Related Experiment Videos
Kinetic parameters for reversal of the multidrug pump as measured for drug accumulation and cell killing
1Biochemistry Department, Silberman Institute of Life Sciences, Hebrew University, Jerusalem, Israel.
Abstract:
We determined the kinetic parameters that describe the effect of 20 different modulators of the multidrug resistance pump on the reversal of cytotoxin accumulation in a resistant strain of P388 leukemia cells (P388/ADR), and on the reversal of cell killing for these cells. When measured by a direct comparison of the amplitude of the pertinent protocol (accumulation or cell killing), the Ki for reversal of accumulation was generally some four or five times larger than that for reduction of cytotoxicity. We showed that this was only an apparent discrepancy, since a full theoretical analysis of the two protocols allowed the intrinsic Ki to be obtained for the two procedures and these computed Ki values were then almost identical. We found that for six of the modulators studied (namely, cyclosporin A, quinidine, dipyridamole, propafenone, mefloquine, tamoxifen) the extent of pump reversal should be better than 90% at tolerated plasma levels culled from the literature.
Insights
This study quantifies how modulators affect multidrug resistance pumps in leukemia cells. Six key modulators show over 90% pump reversal at safe plasma levels, offering promising therapeutic potential.
Area of Science:
- Pharmacology
- Cancer Biology
- Biochemistry
Background:
- Multidrug resistance (MDR) in cancer, particularly P388 leukemia cells (P388/ADR), poses a significant therapeutic challenge.
- The multidrug resistance-associated protein (MRP) pump is a key factor in conferring cellular resistance to cytotoxic drugs.
- Modulators targeting the MDR pump are crucial for overcoming drug resistance in cancer treatment.
Purpose of the Study:
- To determine kinetic parameters for 20 MDR pump modulators.
- To assess the reversal of cytotoxin accumulation and cell killing in P388/ADR cells.
- To evaluate the efficacy of modulators at tolerated plasma levels.
Main Methods:
- Utilized kinetic analysis to determine inhibition constants (Ki) for MDR pump modulators.
- Compared the reversal of cytotoxin accumulation versus cell killing protocols.
- Performed theoretical analysis to reconcile discrepancies between accumulation and cytotoxicity data.
Main Results:
- Apparent discrepancies in Ki values for accumulation reversal versus cytotoxicity reduction were resolved through theoretical analysis.
- Intrinsic Ki values for both protocols were found to be nearly identical.
- Six modulators (cyclosporin A, quinidine, dipyridamole, propafenone, mefloquine, tamoxifen) demonstrated >90% pump reversal at literature-cited tolerated plasma levels.
Conclusions:
- The study provides a robust kinetic framework for evaluating MDR pump modulators.
- Effective reversal of multidrug resistance is achievable with specific modulators at clinically relevant concentrations.
- These findings support the potential of selected modulators in overcoming drug resistance in P388 leukemia and potentially other cancers.