Pharmacological inhibition and specific gene silencing of LCK increases Dex-induced cell death in PPR T-ALL cells. (A-C) ALL-SIL, CCRF-CEM, and TALL-1 cells treated with Dex, dasatinib, bosutinib, nintedanib, and WH-4-023, alone or in combination. ALL-SIL cells were treated with Dex (0.1 μM), dasatinib (0.5 nM), bosutinib (20 nM), nintedanib (0.6 μM), or WH-4-023 (1.25 μM); CCRF-CEM cells were treated with Dex (0.1 μM), dasatinib (10 μM), bosutinib (6.25 μM), nintedanib (5 μM), or WH-4-023 (5 μM); T-ALL1 cells were treated with Dex (60 nM), dasatinib (25 μM), bosutinib (6.25 μM), nintedanib (12.5 μM), or WH-4-023 (6.25 μM). Cell mortality was determined by flow cytometry and annexin V/PI staining after 48 hr of treatment. The percentage of dead cells was established after normalizing cells on DMSO-treated cells. Paired t test; n = 3 for all experiments. Results are presented as means ± SEM. Dex and LCK inhibitor concentrations used in these experiments were selected on the basis of MTT test results, by choosing the ones most able to reduce cell viability in combination. (D) Inhibition of LCK mRNA expression in ALL-SIL cells after 48 hr with sh LCK 1 and sh LCK 2. LCK mRNA expression in control cells was arbitrarily set at 1. sh CTRL vs sh LCK 1, paired t test P = .016; sh CTRL vs sh LCK 2, paired t test P = .001; n = 3 for all experiments. Results are presented as means ± SEM. (E) Inhibition of LCK protein expression was examined by WB after 72 hr in control (sh CTRL) and silenced (sh LCK 1, sh LCK 2) ALL-SIL cells. (F) Cell viability after LCK silencing and 48 hr of Dex treatment in ALL-SIL cells was evaluated by MTT assay (n = 3). Results are presented as means ± SEM. *P < .05; **P < .01; ***P < .001.