title: N-(4-Hydroxyphenyl)retinamide increases dihydroceramide and synergizes with dimethylsphingosine to enhance cancer cell killing.
abstract: Fenretinide [N-(4-hydroxyphenyl)retinamide (4-HPR)] is cytotoxic in many cancer cell types. Studies have shown that elevation of ceramide species plays a role in 4-HPR cytotoxicity. To determine 4-HPR activity in a multidrug-resistant cancer cell line as well as to study ceramide metabolism, MCF-7/AdrR cells (redesignated NCI/ADR-RES) were treated with 4-HPR and sphingolipids were analyzed. TLC analysis of cells radiolabeled with [3H]palmitic acid showed that 4-HPR elicited a dose-responsive increase in radioactivity migrating in the ceramide region of the chromatogram and a decrease in cell viability. Results from liquid chromatography/electrospray tandem mass spectrometry revealed large elevations in dihydroceramides (N-acylsphinganines), but not desaturated ceramides, and large increases in complex dihydrosphingolipids (dihydrosphingomyelins, monohexosyldihydroceramides), sphinganine, and sphinganine 1-phosphate. To test the hypothesis that elevation of sphinganine participates in the cytotoxicity of 4-HPR, cells were treated with the sphingosine kinase inhibitor d-erythro-N,N-dimethylsphingosine (DMS), with and without 4-HPR. After 24 h, the 4-HPR/DMS combination caused a 9-fold increase in sphinganine that was sustained through +48 hours, decreased sphinganine 1-phosphate, and increased cytotoxicity. Increased dihydrosphingolipids and sphinganine were also found in HL-60 leukemia cells and HT-29 colon cancer cells treated with 4-HPR. The 4-HPR/DMS combination elicited increased apoptosis in all three cell lines. We propose that a mechanism of 4-HPR-induced cytotoxicity involves increases in dihydrosphingolipids, and that the synergy between 4-HPR and DMS is associated with large increases in cellular sphinganine. These studies suggest that enhanced clinical efficacy of 4-HPR may be realized through regimens containing agents that modulate sphingoid base metabolism.
authors.affiliation: Childrens Hospital Los Angeles, Keck School of Medicine, University of Southern California, Los Angeles, California, USA.
authors.forename: Hongtao
authors.initials: H
authors.lastname: Wang
authors.forename: Barry J
authors.initials: BJ
authors.lastname: Maurer
authors.forename: Yong-Yu
authors.initials: YY
authors.lastname: Liu
authors.forename: Elaine
authors.initials: E
authors.lastname: Wang
authors.forename: Jeremy C
authors.initials: JC
authors.lastname: Allegood
authors.forename: Samuel
authors.initials: S
authors.lastname: Kelly
authors.forename: Holly
authors.initials: H
authors.lastname: Symolon
authors.forename: Ying
authors.initials: Y
authors.lastname: Liu
authors.forename: Alfred H
authors.initials: AH
authors.lastname: Merrill
authors.forename: Valérie
authors.initials: V
authors.lastname: Gouazé-Andersson
authors.forename: Jing Yuan
authors.initials: JY
authors.lastname: Yu
authors.forename: Armando E
authors.initials: AE
authors.lastname: Giuliano
authors.forename: Myles C
authors.initials: MC
authors.lastname: Cabot
mesh_terms: D016923:Cell Death / Q000187:drug effects; D045744:Cell Line, Tumor; D002518:Ceramides / Q000378:metabolism*; D004305:Dose-Response Relationship, Drug; D004357:Drug Synergism; D017313:Fenretinide / Q000494:pharmacology*; D006801:Humans; D009369:Neoplasms / Q000473:pathology*; D013107:Sphingolipids / Q000032:analysis; D013110:Sphingosine / Q000031:analogs & derivatives* / Q000494:pharmacology; D013997:Time Factors
chemical_list: D002518:Ceramides; D013107:Sphingolipids; C109343:dihydroceramide; D017313:Fenretinide; C061800:N,N-dimethylsphingosine; D013110:Sphingosine