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Evaluating the Effectiveness of Cancer Drug Sensitization In Vitro and In Vivo
Published on: February 6, 2015
Differential chemosensitizing effect of two glucosylceramide synthase inhibitors in hepatoma cells
1Department of Biology, University of Rome Tor Vergata, Via della Ricerca Scientifica, 00133 Rome, Italy.
Abstract:
It has been proposed that ceramide mediates anthracyclin-induced apoptosis and that drug resistance may arise due to upregulated removal of this active lipid through glucosylation. We report that HepG2 hepatoma cells displayed only a modest apoptotic response to doxorubicin treatment, accompanied by a substantial elevation of ceramide levels only at toxic drug concentrations. D,L-threo-1-phenyl-2-decanoylamino-3-morpholino-1-propanol (PDMP) and D,L-threo-1-phenyl-2-hexadecanoylamino-3-pyrrolidino-1-propanol (PPPP), used at concentrations causing a 90% inhibition of ceramide glucosylation, enhanced doxorubicin-elicited ceramide elevation, but only PDMP potentiated apoptosis. Exogenously administered ceramide had only a marginal apoptotic effect on HepG2 cells; moreover, even in this case, apoptosis was propagated by PDMP but not by PPPP. PDMP moderately inhibited P-glycoprotein activity only at the highest concentration tested, but its chemosensitizing effect was still outstanding at lower concentrations, at which P-gp inhibition was no longer observed. These results demonstrate that the chemosensitizing effect of PDMP is, at least partly, independent from its activity as a glucosylceramide synthase inhibitor. Moreover, P-glycoprotein inhibition is not central to the phenomenon.
Insights
Ceramide elevation alone does not induce apoptosis in HepG2 cells treated with doxorubicin. The drug resistance modulator PDMP potentiates apoptosis independently of its glucosylceramide synthase inhibition and P-glycoprotein activity.
Area of Science:
- Molecular Biology
- Biochemistry
- Cancer Research
Background:
- Ceramide is implicated in anthracycline-induced apoptosis.
- Drug resistance may involve increased ceramide removal via glucosylation.
- HepG2 cells show limited apoptosis and ceramide elevation with doxorubicin.
Purpose of the Study:
- To investigate the role of ceramide in doxorubicin-induced apoptosis in HepG2 cells.
- To evaluate the effects of glucosylceramide synthase inhibitors (PDMP and PPPP) on doxorubicin response.
- To determine the contribution of P-glycoprotein inhibition to chemosensitization.
Main Methods:
- Treatment of HepG2 cells with doxorubicin, PDMP, and PPPP.
- Measurement of ceramide levels and apoptosis induction.
- Assessment of glucosylceramide synthase inhibition and P-glycoprotein activity.
Main Results:
- Doxorubicin induced modest apoptosis and significant ceramide elevation only at toxic concentrations.
- PDMP and PPPP enhanced doxorubicin-induced ceramide elevation, but only PDMP potentiated apoptosis.
- PDMP's chemosensitizing effect was observed at concentrations independent of P-glycoprotein inhibition.
Conclusions:
- PDMP's ability to potentiate doxorubicin-induced apoptosis is partly independent of its glucosylceramide synthase inhibitory activity.
- P-glycoprotein inhibition is not the primary mechanism behind PDMP's chemosensitizing effect in this context.
- Ceramide accumulation alone has a marginal apoptotic effect in HepG2 cells.