; NK cell, natural killer cell; PBMC, peripheral blood mononuclear cell; scIgG-T, single hinge cleaved trastuzumab; WB, Western blotting.Back to article page