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Protein kinase C isoforms in multidrug resistant P388/ADR cells: a possible role in daunorubicin transport
1Division of Basic and Clinical Immunology, University of California, Irvine 92717.
Abstract:
To identify the role of protein kinase C (PKC) isoforms in multidrug resistance in tumor cells, we examined the PKC isoform pattern in the multidrug resistant P388/ADR cell line and studied the effect of down regulation of PKC isoforms on intracellular daunorubicin accumulation and P-glycoprotein expression. Using monoclonal antibodies to PKC alpha, beta and gamma and flow cytometry technique we showed that P388/ADR cells overexpressed PKC alpha and beta as compared to drug sensitive P388 cells. Prolonged treatment of P388/ADR cells with phorbol myristate acetate (PMA), a procedure that is known to down regulate PKC, resulted in the down regulation of total PKC activity and the PKC beta isoform (at the protein level) that was accompanied by the correction of daunorubicin accumulation in P388/ADR cells. The level of expression of P-glycoprotein in PMA treated cells was similar to that of untreated cells. These results suggest that PKC beta regulates the drug efflux function of P-glycoprotein.
Insights
Protein Kinase C (PKC) beta isoform is implicated in multidrug resistance in tumor cells. Down-regulating PKC beta corrected daunorubicin accumulation, suggesting it regulates P-glycoprotein drug efflux.
Area of Science:
- Biochemistry
- Molecular Biology
- Cancer Research
Background:
- Multidrug resistance (MDR) in tumor cells poses a significant challenge in cancer therapy.
- Protein Kinase C (PKC) isoforms are implicated in various cellular processes, including drug resistance.
Purpose of the Study:
- To investigate the role of specific PKC isoforms in multidrug resistance.
- To determine the effect of PKC isoform downregulation on drug accumulation and P-glycoprotein expression in resistant tumor cells.
Main Methods:
- Utilized monoclonal antibodies against PKC alpha, beta, and gamma isoforms.
- Employed flow cytometry to analyze PKC isoform expression in P388/ADR and P388 cells.
- Investigated the impact of phorbol myristate acetate (PMA) treatment on PKC activity and daunorubicin accumulation.
Main Results:
- P388/ADR cells exhibited overexpression of PKC alpha and beta isoforms compared to sensitive P388 cells.
- PMA treatment led to downregulation of total PKC activity and the PKC beta isoform.
- Downregulation of PKC beta corrected intracellular daunorubicin accumulation without altering P-glycoprotein expression levels.
Conclusions:
- PKC beta isoform plays a crucial role in regulating the drug efflux function mediated by P-glycoprotein.
- Targeting PKC beta may offer a strategy to overcome P-glycoprotein-mediated multidrug resistance in cancer.