肿瘤的基因治疗可以用一句话概括为:将核苷酸转移到靶细胞中以扰乱或纠正某些病理生理过程.基因转导大致可分二大类:体外和体内基因治疗.体外基因治疗是基因在离休(ex vivo)情况下被转移或转导到靶细胞中后再放回到动物或人体中.体内基因治疗是基因在体内直接被转导到靶细胞中.要完成这一任务,牵扯到两个相互独立而又有关联的因素,即治疗性的核苷酸或基因和运载系统.基因的作用机制、大小、表达的稳定性、预期的效果等均是重要选择因素.第二个因素决定了能否把一个治疗性的基因有效地运载到靶细胞并进行表达.运载系统也叫载体(Vector),是一个微基因盒(Minigene cassette),由一段能启动靶基因或转基因转录的核苷酸或叫启动子的成份和一个聚腺苷酸化信号(Polyadenylation signal)组成.后者能稳定转录了的mRNA.这个微基因盒通常位于一大段核苷酸的主链骨架里.这一骨架的序列可以简单到象在噬菌体里的一样,因此可使载体在体外随细菌而增殖.也可复杂到象大DNA病毒一样.此外,这个微基因盒通常由其他一些大分子 Gene therapy for tumors can be summarized in one sentence: transfer of nucleotides to target cells to disrupt or correct certain pathophysiological processes. Gene transduction can be broadly divided into two major categories: in vitro and in vivo gene therapy. In vitro gene therapy is Genes are transferred or transduced into target cells in ex vivo conditions and then returned to animals or humans. In vivo gene therapy is the direct transduction of genes into target cells in vivo. To accomplish this task, Two independent and related factors are involved, therapeutic nucleotides or genes and delivery systems. The mechanisms of action, size, stability of expression, and expected effects of genes are all important selection factors. These factors determine whether or not a therapeutic gene can be efficiently delivered to a target cell and expressed. The delivery system, also called Vector, is a Minigene cassette, which is capable of initiating transcription of a target gene or transgene. The nucleotide or promoter is composed of a polyadenylation signal. The latter stabilizes the transcribed mRNA. The minigene cassette is usually located in the backbone of a large stretch of nucleotides. In the framework, the sequence of this skeleton can be as simple as in the phage, so that the vector can be propagated in vitro with bacteria. It can also be complicated to be like a large DNA virus. In addition, this microgene cassette is usually composed of other large molecular