Educational leadership during a decade of medical curricular innovation and renewal.

BACKGROUND: The past decade has witnessed successful expansion, distribution and curricular renewal at the University of British Columbia (UBC) medical school. The expansion and distribution of the medical program doubled enrollment and established the first North American medical school training students across multiple geographical locations. The more recent competency-based curriculum renewal demonstrates sustained innovation within UBC medicine. AIMS: This paper describes that a significant contributor to these successes has been a team of teaching faculty whose exclusive roles have been providing curricular support. Over the past decade, this group has evolved into a vital component of the day-to-day operations and performance of the distributed medical curriculum; they now provide continuity in leadership and innovation across multiple educational facets of the program. METHOD/RESULTS: This paper reports on the evolution and significance of these faculty members. The descriptions establish the success of an investment in teaching faculty and underscore the importance of engaging faculty whose primary commitments are to teaching, educational pedagogy, and student support. CONCLUSIONS: This efficacious model of supporting and advancing a complex distributed medical program over more than a decade of pivotal change will be of interest to faculties and programs that are contemplating or navigating similar pursuits.

High ceramide content liposomes with in vivo antitumor activity.

BACKGROUND: The pro-apoptotic activity of ceramide lipids has made this an exciting new target for therapeutic manipulation. While approaches using exogenous application of short-chain ceramides and modulation of endogenous ceramide levels via manipulation of metabolic pathways have been explored, controlled delivery of natural ceramide has not been previously reported. In this paper we describe the formulation of novel liposomes containing high levels of natural ceramide in the lipid bilayer for the purpose of controlled ceramide delivery. MATERIALS AND METHODS: Liposomes were characterized by cryo-transmission electron microscopy, quasi-elastic light scattering and trapped volume analysis. Pharmacokinetic analysis was performed following i.v. bolus dosing, and antitumor activity was evaluated following i.v. bolus and i.p. dosing in the J774 ascites tumor model. RESULTS: Stable ceramide-containing liposomes exhibited pharmacokinetic properties suitable for in vivo applications and resulted in an increase in lifespan of greater than 20% compared to control liposomes following i.v. bolus and i.p. administration. CONCLUSION: This work demonstrates proof-of-concept that delivery of exogenous natural ceramide lipid has antitumor activity in vivo, and highlights the potential utility of ceramide-based liposomes as a novel strategy for cancer chemotherapy based on controlled ceramide delivery.

Intracellular delivery of ceramide lipids via liposomes enhances apoptosis in vitro.

Ceramide lipids have emerged as important intracellular signalling molecules that mediate diverse cellular effects, of which programmed cell death, or apoptosis, has attracted significant interest. Although the exact mechanism(s) by which ceramides trigger apoptosis is not fully understood, there is considerable evidence that they are key mediators of this response. Exogenously applied, cell-permeable ceramides have been shown to induce apoptosis when incubated with cells in culture. We examined here the cytotoxicity of ceramides with varying acyl chain lengths in order to determine whether acyl chain length affects pro-apoptotic activity within the concentration range of 0-100 microM. We found that for C(6)-, C(8)-, C(10)-, C(14)- and C(16)-ceramide, the chain length was inversely proportional to cytotoxic activity, with C(6)-ceramide being most active (IC(50) values in the 3-14 microM range) and C(16)-ceramide being least active (IC(50) values in excess of 100 microM) in the MDA435/LCC6 human breast cancer and J774 mouse macrophage cell lines investigated. Using these two ceramide forms we were able to correlate the observed cytotoxicity with cellular uptake, and we observed that a lack of intracellular delivery may be responsible for the weak activity of C(16)-ceramide. We therefore investigated the possibility of incorporating ceramide lipids into liposome bilayers to enhance this delivery. We demonstrate that stable, ceramide-containing liposomes can be formulated, and that they are cytotoxic when taken up by cells in vitro. These results provide an increased understanding of the differences in cytotoxic activity of exogenous short- and long-chain ceramide lipids, and their incorporation into biologically active liposomal formulations opens new avenues for apoptosis induction.

P-glycoprotein modulates ceramide-mediated sensitivity of human breast cancer cells to tubulin-binding anticancer drugs.

Alterations in metabolism of ceramide (Cer) to the noncytotoxic metabolite glucosylceramide have been implicated in the multidrug resistance (MDR) phenomenon. This observation has been made with tumor cells that also overexpress P-glycoprotein (Pgp), raising the possibility that Pgp plays a role in regulating Cer metabolism. We investigated the effect of the glucosylceramide synthase inhibitor 1-phenyl-2-decanoylamino-3-morpholino-1-propanol (PDMP) on the chemosensitivity of two wild-type and multidrug-resistant human breast tumor cell lines. Subtoxic concentrations of PDMP sensitized drug-selected MCF7/AdrR and Pgp-overexpressing MDA435/LCC6MDR1 (MDR1 gene-transfected) cell lines to Taxol and vincristine but did not alter the chemosensitivity of the wild-type cells. Evaluation of Taxol uptake indicated that the effect of PDMP was not due to membrane permeability alterations because anticancer drug accumulation was unaffected by PDMP. Whereas both multidrug-resistant cell lines overexpress Pgp, only the MCF7/AdrR cell line overexpresses the glucosylceramide synthase enzyme. This difference enabled us to distinguish between sensitization effects associated with Cer metabolism versus Pgp-mediated transport. Interestingly, when Pgp function was blocked, the PDMP effect was reduced 3-fold in MCF7/AdrR cells and was no longer observed in the MDA435/LCC6MDR1 cells. These observations imply that Cer metabolism and apoptosis effects are regulated not only by enzymes that convert Cer to nontoxic metabolites but also by Pgp-mediated transport. Given the intracellular distribution patterns of Pgp, we propose that this effect is related to glucosylceramide translocation across the Golgi bilayer. We have applied this model to the situation of Cer metabolism-based chemosensitization and demonstrate that MDR modulation strategies aimed primarily at altering drug transport mechanisms can influence other MDR mechanisms such as glycosphingolipid metabolism. This work highlights the relationship between drug transport and Cer metabolism in the context of chemosensitization and cautions against making oversimplified assumptions that these mechanisms act independently.

Development of an in vitro drug release assay that accurately predicts in vivo drug retention for liposome-based delivery systems.

The therapeutic activity of numerous drugs can be dramatically improved by liposomal encapsulation. However, this requires that liposomes retain their encapsulated drugs following systemic administration. Often, in vitro drug release assays do not accurately predict the liposomal drug retention properties observed in vivo. We postulate that this discrepancy is due to the large membrane pool present in blood cells and tissues, into which drugs can distribute after in vivo administration. Herein we describe an in vitro drug release assay that more accurately predicts in vivo drug release from liposomes following systemic administration. Drug-encapsulated large unilamellar vesicles (LUVs) approximately 100 nm in diameter were incubated with a 100-fold excess of multilamellar vesicles (MLVs) containing 300 mM sucrose, which served as 'acceptors' for drug release and transfer from 'donor' LUVs. Following incubation at 37 degrees C, the donor and acceptor populations were separated with greater than 90% efficiency by centrifugation at 1600xg for 10 min. The amount of drug in the MLV pellet reflects the degree of drug leakage from the donor liposomes. Drug release profiles using this in vitro assay were compared to those obtained using dialysis-based assays and in vivo results following systemic administration to mice. Our results indicate that this release assay is a better predictor of in vivo drug transfer than dialysis-based systems. We also demonstrate its utility in measuring exchange of lipophilic components.