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

Heavy-ion beams are more effective than γ-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 γ-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 γ-rays. To the contrary, Cdc2 protein levels were increased more by γ-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.