Low Amount Expression of Ku 70 Protein Related to Radiation-induced Chromosome Instability and Radiosensitivity in Normal Lymphocytes, and Leukemia and Lymphoma Cell Lines

摘要

Previous our experiment showed that B-lymphoid cell lines established from α ray- and γ-ray irradiated lymphocytes had higher chromosome instabilities through many passages than that from non-irradiated lymphocytes. Present protein study revealed that these B-cell lines had low amount of Ku 70 protein expression before and after second irradiation, longer localization of Ku 70 protein in nucleus, longer period of cell cycle delay at G1 or G2 phases and high activity of DNA-PK. The first αray- or γ-ray irradiation had an effect of persisting impaired DNA repair system in cells, which resulted in a decreased repair capacity after the second irradiation. Leukemia and lymphoma cell lines also showed similar characteristics after irradiation to those of the B-cell lines having high chromosome instability. These similarities are suggesting that characteristics on abnormal Ku 70 protein might persist long term and might be related to initiating leukemogenesis and lymphomagenesis as well as that such an ability of DNA repair protein might apply to prediction of radiosensitivity of leukemia or lymphoma cells.