Characterization of the Contribution of Ceramide to Chemotherapy Sensitization in Breast Cancer Cells

摘要

Our previous studies show that the drug resistance modulator, PSC 833, an analog of cyclosporin A, increases cellular ceramide levels, thus initiating caspase- apoptotic signaling. The mechanism of PSC 833 induced ceramide generation is, however, unknown. In order to use ceramide targeting as a therapeutic approach to chemotherapy sensitization in breast cancer, mechanism information is essential. To this end, during the past year, I have mastered techniques of lipid analysis, developed and standardized enzyme assays for ceramide synthase, serine palmitoyltransferase, and palmitoyl coenzyme A synthetase, and utilized human breast cancer cell lines in model systems. Our studies demonstrate that PSC 833 induces ceramide generation via the de novo biochemical pathway, as opposed to degradation of sphingomyelin. We have shown, for the first time, that serine palmitoyltransferase, and not ceramide synthase or palmitoyl coenzyme A synthetase is activated by PSC 833 in breast cancer cells. Furthermore, we also demonstrate a close structure-activity relationship for activation of serine palmitoyltransferase, based on studies with analogs of cyclosporin. This is a significant finding which sets the stage for continued drug studies aimed at targeting ceramide metabolism to enhance chemotherapy response in the treatment of breast cancer.