The proteasome inhibitor NPI-0052 is a more effective inducer of apoptosis than bortezomib in lymphocytes from patients with chronic lymphocytic leukemia

Stacey Ruiz, Yelena Krupnik, Michael Keating, Joya Chandra, Michael Palladino, David McConkey

Research output: Contribution to journalArticle

Abstract

Proteasome inhibitors are potent inducers of apoptosis in isolated lymphocytes from patients with chronic lymphocytic leukemia (CLL). However, the reversible proteasome inhibitor bortezomib (PS-341; Velcade) did not display substantial antitumor activity in CLL patients. Here, we compared the effects of bortezomib and a new irreversible proteasome inhibitor (NPI-0052) on 20S chymotryptic proteasome activity and apoptosis in isolated CLL cells in vitro. Although their steady-state (3 hours) IC50s as proteasome inhibitors were similar, NPI-0052 exerted its effects more rapidly than bortezomib, and drug washout experiments showed that short exposures to NPI-0052 resulted in sustained (≥24 hours) 20S proteasome inhibition, whereas 20S activity recovered in cells exposed to even 10-fold higher concentrations of bortezomib. Thus, brief (15 minutes) pulses of NPI-0052 were sufficient to induce substantial apoptosis in CLL cells, whereas longer exposure times (≥8 hours) were required for commitment to apoptosis in cells exposed to equivalent concentrations of bortezomib. Commitment to apoptosis seemed to be related to caspase-4 activation, in that cells exposed to bortezomib or NPI-0052 could be saved from death by addition of a selective caspase-4 inhibitor up to 8 hours after drug exposure. Our results show that NPI-0052 is a more effective proapoptotic agent than bortezomib in isolated CLL cells and suggest that the chemical properties of NPI-0052 might also make it an effective therapeutic agent in CLL patients.

Original languageEnglish (US)
Pages (from-to)1836-1843
Number of pages8
JournalMolecular cancer therapeutics
Volume5
Issue number7
DOIs
StatePublished - Jul 1 2006
Externally publishedYes

ASJC Scopus subject areas

  • Oncology
  • Cancer Research

Fingerprint Dive into the research topics of 'The proteasome inhibitor NPI-0052 is a more effective inducer of apoptosis than bortezomib in lymphocytes from patients with chronic lymphocytic leukemia'. Together they form a unique fingerprint.

  • Cite this