A dominant-negative F-box deleted mutant of E3 ubiquitin ligase, β-TrCP1/FWD1, markedly reduces myeloma cell growth and survival in mice

Oncotarget. 2015 Aug 28;6(25):21589-602. doi: 10.18632/oncotarget.4120.


Treatment of multiple myeloma with bortezomib can result in severe adverse effects, necessitating the development of targeted inhibitors of the proteasome. We show that stable expression of a dominant-negative F-box deleted (∆F) mutant of the E3 ubiquitin ligase, SCFβ-TrCP/FWD1, in murine 5TGM1 myeloma cells dramatically attenuated their skeletal engraftment and survival when inoculated into immunocompetent C57BL/KaLwRij mice. Similar results were obtained in immunodeficient bg-nu-xid mice, suggesting that the observed effects were independent of host recipient immune status. Bone marrow stroma offered no protection for 5TGM1-∆F cells in cocultures treated with tumor necrosis factor (TNF), indicating a cell-autonomous anti-myeloma effect. Levels of p100, IκBα, Mcl-1, ATF4, total and cleaved caspase-3, and phospho-β-catenin were elevated in 5TGM1-∆F cells whereas cIAP was down-regulated. TNF also activated caspase-3 and downregulated Bcl-2, correlating with the enhanced susceptibility of 5TGM1-∆F cells to apoptosis. Treatment of 5TGM1 tumor-bearing mice with a β-TrCP1/FWD1 inhibitor, pyrrolidine dithiocarbamate (PDTC), significantly reduced tumor burden in bone. PDTC also increased levels of cleaved Mcl-1 and caspase-3 in U266 human myeloma cells, correlating with our murine data and validating the development of specific β-TrCP inhibitors as an alternative therapy to nonspecific proteasome inhibitors for myeloma patients.

Keywords: 5TGM1; FWD1/β-TrCP1; myeloma; plasmacytoma; proteasome.

Publication types

  • Research Support, N.I.H., Extramural

MeSH terms

  • Animals
  • Apoptosis
  • Bone Marrow / metabolism
  • Bone Marrow Cells / cytology
  • Bortezomib / chemistry
  • Caspase 3 / metabolism
  • Cell Line, Tumor
  • Down-Regulation
  • Enzyme Activation
  • Female
  • Genes, Dominant
  • Humans
  • Mice
  • Mice, Inbred C57BL
  • Multiple Myeloma / metabolism*
  • Mutation*
  • Neoplasm Transplantation
  • Proteasome Endopeptidase Complex / chemistry
  • Pyrrolidines / chemistry
  • Stromal Cells / cytology
  • Thiocarbamates / chemistry
  • Tumor Necrosis Factor-alpha / metabolism
  • Ubiquitin-Protein Ligases / genetics*
  • Ubiquitin-Protein Ligases / metabolism
  • beta Catenin / chemistry
  • beta-Transducin Repeat-Containing Proteins / genetics*
  • beta-Transducin Repeat-Containing Proteins / metabolism


  • BTRC protein, human
  • Btrc protein, mouse
  • Pyrrolidines
  • Thiocarbamates
  • Tumor Necrosis Factor-alpha
  • beta Catenin
  • beta-Transducin Repeat-Containing Proteins
  • pyrrolidine dithiocarbamic acid
  • Bortezomib
  • Ubiquitin-Protein Ligases
  • Caspase 3
  • Proteasome Endopeptidase Complex