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By-passing of P-glycoprotein using immunoliposomes
Jörg Huwyler1, Andrin Cerletti, Gert Fricker
1Department of Research, University Hospital/Kantonsspital, Basel, Switzerland.
Abstract:
The over-expression of MDR1 P-glycoprotein has been associated with the development of multidrug-resistance in cancer cells. Methods used to overcome multidrug-resistance often involve the co-administration of inhibitors of P-glycoprotein. Here, we test the hypothesis that an immunoliposome-based drug delivery system may be used as an alternative approach to overcome multidrug-resistance since immunoliposomes penetrate target cells by receptor-mediated endocytosis which allows to by-pass membrane-associated P-glycoprotein. Targeting of immunoliposomes was achieved by the use of an anti-transferrin receptor monoclonal antibody (OX26 mAb). Incorporation of radiolabelled digoxin within OX26-immunoliposomes enhanced cellular uptake of digoxin by a factor of 25 in immortalised RBE4 rat brain capillary endothelial cells. Uptake of liposomal digoxin was insensitive to ritonavir, a P-glycoprotein inhibitor, and was reduced in presence of increasing free concentrations of OX26 mAb or nocodazole, a reversible inhibitor of endocytosis. In contrast, uptake of free digoxin was enhanced by a factor of 1.8 in presence of ritonavir and was insensitive to OX26 mAb or nocodazole. Cellular uptake and intracellular accumulation of liposomal digoxin (55% internalisation within 30 min) was demonstrated by acid wash of the cells and was confirmed by confocal microscopy studies. Endosomal release to the cytosol of propidium iodide loaded immunoliposomes was shown. These in vitro studies suggest that immunoliposome-based drug delivery systems can be used to by-pass P-glycoprotein and thus deliver drugs to the cytosol of a target cell.
Insights
Immunoliposomes bypass multidrug resistance by using receptor-mediated endocytosis to deliver drugs. This novel drug delivery system overcomes P-glycoprotein efflux, enhancing drug uptake in target cells.
Area of Science:
- Nanotechnology
- Pharmacology
- Cell Biology
Background:
- Multidrug resistance (MDR) in cancer is often mediated by P-glycoprotein (P-gp) efflux pumps.
- Conventional strategies to overcome MDR involve co-administering P-gp inhibitors, which can have systemic side effects.
Purpose of the Study:
- To investigate immunoliposomes as an alternative strategy to overcome P-gp-mediated MDR.
- To assess if immunoliposomes can bypass P-gp efflux via receptor-mediated endocytosis.
Main Methods:
- Targeted immunoliposomes were constructed using the OX26 monoclonal antibody against the transferrin receptor.
- Radiolabeled digoxin was encapsulated within OX26-immunoliposomes.
- Cellular uptake studies were performed on RBE4 rat brain capillary endothelial cells.
- Experiments included P-gp inhibition (ritonavir) and endocytosis inhibition (nocodazole).
Main Results:
- OX26-immunoliposomes enhanced digoxin cellular uptake by 25-fold compared to free digoxin.
- Liposomal digoxin uptake was unaffected by P-gp inhibition (ritonavir) but sensitive to endocytosis inhibition.
- Free digoxin uptake was enhanced by ritonavir, confirming P-gp activity.
- Confocal microscopy and acid wash assays confirmed efficient cellular internalization and endosomal escape.
Conclusions:
- Immunoliposome-based drug delivery systems can effectively bypass P-glycoprotein efflux pumps.
- Receptor-mediated endocytosis facilitates the intracellular delivery of drugs encapsulated in immunoliposomes.
- This approach offers a promising strategy for overcoming MDR in cancer therapy.