Figure 1

The second-generation inhibitors of the 20S proteasome delanzomib, carfilzomib and ixazomib effectively induce cell cycle arrest and apoptosis in imatinib (IM)-sensitive and IM-resistant GIST cells. (A,B) Dose-dependent effect of delanzomib (DLZ), carfilzomib (CFZ) and ixazomib (IXA) in comparison to bortezomib (BO) as well as control (DMSO) treatment on cell viability (A) and induction of apoptosis (B) of IM-sensitive (GIST882, GIST-T1) and IM-resistant (GIST48, GIST430) GIST cells as measured by luminescence-based assays (mean +/− SE). (C,D) Immunoblot analysis for markers of cell cycle regulation and apoptosis after treatment of GIST cells with increasing concentrations (0.0001 μM–10 μM; 72 h) of delanzomib (C), carfilzomib (D, top panels) or ixazomib (D, bottom panels). (E) Dose-dependent effect of delanzomib on induction of apoptosis in GIST882 and GIST48 cells as measured by TUNEL assay. Cells were treated for 72 h. Graphs represent mean and standard error of at least three experiments with at least 100 cells counted each. Scale bars, 50 μm. *p ≤ 0.05 in comparison to control; **p ≤ 0.01 in comparison to control; ***p ≤ 0.001 in comparison to control (Student’s t-test, 2-tailed). (F) Immunoblot analysis for markers of cell cycle regulation and apoptosis after treatment of GIST cells with DMSO or delanzomib (0.1 μM) for the indicated times. (C,D,F) Grouped immunoblot images are either cropped from different parts of the same gel or from a separate gel run with another aliquot of the same protein lysate.