Fig. 4
Inhibition of cytotoxic granule secretion in NK cells by DPEP1. (A) rDPEP1 suppresses the mRNA expression of perforin 1 and granzyme B. NK92 and HCT116 cells were cocultured with or without rDPEP1, and qRT-PCR was performed to assess mRNA levels. (B) Western blot analysis of perforin 1 and granzyme B protein levels after coculture of NK92 and HCT116 cells in the presence or absence of rDPEP1. (C) Representative confocal microscopy images showing the effect of rDPEP1 on perforin 1 localization in NK92 cells treated with resveratrol alone or in combination with rDPEP1. Cells were stained with perforin 1/FITC and DAPI. (D) CD107a expression is inhibited by rDPEP1. NK92 and HCT116 cells were cocultured and treated with resveratrol, rDPEP1, or cilastatin (alone or in combination). CD107a and CD56 expression was analyzed by flow cytometry. (E) Inhibition of IFN-γ secretion by rDPEP1. NK92 cells were treated with resveratrol, rDPEP1, or cilastatin, and IFN-γ levels in the culture medium were measured by ELISA. (F, G) rDPEP1 inhibits IFN-γ and granzyme B secretion induced by IL-2 and IL-15. NK92 cells were treated with IL-2 and/or IL-15, with or without rDPEP1. Secreted IFN-γ (F) and granzyme B (G) were quantified. Data are presented as mean ± SD from three independent experiments (n = 3), each performed in triplicate. Statistical significance was determined using Student’s t-test (**P < 0.01, ***P < 0.001; NS, not significant).
