SUICIDEAND IMMUNE GENE THERAPY USING TUMOR SPECIFIC PROMOTOR FOR BREAST CANCER

自杀基因或免疫基因在肿瘤细胞中的选择性表达可能会对肿瘤产生优先的细胞毒性作用，并为癌症治疗提供有用的策略。由于基因扩增和/或转录升高，c-erbB-2和midkine基因在人类乳腺癌中经常过度表达。因此，我们研究了c-erbB-2启动子区域和midkine基因在乳腺癌细胞中优先表达自杀基因的可能性。目前使用c-erbB-2启动子区域缺失突变体的报告基因检测表明，251-bp（转录起始位点-213/+38）而不是125-hp片段（-87/+38）在乳腺癌细胞中比SV40直接早期启动子更能指导相关荧光素酶基因的转录。midkine基因的1.0 kb启动子区域也可以激活人乳腺癌细胞中融合的报告基因和自杀基因的转录。相比之下，在非乳腺癌细胞和正常成纤维细胞中，251-bp片段介导的pro…More mother活性低于SV40启动子的活性。因此，126-bp片段（-213/-87）包含一个负责乳腺癌细胞中优先转录活性的精确元件。电泳迁移率转移试验表明，一个可能的修饰转录因子参与肿瘤特异性。与含有251 bp启动子（p256-TK）的单纯疱疹病毒胸苷激酶基因的质粒DNA进行交易，导致乳腺癌细胞对更昔洛韦（GCV）的敏感性增加，而非乳腺癌细胞对更昔洛韦（GCV）的敏感性增加。将GCV注入转染p256-TK DNA的人乳腺肿瘤裸鼠体内，可抑制移植肿瘤的生长。这些结果表明，传递与这些1.0 kb midkine或251 bp c-erbB-2启动子相关的自杀基因可能是一种可行的乳腺癌特异性治疗策略。少

A selective expression of suicide or immune gene(s) in tumor cells should produce a preferential cytotoxic effect on tumors and a useful strategy for cancer treatment. The c-erbB-2 and midkine gene are frequently overexpressed in human breast cancers as a result of gene amplification and/or elevated transcription. We therefore examined a possible usage of promoter regions of the c-erbB-2 and midkine gene to express a suicide gene preferentially in breast cancer cells. The present reporter gene assays using deletion mutants of the c-erbB-2 promoter region demonstrated that the 251-bp (-213/+38 from the transcriplional start site) but not the 125-hp fragment (-87/+38) could direct transcription of the linked luciferase gene better than the SV40 immediate early promoter in breast cancer cells. Also the 1.0 kb promoter region of the midkine gene could activate transcription of a fused reporter gene and suicide gene in human breast cancer cells. In contrast, the 251-bp fragment-mediated pro … More moter activity in nonbreast cancer cells and in normal fibroblasts was lower than the activity by the SV40 promoter. The 126-bp fragment (-213/-87) thereby contains a exacting element(s) which is responsible for the preferential transcriptional activity in breast cancer cells. An electrophoretic mobility shift assay suggested that a possible modification of a transcriptional factor was involved in the tumor specificity. Transaction with the plasmid DNA containing the herpes simplex virus-thymidine kinase gene linked with the 251-bp promoter (p256-TK) resulted in increased sensitivity to ganciclovir (GCV) in breast cancer but not in nonbreast cancer cells. Administration of GCV into nude mice bearing human breast tumors that were transfecled with the p256-TK DNA suppressed subsequent growth of the transplanted tumors. These results suggest that delivery of a suicide gene linked with the these 1.0 kb midkine or 251 bp c-erbB-2 promoter can be a feasible therapeutic strategy specific to breast cancer. Less