Published in Cancer Detection and Prevention 2000; 24(Supplement 1).

Analysis of DNA repair kinetics and chromosome aberration following ionizing radiation exposure using drug induced premature chromosome condensation

E Gotoh MD PhD 1, K Takakura PhD 2, M Durante PhD

1 Div Genetic Resources, National Institute of Infectious Diseases, Tokyo, Japan, 2 Dept Physics, International Christian University, Tokyo, Japan, 3 Dept Physics, University 'Federico II', Naples, Italy,

AIMS: Cytogenetic study has been widely used in oncologic study. However, it is also well known that the conventional colcemid method often fails to obtain mitotic chromosomes. Premature chromosome condensation (PCC) is possible overcoming way, but the conventional fusion PCC technique is technically demanding and the efficiency is often very low. Calyculin A is an new inducer of PCC with high efficiency. In order to analyze the DNA repair kinetics and chromosome aberration formation after ionizing irradiation, we used this new technique of drug induced premature chromosome condensation. METHODS: Human cells were irradiated with gamma-rays or heavy ion particles and chromosomes were then prematurely condensed using calyculin A. The number of chromatid breaks and exchanges were scored, and the repair kinetics were analyzed. RESULTS: Calyculin A effectively induced premature chromosome condensation even in cells immediately after irradiation. Kinetics of rejoining of chromatid breaks, in general, consisted of two component with rapid and slow phase, however differ from each other in different ionizing sources. The different formation of chromosome aberration was also seemed to dependent on the types of irradiation. CONCLUSION: Chemically induced premature chromosome condensation technique allows a simple, rapid and precise analysis of chromosome aberration and DNA repair kinetics. This technique seems to be useful for study the biological effect of ionizing irradiation, particularly for radiation cancer therapy.

KEY WORDS: mitosis, premature chromosome condensation (PCC), calyculin A, cytogenetics, DNA damages.

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Paper presented at the International Symposium on Impact of Biotechnology on Cancer Diagnostic & Prognostic Indicators; Geneva, Switzerland; October 28 - 31, 2000; in the section on genetic risk assessment.