Over-expression of APAF-1 and caspase-9 augments radiation-induced apoptosis in U-373MG glioma cells.
The p53 tumor-suppressor gene plays a critical role in radiation-induced apoptosis. Several genes, including Bax and Fas, are involved in p53-mediated apoptosis, and their over-expression enhances the degree of radiation-induced apoptosis. Apaf-1 and caspase-9 have been reported to be downstream components of p53-mediated apoptosis, suggesting that these genes play a role in radiation-induced apoptosis. In this study, we transduced U-373MG cells harboring mutant p53 with the Apaf-1 and/or caspase-9 genes via adenoviral (Adv) vectors concomitant with X-ray irradiation and evaluated the degree of apoptosis. The percentage of apoptotic cells in U-373MG cells co-infected with the Adv for Apaf-1 (Adv-APAF-1) and that for caspase-9 (Adv-Casp9) and treated with irradiation (24%) was much higher than that in cells co-infected with Adv-APAF-1 and Adv-Casp9 and not treated with irradiation (0.86%) and that in cells infected with either Adv-APAF-1 or Adv-Casp9 and treated with irradiation (2.0% or 2.6%, respectively). The apoptosis induced by co-transduction of Apaf-1 and caspase-9 and irradiation was repressed in cells that were co-infected with the Adv for Bcl-X(L) but not in cells co-infected with the Adv for Bcl-2. These results indicate that Apaf-1 and caspase-9 play a role in radiation-induced apoptosis in cancer cells harboring mutant p53. Bcl-X(L) may be critically involved in the radioresistance of cancer cells by repressing Apaf-1- and caspase-9-mediated apoptosis. Expression of Apaf-1 and caspase-9 in tumors may be an important determinant of the therapeutic effect of irradiation in cancer treatment.
Shinoura
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Department of Molecular Biotherapy Research, Cancer Chemotherapy Center, Cancer Institute, Tokyo, Japan. shinoura-k@komagome-hospital.bunkyo.tokyo.jp
Sakurai
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S
Asai
A
A
Kirino
T
T
Hamada
H
H
D000256:Adenoviridae / Q000235:genetics; D017209:Apoptosis / Q000235:genetics; D053477:Apoptotic Protease-Activating Factor 1; D053453:Caspase 9; D020169:Caspases / Q000235:genetics / Q000378:metabolism*; D005822:Genetic Vectors; D005910:Glioma / Q000201:enzymology / Q000378:metabolism / Q000473:pathology*; D006801:Humans; D011506:Proteins / Q000235:genetics / Q000378:metabolism*; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000378:metabolism; D014161:Transduction, Genetic; D014407:Tumor Cells, Cultured / Q000473:pathology / Q000528:radiation effects; D051020:bcl-X Protein
C506592:APAF1 protein, human; D053477:Apoptotic Protease-Activating Factor 1; C494811:BCL2L1 protein, human; D011506:Proteins; D019253:Proto-Oncogene Proteins c-bcl-2; D051020:bcl-X Protein; C506433:CASP9 protein, human; D053453:Caspase 9; D020169:Caspases