Published in Cancer Detection and Prevention 2003; 27(3).

Comparative analysis of G2 arrest after irradiation with 75 keV carbon-ion beams and 137Cs -rays in a human lymphoblastoid cell line

Satoko Matsumura PhD a, Tatsushi Matsumura PhD b, Shuji Ozeki MSc c, Shoko Fukushima MD d, Hideya Yamazaki PhD a, Takehiro Inoue PhD a, Toshihiko Inoue PhD a, Yoshiya Furusawa PhD e and Kiyomi Eguchi-Kasai PhD e

a Division of Multidisciplinary Radiotherapy, Biomedical Research Center, Osaka University Graduate School of Medicine D10, 2-2 Yamadaoka, Suita, Osaka 5650871, Japan; b Second Department of Oral and Maxillofacial Surgery, Osaka University Graduate School of Dentistry, 1-8 Yamadaoka, Suita, Osaka, Japan; c Genome Information Research Center, Osaka University, 3-1 Yamadaoka, Suita, Osaka, Japan; d Nihon University Surugadai Hospital, 1-8-13 Kanda-Surugadai, Chiyoda-ku, Tokyo, Japan; e National Institute of Radiological Sciences, 4-9-1 Anagawa, Inage-ku 263-8555, Chiba, Japan

Heavy-ion beams are more effective than gamma-rays in causing G2 arrest. In this study, we investigated the expression of Wee1 and Cdc2 protein levels in order to analyze the G2 arrest caused by carbon-ion beam irradiation. Human lymphoblastoid TK6 cells were exposed to a 75 keV carbon-ion beam or 137Cs gamma-rays. Although the levels of Wee1 and Cdc2 protein were increased after exposure to either beam, Wee1 protein levels were influenced more by carbon-ion beam irradiation than by gamma-rays. To the contrary, Cdc2 protein levels were increased more by gamma-rays than by carbon-ion beams. These findings suggest that the G2 arrest produced by heavy-ion beams, such as the carbon-ion irradiation used in this study, might be associated with the overexpression of the Wee1 protein and of Cdc2 phosphorylation regulated by Wee1. Together, these events may act to prolong the length of G2 arrest.

KEY WORDS: 75 keV carbon-ion beams, 137Cs gamma-rays, TK6 cells, G2 arrest, Wee1, Cdc2.