title: Epigenetic silencing of apoptosis-inducing gene expression can be efficiently overcome by combined SAHA and TRAIL treatment in uterine sarcoma cells.
abstract: The lack of knowledge about molecular pathology of uterine sarcomas with a representation of 3-7% of all malignant uterine tumors prevents the establishment of effective therapy protocols. Here, we explored advanced therapeutic options to the previously discovered antitumorigenic effects of the histone deacetylase (HDAC) inhibitor suberoylanilide hydroxamic acid (SAHA) by combined treatment with the tumor necrosis factor-related apoptosis-inducing ligand (TRAIL/Apo-2L). In addition, we investigated the uterine sarcoma cell lines, MES-SA and ESS-1, regarding the underlying molecular mechanisms of SAHA and TRAIL-induced apoptosis and their resistance towards TRAIL. Compared to single SAHA or TRAIL treatment, the combination of SAHA with TRAIL led to complete cell death of both tumor cell lines after 24 to 48 hours. In contrast to single SAHA treatment, apoptosis occured faster and was more pronounced in ESS-1 cells than in MES-SA cells. Induction of SAHA- and TRAIL-induced apoptosis was accompanied by upregulation of the intrinsic apoptotic pathway via reduction of mitochondrial membrane potential, caspase-3, -6, and -7 activation, and PARP cleavage, but was also found to be partially caspase-independent. Apoptosis resistance was caused by reduced expression of caspase-8 and DR 4/TRAIL-R1 in ESS-1 and MES-SA cells, respectively, due to epigenetic silencing by DNA hypermethylation of gene promoter sequences. Treatment with the demethylating agent 5-Aza-2'-deoxycytidine or gene transfer therefore restored gene expression and increased the sensitivity of both cell lines against TRAIL-induced apoptosis. Our data provide evidence that deregulation of epigenetic silencing by histone acetylation and DNA hypermethylation might play a fundamental role in the origin of uterine sarcomas. Therefore, tumor growth might be efficiently overcome by a cytotoxic combinatorial treatment of HDAC inhibitors with TRAIL.
authors.affiliation: Molecular Pathology Laboratory, Medical University of Graz, Graz, Austria.
authors.forename: Leopold F
authors.initials: LF
authors.lastname: Fröhlich
authors.affiliation: Center for Medical Research, Medical University of Graz, Graz, Austria.
authors.forename: Maria
authors.initials: M
authors.lastname: Mrakovcic
authors.affiliation: Molecular Pathology Laboratory, Medical University of Graz, Graz, Austria.
authors.forename: Claudia
authors.initials: C
authors.lastname: Smole
authors.affiliation: Molecular Pathology Laboratory, Medical University of Graz, Graz, Austria.
authors.forename: Pooja
authors.initials: P
authors.lastname: Lahiri
authors.affiliation: Molecular Pathology Laboratory, Medical University of Graz, Graz, Austria.
authors.forename: Kurt
authors.initials: K
authors.lastname: Zatloukal
mesh_terms: D017209:Apoptosis / Q000235:genetics*; D053148:Caspase 3 / Q000378:metabolism; D053181:Caspase 8 / Q000235:genetics / Q000378:metabolism; D045744:Cell Line, Tumor; D019175:DNA Methylation; D019008:Drug Resistance, Neoplasm / Q000235:genetics; D004357:Drug Synergism; D004789:Enzyme Activation / Q000187:drug effects; D044127:Epigenesis, Genetic; D005260:Female; D015972:Gene Expression Regulation, Neoplastic; D018014:Gene Transfer Techniques; D056572:Histone Deacetylase Inhibitors; D006801:Humans; D006877:Hydroxamic Acids / Q000494:pharmacology* / Q000633:toxicity; D053078:Membrane Potential, Mitochondrial; D008928:Mitochondria / Q000187:drug effects / Q000378:metabolism; D011401:Promoter Regions, Genetic; D053220:Receptors, TNF-Related Apoptosis-Inducing Ligand / Q000235:genetics / Q000378:metabolism; D012509:Sarcoma / Q000235:genetics*; D053221:TNF-Related Apoptosis-Inducing Ligand / Q000494:pharmacology* / Q000633:toxicity; D014594:Uterine Neoplasms / Q000235:genetics*; D000077337:Vorinostat
chemical_list: D056572:Histone Deacetylase Inhibitors; D006877:Hydroxamic Acids; D053220:Receptors, TNF-Related Apoptosis-Inducing Ligand; D053221:TNF-Related Apoptosis-Inducing Ligand; D000077337:Vorinostat; D053148:Caspase 3; D053181:Caspase 8