Fig. 5

The presence of membrane-bound MUC21 on cancer cells obstructs their interaction with immune cells. (A-B) K562 cells were co-cultured with NK-92 cells at an E:T ratio of 0.5:1 for four hours in the presence of varying concentrations of rMUC21-mFc. (A) The cytotoxicity against K562 cells was measured by the luciferase activity of the surviving cells. (B) Representative flow cytometry analysis of surface CD107a expression on NK cells. (C) Human CD8⁺T cells were activated with anti-CD3 antibody in the presence of varying concentrations of rMUC21-mFc. ELISA of IFN-γ secretion by CD8⁺T cells. (D) FACS analysis showing the binding of rMUC21-mFc to resting and IL-15-stimulated primary NK cells (above), as well as resting and activated primary CD3⁺ T cells (below). (F) K562-tet-MUC21 cells were cultured in the presence or absence of Dox for 24 h. These cells were then co-incubated with CTV-labeled NK-92 cells for 15 min. Representative FACS plots (above) and a summary plot (below) showing the percentages of cell-to-cell conjugation. (G) Raji-tet-MUC21 cells were co-incubated with CTV-labeled CD19 CAR-T cells for 15 min. Representative FACS plots (above) and a summary plot (below) showing the percentages of the cell-to-cell binding. Data were compiled from two independent experiments. Statistical significance was determined by two-tailed unpaired t-tests. ns: not significant. ****P < 0.001