title: Histone deacetylase inhibitor-mediated radiosensitization of human cancer cells: class differences and the potential influence of p53.
abstract: Histone deacetylase inhibitors (HDI) are emerging as potentially useful components of the anticancer armamentarium and as useful tools to dissect mechanistic pathways. HDIs that globally inhibit histone deacetylases (HDAC) have radiosensitizing effects, but the relative contribution of specific HDAC classes remains unclear. Newly characterized HDIs are now available that preferentially inhibit specific HDAC classes, including SK7041 (inhibits class I HDACs) and splitomicin (inhibits class III HDACs). We investigated in human cancer cells the relative radiosensitizations that result from blocking specific HDAC classes. We found that trichostatin A (TSA; inhibitor of both class I and II HDACs) was the most effective radiosensitizer, followed by the class I inhibitor SK7041, whereas splitomicin (inhibitor of class III) had least effect. Interestingly, radiosensitization by TSA in cell lines expressing p53 was more pronounced than in isogenic lines lacking p53. Radiosensitization of cells expressing p53 by TSA was reduced by pifithrin-alpha, a small-molecule inhibitor of p53. In contrast, the radiosensitization by TSA of cells expressing low levels of p53 was enhanced by transfection of wild-type p53-expressing vector or pretreatment with leptomycin B, an inhibitor of nuclear export that increased intracellular levels of p53. These effects on radiosensitization were respectively muted or not seen in cells treated with SK7041 or splitomicin. To our knowledge, this may be among the first systematic investigations of the comparative anticancer effects of inhibiting specific classes of HDACs, with results suggesting differences in the degrees of radiosensitization, which in some cell lines may be influenced by p53 expression.
authors.affiliation: Department of Radiation Oncology, Seoul National University College of Medicine, Jongno-gu, Seoul, Korea.
authors.forename: In Ah
authors.initials: IA
authors.lastname: Kim
authors.forename: Jin Hee
authors.initials: JH
authors.lastname: Shin
authors.forename: Il Han
authors.initials: IH
authors.lastname: Kim
authors.forename: Jin Ho
authors.initials: JH
authors.lastname: Kim
authors.forename: Jae Sung
authors.initials: JS
authors.lastname: Kim
authors.forename: Hong Gyun
authors.initials: HG
authors.lastname: Wu
authors.forename: Eui Kyu
authors.initials: EK
authors.lastname: Chie
authors.forename: Sung Whan
authors.initials: SW
authors.lastname: Ha
authors.forename: Charn Il
authors.initials: CI
authors.lastname: Park
authors.forename: Gary D
authors.initials: GD
authors.lastname: Kao
mesh_terms: D000577:Amides / Q000494:pharmacology; D052160:Benzothiazoles; D001713:Biphenyl Compounds / Q000494:pharmacology; D002453:Cell Cycle / Q000187:drug effects / Q000528:radiation effects; D045744:Cell Line, Tumor; D049109:Cell Proliferation / Q000187:drug effects / Q000528:radiation effects; D004305:Dose-Response Relationship, Drug; D004307:Dose-Response Relationship, Radiation; D004791:Enzyme Inhibitors / Q000494:pharmacology*; D005231:Fatty Acids, Unsaturated / Q000494:pharmacology; D005786:Gene Expression Regulation / Q000187:drug effects; D006367:HeLa Cells; D056572:Histone Deacetylase Inhibitors; D006655:Histone Deacetylases / Q000145:classification* / Q000528:radiation effects; D006801:Humans; D006877:Hydroxamic Acids / Q000037:antagonists & inhibitors / Q000494:pharmacology; D009281:Naphthalenes / Q000494:pharmacology; D011753:Pyrones / Q000494:pharmacology; D011838:Radiation-Sensitizing Agents / Q000494:pharmacology*; D013844:Thiazoles / Q000494:pharmacology; D014050:Toluene / Q000031:analogs & derivatives / Q000494:pharmacology; D014407:Tumor Cells, Cultured; D016159:Tumor Suppressor Protein p53 / Q000187:drug effects* / Q000235:genetics / Q000528:radiation effects
chemical_list: D000577:Amides; D052160:Benzothiazoles; D001713:Biphenyl Compounds; D004791:Enzyme Inhibitors; D005231:Fatty Acids, Unsaturated; D056572:Histone Deacetylase Inhibitors; D006877:Hydroxamic Acids; D009281:Naphthalenes; D011753:Pyrones; D011838:Radiation-Sensitizing Agents; C497103:SK-7041; D013844:Thiazoles; D016159:Tumor Suppressor Protein p53; D014050:Toluene; C012589:trichostatin A; C444426:splitomicin; C121565:pifithrin; D006655:Histone Deacetylases; C038753:leptomycin B