Study of NHEJ Function and Expression of Protein Ku70 in CML Patients.

The abnormal activity of DNA repair after DNA double strand breakage results in genome instability. It is also thought that the malfunction in DNA repair may be involved in the generation of variety of chromosomal translocations in human leukemia. To investigate the relationship between the activity of DNA repairing by NHEJ and the expression of protein Ku70 in CML cells, the expression of protein Ku70 deprived from the chromatin was determined by Western Blot, using TBP(TATA Box Binding Protein)as the internal control, in bone marrow cells of CML patients as well as the normal controls. Our preliminary result showed that the gray ratios of Ku70 protein band over TBP band in 24 normal BM cells were 0 to 0.235, with a mean level of 0.0983±0.0875, while which were 0.173 to 0.890 with a mean of 0.401±0.207 (p<0.001) in 27 CML cases. Furthermore, Among these 27 CML cases, the gray ratio of Ku70 versus TBP in 12 CML cases in accelerating of acute phase was significantly higher than that in 15 CML patients in chronic phase with a mean value of 0.565±0.2159 vs. 0.269±0.0381 (p<0.001). These results indicated that the activity NHEJ in CML cells was approximately 2-fold higher than that in normal controls. Ku70, as the key protein of NHEJ, was expressed significantly higher in CML than that in normal BM cells. Moreover, as the CML progressed from chronic phase to accelerating or acute phase in company with a remarkable increase of Ku70 expression, more clones with variety of chromosome abnormalities other than the typical t (9;22) translocation emerged, suggesting an error-prone repair activity of the increased NHEJ in CML. The overactive DNA repair ability of NHEJ associated Ku70 proteins found in CML cells may highly correlated to the chromosome aberration in CML, especially to the genome instability during the disease progression.