Related Experiment Videos
Transfection with protein kinase C alpha confers increased multidrug resistance to MCF-7 cells expressing
1Laboratory of Biological Chemistry, National Cancer Institute, National Institutes of Health, Bethesda, MD 20892.
Abstract:
Cross-resistance to anticancer drugs, termed multidrug resistance (mdr), has been functionally associated with the expression of a plasma membrane energy-dependent efflux pump, termed P-glycoprotein, the product of the mdr1 gene. When MCF-7 breast carcinoma cells were transfected with the human mdr1 gene (BC-19 cells), they expressed levels of P-glycoprotein equivalent to those of cells selected for resistance to doxorubicin (MCF-7/ADR) but exhibited 10- to 50-fold less resistance to doxorubicin and vinblastine. We have now demonstrated that when BC-19 cells were stably transfected with protein kinase C alpha (PKC alpha), resistance to doxorubicin and vinblastine was increased; wild-type MCF-7 cells transfected with PKC alpha did not exhibit any change in drug resistance. Increased resistance in PKC alpha-transfected BC-19 cells was associated with enhanced PKC activity and phosphorylation of P-glycoprotein and decreased drug accumulation. The PKC activator, phorbol dibutyrate, further increased resistance to doxorubicin and stimulated P-glycoprotein phosphorylation. These results demonstrate that transfection of P-glycoprotein-expressing cells with PKC resulted in increased mdr and that PKC may have served as an important modulator of this process.
Insights
Protein kinase C alpha (PKC alpha) enhances multidrug resistance (mdr) in cancer cells expressing P-glycoprotein. This suggests PKC alpha plays a key role in modulating drug efflux and increasing resistance to chemotherapy agents.
Area of Science:
- Molecular Biology
- Cell Biology
- Pharmacology
Background:
- Multidrug resistance (mdr) in cancer is linked to P-glycoprotein, an efflux pump encoded by the mdr1 gene.
- MCF-7 cells transfected with the mdr1 gene (BC-19) express P-glycoprotein but show less drug resistance than expected.
Purpose of the Study:
- To investigate the role of protein kinase C alpha (PKC alpha) in modulating P-glycoprotein-mediated multidrug resistance.
- To determine if PKC alpha influences drug accumulation and resistance in cancer cells.
Main Methods:
- Stable transfection of BC-19 cells (mdr1-expressing MCF-7) with PKC alpha.
- Assessing drug resistance to doxorubicin and vinblastine.
- Measuring PKC activity, P-glycoprotein phosphorylation, and intracellular drug accumulation.
Main Results:
- Transfection with PKC alpha significantly increased doxorubicin and vinblastine resistance in BC-19 cells.
- Increased resistance correlated with enhanced PKC activity, P-glycoprotein phosphorylation, and reduced drug accumulation.
- PKC activation by phorbol dibutyrate further enhanced resistance and P-glycoprotein phosphorylation.
Conclusions:
- PKC alpha acts as a modulator of multidrug resistance in P-glycoprotein-expressing cancer cells.
- PKC alpha enhances drug resistance by increasing P-glycoprotein activity and reducing intracellular drug levels.