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(N4- methyl-semicarbazone) (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 iso-chromatid breaks caused by CuK-H X-ray irradiation to that by 200 kVp X-rays was ∼2.8. About 5.6 times of the remaining iso-chromatid breaks were observed at 4 h in Cu-PTSM treated samples irradiated with CuK-H X-rays comparing to that with 200 kVp 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. (authors)