Molecular mechanisms of nutlin-induced apoptosis in multiple myeloma: evidence for p53-transcription-dependent and -independent pathways

Cancer Biol Ther. 2010 Sep 15;10(6):567-78. doi: 10.4161/cbt.10.6.12535. Epub 2010 Oct 1.


Multiple myeloma (MM) is an incurable plasma cell malignancy in which p53 is rarely mutated. Thus, activation of the p53 pathway by a small molecule inhibitor of the p53-MDM2 interaction, nutlin, in MM cells retaining wild type p53 is an attractive therapeutic strategy. Recently we reported that nutlin plus velcade (a proteasome inhibitor) displayed a synergistic response in MM. However, the mechanism of the p53-mediated apoptosis in MM has not been fully understood. Our data show that nutlin-induced apoptosis correlated with reduction in cell viability, upregulation of p53, p21 and MDM2 protein levels with a simultaneous increase in pro-apoptotic targets PUMA, Bax and Bak and downregulation of anti-apoptotic targets Bcl2 and survivin and activation of caspase in MM cells harboring wild type p53. Nutlin-induced apoptosis was inhibited when activation of caspase was blocked by the caspase inhibitor. Nutlin caused mitochondrial translocation of p53 where it binds with Bcl2, leading to cytochrome C release. Moreover, blocking the transcriptional arm of p53 by the p53-specific transcriptional inhibitor, pifithrin-α, not only inhibited nutlin-induced upregulation of p53-transcriptional targets but also augmented apoptosis in MM cells, suggesting an association of transcription-independent pathway of apoptosis. However, inhibitor of mitochondrial translocation of p53, PFT-μ, did not prevent nutlin-induced apoptosis, suggesting that the p53 transcription-dependent pathway was also operational in nutlin-induced apoptosis in MM. Our study provides the evidence that nutlin-induced apoptosis in MM cells is mediated by transcription-dependent and -independent pathways and supports further clinical evaluation of nutlin as a novel therapeutic agent in MM.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Apoptosis / drug effects*
  • Apoptosis Regulatory Proteins / genetics
  • Apoptosis Regulatory Proteins / metabolism
  • Benzothiazoles / pharmacology
  • Cell Line, Tumor
  • Cell Proliferation / drug effects
  • Cell Survival / drug effects
  • Cyclin-Dependent Kinase Inhibitor p21 / genetics
  • Cyclin-Dependent Kinase Inhibitor p21 / metabolism
  • Dose-Response Relationship, Drug
  • Flow Cytometry
  • Gene Expression Profiling
  • Gene Expression Regulation, Neoplastic / drug effects
  • Humans
  • Imidazoles / pharmacology*
  • Immunoblotting
  • Multiple Myeloma / genetics
  • Multiple Myeloma / metabolism
  • Multiple Myeloma / pathology
  • Piperazines / pharmacology*
  • Protein Binding / drug effects
  • Protein Transport / drug effects
  • Proto-Oncogene Proteins c-bcl-2 / genetics
  • Proto-Oncogene Proteins c-bcl-2 / metabolism
  • Proto-Oncogene Proteins c-mdm2 / genetics
  • Proto-Oncogene Proteins c-mdm2 / metabolism
  • Reverse Transcriptase Polymerase Chain Reaction
  • Signal Transduction / drug effects
  • Sulfonamides / pharmacology
  • Toluene / analogs & derivatives
  • Toluene / pharmacology
  • Transcription, Genetic / drug effects
  • Tumor Suppressor Protein p53 / genetics
  • Tumor Suppressor Protein p53 / metabolism*


  • 2-phenylacetylenesulfonamide
  • Apoptosis Regulatory Proteins
  • Benzothiazoles
  • Cyclin-Dependent Kinase Inhibitor p21
  • Imidazoles
  • Piperazines
  • Proto-Oncogene Proteins c-bcl-2
  • Sulfonamides
  • Tumor Suppressor Protein p53
  • Toluene
  • nutlin 3
  • pifithrin
  • MDM2 protein, human
  • Proto-Oncogene Proteins c-mdm2