title: P53-dependent antiproliferative and pro-apoptotic effects of trichostatin A (TSA) in glioblastoma cells.
abstract: Glioblastomas are known to be highly chemoresistant, but HDAC inhibitors (HDACi) have been shown to be of therapeutic relevance for this aggressive tumor type. We treated U87 glioblastoma cells with trichostatin A (TSA) to define potential epigenetic targets for HDACi-mediated antitumor effects. Using a cDNA array analysis covering 96 cell cycle genes, cyclin-dependent kinase inhibitor p21(WAF1) was identified as the major player in TSA-induced cell cycle arrest. TSA slightly inhibited proliferation and viability of U87 cells, cumulating in a G1/S cell cycle arrest. This effect was accompanied by a significant up-regulation of p53 and its transcriptional target p21(WAF1) and by down-regulation of key G1/S regulators, such as cdk4, cdk6, and cyclin D1. Nevertheless, TSA did not induce apoptosis in U87 cells. As expected, TSA promoted the accumulation of total acetylated histones H3 and H4 and a decrease in endogenous HDAC activity. Characterizing the chromatin modulation around the p21(WAF1) promoter after TSA treatment using chromatin immunoprecipitation, we found (1) a release of HDAC1, (2) an increase of acetylated H4 binding, and (3) enhanced recruitment of p53. p53-depleted U87 cells showed an abrogation of the G1/S arrest and re-entered the cell cycle. Immunofluorescence staining revealed that TSA induced the nuclear translocation of p21(WAF1) verifying a cell cycle arrest. On the other hand, a significant portion of p21(WAF1) was present in the cytoplasmic compartment causing apoptosis resistance. Furthermore, TSA-treated p53-mutant cell line U138 failed to show an induction in p21(WAF1), showed a deficient G2/M checkpoint, and underwent mitotic catastrophe. We suggest that HDAC inhibition in combination with other clinically used drugs may be considered an effective strategy to overcome chemoresistance in glioblastoma cells.
authors.affiliation: Institute of Pathology, University of Magdeburg, 39120 Magdeburg, Germany.
authors.forename: K
authors.initials: K
authors.lastname: Bajbouj
authors.forename: C
authors.initials: C
authors.lastname: Mawrin
authors.forename: R
authors.initials: R
authors.lastname: Hartig
authors.forename: J
authors.initials: J
authors.lastname: Schulze-Luehrmann
authors.forename: A
authors.initials: A
authors.lastname: Wilisch-Neumann
authors.forename: A
authors.initials: A
authors.lastname: Roessner
authors.forename: R
authors.initials: R
authors.lastname: Schneider-Stock
mesh_terms: D000970:Antineoplastic Agents / Q000494:pharmacology; D017209:Apoptosis / Q000187:drug effects*; D045744:Cell Line, Tumor; D049109:Cell Proliferation / Q000187:drug effects*; D047369:Chromatin Immunoprecipitation; D050759:Cyclin-Dependent Kinase Inhibitor p21 / Q000235:genetics / Q000378:metabolism; D005434:Flow Cytometry; D005455:Fluorescent Antibody Technique; D020869:Gene Expression Profiling; D005909:Glioblastoma / Q000235:genetics / Q000378:metabolism*; D056572:Histone Deacetylase Inhibitors / Q000494:pharmacology*; D006801:Humans; D006877:Hydroxamic Acids / Q000494:pharmacology*; D015151:Immunoblotting; D020411:Oligonucleotide Array Sequence Analysis; D060888:Real-Time Polymerase Chain Reaction; D020133:Reverse Transcriptase Polymerase Chain Reaction; D016159:Tumor Suppressor Protein p53 / Q000235:genetics / Q000378:metabolism*
chemical_list: D000970:Antineoplastic Agents; C493956:CDKN1A protein, human; D050759:Cyclin-Dependent Kinase Inhibitor p21; D056572:Histone Deacetylase Inhibitors; D006877:Hydroxamic Acids; C495901:TP53 protein, human; D016159:Tumor Suppressor Protein p53; C012589:trichostatin A