Enhancement of chromosomal aberrations in tumor cells with a non-labeled Cu-PTSM and irradiation with Cu K-shell monochromatic X rays.

This study aims to clarify the enhancement effect on chromosomal aberrations via selective energy absorption by Cu atoms in cultured bone cancer cells with non-labelled Cu-pyruvaldehyde-bis(N(4)-methylsemicarbazone) (Cu-PTSM) and monochromatic X rays. The X rays having the energy of the Cu K-shell absorption edge arising from synchrotron radiation (KEK-PF) was used as radiation source. Cu-PTSM labelled with copper radionuclides has been developed for medical imaging using positron emission tomography (PET). Evidence clearly showed that the absorption of X rays in the Cu K-shell caused this enhancement. After cells were treated with 1000 nM Cu-PTSM, the enhancement ratio of the initial yield of isochromatid breaks caused by CuK-H X-ray irradiation to that by 200 kV(p) X rays was approximately 2.8. About 5.6 times of the remaining isochromatid breaks were observed at 4 h in Cu-PTSM treated samples irradiated with CuK-H X rays comparing to that with 200 kV(p) X rays. In this study, uniqueness in physical property such as Cu atom K-shell ionisation was applied for the enhancement of biological effects in cancer cells.