title: Combination of suberoylanilide hydroxamic acid with heavy ion therapy shows promising effects in infantile sarcoma cell lines.
abstract: BACKGROUND
  The pan-HDAC inhibitor (HDACI) suberoylanilide hydroxamic acid (SAHA) has previously shown to be a radio-sensitizer to conventional photon radiotherapy (XRT) in pediatric sarcoma cell lines. Here, we investigate its effect on the response of two sarcoma cell lines and a normal tissue cell line to heavy ion irradiation (HIT).
  
  
  METHODS
  Clonogenic assays after different doses of heavy ions were performed. DNA damage and repair were evaluated by measuring γH2AX via flow-cytometry. Apoptosis and cell cycle analysis were also measured via flow cytometry. Protein expression of repair proteins, p53 and p21 were measured using immunoblot analysis. Changes of nuclear architecture after treatment with SAHA and HIT were observed in one of the sarcoma cell lines via light microscopy after staining towards chromatin and γH2AX.
  
  
  RESULTS
  Corresponding with previously reported photon data, SAHA lead to an increase of sensitivity to heavy ions along with an increase of DSB and apoptosis in the two sarcoma cell lines. In contrast, in the osteoblast cell line (hFOB 1.19), the combination of SAHA and HIT showed a significant radio-protective effect. Laser scanning microscopy revealed no significant morphologic changes after HIT compared to the combined treatment with SAHA. Immunoblot analysis revealed no significant up or down regulation of p53. However, p21 was significantly increased by SAHA and combination treatment as compared to HIT only in the two sarcoma cell lines--again in contrast to the osteoblast cell line. Changes in the repair kinetics of DSB p53-independent apoptosis with p21 involvement may be part of the underlying mechanisms for radio-sensitization by SAHA.
  
  
  CONCLUSIONS
  Our in vitro data suggest an increase of the therapeutic ratio by the combination of SAHA with HIT in infantile sarcoma cell lines.
authors.affiliation: Department of Radiooncology, University of Heidelberg, (INF 400), Heidelberg 69120, Germany. susanne.oertel@med.uni-heidelberg.de
authors.forename: Susanne
authors.initials: S
authors.lastname: Oertel
authors.forename: Markus
authors.initials: M
authors.lastname: Thiemann
authors.forename: Karsten
authors.initials: K
authors.lastname: Richter
authors.forename: Klaus J
authors.initials: KJ
authors.lastname: Weber
authors.forename: Peter E
authors.initials: PE
authors.lastname: Huber
authors.forename: Ramon Lopez
authors.initials: RL
authors.lastname: Perez
authors.forename: Stephan
authors.initials: S
authors.lastname: Brons
authors.forename: Marc
authors.initials: M
authors.lastname: Bischof
authors.forename: Andreas E
authors.initials: AE
authors.lastname: Kulozik
authors.forename: Volker
authors.initials: V
authors.lastname: Ehemann
authors.forename: Jürgen
authors.initials: J
authors.lastname: Debus
authors.forename: Claudia
authors.initials: C
authors.lastname: Blattmann
mesh_terms: D000970:Antineoplastic Agents / Q000494:pharmacology; D017209:Apoptosis; D045744:Cell Line, Tumor; D002469:Cell Separation; D002843:Chromatin / Q000737:chemistry / Q000378:metabolism; D003131:Combined Modality Therapy / Q000379:methods*; D050759:Cyclin-Dependent Kinase Inhibitor p21 / Q000378:metabolism; D005434:Flow Cytometry / Q000379:methods; D020450:Heavy Ions; D006657:Histones / Q000737:chemistry; D006801:Humans; D006877:Hydroxamic Acids / Q000627:therapeutic use*; D007231:Infant, Newborn; D018613:Microscopy, Confocal / Q000379:methods; D010006:Osteoblasts / Q000378:metabolism; D011878:Radiotherapy / Q000379:methods*; D012509:Sarcoma / Q000628:therapy*; D016159:Tumor Suppressor Protein p53 / Q000378:metabolism; D000077337:Vorinostat
chemical_list: D000970:Antineoplastic Agents; D002843:Chromatin; D050759:Cyclin-Dependent Kinase Inhibitor p21; C468783:H2AX protein, human; D006657:Histones; D006877:Hydroxamic Acids; D016159:Tumor Suppressor Protein p53; D000077337:Vorinostat