Pevonedistat can enhance the cytotoxicities of anti–PD-L1 monoclonal antibody avelumab in ATLL cells. (A) Values of specific lysis of the target KK1 cells with or without ectopic STAT3Y640F cDNA expression under cocultivation with the effector PBMNC. The target cells were stained with CellBriteTM Red Cytoplasmic Membrane dye for the discrimination from effector cells and treated with 1 μg/mL avelumab for 1 hour before coculture. After the cocultivation of the target KK1 cells and the effector PBMNC for the indicated time, the dye-stained target cell numbers were analyzed by flow cytometry. The numbers were normalized by cell counting beads. (B) The target KK1 wild type or KK1 PD-L1-SV#7 cells were analyzed as shown in panel A. (C-D) The target KK1 wild-type cells (C) or KK1 PD-L1-SV#7 (D) were pretreated with or without pevonedistat for 24 hours. After washing, the target cells were analyzed as shown in panel A. Error bars represent the mean with SEM of replicates. ∗P < .05; ∗∗P < .01; ∗∗∗P < .001; Welch 2-sample t test. All experiments were repeated at least 2 times. cDNA, complementary DNA.
