title: Resistance to TRAIL is associated with defects in ceramide signaling that can be overcome by exogenous C6-ceramide without requiring down-regulation of cellular FLICE inhibitory protein.
abstract: Tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) is a member of the tumor necrosis factor superfamily that selectively induces apoptosis in malignant cells. However, not all cancer cells are susceptible to TRAIL and mechanisms of resistance and new strategies to enhance sensitivity are an area of intense investigation. Glucose withdrawal or paclitaxel increase intracellular ceramide, down-regulate cellular FLICE inhibitory protein (cFLIP), and sensitize cells to TRAIL. Therefore, we investigated whether TRAIL resistance is due to ceramide levels and/or defects in ceramide generation following ligand binding. Colon cancer cells isolated from the primary tumor (SW480) and a subsequent metastasis (SW620) of the same patient have different sensitivities to TRAIL. Mass spectrometry was used to compare ceramide content in untreated and TRAIL-treated cells. Overall levels of ceramide were comparable in the cell lines but TRAIL-sensitive SW480 cells contained a higher percentage of C(16)-, and C(18)-ceramide and lower C(24)-ceramides than TRAIL-resistant SW620 cells. Upon TRAIL treatment, ceramide (primarily C(16)-ceramide) increased in SW480 but not SW620 cells. The increase in ceramide occurred with slow kinetics, paralleling caspase-3/7 activation. Combination of C(6)-ceramide with TRAIL resulted in apoptosis of SW620 cells. However, exogenous C(6)-ceramide did not affect levels of cFLIP nor did pretreatment sensitize cells to TRAIL. Exposure to TRAIL prior to ceramide was required to induce apoptosis, suggesting that ceramide plays a role in enhancing or amplifying TRAIL-mediated signaling. Our results suggest that ceramide plays a role in promoting TRAIL-mediated apoptosis and that TRAIL-resistant cancers may benefit from combination therapy with ceramide or agents that enhance ceramide accumulation.
authors.affiliation: Department of Microbiology and Immunology, Medical University of South Carolina, Charleston, 29403, USA. johnsocv@musc.edu
authors.forename: Christina
authors.initials: C
authors.lastname: Voelkel-Johnson
authors.forename: Yusuf A
authors.initials: YA
authors.lastname: Hannun
authors.forename: Ahmed
authors.initials: A
authors.lastname: El-Zawahry
mesh_terms: D000972:Antineoplastic Agents, Phytogenic / Q000494:pharmacology; D017209:Apoptosis / Q000187:drug effects*; D051017:Apoptosis Regulatory Proteins / Q000494:pharmacology*; D053446:CASP8 and FADD-Like Apoptosis Regulating Protein; D020169:Caspases / Q000378:metabolism; D002518:Ceramides / Q000494:pharmacology*; D003110:Colonic Neoplasms / Q000188:drug therapy / Q000378:metabolism* / Q000556:secondary; D015536:Down-Regulation; D004338:Drug Combinations; D004789:Enzyme Activation / Q000187:drug effects; D005434:Flow Cytometry; D005947:Glucose / Q000378:metabolism; D006801:Humans; D047908:Intracellular Signaling Peptides and Proteins / Q000378:metabolism*; D007700:Kinetics; D008562:Membrane Glycoproteins / Q000494:pharmacology*; D017239:Paclitaxel / Q000494:pharmacology; D015398:Signal Transduction; D053221:TNF-Related Apoptosis-Inducing Ligand; D014407:Tumor Cells, Cultured; D014409:Tumor Necrosis Factor-alpha / Q000494:pharmacology*
chemical_list: D000972:Antineoplastic Agents, Phytogenic; D051017:Apoptosis Regulatory Proteins; D053446:CASP8 and FADD-Like Apoptosis Regulating Protein; C506386:CFLAR protein, human; D002518:Ceramides; D004338:Drug Combinations; D047908:Intracellular Signaling Peptides and Proteins; D008562:Membrane Glycoproteins; D053221:TNF-Related Apoptosis-Inducing Ligand; C505653:TNFSF10 protein, human; D014409:Tumor Necrosis Factor-alpha; C101954:N-caproylsphingosine; D020169:Caspases; D005947:Glucose; D017239:Paclitaxel