Ku DEB activity according to the two groups of samples. (A) The Ku DEB activity was determined by EMSA experiments and bands that corresponded to the Ku-DNA complexes were excised and counted by scintillation as described in Materials and Methods. For each sample, the results represent the mean of at least two experiments with variability of less than 10%. (B) Correlation of Ku DEB activity with the DNA-PK kinase activity as determined for 32 samples. Each point represents the result from an individual patient's sample. (□), Lymphocytes obtained from untreated patients; (▪), lymphocytes obtained from treated-resistant patients.