title: Histone deacetylase inhibitor-induced sensitization to TNFalpha/TRAIL-mediated apoptosis in cervical carcinoma cells is dependent on HPV oncogene expression.
abstract: Histone-deacetylase (HDAC) inhibitors (HDACi) can block proliferation and induce intrinsic apoptosis in human papillomavirus (HPV)-positive cervical carcinoma cells, independently of copy number and integration locus of the viral DNA. Using HPV18-positive HeLa cells as model systems, we provide evidence that HDAC inhibition leads to transcriptional suppression of c-FLIP, which negatively regulates extrinsic apoptosis by preventing the recruitment of caspase-8 to the death-inducing signaling complex. Consequently, HDACi pretreatment renders cervical cancer cells sensitive to TNFalpha and TRAIL-induced apoptosis. Already 5-hr incubation with TNFalpha or TRAIL was sufficient to eradicate more than 40% of pretreated cells, which are normally completely refractory against respective death-ligands alone even under long-term incubation. Ectopic expression of either short or long splicing variant of c-FLIP, c-FLIP(s) and c-FLIP(L), abrogates sensitization. Notably, combined HDACi/death ligand treatment did not result in eradication of HPV-negative cells, despite the fact that both c-FLIP isoforms were also downregulated. However, knocking down HPV18 E6/E7 transcription by siRNA prevents HDACi/death-ligand mediated apoptosis, indicating that continued viral oncogene expression favors sensitization. Here, the viral oncoprotein E7 seems to play a functional role, since only HPV16 E7-immortalized human keratinocytes underwent significant apoptosis on HDACi/TNFalpha treatment, whereas keratinocytes expressing only HPV16 E6 or primary keratinocytes were refractory under the same experimental conditions. Taken together, HDACi can be considered as an alternative therapeutic option in the treatment of premalignant and malignant lesions.
authors.affiliation: Infektionen und Krebs, Deutsches Krebsforschungszentrum, Abteilung Virale Transformationsmechanismen, Heidelberg, Germany.
authors.forename: Katalin
authors.initials: K
authors.lastname: Darvas
authors.forename: Simone
authors.initials: S
authors.lastname: Rosenberger
authors.forename: Dirk
authors.initials: D
authors.lastname: Brenner
authors.forename: Cornelius
authors.initials: C
authors.lastname: Fritsch
authors.forename: Nadine
authors.initials: N
authors.lastname: Gmelin
authors.forename: Peter H
authors.initials: PH
authors.lastname: Krammer
authors.forename: Frank
authors.initials: F
authors.lastname: Rösl
mesh_terms: D052685:Alphapapillomavirus / Q000235:genetics*; D017209:Apoptosis / Q000187:drug effects*; D015153:Blotting, Western; D005260:Female; D005434:Flow Cytometry; D006367:HeLa Cells; D056572:Histone Deacetylase Inhibitors / Q000494:pharmacology*; D006801:Humans; D009857:Oncogenes; D020133:Reverse Transcriptase Polymerase Chain Reaction; D053221:TNF-Related Apoptosis-Inducing Ligand / Q000502:physiology*; D014409:Tumor Necrosis Factor-alpha / Q000502:physiology*; D002583:Uterine Cervical Neoplasms / Q000473:pathology* / Q000821:virology
chemical_list: D056572:Histone Deacetylase Inhibitors; D053221:TNF-Related Apoptosis-Inducing Ligand; C505653:TNFSF10 protein, human; D014409:Tumor Necrosis Factor-alpha