The small heat shock protein B8 (HSPB8) confers resistance to bortezomib by promoting autophagic removal of misfolded proteins in multiple myeloma cells

Oncotarget. 2014 Aug 15;5(15):6252-66. doi: 10.18632/oncotarget.2193.

Abstract

Velcade is one of the inescapable drug to treat patient suffering from multiple myeloma (MM) and resistance to this drug represents a major drawback for patients. However, the mechanisms underlying velcade resistance remain incompletely understood. We derived several U266 MM cell clones that resist to velcade. U266-resistant cells were resistant to velcade-induced cell death but exhibited a similar sensitivity to various proapoptotic stimuli. Careful analysis of proteosomal subunits and proteasome enzymatic activities showed that neither the composition nor the activity of the proteasome was affected in velcade-resistant cells. Elimination of velcade-induced poly-ubiquitinated proteins and protein aggregates was drastically stimulated in the resistant cells and correlated with increased cell survival. Inhibition of the lysosomal activity in velcade-resistant cells resulted in an increase of cell aggregates and decrease survival, indicating that aggregates are eliminated through lysosomal degradation. In addition, pangenomic profiling of velcade-sensitive and resistant cells showed that the small heat shock protein HSPB8 was overexpressed in resistant cells. Finally, gain and loss of function experiment demonstrated that HSPB8 is a key factor for velcade resistance. In conclusion, HSPB8 plays an important role for the elimination of aggregates in velcade-resistant cells that contributes to their enhanced survival.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Antineoplastic Agents / pharmacology*
  • Autophagy / drug effects
  • Bortezomib / pharmacology*
  • Cell Line, Tumor
  • Drug Resistance, Neoplasm
  • Heat-Shock Proteins / metabolism*
  • Humans
  • Molecular Chaperones
  • Multiple Myeloma / drug therapy*
  • Multiple Myeloma / metabolism*
  • Multiple Myeloma / pathology
  • Protein Folding
  • Protein Serine-Threonine Kinases / metabolism*

Substances

  • Antineoplastic Agents
  • HSPB8 protein, human
  • Heat-Shock Proteins
  • Molecular Chaperones
  • Bortezomib
  • Protein Serine-Threonine Kinases