Response to multiple radiation doses of human colorectal carcinoma cells infected with recombinant adenovirus containing dominant-negative Ku70 fragment.
OBJECTIVE
To investigate the effect of recombinant replication-defective adenovirus containing dominant-negative Ku70 fragment on the response of tumor cells to multiple small radiation doses. Our ultimate goal is to demonstrate the feasibility of using this virus in gene-radiotherapy to enhance the radiation response of tumor cells.


METHODS
Human colorectal HCT8 and HT29 carcinoma cells were plated in glass tubes, infected with virus (25 multiplicity of infection), and irradiated with a single dose or zero to five doses of 3 Gy each at 6-h intervals. Hypoxia was induced by flushing with 100% nitrogen gas. The cells were trypsinized 0 or 6 h after the final irradiation, and cell survival was determined by colony formation. The survival data were fitted to linear-quadratic model or exponential line.


RESULTS
Virus infection enhanced the radiation response of the HCT8 and HT29 cells. The virus enhancement ratio for single-dose irradiation at a surviving fraction of 0.1 was approximately 1.3 for oxic and hypoxic HCT8 and 1.4 and 1.1 for oxic and hypoxic HT29, respectively. A similar virus enhancement ratio of 1.2-1.3 was observed for both oxic and hypoxic cells irradiated with multiple doses; however, these values were smaller than the values found for dominant-negative Ku70-transfected Rat-1 cells. This difference has been discussed. The oxygen enhancement ratio for HCT8 and HT29 receiving fractionated doses was 1.2 and 2.0, respectively, and virus infection altered them slightly.


CONCLUSIONS
Infection of recombinant replication-defective adenovirus containing dominant-negative Ku70 fragment enhanced the response of human colorectal cancer cells to single and multiple radiation doses.
Urano
Muneyasu
M
Department of Radiation Oncology, Memorial Sloan-Kettering Cancer Center, New York, NY 10021, USA. uranom@mskcc.org
He
Fuqiu
F
Minami
Akiko
A
Ling
C Clifton
CC
Li
Gloria C
GC
D000256:Adenoviridae / Q000235:genetics / Q000502:physiology*; D000818:Animals; D034961:Antigens, Nuclear / Q000235:genetics / Q000378:metabolism*; D015687:Cell Hypoxia / Q000502:physiology; D045744:Cell Line, Tumor / Q000528:radiation effects / Q000821:virology; D002470:Cell Survival; D003114:Colony-Forming Units Assay / Q000379:methods; D015179:Colorectal Neoplasms / Q000473:pathology / Q000532:radiotherapy / Q000821:virology; D004249:DNA Damage; D004260:DNA Repair; D051747:DNA-Activated Protein Kinase / Q000037:antagonists & inhibitors*; D004268:DNA-Binding Proteins / Q000172:deficiency / Q000235:genetics / Q000378:metabolism*; D003673:Defective Viruses / Q000235:genetics / Q000502:physiology*; D015316:Genetic Therapy / Q000379:methods; D019073:HT29 Cells / Q000528:radiation effects / Q000821:virology; D006801:Humans; D000072200:Ku Autoantigen; D016014:Linear Models; D009363:Neoplasm Proteins / Q000172:deficiency / Q000235:genetics / Q000378:metabolism; D011829:Radiation Dosage; D011836:Radiation Tolerance / Q000502:physiology*; D051381:Rats; D014162:Transfection / Q000379:methods
D034961:Antigens, Nuclear; D004268:DNA-Binding Proteins; D009363:Neoplasm Proteins; D051747:DNA-Activated Protein Kinase; C000606509:Xrcc6 protein, human; C000606511:Xrcc6 protein, rat; D000072200:Ku Autoantigen