title: Heterogeneous role of caspase-8 in fenretinide-induced apoptosis in epithelial ovarian carcinoma cell lines.
abstract: The mechanism of action of fenretinide, a synthetic retinoid currently undergoing testing as a chemopreventive and chemotherapeutic agent, is incompletely understood. In the present study, fenretinide caused apoptotic changes, including DNA fragmentation and cleavage of caspase substrates, in six low-passage ovarian cancer cell lines. However, the caspase activation pathway used by this agent varied. Transient transfection of cDNA-encoding cytokine response modifier A (CrmA), a caspase-8 inhibitor, diminished fenretinide-induced death in OV177 cells. Likewise, IETD(OMe)-fluoromethylketone (fmk) inhibited fenretinide-induced apoptosis by >80% in OV177 or OV266 cells and by approximately 50% in OV17, OV167, or OV207 cells. Further analysis demonstrated that inhibition of Fas ligand, tumor necrosis factor-alpha, or TRAIL signaling with blocking reagents did not affect fenretinide-induced apoptosis, raising the possibility that fenretinide activates caspase-8 in a death receptor-independent manner. In contrast, CrmA transfection or IETD(OMe)-fmk treatment did not inhibit fenretinide-induced apoptosis in OV202 cells. These divergent behaviors did not correlate with increased levels of procaspase-10, which is relatively resistant to CrmA and IETD(OMe)-fmk, nor with the expression of procaspase-8 and -9, apoptotic protease activating factor-1, or cellular FLICE-like inhibitory protein. Similarly, fenretinide treatment increased ceramide levels equally in cells that do (OV177) and do not (OV202) rely on caspase-8 to initiate apoptosis. These results indicate that synthetic retinoids can use caspase-8 as an initiating caspase, but they also indicate unexpected heterogeneity in caspase activation pathways among closely related cell lines.
authors.affiliation: Endocrine Research Unit, Joseph 5-194, Mayo Clinic and Foundation, 200 First Street S.W., Rochester, MN 55905, USA. kalli.kimberly@mayo.edu
authors.forename: Kimberly R
authors.initials: KR
authors.lastname: Kalli
authors.forename: Kathryn E
authors.initials: KE
authors.lastname: Devine
authors.forename: Myles C
authors.initials: MC
authors.lastname: Cabot
authors.forename: Christina R
authors.initials: CR
authors.lastname: Arnt
authors.forename: Michael P
authors.initials: MP
authors.lastname: Heldebrant
authors.forename: Phyllis A
authors.initials: PA
authors.lastname: Svingen
authors.forename: Charles
authors.initials: C
authors.lastname: Erlichman
authors.forename: Lynn C
authors.initials: LC
authors.lastname: Hartmann
authors.forename: Cheryl A
authors.initials: CA
authors.lastname: Conover
authors.forename: Scott H
authors.initials: SH
authors.lastname: Kaufmann
mesh_terms: D017209:Apoptosis / Q000187:drug effects* / Q000502:physiology; D053181:Caspase 8; D053453:Caspase 9; D020169:Caspases / Q000378:metabolism*; D045744:Cell Line, Tumor; D004305:Dose-Response Relationship, Drug; D004789:Enzyme Activation / Q000187:drug effects / Q000502:physiology; D005260:Female; D017313:Fenretinide / Q000494:pharmacology*; D006801:Humans; D009375:Neoplasms, Glandular and Epithelial / Q000201:enzymology*; D010051:Ovarian Neoplasms / Q000201:enzymology*
chemical_list: D017313:Fenretinide; C505530:CASP8 protein, human; C506433:CASP9 protein, human; D053181:Caspase 8; D053453:Caspase 9; D020169:Caspases