High linear energy transfer carbon radiation effectively kills cultured glioma cells with either mutant or wild-type p53

Abstract

Purpose: A mutation in the p53 gene is believed to play an important role in the radioresistance of many cancer cell lines. We studied cytotoxic effects of high linear energy transfer (LET) carbon beams on glioma cell lines with either mutant or wild-type p53. Methods and Materials: Cell lines U-87 and U-138 expressing wild-type p53 and U-251 and U-373 expressing mutant p53 were used. These cells were irradiated with 290 MeV/u carbon beams generated by the Heavy Ion Medical Accelerator in the National Institute of Radiologic Science or X-rays. A standard colony-forming assay and flow cytometric detection of apoptosis were performed. Cell cycle progression and the expression of p53, p21, and bax proteins were examined. Results: High LET carbon radiation was more cytotoxic than low LET X-ray treatment against glioma cells. The effects of the carbon beams were not dependent on the p53 gene status but were reduced by G 1 arrest, which was independent of p21 expression. The expression of bax remained unchanged in all four cell lines. Conclusion: These results indicate that high LET charged particle radiation can induce cell death in glioma cells more effectively than X-rays and that cell death other than p53-dependent apoptosis may participate in the cytotoxicity of heavy charged particles. Thus, it might prove to be an effective alternative radiotherapy for patients with gliomas harboring mutated p53 gene.