Fig. 1: T-DXd cytotoxicity against HER2-Low and HER2-Negative tumors in vivo occurs independently of HER2-High cells in proximity. | Nature Communications

Fig. 1: T-DXd cytotoxicity against HER2-Low and HER2-Negative tumors in vivo occurs independently of HER2-High cells in proximity.

From: Effective extracellular payload release and immunomodulatory interactions govern the therapeutic effect of trastuzumab deruxtecan (T-DXd)

Fig. 1

a T-DXd internalization in cancer lines with different HER2 expression levels. T-DXd or control antibody (rituximab) were labeled with pHrodo to assess internalization into the endosome. Endocytosis was analyzed at 24 h post treatment. Representative flow histograms are shown for each T-DXd concentration. b Summary of T-DXd internalization. c Cell lines with different HER2 expression were treated with indicated ADCs or antibodies for 4 days, and cell viability was assessed by cellular ATP quantification. d In vitro bystander killing analysis. Vybrant DiD-labeled Au565 cells and Cell-Trace Violet-labeled MDA-MB-468 cells were co-cultured (1:2 ratio) with antibodies/ADCs (100 ng/mL) for 2 and 6 days. Apoptosis was assessed by AnnexinV/PI staining. e, f Summary of direct Au565 killing and bystander MDA-MB-468 killing. Total AnnexinV+ percentages (early and late apoptosis combined) are plotted. g, h Similar co-culture experiment using labeled HER2-low CAPAN-1 and MDA-MB-468, treated with 1 µg/mL of antibodies/ADCs. Apoptosis was assessed by AnnexinV/PI staining. b, c, e–h Two-way ANOVA with Tukey’s multiple comparisons test (n = 3). i–k HER2-ADC therapeutic efficacies on various BC xenografts with different HER2 expression engrafted in mammary fat pads of SCID mice. Tumor-bearing animals were treated weekly (arrows indicated) with T-DXd or T-DM1 (10 mg/kg each) or vehicle control PBS. l Diagram of KPL4 and MDA-MB-468 dual-implantation into the right and left mammary fat pads of SCID mice. Created in BioRender. Hartman, Z. (2025) https://BioRender.com/f86p031. m, n Tumor-bearing mice in (l) were treated weekly with rituximab, T-DXd, or T-DM1 (10 mg/kg, arrows indicated). Tumor growths from each side are plotted. i–n Mixed-effects analysis (REML) with Tukey’s multiple comparisons. i, k, m, n n = 5, (j) (n = 10). All data is presented as mean ± SEM with p values. n.s. = not significant.

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