The proteasome inhibitor PS-341 potentiates sensitivity of multiple myeloma cells to conventional chemotherapeutic agents: therapeutic applications

Nicholas Mitsiades, Constantine S. Mitsiades, Paul G. Richardson, Vassiliki Poulaki, Yu-Tzu Tai, Dharminder Chauhan, Galinos Fanourakis, Xuesong Gu, Charles Bailey, Marie Joseph, Towia A. Libermann, Robert Schlossman, Nikhil C. Munshi, Teru Hideshima and Kenneth C. Anderson


The proteasome inhibitor PS-341 inhibits nuclear factor-κB (NF-κB) activation, induces apoptosis in cancer cells, including multiple myeloma (MM) cells, and has marked clinical activity as a monotherapy for MM. In this study, we found that subtoxic concentrations of PS-341 potently sensitized MM cell lines and patient cells to DNA-damaging chemotherapeutic agents such as doxorubicin and melphalan, including cells resistant to these drugs and those isolated from a patient who had relapsed after PS-341 monotherapy. Moreover, PS-341 abolished cell adhesion–mediated drug resistance. Using gene expression profiling and proteomic analysis, we demonstrate that PS-341, among its other proapoptotic effects, down-regulates the expression of several effectors involved in the cellular response to genotoxic stress. These data suggest that, in addition to down-regulating the expression of apoptosis inhibitors, PS-341 inhibits genotoxic stress response pathways and thereby restores sensitivity to DNA-damaging chemotherapeutic agents. These studies, therefore, provide the framework for clinical use of this agent in combination with conventional chemotherapy.

  • Submitted June 14, 2002.
  • Accepted October 17, 2002.
View Full Text