Gene therapy specific for lung cancer using cell-type specific promoter

(1)产生CEA的肺癌的特异性基因治疗不能通过瘤内注射重组腺病毒载体(Ad.)在CEA启动子(Ad.CEA-TK)下表达HSV-tk基因，然后用更昔洛韦(GCV)体内治疗。可以想象，CPA启动子的低活性导致HSV-tk基因在癌细胞中表达不足，并且没有显著的抗肿瘤作用。为了获得HSV-tk基因仅在肿瘤细胞中的增强表达和随后显著的体内抗肿瘤作用，我们将Cre/loxP系统应用于HSV-tk/GCV治疗CEA肿瘤。我们构建了由CEA启动子驱动的Cre重组酶(Ad.CEA-Cre)和Cre可诱导表达HSV-tk基因的Ad(Ad.CAG-loxP-TK)。与单独感染Ad.CEA-TK相比，这两种重组腺病毒共同感染使产生CEA的人癌细胞对GCV的敏感性提高了8.4倍。在…上瘤内注射Ad.CEA-Cre联合Ad.CAG-loxP-TK，再用GCV治疗，7只裸鼠中有6只能完全根除皮下CEA生成肿瘤。而单独注射Ad.CEA-TK和GCV注射最多只能延缓接种肿瘤的生长。这些结果表明，Cre/loxP系统应用于传统的细胞类型特异性抗癌基因治疗具有明显的优势。我们正在评估该系统在小鼠腹膜癌腹膜炎模型中的疗效和副作用，以模拟未来临床应用于人类的肺癌胸膜炎。(2)Myc高表达小细胞肺癌的特异性基因治疗(Myc-SCLC)我们首次报道了一种Ad。将HSV-tk基因与Myc结合基序连接(Ad.Myc-TK)后，在Myc-SCLC细胞系中显示了HSV-tk基因的细胞型特异性表达。我们分析了在裸鼠腹膜腔内注射Ad.Myc-TK和GCV治疗的效果。较少

(1) Gene therapy specific for CEA-producing lung cancerRejection of CEA-producing tumors was not observed by intra-tumoral injection with a recombinant adenoviral vector (Ad.) expressing the HSV-tk gene under the CEA promoter (Ad.CEA-TK) followed by ganciclovir (GCV) treatment in vivo.It is conceivable that the low activity of the CPA promoter results in insufficient expression of the HSV-tk gene in cancer cells as well as in insignificant antitumor effects.To obtain enhanced expression of the HSV-tk gene exclusively in tumor cells and subsequent significant in vivo antitumor effects, we applied the Cre/loxP system to HSV-tk/GCV therapy for CEA-producing cancer.We constructed an Ad producing Cre recombinase driven by the CEA promoter (Ad.CEA-Cre) and another Ad designed for inducible expression of the HSV-tk gene by Cre (Ad.CAG-loxP-TK).Co-infection by these Ads rendered a human CEA-producing cancer cell line 8.4-fold more sensitive to GCV compared with infection by Ad.CEA-TK alone.On … More the other hand, co-infection with these Ads did not significantly change GCV sensitivity of CEA-non-producing cells.Intra-tumoral injection of Ad.CEA-Cre combined with Ad.CAG-loxP-TK followed by GCV treatment completely eradicated CEA-producing tumors established in the subcutis of 6 out of 7 athymic mice, whereas injection of Ad.CEA-TK alone with GCV administration at most retarded the growth of inoculated tumors.These results suggest distinct advantages of the Cre/loxP system applied in the conventional cell type-specific gene therapy against cancer.We are now evaluating the efficacy and side effects of this system in the peritonitis carcinomatosa model in mice, mimicking pleuritis for lung cancer in future clinical applications to human beings.(2) Gene therapy specific for Myc-overexpressing small cell lung cancer (Myc-SCLC)We previousely reported that an Ad. containing the HSV-tk gene ligated with the Myc-binding motif (Ad.Myc-TK) showed a cell-type specific expression of the HSV-tk gene in Myc-SCLC cell lines.We analyzed the efficacy of the intraperitoneal injection of Ad.Myc-TK followed by GCV treatment on Myc-SCLC inoculated in the peritoneal cavity of athymic mice.This treatment successfully reduced the weight of tumors to one fourteenth of that of untreated mice and completely eradicated tumors in 2 of 8 mice. Less