Minton N P, Mauchline M L, Lemmon M J, Brehm J K, Fox M, Michael N P, Giaccia A, Brown J M
Department of Molecular Microbiology, Centre for Applied Microbiology and Research, Porton Down, Salisbury, Wiltshire, UK.
FEMS Microbiol Rev. 1995 Oct;17(3):357-64. doi: 10.1111/j.1574-6976.1995.tb00219.x.
The toxicity associated with conventional cancer chemotherapy is primarily due to a lack of specificity for tumour cells. In contrast, intravenously injected clostridial spores exhibit a remarkable specificity for tumours. This is because, following their administration, clostridial spores become exclusively localised to, and germinate in, the hypoxic/necrotic tissue of tumours. This unique property could be exploited to deliver therapeutic agents to tumours. In particular, genetic engineering could be used to endow a suitable clostridial host with the capacity to produce an enzyme within the tumour which can metabolise a systemically introduced, non-toxic prodrug into a toxic metabolite. The feasibility of this strategy (clostridial-directed enzyme prodrug therapy, CDEPT) has been demonstrated by cloning the Escherichia coli B gene encoding nitroreductase (an enzyme which converts the prodrug CB1954 to a highly toxic bifunctional alkylating agent) into a clostridial expression vector and introducing the resultant plasmid into Clostridium beijerinckii (formerly C. acetobutylicum) NCIMB 8052. The gene was efficiently expressed, with recombinant nitroreductase representing 8% of the cell soluble protein. Following the intravenous injection of the recombinant spores into mice, tumour lysates have been shown, by Western blots, to contain the E. coli-derived enzyme.
传统癌症化疗所伴随的毒性主要是由于对肿瘤细胞缺乏特异性。相比之下，静脉注射的梭菌孢子对肿瘤表现出显著的特异性。这是因为，在给药后，梭菌孢子仅定位于肿瘤的缺氧/坏死组织并在其中萌发。这种独特的特性可被利用来将治疗剂递送至肿瘤。特别是，基因工程可用于赋予合适的梭菌宿主在肿瘤内产生一种酶的能力，该酶可将全身引入的无毒前药代谢为有毒代谢物。通过将编码硝基还原酶（一种将前药CB1954转化为高毒性双功能烷基化剂的酶）的大肠杆菌B基因克隆到梭菌表达载体中，并将所得质粒导入拜氏梭菌（以前称为丙酮丁醇梭菌）NCIMB 8052，已证明了该策略（梭菌导向酶前药疗法，CDEPT）的可行性。该基因得到有效表达，重组硝基还原酶占细胞可溶性蛋白的8%。将重组孢子静脉注射到小鼠体内后，通过蛋白质印迹法显示肿瘤裂解物中含有源自大肠杆菌的酶。
