肿瘤乏氧靶向性基因治疗增强放射治疗的实验研究

乏氧是实体肿瘤组织微环境中的一个重要现象，乏氧肿瘤细胞对放射治疗、化学治疗的耐受性增强，乏氧肿瘤细胞的存在是恶性肿瘤患治疗失败、复发和转移的重要原因之一。乏氧细胞的基因表达与正常细胞有着很大的差异，然而，这些差异使针对肿瘤乏氧细胞的靶向性治疗成为可能。本研究利用乏氧细胞自身的特点，构建乏氧依赖性表达的腺病毒载体，借助该载体引导自杀基因BCD(细菌胞苷脱氨酶，

Adenovirus-mediated gene therapy targeting tumor hypoxia

The work is to construct a hypoxia-activated adenovirus vector expressing suicide gene BCD and to evaluate anti-tumor effects of the hypoxia-targeted suicide gene therapy system with or without combination radiotherapy. The recombinant adenovirus Ad-5HRE/hCMVmp-BCD was generated by the COS-TPC methods. Hela cells were treated with Ad-5HRE/hCMVmp-BCD infection, followed by incubated with 5FC-containing medium un- der the aerobic conditions or hypoxic conditions for 24h. Cell growth inhibition was determined by MTS assay. Tumor xenografts were established by injecting Hela cells s.c into the right leg ofnu/nu BALB/c mice. The tu- mor-bearing mice were given Ad-5HRE/hCMVmp-BCD- mediated gene therapy or combination therapy with radiotherapy. Western blot analysis clearly indicated that significant hypoxia-induced expression of BCD protein after Hela cells were infected with Ad-5HRE/hCMVmp-BCD. The actual amounts and the ratio of the BCD ex- pression under aerobic and hypoxic conditions were increased with increasing MOI. MTS assay results indicated that hypoxia-induced sensitization to 5FC. Under the hypoxic incubation the IC50 is 20 folds lower than that of the aerobic condition. The increased cytotoxicity at each MOI of Ad-5HRE/hCMVmp-BCD infection with increasing 5FC concentration was also observed. Tumor growth delay assay results showed that with single radiation or frac- tionated radiation, the Ad-5HRE/hCMVmp-BCD+5FC +radiation group produced the longest times to tumor re- growth and average tumor doubling compared with the various control treatment groups. In vitro and in vivo studies demonstrated the combination of Ad-5HRE/hCMVmp-BCD and prodrug 5-FC can obviously inhibit the growth of Hela cells. Using the mouse xenografts model, we demonstrated the Ad-5HRE/hCMVmp-BCD and 5-FC can enhance the antitumor effects of conventional radiation therapy.