Increasing intracellular ceramide: an approach that enhances the cytotoxic response in prostate cancer cells.
OBJECTIVE
To investigate the feasibility of targeting ceramide metabolism to enhance chemotherapy cytotoxicity in prostate cancer. Discovering new targets for cancer treatment is an important endeavor, especially in prostate malignancies, which often revert to hormone- and chemotherapy-refractory disease states.


METHODS
Ceramide metabolism was measured in human prostate cancer cell lines using [(3)H]palmitic acid as the tracer. Cellular lipids were analyzed by thin-layer chromatography and liquid scintillation counting. Cell viability in response to drug exposure was measured spectrophotometrically using commercial cell proliferation reagents.


RESULTS
LNCaP cells were five times more sensitive to N-(4-hydroxyphenyl)retinamide (4-HPR), a synthetic retinoid, compared with PC-3 cells. Ceramide levels increased only twofold in PC-3 cells versus 10-fold in LNCaP cells in response to 10 microM 4-HPR. PC-3 resistance to 4-HPR could be reversed by the addition of tamoxifen or other agents that block the metabolism of ceramide to glucosylceramide, and with tamoxifen this was marked by a ninefold increase in cellular ceramide levels. The influence of 4-HPR on ceramide metabolism was shown to be through activation of serine palmitoyltransferase, the rate-limiting enzyme in the ceramide synthesis pathway. Blocking the ceramide generated by 4-HPR reduced the extent of apoptosis.


CONCLUSIONS
Increasing intracellular concentrations of ceramide may be an avenue to enhance the cytotoxic response to chemotherapy in human prostate cancer.
Division of Experimental Therapeutics, John Wayne Cancer Institute, Santa Monica, California 90404, USA.
Hongtao
H
Wang
Anthony G
AG
Charles
Aaron J
AJ
Frankel
Myles C
MC
Cabot
D000217:Acyltransferases / Q000378:metabolism; D000970:Antineoplastic Agents / Q000494:pharmacology* / Q000633:toxicity; D000971:Antineoplastic Combined Chemotherapy Protocols / Q000494:pharmacology / Q000633:toxicity; D017209:Apoptosis / Q000187:drug effects; D002470:Cell Survival / Q000187:drug effects; D002518:Ceramides / Q000096:biosynthesis / Q000378:metabolism*; D004305:Dose-Response Relationship, Drug; D004354:Drug Screening Assays, Antitumor; D017313:Fenretinide / Q000494:pharmacology / Q000633:toxicity; D005963:Glucosylceramides / Q000378:metabolism; D006801:Humans; D007424:Intracellular Fluid / Q000201:enzymology / Q000378:metabolism*; D008297:Male; D010088:Oxidoreductases / Q000378:metabolism; D011471:Prostatic Neoplasms / Q000188:drug therapy / Q000201:enzymology / Q000378:metabolism* / Q000473:pathology*; D051102:Serine C-Palmitoyltransferase; D013629:Tamoxifen / Q000494:pharmacology / Q000633:toxicity; D014407:Tumor Cells, Cultured
D000970:Antineoplastic Agents; D002518:Ceramides; D005963:Glucosylceramides; D013629:Tamoxifen; D017313:Fenretinide; D010088:Oxidoreductases; C108138:dihydroceramide desaturase; D000217:Acyltransferases; D051102:Serine C-Palmitoyltransferase