Bortezomib inhibits HR-mediated repair of DNA DSBs. (A) Schema representing the phenotypic DR-GFP assay to measure HR-mediated DNA DSB repair. (B-C) Representative flow cytometric profile to measure the proportion of viable (PI⁻) and GFP⁺ MM1S-DR-GFP cells after infection with adenovirus control or AdNGUS24i adenovirus expressing the I-Sce1 endonuclease and incubation for 12 hours with or without bortezomib (1.25-5nM). Shown in panel C are the percentage of GFP⁺/PI⁻ cells calculated from 3 independent experiments. (D) A representative flow cytometric profile to measure the percentage of PI⁻ and GFP⁺ MM1S-DR-GFP cells after AdNGUS24i expression of the I-Sce1 endonuclease and treatment with bortezomib (5nM) alone or with Z-VAD (20μM) and melphalan (5μM). (E) Histograms representing the percentage of PI⁺ and GFP⁺ cells treated as described above. SD was calculated from 3 independent experiments.