Selective brain tumor cell death caused by synchrotron microbeam X-ray radiation

采用共面或交叉面宽峰宽（100 μm）的微束放射治疗（MRT）对人U251胶质瘤细胞进行治疗，并与窄峰宽（20 μm）的MRT进行比较。x射线是在大型同步辐射装置SPring-8上产生的，使用了新设计的可调准直仪。宽微束和窄微束的光束中心间距分别为500 μm和100 μm，与光束宽度的比值相同，为5。窄幅MRT在峰值剂量为130 Gy时具有足够的抗肿瘤效果。宽的MRT效果较小，但在交叉平面或重复两次时，宽的MRT效果与窄的MRT效果相当。在宽MRT和窄MRT中，凋亡细胞死亡均未增加，表明直接细胞死亡不能解释肿瘤生长抑制。细胞和组织生物学的功能机制对MRT的临床目的至关重要。

Microbeam radiation therapy (MRT) with wide (100 μm) peak width in co-planar or cross planar manner was applied on human U251 glioma cells and compared with narrow (20 μm) MRT. X-ray was generated at SPring-8, a large scale shynchrotron radiation facility, and newly designed adjustable collimeter was used. Spacing distances on center of beams in wide and narrow width microbeam were 500 μm and 100 μm, setting the same ratio to beam width of five. Narrow width MRT provide sufficient antitumoral effect at the peak dose of 130 Gy. Wide MRT has less effect, but in cross-planar manner or by repeating twice, wide MRT showed comparative effect to narrow MRT. Apoptotic cell death did not increased in neither wide nor narrow MRT, indicating direct cell death did not account for tumor growth suppression. Functional mechanisms in cell and tissue biology is essential for clinical purpose of MRT.