EZH2 loss of ubiquitination mediates bortezomib-sensitivity for NKTL cell lines. (A-B) Relative cell viability for treatment with bortezomib in (A) NKYS and (B) KHYG-1 cells overexpressing EZH2 wild-type. (C-D) Relative cell viability for treatment with bortezomib on (C) NKYS (5 nM) and (D) KHYG-1 (10 nM) cells upon EZH2 knock-down using siRNA. (E-F) Relative cell viability for treatment with bortezomib on (E) NK-S1 and (F) KHYG-1 cells overexpressing MELK wild-type or MELK T167A mutant. (G-H) Relative cell viability for treatment with bortezomib in (G) NKYS and (H) NK-S1 cells upon MELK knock-down. (I-J) Relative cell viability for treatment with 5 nM bortezomib in (I) NKYS and (J) KHYG-1 cells overexpressing EZH2 wild-type or EZH2 S220A mutant. Twenty hours of bortezomib treatment was used in all of these experiments. Cell survival was measured using CellTiter-Glo reagent. For all siRNA knock-down, bortezomib was added 48 hours after transfection. For all plasmid transfections, bortezomib was added 20 hours after transfection, and puromycin selection were used (1 µg/mL) along with bortezomib treatment. Data are shown as mean ± SD, N ≥ 3. *P < .05; **P < .01; ***P < .001.