Radiosensitization of head/neck squamous cell carcinoma by adenovirus-mediated expression of the Nbs1 protein.
OBJECTIVE
Local failure and toxicity to adjacent critical structures is a significant problem in radiation therapy of cancers of the head and neck. We are developing a gene therapy based method of sensitizing head/neck squamous cell carcinoma (HNSCC) to radiation treatment. As patients with the rare hereditary disorder, Nijmegen breakage syndrome, show radiation sensitivity we hypothesized that tumor-specific disruption of the function of the Nbs1 protein would lead to enhanced cellular sensitivity to ionizing radiation.


METHODS
We constructed two recombinant adenoviruses by cloning the full-length Nbs1 cDNA as well as the C-terminal 300 amino acids of Nbs1 into an adenovirus backbone under the control of a CMV promoter. The resulting adenoviruses were used to infect HNSCC cell line JHU011. These cells were evaluated for expression of the viral based constructs and assayed for clonogenic survival following radiation exposure.


RESULTS
Exposure of cells expressing Nbs1-300 to ionizing radiation resulted in a small reduction in survival relative to cells infected with control virus. Surprisingly, expression of full-length Nbs1 protein resulted in markedly enhanced sensitivity to ionizing radiation. Furthermore, the use of a fractionated radiation scheme following virus infection demonstrates that expression of full-length Nbs1 protein results in significant reduction in cell survival.


CONCLUSIONS
These results provide a proof of principle that disruption of Nbs1 function may provide a means of enhancing the radiosensitivity of head and neck tumors. Additionally, this work highlights the Mre11 complex as an attractive target for development of radiation sensitizers.
Rhee
Juong G
JG
The Radiation Oncology Research Laboratory, Department of Radiation Oncology, University of Maryland School of Medicine, Baltimore, MD, USA.
Li
Daqing
D
Suntharalingam
Mohan
M
Guo
Chuanfa
C
O'Malley
Bert W
BW
Carney
James P
JP
D000256:Adenoviridae / Q000235:genetics / Q000378:metabolism; D000818:Animals; D002294:Carcinoma, Squamous Cell / Q000532:radiotherapy*; D018797:Cell Cycle Proteins / Q000235:genetics / Q000378:metabolism*; D018014:Gene Transfer Techniques; D006258:Head and Neck Neoplasms / Q000532:radiotherapy*; D006801:Humans; D051379:Mice; D008807:Mice, Inbred BALB C; D008819:Mice, Nude; D049932:Nijmegen Breakage Syndrome / Q000378:metabolism; D009687:Nuclear Proteins / Q000235:genetics / Q000378:metabolism*; D011836:Radiation Tolerance / Q000235:genetics*; D011994:Recombinant Proteins / Q000235:genetics / Q000378:metabolism
D018797:Cell Cycle Proteins; C112156:NBN protein, human; D009687:Nuclear Proteins; D011994:Recombinant Proteins