title: Membrane expression of DR4, DR5 and caspase-8 levels, but not Mcl-1, determine sensitivity of human myeloma cells to Apo2L/TRAIL.
abstract: The improved recombinant form of the death ligand Apo2L/TRAIL (Apo2L/TRAIL.0) is not cytotoxic for normal human cells and is a good candidate for the therapy of multiple myeloma (MM), a B-cell neoplasia that remains incurable. We have analyzed the molecular determinants of myeloma sensitivity to Apo2L/TRAIL.0 in a number of MM cell lines, the mechanisms of resistance and a possible way of overcoming it. Expression of one death receptor for Apo2L/TRAIL (DR4 or DR5) is sufficient to transduce death signals, though DR5 was more efficient when both receptors were present. Membrane expression of decoy receptors (DcR1, DcR2) and intracellular levels of c-FLIP(L), XIAP and Mcl-1 were not predictive of resistance to Apo2L/TRAIL. Inhibition of Mcl-1 degradation did not prevent Apo2L/TRAIL-induced apoptosis. In IM-9 cells, resistance was associated to a reduced caspase-8 expression. U266 cells, though expressing significant levels of DR4 and caspase-8, were nevertheless resistant to Apo2L/TRAIL. This resistance could be overcome by co-treatment with valproic acid (VPA), a histone deacetylase inhibitor. VPA caused the redistribution of DR4 to plasma membrane lipid rafts and restored DR4 signaling. Overexpression of Mcl-1 in U266 cells did not prevent Apo2L/TRAIL cytotoxicity in VPA-sensitized cells. These results, taken together, support the possible use of Apo2L/TRAIL.0 in the treatment of MM.
authors.affiliation: Departamento de Bioquímica y Biologia Molecular y Celular, Facultad de Ciencias, Universidad de Zaragoza, Zaragoza, Spain.
authors.forename: Maria
authors.initials: M
authors.lastname: Gómez-Benito
authors.forename: Maria José
authors.initials: MJ
authors.lastname: Martinez-Lorenzo
authors.forename: Alberto
authors.initials: A
authors.lastname: Anel
authors.forename: Isabel
authors.initials: I
authors.lastname: Marzo
authors.forename: Javier
authors.initials: J
authors.lastname: Naval
mesh_terms: D017209:Apoptosis; D053446:CASP8 and FADD-Like Apoptosis Regulating Protein / Q000378:metabolism; D053181:Caspase 8 / Q000032:analysis / Q000378:metabolism*; D045744:Cell Line, Tumor; D002462:Cell Membrane / Q000737:chemistry / Q000378:metabolism; D019008:Drug Resistance, Neoplasm / Q000187:drug effects; D058851:GPI-Linked Proteins; D006801:Humans; D009101:Multiple Myeloma / Q000378:metabolism*; D064549:Myeloid Cell Leukemia Sequence 1 Protein; D009363:Neoplasm Proteins / Q000032:analysis / Q000378:metabolism; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000032:analysis / Q000378:metabolism; D053220:Receptors, TNF-Related Apoptosis-Inducing Ligand / Q000032:analysis / Q000378:metabolism*; D053320:Receptors, Tumor Necrosis Factor, Member 10c; D011994:Recombinant Proteins / Q000494:pharmacology; D053221:TNF-Related Apoptosis-Inducing Ligand / Q000494:pharmacology*; D053319:Tumor Necrosis Factor Decoy Receptors / Q000032:analysis / Q000378:metabolism; D014635:Valproic Acid / Q000494:pharmacology; D051636:X-Linked Inhibitor of Apoptosis Protein / Q000378:metabolism
chemical_list: D053446:CASP8 and FADD-Like Apoptosis Regulating Protein; D058851:GPI-Linked Proteins; D064549:Myeloid Cell Leukemia Sequence 1 Protein; D009363:Neoplasm Proteins; D019253:Proto-Oncogene Proteins c-bcl-2; D053220:Receptors, TNF-Related Apoptosis-Inducing Ligand; D053320:Receptors, Tumor Necrosis Factor, Member 10c; D011994:Recombinant Proteins; D053221:TNF-Related Apoptosis-Inducing Ligand; C108661:TNFRSF10C protein, human; C451501:TNFRSF10D protein, human; D053319:Tumor Necrosis Factor Decoy Receptors; D051636:X-Linked Inhibitor of Apoptosis Protein; C496866:XIAP protein, human; D014635:Valproic Acid; D053181:Caspase 8