Fig. 5.

Homophilic interaction of CD56 enhanced the antitumor activity of CAR-T cells. a Graph shows the emission ratio of FRET between the CFP-CD56 and YFP-CD56. Data were plotted as 500~550 nm/495~505 nm ratios vs. the concentration of P3DE + P3G peptides. b, c The effect of the P3DE + P3G on the function of PTL-Her2-CAR-T cells targeting SKOV3 cells were detected by cytotoxic activity (n = 4, 4 healthy donors) (b) and IFN-γ ELISpot assay (n = 2, 2 healthy donors) (c). All peptides were used at a concentration of 200 μg ml⁻¹. d–h SKOV3-bearing NSG mice were infused via tail with various CAR-T cells. The mice receiving PTL-Her2-CAR-T cells infusion were divided into two groups, with P3DE + P3G or PNC peptide, respectively. Thirteen days later, mice were killed and tumor tissues were digested for FACS. d Volume of mice (n = 4–5 mice for each group). e The representative flow cytometry analysis of CAR-T cells by detecting the scFv fragment of CAR moiety with anti-Fab antibody. f The representative flow cytometry analysis of IFN-γ-positive cells in tumor-infiltrating CAR-T cells of different groups. g Immunofluorescence staining of the frozen tissue sections of xenograft tumors treated with PTL-Her2-CAR-T cells, in the presence of P3DE + P3G peptides or PNC. CAR-T cells were stained with anti-mouse IgG H&L (green). CD56 was stained with anti-human CD56 (white), IFN-γ was stained with anti-human IFN-γ (red), and nuclei were stained with DAPI (blue). Scale bar, 20 µm. h Left panel, the percentages of CAR⁺ T cells per mm² found in different CAR-T treatment groups; middle panel, the percentages of CD56⁺ cells per mm² in different groups; right panel, the percentages of IFN-γ⁺ spots per mm² in different groups. At least three separate fields from each mice and three mice from each group were calculated. **P < 0.01, ***P < 0.001, ****P < 0.0001. ns, no significant difference (one-way ANOVA with Tukey’s post hoc tests (b, d); two-tailed Student’s t-test (c, h)). All data are means ± SEM. The source data underlying a–d and h are provided as a Source Data file