23. Chromosome Breakage and Cell Lethality in Human Hepatoma Cells Irradiated with X-rays and Carbon Ion Beams

Masao Suzuki, Toru Ofuchi, Yoko Kase and Koichi Ando

Keywords: hepatoma, colony formation, chromosome damage, premature chromosome condensation, heavy

Prediction of radiosensitivity would be valuable for heavy ion radiotherapy. The premature chromosome condensation (PCC) technique is a potential predictive assay in photon radiotherapy, but it has not been investigated for hepatomas receiving heavy ions. Two human hepatoma cell lines, i.e., HLE and HLF, were irradiated with either 290 MeV/u carbon ions or 200 kVp X-rays. Cell lethality was assayed by colony formation and compared with the unrejoined fraction of chromatin breaks as measured by the PCC technique. Carbon ions at linear energy transfer (LET) of 76 keV/m produced cell death more effectively than those of 13 keV/m and X rays. Regardig the cell killing, relative biological effectivenesses (RBEs) of 13 and 76 keV/m carbon ions, compared with X-rays, were 1.10-1.24 and 2.57-2.59, respectively. Mean numbers of chromosomes in HLE and HLF cells were similar i.e., 60.48 and 60.28. RBEs for chromatin breaks of 13 and 76 keV/m carbon ions were 1.30-1.31 and 2.64-2.79 respectively. A strong correlation between unrejoined chromatin breaks and cell killing for human hepatoma cells was observed irrespective of radiation quality. We conclude that PCC is a potential predictor for the radiosensitivity of individual hepatoma that are treated with photons as well as heavy ion irradiatuon.

Publication:
Ofuchi, T., Suzuki, M., Kase, Y., Ando, K., lsono, K. and Ochiai,T. : J. Radiat. Res., 40, 125-133, 1999.