Figure 1

HER2-trogocytosis and CD107a expression on immune effector cells in human breast cancer cell lines. HER2+ SK-BR-3 and BT-474 cell lines and HER2⁻ MCF7 and MDA-MB-231 cell lines were used as target cells, and healthy human PBMCs were used as effectors. Cells were co-cultured for 60 min in the trogocytosis assay and 90 min in the CD107a degranulation assay. Cells were stained with FITC-CD14, PE-CD56, APC-HER2, and PE-Cy5-CD107a antibodies and subjected to flow cytometry. A The trogocytosis assay was performed with an effector:target (E:T) cell ratio of 10:1 and various concentrations of trastuzumab (H: H0, without trastuzumab; H0.1, 0.1 μg/mL of trastuzumab; H1, 1 μg/mL of trastuzumab). *P < 0.05; **P < 0.001. B The trogocytosis assay was performed with an E:T cell ratio of 10:1 and 1 μg/mL of trastuzumab (H1). Normal human plasma was added to the co-culture medium at various dilutions (1:50, 1:10, 1:5, and 1:2). The target cancer cells used in the assay were SK-BR-3. *P < 0.05. C The antibody-dependent cellular cytotoxicity (ADCC) assay was performed with an E:T cell ratio of 10:1 and various concentrations of trastuzumab (H). CD107a positivity is indicative of CD14⁺ and CD56⁺ cell target cancer cell cytotoxicity. *P < 0.05. D CD107a positivity on HER2⁺/CD14⁺, HER2⁻/CD14⁺, HER2⁺/CD56⁺, and HER2⁻/CD56⁺ cells is shown. The target cancer cells used in the assay were SK-BR-3. *P < 0.05; **P < 0.001. HER2 positivity represents the uptake of HER2 onto CD14⁺ and CD56⁺ effector cells. All figures show the mean ± SEM. Experiments were performed for 3 healthy volunteers at least 2 times and similar data were obtained each time. All figures show the results from a single representative experiment.