Enhancement of radiation response in osteosarcoma and rhabdomyosarcoma cell lines by histone deacetylase inhibition.
OBJECTIVE
Histone deacetylase inhibitors (HDACIs) can enhance the sensitivity of cells to photon radiation treatment (XRT) by altering numerous molecular pathways. We investigated the effect of pan-HDACIs such as suberoylanilide hydroxamic acid (SAHA) on radiation response in two osteosarcoma (OS) and two rhabdomyosarcoma (RMS) cell lines.


METHODS
Clonogenic survival, cell cycle analysis, and apoptosis were examined in OS (KHOS-24OS, SAOS2) and RMS (A-204, RD) cell lines treated with HDACI and HDACI plus XRT, respectively. Protein expression was investigated via immunoblot analysis, and cell cycle analysis and measurement of apoptosis were performed using flow cytometry.


RESULTS
SAHA induced an inhibition of cell proliferation and clonogenic survival in OS and RMS cell lines and led to a significant radiosensitization of all tumor cell lines. Other HDACI such as M344 and valproate showed similar effects as investigated in one OS cell line. Furthermore, SAHA significantly increased radiation-induced apoptosis in the OS cell lines, whereas in the RMS cell lines radiation-induced apoptosis was insignificant with and without SAHA. In all investigated sarcoma cell lines, SAHA attenuated radiation-induced DNA repair protein expression (Rad51, Ku80).


CONCLUSIONS
Our results show that HDACIs enhance radiation action in OS and RMS cell lines. Inhibition of DNA repair, as well as increased apoptosis induction after exposure to HDACIs, can be mechanisms of radiosensitization by HDACIs.
Blattmann
Claudia
C
Department of Pediatric Oncology, University of Heidelberg, Heidelberg, Germany. claudia.blattmann@med.uni-heidelberg.de
Oertel
Susanne
S
Ehemann
Volker
V
Thiemann
Markus
M
Huber
Peter E
PE
Bischof
Marc
M
Witt
Olaf
O
Deubzer
Hedwig E
HE
Kulozik
Andreas E
AE
Debus
Jürgen
J
Weber
Klaus-J
KJ
D034961:Antigens, Nuclear / Q000378:metabolism; D017209:Apoptosis / Q000187:drug effects / Q000528:radiation effects; D002352:Carrier Proteins / Q000378:metabolism; D002453:Cell Cycle / Q000528:radiation effects; D045744:Cell Line, Tumor; D002470:Cell Survival / Q000187:drug effects / Q000528:radiation effects; D004260:DNA Repair / Q000187:drug effects; D004268:DNA-Binding Proteins / Q000378:metabolism; D005434:Flow Cytometry; D056572:Histone Deacetylase Inhibitors / Q000627:therapeutic use*; D006801:Humans; D006877:Hydroxamic Acids / Q000627:therapeutic use*; D000072200:Ku Autoantigen; D012516:Osteosarcoma / Q000532:radiotherapy*; D017785:Photons / Q000627:therapeutic use; D011836:Radiation Tolerance / Q000187:drug effects*; D011838:Radiation-Sensitizing Agents / Q000627:therapeutic use*; D012208:Rhabdomyosarcoma / Q000532:radiotherapy*; D014410:Tumor Stem Cell Assay / Q000379:methods; D014635:Valproic Acid / Q000627:therapeutic use; D000077337:Vorinostat
D034961:Antigens, Nuclear; D002352:Carrier Proteins; D004268:DNA-Binding Proteins; D056572:Histone Deacetylase Inhibitors; D006877:Hydroxamic Acids; C515554:RAD51 associated protein 2, human; D011838:Radiation-Sensitizing Agents; D000077337:Vorinostat; D014635:Valproic Acid; C000606509:Xrcc6 protein, human; D000072200:Ku Autoantigen