title: Dihydroceramide accumulation and reactive oxygen species are distinct and nonessential events in 4-HPR-mediated leukemia cell death.
abstract: 4-(Hydroxyphenyl)retinamide (4-HPR) is a synthetic retinoid with a strong apoptotic effect towards different cancer cell lines in vitro, and it is currently tested in clinical trials. Increases of reactive oxygen species (ROS) and modulation of endogenous sphingolipid levels are well-described events observed upon 4-HPR treatment, but there is still a lack of understanding of their relationship and their contribution to cell death. LC-MS analysis of sphingolipids revealed that in human leukemia CCRF-CEM and Jurkat cells, 4-HPR induced dihydroceramide but not ceramide accumulation even at sublethal concentrations. Myriocin prevented the 4-HPR-induced dihydroceramide accumulation, but it did not prevent the loss of viability and increase of intracellular ROS production. On the other hand, ascorbic acid, Trolox, and vitamin E reversed 4-HPR effects on cell death but not dihydroceramide accumulation. NDGA, described as a lipoxygenase inhibitor, exerted a significantly higher antioxidant activity than vitamin E and abrogated 4-HPR-mediated ROS. It did not however rescue cellular viability. Taken together, this study demonstrates that early changes observed upon 4-HPR treatment, i.e., sphingolipid modulation and ROS production, are mechanistically independent events. Furthermore, the results indicate that 4-HPR-driven cell death may occur even in the absence of dihydroceramide or ROS accumulation. These observations should be taken into account for an improved design of drug combinations.
authors.affiliation: Department of Cell Biology and Histology, School of Medicine and Dentistry, University of the Basque Country, Sarriena s/n, 48940 Leioa (Bizkaia), Spain. aintzane.asumendi@ehu.es
authors.forename: Aintzane
authors.initials: A
authors.lastname: Apraiz
authors.forename: Jolanta
authors.initials: J
authors.lastname: Idkowiak-Baldys
authors.forename: Naiara
authors.initials: N
authors.lastname: Nieto-Rementería
authors.forename: María Dolores
authors.initials: MD
authors.lastname: Boyano
authors.forename: Yusuf A
authors.initials: YA
authors.lastname: Hannun
authors.forename: Aintzane
authors.initials: A
authors.lastname: Asumendi
mesh_terms: D000970:Antineoplastic Agents / Q000494:pharmacology*; D000975:Antioxidants / Q000494:pharmacology; D017209:Apoptosis / Q000187:drug effects*; D001205:Ascorbic Acid / Q000494:pharmacology; D045744:Cell Line, Tumor; D002470:Cell Survival / Q000187:drug effects; D002518:Ceramides / Q000378:metabolism*; D017313:Fenretinide / Q000494:pharmacology*; D044950:Flavanones / Q000494:pharmacology; D006801:Humans; D007938:Leukemia; D015227:Lipid Peroxidation; D016859:Lipoxygenase Inhibitors / Q000494:pharmacology; D009637:Masoprocol / Q000494:pharmacology; D008928:Mitochondria / Q000378:metabolism; D018384:Oxidative Stress; D010088:Oxidoreductases / Q000378:metabolism; D017382:Reactive Oxygen Species / Q000378:metabolism*; D013107:Sphingolipids / Q000096:biosynthesis; D014810:Vitamin E / Q000494:pharmacology
chemical_list: D000970:Antineoplastic Agents; D000975:Antioxidants; D002518:Ceramides; D044950:Flavanones; D016859:Lipoxygenase Inhibitors; D017382:Reactive Oxygen Species; D013107:Sphingolipids; C109343:dihydroceramide; D014810:Vitamin E; D017313:Fenretinide; C006680:baicalein; D009637:Masoprocol; D010088:Oxidoreductases; C108138:dihydroceramide desaturase; D001205:Ascorbic Acid