Blockade of interleukin-6 signalling with siltuximab enhances melphalan cytotoxicity in preclinical models of multiple myeloma

Br J Haematol. 2011 Mar;152(5):579-92. doi: 10.1111/j.1365-2141.2010.08533.x. Epub 2011 Jan 17.


Signalling through the interleukin (IL)-6 pathway induces proliferation and drug resistance of multiple myeloma cells. We therefore sought to determine whether the IL-6-neutralizing monoclonal antibody siltuximab, formerly CNTO 328, could enhance the activity of melphalan, and to examine some of the mechanisms underlying this interaction. Siltuximab increased the cytotoxicity of melphalan in KAS-6/1, INA-6, ANBL-6, and RPMI 8226 human myeloma cell lines (HMCLs) in an additive-to-synergistic manner, and sensitized resistant RPMI 8226.LR5 cells to melphalan. These anti-proliferative effects were accompanied by enhanced activation of drug-specific apoptosis in HMCLs grown in suspension, and in HMCLs co-cultured with a human-derived stromal cell line. Siltuximab with melphalan enhanced activation of caspase-8, caspase-9, and the downstream effector caspase-3 compared with either of the single agents. This increased induction of cell death occurred in association with enhanced Bak activation. Neutralization of IL-6 also suppressed signalling through the phosphoinositide 3-kinase/Akt pathway, as evidenced by decreased phosphorylation of Akt, p70 S6 kinase and 4E-BP1. Importantly, the siltuximab/melphalan regimen demonstrated enhanced anti-proliferative effects against primary plasma cells derived from patients with myeloma, monoclonal gammopathy of undetermined significance, and amyloidosis. These studies provide a rationale for translation of siltuximab into the clinic in combination with melphalan-based therapies.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Antibodies, Monoclonal / administration & dosage
  • Antibodies, Monoclonal / pharmacology
  • Antineoplastic Combined Chemotherapy Protocols / pharmacology*
  • Apoptosis / drug effects
  • BH3 Interacting Domain Death Agonist Protein / metabolism
  • Cell Survival / drug effects
  • Dose-Response Relationship, Drug
  • Drug Screening Assays, Antitumor
  • Humans
  • Interleukin-6 / antagonists & inhibitors*
  • Melphalan / administration & dosage
  • Melphalan / pharmacology
  • Multiple Myeloma / metabolism
  • Multiple Myeloma / pathology*
  • Neoplasm Proteins / metabolism
  • Plasma Cells / drug effects
  • Proto-Oncogene Proteins c-akt / metabolism
  • Signal Transduction / drug effects
  • Tumor Cells, Cultured
  • bcl-2 Homologous Antagonist-Killer Protein / metabolism
  • bcl-2-Associated X Protein / metabolism


  • Antibodies, Monoclonal
  • BAK1 protein, human
  • BAX protein, human
  • BH3 Interacting Domain Death Agonist Protein
  • BID protein, human
  • Interleukin-6
  • Neoplasm Proteins
  • bcl-2 Homologous Antagonist-Killer Protein
  • bcl-2-Associated X Protein
  • Proto-Oncogene Proteins c-akt
  • Melphalan
  • siltuximab