Related Experiment Video
Updated: Jul 15, 2026
09:25
Quantifying Subcellular Ubiquitin-proteasome Activity in the Rodent Brain
Published on: May 21, 2019
Proteasome inhibition measurements: clinical application
E S Lightcap1, T A McCormack, C S Pien
1Millennium Pharmaceuticals, Inc., 38 Sidney St., Cambridge, MA 02139. USA. elightcap@mpi.com
Clinical Chemistry
|May 5, 2000
Summary
A new assay accurately measures proteasome inhibition by anticancer drugs like PS-341 in blood cells. This pharmacodynamic tool is crucial for ongoing clinical trials of proteasome inhibitors.
Area of Science:
- Biochemistry
- Pharmacology
- Oncology
Background:
- PS-341 is a proteasome inhibitor investigated as an anticancer agent.
- Pharmacokinetic studies showed rapid distribution and clearance of PS-341.
- Need for a reliable pharmacodynamic assay to complement pharmacokinetic measurements.
Purpose of the Study:
- Develop and validate a novel pharmacodynamic assay for proteasome inhibitors.
- Assess proteasome activity in whole blood and blood cells.
- Evaluate the assay's performance using PS-341 and lactacystin.
Main Methods:
- Optimized fluorogenic kinetic assays for chymotryptic and tryptic proteasome activities.
- Developed a ratio method to calculate percentage of proteasome inhibition.
- Validated the assay using whole blood and isolated leukocytes.
Main Results:
- The ratio method demonstrated high sensitivity, specificity, accuracy, and precision.
- Proteasomes were detected in both erythrocytes and leukocytes.
- Pharmacodynamic data for PS-341 using the whole-blood method correlated with leukocyte-based results.
Conclusions:
- The developed assay reliably measures proteasome inhibitor pharmacodynamics.
- This assay is currently utilized in Phase I clinical trials involving PS-341.
- The assay provides a valuable tool for advancing proteasome inhibitor research.
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In this pathway, the target proteins are first tagged with small proteins called ubiquitin. A series of enzymes carry out the ubiquitination of the target proteins - E1 (ubiquitin-activating enzyme), E2 (ubiquitin-conjugating enzyme), and E3...
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In this pathway, the target proteins are first tagged with small proteins called ubiquitin. This involves participation of a series of enzymes including— E1 (ubiquitin-activating enzyme), E2 (ubiquitin-conjugating enzyme), and E3 (ubiquitin...
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