DNA-dependent protein kinase activity correlates with Ku70 expression and radiation sensitivity in esophageal cancer cell lines.

We investigated the relationship between DNA-dependent protein kinase (DNA-PK) activity and radiation sensitivity using 14 esophageal cancer cell lines, TE 1-14. DNA-PK activities differed significantly among the cell lines. The highest DNA-PK activity observed in TE-8 was more than two times higher than the lowest DNA-PK activity observed in TE-5. Significant correlation was observed between DNA-PK activity and D0 (r = 0.766; P = 0.0008). Western blots analysis revealed a significant correlation between DNA-PK activity and Ku70 expression, suggesting that the regulation in DNA-PK activity was associated with Ku70 expression. The data suggest that the measurement of DNA-PK activity and/or Ku70 expression may provide a useful way to predict radiation sensitivity.