Li Binghua, Fan Junkai, Liu Xinran, Qi Rong, Bo Linan, Gu Jinfa, Qian Cheng, Liu Xinyuan
Institute of Biochemistry and Cell Biology, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, 320 Yueyang Road, Shanghai 200031, China.
J Mol Med (Berl). 2006 Dec;84(12):1077-86. doi: 10.1007/s00109-006-0106-9. Epub 2006 Nov 1.
A major goal in cancer gene therapy is to develop efficient gene transfer protocols that allow tissue-specific and tightly regulated expression of therapeutic genes. The ideal vector should efficiently transduce cancer cells with minimal toxicity on normal tissues and persistently express foreign genes. One of the most promising regulatory systems is the mifepristone/RU486-regulated system, which has much lower basal transcriptional activity and high inducibility. In this work, we modified this system by incorporating a cancer-specific promoter, the human telomerase reverse transcriptase (hTERT) promoter. By utilizing hTERT promoter to control the regulator, RU486 could specifically induce the expression of foreign genes in cancer cells but not in normal cells. In the context of this system, a dominant negative mutant of survivin (surDN) was controllably expressed in colorectal tumor cells. The surDN expression induced by RU486 showed a dosage- and time-dependent pattern. Regulated expression of surDN caused caspase-dependent apoptosis in colorectal tumor cells but had little effect on normal cells. Analysis of cell viability showed that RU486-induced expression of surDN suppressed colorectal tumor cell growth and had synergic effect in combination with chemotherapeutic agents. The potential of this system in cancer therapy was evaluated in experimental animals. Tumor xenograft models were established in nude mice with colorectal tumor cells, and RU486 was intraperitoneally administered. The results showed that conditional expression of surDN efficiently inhibited tumor growth in vivo and prolonged the life of tumor-burdened mice. Synergized with the chemotherapeutic drug cisplatin, regulated surDN expression completely suppressed tumor growth. These results indicated that this modified RU486-regulated system could be useful in cancer-targeting therapy.
癌症基因治疗的一个主要目标是开发高效的基因转移方案，使治疗性基因能够在组织特异性且严格调控的状态下表达。理想的载体应能高效转导癌细胞，同时对正常组织的毒性最小，并能持续表达外源基因。最有前景的调控系统之一是米非司酮/ RU486调控系统，其基础转录活性低且诱导性高。在这项研究中，我们通过整合一个癌症特异性启动子——人端粒酶逆转录酶（hTERT）启动子，对该系统进行了改良。通过利用hTERT启动子来控制调控因子，RU486能够特异性地诱导癌细胞而非正常细胞中外源基因的表达。在这个系统中，survivin的显性负性突变体（surDN）在结直肠肿瘤细胞中受到可控表达。RU486诱导的surDN表达呈现出剂量和时间依赖性模式。surDN的调控表达在结直肠肿瘤细胞中引发了依赖半胱天冬酶的凋亡，但对正常细胞影响很小。细胞活力分析表明，RU486诱导的surDN表达抑制了结直肠肿瘤细胞的生长，并与化疗药物具有协同作用。在实验动物中评估了该系统在癌症治疗中的潜力。用结直肠肿瘤细胞在裸鼠中建立肿瘤异种移植模型，并腹腔注射RU486。结果表明，surDN的条件性表达在体内有效抑制了肿瘤生长，并延长了荷瘤小鼠的生存期。与化疗药物顺铂协同作用时，调控的surDN表达完全抑制了肿瘤生长。这些结果表明，这种改良的RU486调控系统可用于癌症靶向治疗。
