Okada S, Ono K, Hamada N, Inada T, Kubota N
Department of Radiological Sciences, Ibaraki Prefectural University of Health Sciences, Ami-machi, Ibaraki, Japan.
Int J Radiat Oncol Biol Phys. 2001 Mar 15;49(4):1149-56. doi: 10.1016/s0360-3016(00)01429-2.
The radiosensitizing effect of wortmannin on human tumor cells in a low-pH microenvironment was compared with that in a neutral-pH environment.
A172 human glioblastoma cells, A549 human lung adenocarcinoma cells, and HMV-1 human melanoma cells were treated with 20 microM wortmannin 2 h before irradiation, and cell survival was examined. A low-pH microenvironment was simulated by exposing cells to low-pH culture medium for 24 h before wortmannin treatment. The effects of wortmannin on the repair of DNA double-strand breaks (dsbs) after 50-Gy irradiation in both low- and neutral-pH conditions were measured by pulsed-field gel electrophoresis. Expression of the catalytic subunit of DNA-dependent protein kinase (DNA-PKcs) in low-pH conditions was also compared with that in neutral-pH conditions by Western blot analysis.
The radiosensitizing effect of wortmannin was greater in low-pH cultures than in neutral-pH cultures for all cell lines. The fast-rejoining component of DNA dsb repair was inhibited more strongly in low-pH than in neutral-pH conditions, although there was little difference in DNA-PKcs expression between groups.
The low-pH culture condition, which was designed to mimic the microenvironment of the central tumor mass in actively proliferating solid tumors, enhanced the radiosensitizing effect of wortmannin by inhibiting the fast-rejoining component of DNA dsb repair and by prolonging the retention of nonrejoined DNA dsbs.
比较渥曼青霉素在低pH微环境和中性pH环境中对人肿瘤细胞的放射增敏作用。
在照射前2小时，用20微摩尔渥曼青霉素处理A172人胶质母细胞瘤细胞、A549人肺腺癌细胞和HMV-1人黑色素瘤细胞，然后检测细胞存活率。在渥曼青霉素处理前，通过将细胞暴露于低pH培养基24小时来模拟低pH微环境。通过脉冲场凝胶电泳测量渥曼青霉素在低pH和中性pH条件下对50戈瑞照射后DNA双链断裂（dsb）修复的影响。还通过蛋白质印迹分析比较了低pH条件和中性pH条件下DNA依赖性蛋白激酶催化亚基（DNA-PKcs）的表达。
对于所有细胞系，渥曼青霉素在低pH培养中的放射增敏作用比在中性pH培养中更强。尽管各组之间DNA-PKcs表达差异不大，但低pH条件下DNA dsb修复的快速重新连接成分比中性pH条件下受到更强的抑制。
旨在模拟活跃增殖实体瘤中央肿瘤块微环境的低pH培养条件，通过抑制DNA dsb修复的快速重新连接成分和延长未重新连接的DNA dsb的保留时间，增强了渥曼青霉素的放射增敏作用。
