title: Interleukin-6-induced inhibition of multiple myeloma cell apoptosis: support for the hypothesis that protection is mediated via inhibition of the JNK/SAPK pathway.
abstract: The mechanism by which interleukin-6 (IL-6) protects multiple myeloma (MM) plasma cells from apoptosis induced by anti-fas antibodies and dexamethasone was studied. Anti-apoptotic concentrations of IL-6 had no effect on cell-cycle distribution or activation of RAF-1 or ERK in dexamethasone- or anti-fas-treated 8226 and UCLA #1 MM cell lines. However, IL-6-dependent protection of viability correlated with an inhibition of dexamethasone- and anti-fas-induced activation of jun kinase (JNK) and AP-1 transactivation. To test the hypothesis that cytokine-induced protection was mediated through inhibition of JNK/c-jun, we also inhibited c-jun function in 8226 cells via introduction of a mutant dominant negative c-jun construct. Mutant c-jun-containing MM cells were also resistant to anti-fas-induced apoptosis but were significantly more sensitive to dexamethasone-induced apoptosis. These results support the notion that IL-6 protects MM cells against anti-fas through its inhibitory effects on JNK/c-jun but indicate protection against dexamethasone occurs through separate, yet unknown pathways.
authors.affiliation: Department of Medicine, West LA VA Medical Center, and Jonsson Comprehensive Cancer Center, Los Angeles, CA, USA.
authors.forename: F H
authors.initials: FH
authors.lastname: Xu
authors.forename: S
authors.initials: S
authors.lastname: Sharma
authors.forename: A
authors.initials: A
authors.lastname: Gardner
authors.forename: Y
authors.initials: Y
authors.lastname: Tu
authors.forename: A
authors.initials: A
authors.lastname: Raitano
authors.forename: C
authors.initials: C
authors.lastname: Sawyers
authors.forename: A
authors.initials: A
authors.lastname: Lichtenstein
mesh_terms: D017209:Apoptosis / Q000187:drug effects*; D006801:Humans; D015850:Interleukin-6 / Q000494:pharmacology*; D048031:JNK Mitogen-Activated Protein Kinases; D048670:MAP Kinase Kinase 4; D020929:Mitogen-Activated Protein Kinase Kinases; D009101:Multiple Myeloma / Q000473:pathology* / Q000503:physiopathology; D009154:Mutation; D011494:Protein Kinases / Q000502:physiology*; D016755:Proto-Oncogene Proteins c-jun / Q000502:physiology; D015398:Signal Transduction / Q000187:drug effects; D014407:Tumor Cells, Cultured
chemical_list: D015850:Interleukin-6; D016755:Proto-Oncogene Proteins c-jun; D011494:Protein Kinases; D048031:JNK Mitogen-Activated Protein Kinases; D048670:MAP Kinase Kinase 4; D020929:Mitogen-Activated Protein Kinase Kinases