PURPOSE: To study the relative biological effectiveness-linear energy transfer (RBE-LET) relationship for micronuclei (MN) and cell inactivation, in Chinese hamster cells irradiated with low-energy protons (0.88 and 5.04 MeV, at the cell entrance surface). Chromosome loss was also investigated by means of antikinetochore CREST staining. MATERIALS AND METHODS: Cl-1 cells were exposed to different doses of X-rays, gamma-rays, 7.7 keV/microm and 27.6 keV/microm protons. The induction of MN, the distribution of MN per cell and the frequency of CREST-positive MN were evaluated in cytokinesis-blocked binucleated cells (BN cells) in the dose range 0.125-3 Gy. In parallel, cell survival experiments were carried out in samples irradiated with 0.5 to 4 Gy. RESULTS: MN yield and the frequency of BN cells carrying multiple MN (> or =2) were significantly higher after exposure to 27.6 keV/microm protons, compared with the other radiation types. In contrast, MN induction and MN distribution per BN cell were similar among 7.7 keV/microm protons, X- and gamma-rays up to 1 Gy. Cell survival experiments gave RBE values very close to those obtained with the MN assay. Both X-rays and 27.6 keV/microm protons yielded a significant proportion of CREST-positive MN at the highest doses investigated (0.75-3 Gy). CONCLUSIONS: Good correlations between MN induction and cell inactivation were observed for both low- and high-LET radiation, indicating that the MN assay can be a useful tool to predict cell sensitivity to densely ionizing radiation with implications for tumour therapy with protons.
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Antonella Sgura (2000) studied this question.
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