Protective role of Hsp27 protein against gamma radiation-induced apoptosis and radiosensitization effects of Hsp27 gene silencing in different human tumor cells.
OBJECTIVE
The ability of heat shock protein 27 (Hsp27) to protect cells from stressful stimuli and its increased levels in tumors resistant to anticancer therapeutics suggest that it may represent a target for sensitization to radiotherapy. In this study, we investigate the protective role of Hsp27 against radiation-induced apoptosis and the effect of its attenuation in highly expressing radioresistant cancer cell lines.


METHODS
We examined clonogenic death and the kinetics of apoptotic events in different tumor cell lines overexpressing or underexpressing Hsp27 protein irradiated with photons. The radiosensitive Jurkat cell line, which does not express Hsp27 constitutively or in response to gamma-rays, was stably transfected with Hsp27 complementary DNA. Attenuation of Hsp27 expression was accomplished by antisense or RNAi (interfering RNA) strategies in SQ20B head-and-neck squamous carcinoma, PC3 prostate cancer, and U87 glioblastoma radioresistant cells.


RESULTS
We measured concentration-dependent protection against the cytotoxic effects of radiation in Jurkat-Hsp27 cells, which led to a 50% decrease in apoptotic cells at 48 hours in the highest expressing cells. Underlying mechanisms leading to radiation resistance involved a significant increase in glutathione levels associated with detoxification of reactive oxygen species, a delay in mitochondrial collapse, and caspase activation. Conversely, attenuation of Hsp27 in SQ20B cells, characterized by their resistance to apoptosis, sensitizes cells to irradiation. This was emphasized by increased apoptosis, decreased glutathione basal level, and clonogenic cell death. Sensitization to irradiation was confirmed in PC3 and U87 radioresistant cells.


CONCLUSIONS
Hsp27 gene therapy offers a potential adjuvant to radiation-based therapy of resistant tumors.
Aloy
Marie-Thérèse
MT
Université de Lyon 1, Laboratoire de Radiobiologie Cellulaire et Moléculaire, Faculté de Médecine Lyon-Sud, Oullins, France. marie-therese.aloy@sante.univ-lyon1.fr
Hadchity
Elie
E
Bionda
Clara
C
Diaz-Latoud
Chantal
C
Claude
Line
L
Rousson
Robert
R
Arrigo
André-Patrick
AP
Rodriguez-Lafrasse
Claire
C
D017209:Apoptosis / Q000502:physiology / Q000528:radiation effects*; D020169:Caspases / Q000378:metabolism; D045744:Cell Line, Tumor / Q000528:radiation effects; D015536:Down-Regulation; D004789:Enzyme Activation / Q000528:radiation effects; D005720:Gamma Rays; D020868:Gene Silencing / Q000502:physiology*; D005909:Glioblastoma / Q000378:metabolism / Q000532:radiotherapy; D005978:Glutathione / Q000378:metabolism; D006258:Head and Neck Neoplasms / Q000378:metabolism / Q000532:radiotherapy; D006360:Heat-Shock Proteins / Q000235:genetics / Q000378:metabolism / Q000502:physiology*; D006801:Humans; D019169:Jurkat Cells / Q000528:radiation effects; D008297:Male; D008928:Mitochondria / Q000502:physiology / Q000528:radiation effects; D009363:Neoplasm Proteins / Q000235:genetics / Q000378:metabolism / Q000502:physiology*; D018384:Oxidative Stress / Q000502:physiology / Q000528:radiation effects; D017785:Photons; D011471:Prostatic Neoplasms / Q000378:metabolism / Q000532:radiotherapy; D016372:RNA, Antisense / Q000627:therapeutic use; D034741:RNA, Small Interfering / Q000627:therapeutic use; D011836:Radiation Tolerance / Q000235:genetics / Q000502:physiology*; D017382:Reactive Oxygen Species / Q000378:metabolism; D013997:Time Factors; D014162:Transfection / Q000379:methods; D014410:Tumor Stem Cell Assay
D006360:Heat-Shock Proteins; D009363:Neoplasm Proteins; D016372:RNA, Antisense; D034741:RNA, Small Interfering; D017382:Reactive Oxygen Species; D020169:Caspases; D005978:Glutathione