Shigematsu N, Ihara N, Kawata T, Kawaguchi O, Takeda A, Ishibashi R, Kutsuki S, Kubo A, Kanai T, Furusawa Y, Isobe K, Uno T, Ito H
Department of Radiology, Keio University, School of Medicine, Shinjuku-ku, Tokyo 160-8582, Japan.
Int J Mol Med. 2001 May;7(5):509-13. doi: 10.3892/ijmm.7.5.509.
Carbon beam radiotherapy for cancer patients was initiated in Japan in June 1994. This study attempts to clarify the radiobiological effects of heavy ion beams. In this study, human cancer cell lines (RMG-1, MDA-MB231) and V79 cells were used. The cell killing was determined by colony forming assay, and mutation induction was determined by counting the number of 6-thioguanine resistant colonies (hprt locus mutation assay). The cell lines were irradiated with carbon (20 or 80 keV/microm) or neon beams (80 keV/microm). Carbon ions with a higher LET value (80 keV/microm) had an enhanced cytotoxic effect compared to those with a lower LET value (20 keV/microm). Carbon beams produced a slightly stronger cytotoxic effect than neon beams when irradiated at the same LET level (80 keV/microm), but the difference was not remarkable. The mutant fraction was significantly higher in all cell lines when they were irradiated with heavy ion beams, compared to the results for X-ray irradiation. The mutant fraction increased when the LET of the carbon beams increased. At equivalent LET values, the mutant fraction was lower for neon beams than for carbon beams. Fractionation of carbon beam irradiation had no effect on survival, but reduced the mutant fraction. Neon beams might be more appropriate for heavy ion therapy, especially when higher doses are being used. In addition, the fractionation of heavy ion beam administration might be appropriate for reducing the mutant fraction.
1994年6月，日本开始对癌症患者进行碳离子束放疗。本研究旨在阐明重离子束的放射生物学效应。在本研究中，使用了人类癌细胞系（RMG-1、MDA-MB231）和V79细胞。通过集落形成试验确定细胞杀伤情况，通过计数6-硫鸟嘌呤抗性集落的数量（hprt基因座突变试验）确定突变诱导情况。用碳离子束（20或80 keV/μm）或氖离子束（80 keV/μm）对细胞系进行照射。与低传能线密度值（20 keV/μm）的碳离子相比，高传能线密度值（80 keV/μm）的碳离子具有更强的细胞毒性作用。当在相同传能线密度水平（80 keV/μm）照射时，碳离子束产生的细胞毒性作用略强于氖离子束，但差异不显著。与X射线照射结果相比，当用重离子束照射时，所有细胞系中的突变率均显著更高。随着碳离子束传能线密度的增加，突变率升高。在等效传能线密度值下，氖离子束的突变率低于碳离子束。碳离子束分次照射对细胞存活无影响，但降低了突变率。氖离子束可能更适合重离子治疗，尤其是在使用更高剂量时。此外，重离子束分次给药可能适合降低突变率。
