title: Increased sensitivity of CLL-derived lymphocytes to apoptotic death activation by the proteasome-specific inhibitor lactacystin.
abstract: Ubiquitin-proteasome-dependent protein processing appears to be an essential component in the control of radiation-induced apoptosis in human lymphocytes. This control is altered in chronic lymphocytic leukaemia (CLL), compared to that of normal human lymphocytes which mainly showed high apoptotic values after irradiation, but in some cases no sensitivity was observed. Interestingly, lactacystin activated the apoptotic pathway in both radio-resistant and sensitive CLL cells, at doses which had no effect in normal cells where significantly higher concentrations were required. Therefore the resistance of some CLL cells to apoptosis initiation by radiation does not correlate to observed increased sensitivity to lactacystin. The nuclear level of the transcription factor NF-kappaB or the cytoplasmic level of IkappaBalpha remained unaltered upon irradiation or lactacystin CLL cells treatment, suggesting that the activity of the other factors involved in apoptotic death control were altered through proteasomal inhibition. These results strongly suggest an essential role of the ubiquitin system in apoptotic cell death control in CLL lymphocytes. The inhibition of proteasome-ubiquitin-dependent processing could be a discriminatory apoptotic stimulus between normal versus malignant lymphocytes and therefore might potentially be of use in this specific human pathology.
authors.affiliation: Laboratoire de Recherche Correspondant no. 2 du CEA (DSV/DRR FAR), Paris, France.
authors.forename: P
authors.initials: P
authors.lastname: Masdehors
authors.forename: S
authors.initials: S
authors.lastname: Omura
authors.forename: H
authors.initials: H
authors.lastname: Merle-Béral
authors.forename: F
authors.initials: F
authors.lastname: Mentz
authors.forename: J M
authors.initials: JM
authors.lastname: Cosset
authors.forename: J
authors.initials: J
authors.lastname: Dumont
authors.forename: H
authors.initials: H
authors.lastname: Magdelénat
authors.forename: J
authors.initials: J
authors.lastname: Delic
mesh_terms: D000111:Acetylcysteine / Q000031:analogs & derivatives* / Q000627:therapeutic use; D000368:Aged; D017209:Apoptosis / Q000187:drug effects; D015153:Blotting, Western; D015853:Cysteine Proteinase Inhibitors / Q000627:therapeutic use*; D006801:Humans; D015451:Leukemia, Lymphocytic, Chronic, B-Cell / Q000188:drug therapy / Q000473:pathology*; D008214:Lymphocytes / Q000473:pathology / Q000528:radiation effects; D014407:Tumor Cells, Cultured; D014409:Tumor Necrosis Factor-alpha / Q000494:pharmacology
chemical_list: D015853:Cysteine Proteinase Inhibitors; D014409:Tumor Necrosis Factor-alpha; C067713:lactacystin; D000111:Acetylcysteine