Evaluation of the therapeutic effect of replication-competent adenovirus on thyroid carcinomas

我们在体内外研究了条件复制型腺病毒对甲状腺癌的治疗作用：(1)分化型甲状腺癌-我们构建了复制型腺病毒(AdTgE1A)，其中E1a基因位于甲状腺特异性启动子甲状腺球蛋白(TG)启动子的下游，E1a基因是腺病毒复制必不可少的基因。AdTgElA感染诱导分化后表达TG的甲状腺癌细胞E1a表达、病毒复制(后代产生)和细胞病变效应，而不表达TG的其他细胞则不表达。此外，我们的研究证实了AdTgE1A与其他基因治疗的联合作用，包括表达自杀基因或细胞因子的腺病毒。(2)间变性甲状腺癌-为了实现腺病毒的p53突变细胞特异性复制，我们使用了带有p53反应启动子、Cre-loxP系统和双重感染的“基因失活策略”。这一策略在体外效果很好，但在体内效果不是很好，可能是因为体内传染性很低。由于P53启动子在293细胞中并不是绝对沉默的，因此构建包含所有成分的单一腺病毒是不可能的。

We studied the therapeutic effect of the conditionally replication competent adenovirus on thyroid carcinomas in vitro and in vivo.(1) Differentiated thyroid carcinomas - We constructed the replicative adenovirus (AdTgE1A) in which the E1A gene, an indispensable gene for adenovirus replication, is placed downstream of thyroglobulin (Tg) promoter, a thyroid-specific promoter. Infection of AdTgElA led to E1A expression, virus replication (progeny production) and cytopathic effect in differentiated thyroid carcinoma cells expressing Tg, but not in other cells expressing no Tg. Furthermore, our studies demonstrated the enhanced effect of the combination of AdTgE1A and other gene therapies, including adenoviruses expressing a suicide gene or a cytokine.(2) Anaplastic thyroid carcinomas - To achieve p53-mutated cell-specific replication of adenovirus, we used "gene inactivation strategy" with p53-responseive promoter, Cre-LoxP system and double infection method. This strategy worked very well in vitro, but not so well in vivo, presumably because of low in vivo infectivity. Construction of a single adenovirus containing all the components was found impossible, since p53 promoter is not absolutely silent in 293 cells.