The immunohistochemical expression of DNA-PKCS and Ku (p70/p80) in head and neck cancers: relationships with radiosensitivity.
OBJECTIVE
The DNA-PK complex is one of the major pathways by which mammalian cells respond to DNA double-strand breaks induced by ionizing radiation. This study evaluated the relationship between the immunohistochemical expression of the individual components of DNA-PK and cellular radiosensitivity in head and neck cancers.


METHODS
Biopsies from patients with previously untreated squamous cell carcinomas of the head and neck were assessed for inherent tumor radiosensitivity measured as the surviving fraction at 2 Gy (SF2) using a soft agar clonogenic assay. Paraffin-embedded tumor material from 64 successfully grown specimens was immunohistochemically stained for expression of DNA-PKcs and Ku (p70/p80). The same tumor material was previously analyzed for the immunohistochemical expression of p53.


RESULTS
A significant correlation was found between the degree of expression of DNA-PKcs and Ku (p70/p80) (r = 0.55, p<0.001). There were no overall significant differences in the levels of expression of DNA-PKcs and Ku (p70/p80) in tumors from patients of either sex, different sites, histologies, and stages. No relationship was found between SF2 and the expression of either DNA-PKcs (r = 0.22, p = 0.081) or Ku (p70/p80) (r = 0.064, p = 0.62). Comparison with previous immunohistochemical characterization showed no significant correlations between the expression levels of p53 and either DNA-PKcs (r = 0.093, p = 0.46) or Ku (p70/p80) (r = -0.17, p = 0.17).


CONCLUSIONS
This study suggests that determining the immunohistochemical expression of DNA-PK in head and neck cancers from multiple sites does not have a role as a predictive assay of tumor in vitro radiosensitivity.
Björk-Eriksson
T
T
Department of Oncology, Sahlgrenska University Hospital, Gothenburg, Sweden. thomas.bjork-eriksson@oncology.gu.se
West
C
C
Nilsson
A
A
Magnusson
B
B
Svensson
M
M
Karlsson
E
E
Slevin
N
N
Lewensohn
R
R
Mercke
C
C
D034961:Antigens, Nuclear; D002135:Calcium-Binding Proteins / Q000378:metabolism*; D004265:DNA Helicases; D004273:DNA, Neoplasm / Q000528:radiation effects*; D004268:DNA-Binding Proteins / Q000378:metabolism*; D005260:Female; D006258:Head and Neck Neoplasms / Q000235:genetics / Q000378:metabolism* / Q000532:radiotherapy; D006801:Humans; D007150:Immunohistochemistry; D000072200:Ku Autoantigen; D008297:Male; D009363:Neoplasm Proteins / Q000378:metabolism*; D009687:Nuclear Proteins / Q000378:metabolism*; D011836:Radiation Tolerance
D034961:Antigens, Nuclear; C109198:CIB1 protein, human; D002135:Calcium-Binding Proteins; D004273:DNA, Neoplasm; D004268:DNA-Binding Proteins; D009363:Neoplasm Proteins; D009687:Nuclear Proteins; D004265:DNA Helicases; C106893:XRCC5 protein, human; C000606509:Xrcc6 protein, human; D000072200:Ku Autoantigen