Effects of carbon-ion beam or X-ray irradiation on anti-apoptosis ΔNp73 expression in HeLa cells

Delta Np73 has emerged as an interesting novel factor in cancer research. Here, we report the effect of carbon-ion beams on Delta Np73 expression in human cervix carcinoma HeLa cells in contrast to the effect of X-rays. Cellular sensitivities were determined by colony formation. Radiation-induced cell cycle arrest was investigated with flow cytometry. Additionally, radiation-induced apoptosis was analyzed with flow cytometry and Hoechst staining. Furthermore, Delta Np73 expression was examined by semi-quantitative reverse transcription-PCR (semi-quantitative RT-PCR) as well as by Western blot analysis. Following irradiation, stronger G2/M phase arrest, more significant increase in apoptosis and more pronounced Delta Np73 degradation were observed after exposure to high-LET carbon beams in comparison with X-rays at 4 Gy doses. These observations indicate that there is a differential Delta Np73 expression in response to different LET radiations, and down-regulated Delta Np73 expression might play a critical role in promoting cycle arrest and apoptosis in cancer cells. This study highlights the potential of Delta Np73 in radiotherapy. (C) 2012 Elsevier B.V. All rights reserved.