Proteasome inhibitors decrease viability and induce apoptosis in LGL leukemia cell lines through increased caspase-3 and PARP cleavage and downregulation of c-FLIP. (A) Bortezomib decreases viability in LGL leukemia cell lines. TL-1 and NKL cells were treated with bortezomib at varying concentrations for 48 hours, and cell viability was assessed using an MTS assay. (B) Ixazomib decreases viability in LGL leukemia cell lines. TL-1 and NKL cells were treated with ixazomib at varying concentrations for 48 hours, and cell viability was assessed using an MTS assay. (C) Proteasome inhibitors induce apoptosis in TL-1 cells. TL-1 cells were treated with bortezomib or ixazomib at varying concentrations for 24 or 48 hours, and cells were stained for apoptosis with Annexin-V and 7-AAD and analyzed by flow cytometry. (D) Proteasome inhibitors induce apoptosis in NKL cells. NKL cells were treated with bortezomib or ixazomib at varying concentrations for 24 or 48 hours, and cells were stained for apoptosis with Annexin-V and 7-AAD and analyzed by flow cytometry. (E) Proteasome inhibitors decrease expression of the NF-κB target c-FLIP and induce caspase-3 and PARP cleavage in TL-1 cells. TL-1 cells were treated with bortezomib (5 nM) or ixazomib (100 nM), and protein was harvested at various time points. Western blot analysis was performed for c-FLIP, caspase-3, and PARP. (F) NKL cells were treated with bortezomib (5 nM) or ixazomib (100 nM) and protein was harvested at various time points. Western blot analysis was performed for c-FLIP, caspase-3, and PARP expression. 50% effective concentration (EC50) values were determined by nonlinear regression in GraphPad Prism.
