Matzow Torkjel, Cowen Rachel L, Williams Kaye J, Telfer Brian A, Flint Pamela J, Southgate Thomas D, Saunders Mark P
Paterson Institute for Cancer Research, Christie Hospital NHS Trust, and School of Pharmacy and Pharmaceutical Sciences, University of Manchester, UK.
J Gene Med. 2007 Apr;9(4):244-52. doi: 10.1002/jgm.1016.
The induced expression of carboxylesterase (CE) enzymes, which convert the prodrug irinotecan (CPT-11) into its active cytotoxic metabolite SN-38, constitutes a promising strategy for cancer gene therapy. By incorporating hypoxia-responsive elements (HREs) in conjunction with the transgene, expression can be targeted specifically to hypoxic tissues (such as solid tumours), expressing the hypoxia-inducible factor 1 (HIF-1). We have constructed a recombinant adenoviral vector, AdHRE-rCE, encoding the cDNA for the highly efficient rabbit liver CE (rCE), under the control of a HRE derived from the human phosphoglycerate kinase 1 (PGK-1) gene in conjunction with a minimal SV40 promoter. In vitro, HT1080 fibrosarcoma and SW480 colon carcinoma cells demonstrated an approximately 10-fold hypoxia-dependent induction in CE expression following pre-infection with AdHRE-rCE, which led to a15-30-fold increased sensitivity to CPT-11. Furthermore, in vivo, SW480 tumour xenografts infected with AdHRE-rCE demonstrated a 2-fold decrease in tumour doubling time, when combined with 7 days of CPT-11 treatment, in comparison to mock-infected controls, with rCE expression shown to be limited to hypoxic regions only. As the cytotoxicity of CPT-11 is reduced under hypoxic conditions, over-expression of a highly efficient CE such as rCE under hypoxia control within these hypoxic cells could reverse this effect and, therefore, form the basis for future clinical treatment strategies.
羧酸酯酶（CE）可将前药伊立替康（CPT-11）转化为其具有细胞毒性的活性代谢产物SN-38，诱导该酶的表达是一种很有前景的癌症基因治疗策略。通过将缺氧反应元件（HRE）与转基因相结合，可使表达特异性靶向低氧组织（如实体瘤），这些组织中表达缺氧诱导因子1（HIF-1）。我们构建了一种重组腺病毒载体AdHRE-rCE，其编码高效兔肝CE（rCE）的cDNA，该cDNA在源自人磷酸甘油酸激酶1（PGK-1）基因的HRE与最小SV40启动子的控制下。在体外，HT1080纤维肉瘤细胞和SW480结肠癌细胞在预先感染AdHRE-rCE后，CE表达显示出约10倍的缺氧依赖性诱导，这导致对CPT-11的敏感性增加了15至30倍。此外，在体内与模拟感染的对照组相比，用AdHRE-rCE感染的SW480肿瘤异种移植瘤在联合7天CPT-11治疗时，肿瘤倍增时间缩短了2倍，rCE表达显示仅局限于缺氧区域。由于在缺氧条件下CPT-11的细胞毒性降低，在这些缺氧细胞中缺氧控制下高效CE（如rCE）的过表达可以逆转这种效应，因此可构成未来临床治疗策略的基础。
