凋亡(apoptosis)来源于希腊语,意为叶子从树上凋落,强调其正常生理属性及程序性,故也称为程序性细胞死亡(PCD).1972年Kerr等首先描述凋亡是一个发生于正常组织器官发育分化和维持稳态过程中以及某些毒性因素作用后的细胞死亡过程.现在已发现凋亡在机体生理病理及免疫方面都具有重要意义,并已成为当前研究肿瘤发生发展及防治的重要课题.本文就凋亡及其在肿瘤放射治疗领域中的研究现状予以综述.1 凋亡的特征及其分子生物学进展凋亡的形态表现是一个动态过程.首先核染色质浓聚于核膜周边,同时细胞皱缩,密度增加,然后核逐渐碎块化,膜系统出泡,最后形成膜包绕残存核碎片的凋亡小体.凋亡不同于坏死,坏死常成簇发生,细胞肿胀、崩解,而凋亡发生于单个细胞,凋亡后演变为有膜包统的凋亡小体,并被邻近细胞所吞噬,溶酶体酶未释放,无炎症反应凋亡的生化特点表现为一系列酶的激活,酶激活的机制目前尚未完全明了.这些酶活化后最终作用于细胞膜系统、细胞骨架、核基质、核DNA,特别是活化的核酸内切酶特异地在核小体间切断DNA链,形成由多个核小体组成的DNA片段(180～240bp Apoptosis originates from the Greek language, meaning that the leaf is shed from the tree, emphasizing its normal physiological properties and procedural nature. It is also called programmed cell death (PCD). In 1972, Kerr et al. first described that apoptosis is an occurrence of The process of cell death in the process of development and differentiation of normal tissues and the maintenance of homeostasis and some toxic factors. It has now been found that apoptosis is of great importance in the physiological and pathological and immune aspects of the body, and has become the current research on tumor development and The important topic of prevention and treatment. This article reviews the research progress of apoptosis and its application in the field of radiotherapy of tumors. 1. The characteristics of apoptosis and the progress of its molecular biology The morphological manifestation of apoptosis is a dynamic process. The first is nuclear chromatin condensation. At the periphery of the nuclear membrane, the cells shrink and the density increases, then the nuclei gradually fragment, the membrane system is bubbling, and finally apoptotic bodies are formed that surround the residual nuclear fragments. Apoptosis is different from necrosis, and necrosis often occurs in clusters. The cell swells and disintegrates, and apoptosis occurs in a single cell. After apoptosis, it evolves into apoptotic bodies with membranes and is phagocytized by neighboring cells. Lysosomal enzymes are not released. No inflammatory reaction. Students The characteristics of a series of enzyme activation, the mechanism of enzyme activation is not yet fully understood. After activation, these enzymes eventually act on the cell membrane system, cytoskeleton, nuclear matrix, nuclear DNA, and in particular activated endonucleases specifically in the nuclear Cut DNA strands between bodies to form DNA fragments consisting of multiple nucleosomes (180 to 240 bp