An adenovirus encoding proapoptotic Bax synergistically radiosensitizes malignant glioma.
OBJECTIVE
We explore the utility of the adenovirus-mediated delivery of proapoptotic Bax for enhancing the cytotoxicity of radiotherapy (RT) in RT-refractory glioma cells.


METHODS
Cell lines D54 MG and U87 MG (p53 wild-type), and U251 MG and U373 MG (p53 mutant), and patient-derived astrocytes were evaluated. Cells were irradiated and infected with an inducible adenovirus encoding Bax. Cell proliferation, colony formation assay, quantification of early apoptotic alteration in the plasma membrane by fluorescence-activated cell sorter using annexin V, and nuclear staining with H33258 were used to evaluate apoptosis. The capacity of the combined treatment to induce regression of subcutaneous D54 MG tumors was tested in nude mice. A dose of 5 Gy was administered every other day, four times, for a total dose of 20 Gy. One day after each irradiation, tumors were injected with 1 x 10(9) plaque-forming units (PFU).


RESULTS
Apoptotic death was enhanced by the combination of Ad/Bax and RT. In D54 MG, levels of apoptosis after RT alone, Ad/Bax alone, or the combination were, respectively, 12.3%, 32.1%, and 78.5%. In contrast, treatment of astrocytes did not significantly induce apoptosis. A colony-formation assay showed a 2-log inhibition with respect to controls after combined treatment, irrespective of the endogenous levels of p53. The other apoptosis assays also showed the defining characteristics of apoptosis in the combination group. Remarkably, combined treatment induced regression of tumors in mice.


CONCLUSIONS
Ad/Bax synergistically radiosensitizes glioma, with a seemingly favorable therapeutic index.
Arafat
Waleed O
WO
Division of Human Gene Therapy, University of Alabama at Birmingham, Birmingham, AL 35294, USA.
Buchsbaum
Donald J
DJ
Gómez-Navarro
Jesús
J
Tawil
Sarah A
SA
Olsen
Christine
C
Xiang
Jialing
J
El-Akad
Hazem
H
Salama
Anwar M
AM
Badib
Ahmed O
AO
Stackhouse
Murray A
MA
Curiel
David T
DT
D000256:Adenoviridae / Q000235:genetics*; D000704:Analysis of Variance; D000818:Animals; D017209:Apoptosis / Q000235:genetics / Q000502:physiology*; D001253:Astrocytes / Q000528:radiation effects / Q000821:virology; D001932:Brain Neoplasms / Q000532:radiotherapy / Q000628:therapy*; D002470:Cell Survival / Q000502:physiology; D003131:Combined Modality Therapy; D004307:Dose-Response Relationship, Radiation; D015972:Gene Expression Regulation, Neoplastic; D016147:Genes, Tumor Suppressor / Q000502:physiology; D016158:Genes, p53 / Q000502:physiology; D015316:Genetic Therapy / Q000379:methods*; D005822:Genetic Vectors / Q000627:therapeutic use*; D005910:Glioma / Q000532:radiotherapy / Q000628:therapy*; D006801:Humans; D051379:Mice; D008819:Mice, Nude; D011518:Proto-Oncogene Proteins / Q000235:genetics*; D019253:Proto-Oncogene Proteins c-bcl-2; D014407:Tumor Cells, Cultured; D014410:Tumor Stem Cell Assay; D051028:bcl-2-Associated X Protein
C494826:BAX protein, human; C494827:Bax protein, mouse; D011518:Proto-Oncogene Proteins; D019253:Proto-Oncogene Proteins c-bcl-2; D051028:bcl-2-Associated X Protein