Matthews J H, Meeker B E, Chapman J D
Department of Radiation Oncology, Cross Cancer Institute, Edmonton, Alberta, Canada.
Int J Radiat Oncol Biol Phys. 1989 Jan;16(1):133-8. doi: 10.1016/0360-3016(89)90020-5.
The surviving fraction of human tumor cell lines after 2 Gy (SF2) varies between 0.1 and 0.8. It has been postulated that differences in inherent radiosensitivity of tumor cells are a major determinant of radiation response in vivo. Assays of inherent radiosensitivity based on acute survival are being developed as predictors of tumor response which often assume that the same inherent radiosensitivity persists throughout a fractionated treatment. We have investigated the response of 2 human tumor cell lines (A549 and MCF7) with different inherent radiosensitivities to in vitro fractionated irradiation. A549 cells had an SF2 of 0.62 and a mean inactivation dose (D) of 3.07 Gy whereas MCF7 cells had an SF2 of 0.30 and a D of 1.52 Gy. Split dose repair capacity (at equal survival levels) was less for A549 than for MCF7 cells and recovery kinetics for both cell lines were substantially longer than those of rodent cell lines. Survival after 5 fractions of 2 Gy given 12 hr apart at 37 degrees C was near to that predicted from the acute survival curve, assuming complete repair and no proliferation. Acute survival of A549 cells which survived 5 fractions of 2 Gy given 12 hr apart was similar to the acute survival of unirradiated cells. When A549 cells were incubated at 22 degrees C between 5 fractions of 2 Gy given 12 hr apart, proliferation and split dose repair were substantially inhibited. These studies support the proposals to use in vitro inherent radiosensitivity assays for the prediction of in vivo response of tumors to fractionated treatment.
2戈瑞（Gy）照射后人类肿瘤细胞系的存活分数（SF2）在0.1至0.8之间变化。据推测，肿瘤细胞固有放射敏感性的差异是体内放射反应的主要决定因素。基于急性存活情况的固有放射敏感性检测方法正在被开发，作为肿瘤反应的预测指标，这些方法通常假定在分次治疗过程中相同的固有放射敏感性持续存在。我们研究了两种具有不同固有放射敏感性的人类肿瘤细胞系（A549和MCF7）对体外分次照射的反应。A549细胞的SF2为0.62，平均失活剂量（D）为3.07 Gy，而MCF7细胞的SF2为0.30，D为1.52 Gy。A549细胞在相同存活水平下的分次剂量修复能力低于MCF7细胞，并且两种细胞系的恢复动力学都比啮齿动物细胞系长得多。在37摄氏度下每隔12小时给予5次2 Gy照射后的存活情况接近根据急性存活曲线预测的结果，假定完全修复且无增殖。在每隔12小时给予5次2 Gy照射后存活下来的A549细胞的急性存活情况与未照射细胞的急性存活情况相似。当A549细胞在每隔12小时给予5次2 Gy照射期间于22摄氏度下培养时，增殖和分次剂量修复受到显著抑制。这些研究支持了使用体外固有放射敏感性检测来预测肿瘤对分次治疗的体内反应的提议。
