Radio-inducible Dormancy in Hepatoma Gene Therapy

肿瘤特异性启动子控制的基因治疗对肿瘤的治疗效果较弱。为了提高肝癌基因治疗的效率，我们研究了放射治疗与自杀基因治疗的协同作用。在HSV-tk基因上游插入Egr-1启动子，构建放射诱导自杀基因（Egr-tk），并将AFP增强子/启动子区与HSV-tk（AFP-tk）连接，构建肿瘤特异性自杀基因。在体外基因治疗评估肝癌细胞与高甲胎蛋白生产的特点，是敏感的GCV后，瞬时基因转导与HVJ-脂质体载体。AFP-tk转导细胞与放射治疗联合使用时，对GCV治疗更加敏感。另一方面，Egr-tk转导的肝癌细胞在照射后变得对GCV高度敏感，但不照射则不敏感。在体内，植入裸鼠中的HuH 7或PLC/PRF/5肿瘤的组合放射/基因疗法导致肿瘤大小的显著减小，并且在6个月的随访中，在67%或50%的病例中观察到相应细胞系的完全消退。组织化学研究表明，接受联合治疗的小鼠组织中凋亡细胞的数量是单独基因治疗或照射后的5倍，是对照组的27倍。Fas染色强度在放疗组和联合治疗组中观察到增加。我们的数据表明，辐射增强AFP增强子/启动子控制的肝癌基因治疗的有效性，无论肿瘤细胞产生的AFP水平。这种协同效应可能部分是由于增强Fas介导的细胞凋亡发生作为旁观者effect.Finally，我们感谢从这个补助金的支持和我们的博士后研究员和工作人员的宝贵贡献。

The therapeutic efficiency of tumor specific promoter controlled gene therapy for cancer is rather weak. To improve the efficiency of gene therapy for hepatoma, we examined the synergistic effect of radiation therapy combined with suicide gene therapy. Radio-inducible suicide gene (Egr-tk) was constructed by insertion of Egr-1 promoter upstream of HSV-tk gene, and AFP enhancer/promoter region was ligated to HSV-tk (AFP-tk) to create a tumor specific suicide gene construct. In vitro gene therapy was assessed in hepatoma cells with high AFP-producing characteristics that were sensitive to GCV after the transient gene transduction with HVJ-liposome vehicle. Combined with radiation therapy, the AFP-tk transduced cells became more sensitive to the GCV treatment. On the other hand, Egr-tk-transduced hepatoma cells became highly sensitive to GCV after irradiation, but not without irradiation. In vivo, the combined radiation/gene therapy of HuH7 or PLC/PRF/5 tumors implanted to in nude mice resulted in a significant decrease of tumor size and complete regression was observed in 67% or 50% of case with the respective cell line over a 6-month follow-up. Histochemical studies showed that the number of apoptotic cells in tissues of mice received the combined therapy was five-times greater than after gene therapy or irradiation alone and 27 times greater than control. The increased Fas-staining intensity was observed in radiation and combined therapy groups. Our data indicate that radiation potentiated the effectiveness of the AFP enhancer/promoter controlled gene therapy of hepatomas irrespective of the AFP level produced by tumor cells. This synergistic effect may be partly due to the enhanced Fas-mediated apoptosis occurring as a bystander effect.Finally, we acknowledge a support from this grant and a valuable contribution of our post doc fellows and staffs.