title: Enhanced de novo ceramide generation through activation of serine palmitoyltransferase by the P-glycoprotein antagonist SDZ PSC 833 in breast cancer cells.
abstract: SDZ PSC 833 (PSC 833), a P-glycoprotein-targeted multidrug resistance modulator, sensitizes cancer cells to chemotherapy. Here we show that PSC 833 also potentiates the formation of ceramide. Because ceramide is a second messenger in chemotherapy-induced apoptosis, knowledge of the lipid pathways influenced by PSC 833 is of relevance. In intact MDA-MB 468 breast cancer cells, ceramide generation increased 3-fold 1 h after PSC 833 addition (5.0 microM). Cyclosporine A, a structural analogue, failed to impact ceramide metabolism. Sphinganine, the upstream precursor of ceramide, also increased in response to PSC 833, and this could be blocked by adding L-cycloserine, a serine palmitoyltransferase (SPT) inhibitor. Exposure of cultured cells to PSC 833 (30 min to 4 h; 1-10 microM), followed by isolation of microsomes for in vitro assay, increased SPT activity 60%, whereas palmitoyl CoA synthetase and ceramide synthase activities were not altered. SPT activity was also heightened by pretreating cells with either paclitaxel, N-(4-hydroxyphenyl)retinamide, etoposide, or daunorubicin; however, activation was half that attained by PSC 833. PSC 833 stimulated ceramide generation in other breast cancer cell lines as well, including BT-20, MDA-MB 231, Hs 578T, T-47D, and MCF-7. In summary, several types of anticancer agents and the P-glycoprotein modulator PSC 833 share the ability to increase cellular ceramide levels by activation of SPT, the rate-limiting enzyme in the de novo pathway of ceramide synthesis. These data provide novel insight in the area of lipid-mediated cell death.
authors.affiliation: John Wayne Cancer Institute, Saint John's Health Center, Santa Monica, California 90404, USA.
authors.forename: Hongtao
authors.initials: H
authors.lastname: Wang
authors.forename: Armando E
authors.initials: AE
authors.lastname: Giuliano
authors.forename: Myles C
authors.initials: MC
authors.lastname: Cabot
mesh_terms: D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1 / Q000378:metabolism; D000217:Acyltransferases / Q000378:metabolism*; D000970:Antineoplastic Agents / Q000494:pharmacology; D002478:Cells, Cultured; D002518:Ceramides / Q000378:metabolism*; D003066:Coenzyme A Ligases / Q000378:metabolism; D004305:Dose-Response Relationship, Drug; D004789:Enzyme Activation; D006801:Humans; D050356:Lipid Metabolism; D008954:Models, Biological; D008956:Models, Chemical; D010088:Oxidoreductases / Q000378:metabolism; D012097:Repressor Proteins; D029701:Saccharomyces cerevisiae Proteins; D051102:Serine C-Palmitoyltransferase; D013997:Time Factors; D014407:Tumor Cells, Cultured; D000098859:Long-Chain-Fatty-Acid-CoA Ligase
chemical_list: D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1; D000970:Antineoplastic Agents; D002518:Ceramides; D012097:Repressor Proteins; D029701:Saccharomyces cerevisiae Proteins; D010088:Oxidoreductases; C108138:dihydroceramide desaturase; D000217:Acyltransferases; C495089:SPTLC2 protein, human; D051102:Serine C-Palmitoyltransferase; D003066:Coenzyme A Ligases; C090799:FAA2 protein, S cerevisiae; D000098859:Long-Chain-Fatty-Acid-CoA Ligase