title: Bortezomib restores stroma-mediated APO2L/TRAIL apoptosis resistance in multiple myeloma.
abstract: OBJECTIVE
  Hematopoietic stroma promotes resistance to immune control by APO2L/TRAIL in multiple myeloma (MM) cells in part by increasing synthesis of the anti-apoptotic protein c-FLIP. Here, we tested whether bortezomib can reverse the APO2L/TRAIL environmental mediated-immune resistance (EM-IR).
  
  
  METHODS
  MM cell lines (RPMI 8226 and U266) and CD138+ patient's MM cells were directly adhered to HS5 stroma exposed to HS5 or bone marrow stroma of patients with MM released soluble factors in a transwell system. Cells were treated with either APO2L/TRAIL (10 ng/mL), bortezomib (10 nm) or both.
  
  
  RESULTS
  Pretreatment with bortezomib effectively overcomes APO2L/TRAIL apoptosis resistance in myeloma cell lines and in CD138+ cells while directly adhered or in transwell assay. Bortezomib was not cytotoxic to HS5 stroma cells and only altered monocyte chemotactic protein-2-3 and IL-10 levels in the stroma-myeloma milieu. Factors released by HS5 stroma increased expression of c-FLIP, induced STAT-3 and ERK phosphorylation and reduced DR4 receptor expression in MM cells. HS5 stroma-released factor(s) induced NF-kappaB activation after 20 h exposure in association with an enhanced c-FLIP transcription. Bortezomib effectively reduced c-FLIP protein expression without affecting other proteins. Bortezomib also increased DR4 and DR5 expression in the presence of stroma.
  
  
  CONCLUSIONS
  These findings provide the rationale to combine bortezomib and APO2L/TRAIL to disrupt the influence of the stroma microenvironment on MM cells.
authors.affiliation: Department of Blood and Marrow Transplantation, H. Lee Moffitt Cancer Center, Tampa, FL 33612-9497, USA. lia.perez@moffitt.org
authors.forename: Lia E
authors.initials: LE
authors.lastname: Perez
authors.forename: Nancy
authors.initials: N
authors.lastname: Parquet
authors.forename: Mark
authors.initials: M
authors.lastname: Meads
authors.forename: Claudio
authors.initials: C
authors.lastname: Anasetti
authors.forename: William
authors.initials: W
authors.lastname: Dalton
mesh_terms: D017209:Apoptosis / Q000187:drug effects*; D001897:Boronic Acids / Q000494:pharmacology* / Q000627:therapeutic use; D000069286:Bortezomib; D053446:CASP8 and FADD-Like Apoptosis Regulating Protein / Q000037:antagonists & inhibitors; D045744:Cell Line, Tumor / Q000187:drug effects; D002478:Cells, Cultured / Q000187:drug effects / Q000378:metabolism; D018920:Coculture Techniques; D016207:Cytokines / Q000096:biosynthesis / Q000235:genetics; D004354:Drug Screening Assays, Antitumor; D004357:Drug Synergism; D015972:Gene Expression Regulation, Neoplastic / Q000187:drug effects; D006801:Humans; D009101:Multiple Myeloma / Q000473:pathology*; D009363:Neoplasm Proteins / Q000037:antagonists & inhibitors / Q000096:biosynthesis / Q000235:genetics; D011480:Protease Inhibitors / Q000494:pharmacology* / Q000627:therapeutic use; D011719:Pyrazines / Q000494:pharmacology* / Q000627:therapeutic use; D053220:Receptors, TNF-Related Apoptosis-Inducing Ligand / Q000037:antagonists & inhibitors / Q000502:physiology; D018124:Receptors, Tumor Necrosis Factor / Q000037:antagonists & inhibitors / Q000502:physiology; D011994:Recombinant Proteins / Q000494:pharmacology; D017154:Stromal Cells / Q000187:drug effects* / Q000378:metabolism; D053221:TNF-Related Apoptosis-Inducing Ligand / Q000494:pharmacology / Q000502:physiology*; D019139:Tumor Escape / Q000187:drug effects
chemical_list: D001897:Boronic Acids; D053446:CASP8 and FADD-Like Apoptosis Regulating Protein; C506386:CFLAR protein, human; D016207:Cytokines; D009363:Neoplasm Proteins; D011480:Protease Inhibitors; D011719:Pyrazines; D053220:Receptors, TNF-Related Apoptosis-Inducing Ligand; D018124:Receptors, Tumor Necrosis Factor; D011994:Recombinant Proteins; D053221:TNF-Related Apoptosis-Inducing Ligand; C105190:TNFRSF10A protein, human; C505653:TNFSF10 protein, human; D000069286:Bortezomib