Fig. 4: Chemotherapy-induced O-GlcNAcylation activates pro-survival pathways in cancer cells.

a O-GlcNAcylation of caspase-9/3 is increased in resistant cells compared with sensitive MCF-7 cells. Caspase-9/3 immunoprecipitations were performed and the immunoprecipitated fractions were analysed by immunoblotting for O-GlcNAcylation. b Caspase-9 cleavage can be blocked by O-GlcNAcylation. MCF-7 cells were transfected with the control (pcDNA) or OGT-overexpressing vector (OGT) for 48 h and then treated with 1 μM DOX for the indicated time. Caspase-9 immunoprecipitation was performed and the immunoprecipitated fractions were analysed by immunoblotting for O-GlcNAcylation. c and d O-GlcNAcylation inhibits the apoptotic function of caspases. MCF-7 cells were stable transfected with the control (pcDNA3.1) or OGT-overexpressing vector (OGT) for 48 h and then treated with 1 μM DOX for the indicated time. MCF-7/ADR and SMMC-7721 cells were transfected with scrambled siRNA (siScr) or OGT siRNA (siOGT) for 48 h and then treated with 1 μM DOX for the indicated time, and apoptosis was then analysed through flow-cytometry with Annexin V/PI double staining. e MCF-7/ADR and SMMC-7721 cells were transfected with scrambled siRNA (siScr) or OGT siRNA (siOGT) for 48 h and then treated with 1 μM DOX for the indicated time. Caspase-3/9 immunoprecipitation was performed and the immunoprecipitated fractions were analysed by immunoblotting for O-GlcNAcylation. fand g The pro-survival transcription factors NF-κB and AKT were O-GlcNAcylated during DOX treatment. MCF-7/ADR and SMMC-7721 cells were transfected with scrambled siRNA (siRNA-Scr) or OGT siRNA (siOGT) for 48 h and then treated with 1 μM DOX for the indicated time. NF-κB and AKT immunoprecipitations were performed, and the immunoprecipitated fractions were analysed by immunoblotting