Abstract
In order to understand the LET and nuclide dependency in DNA DSB repair process of cells irradiated with high LET heavy ion particles, we have studied the biological effect in human cells exposed to various heavy ions with different LET values.
We examined cell survival and DNA double strand break (DSB)/chromosome break repair in human cells irradiated with high LET radiation. Normal human fibroblast (HFLIII) and NHEJ deficient cells (180BR) were irradiation with carbon ion (LET; 200keV/micro m), neon ion (LET; 70keV/micro m or 200keV/micro m), and silicon ion (LET; 70keV/micro m or 200keV/micro m) radiation. After 0, 2, 6, 24 hours, the DSB repair process was monitored by the G1-type premature chromosome condensation (PCC) technique. The cell survival assay was also performed with the identical radiation sources.
The repair process of cells irradiated with neon ion (400MeV/u, LET; about 70keV/micro m) and silicon ion (490MeV/u, LET; about 70keV/micro m) were slower than that with x-ray and carbon ions (290MeV/u, LET; about 70keV/micro m). We have observed a higher number of remaining excess chromosome fragments by high LET (200keV/micro m) radiation than that by low LET (70keV/micro m) radiation. These data correlated well with the cell survival data. Upon exposure to the same radiation sources, the PCC rejoining process was significantly slower in 180BR cells than in normal cells, resulting in an excess remaining chromosome fragments in the sensitive cells.
