Micronuclei, CREST-positive micronuclei and cell inactivation induced in Chinese hamster cells by radiation with different quality.
OBJECTIVE
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.


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.
Sgura
A
A
Dipartimento di Biologia, Università Roma Tre, Rome, Italy. Tanzarel@bio.uniroma3.it
Antoccia
A
A
Cherubini
R
R
Dalla Vecchia
M
M
Tiveron
P
P
Degrassi
F
F
Tanzarella
C
C
D000818:Animals; D000906:Antibodies / Q000378:metabolism; D002460:Cell Line; D002467:Cell Nucleus / Q000528:radiation effects*; D002470:Cell Survival / Q000528:radiation effects; D006224:Cricetinae; D003412:Cricetulus; D004307:Dose-Response Relationship, Radiation; D005720:Gamma Rays; D018386:Kinetochores / Q000276:immunology / Q000528:radiation effects*; D018499:Linear Energy Transfer; D008168:Lung / Q000166:cytology / Q000528:radiation effects*; D008297:Male; D048629:Micronuclei, Chromosome-Defective / Q000378:metabolism*; D015162:Micronucleus Tests; D011522:Protons; D012062:Relative Biological Effectiveness; D014965:X-Rays
D000906:Antibodies; D011522:Protons