Y. Nagayama et al., Targeting the replication of adenovirus to p53-defective thyroid carcinomawith a p53-regulated Cre/loxP system, CANC GENE T, 8(1), 2001, pp. 36-44
In this article, we evaluated the feasibility of the restricted replication
-competent adenoviruses for treatment of anaplastic thyroid carcinomas (ATC
s), wh ich are very aggressive and difficult to treat. Because ATCs very of
ten harbor p53 mutations, we used wt-p53 as a regulatory factor to restrict
virus replication and cytopathic effect to p53-mutated cells. The recently
reported "gene inactivation strategy" using p53-regulated Cre/loxP system
was employed; this system consists of two recombinant adenoviruses. One has
an expression unit of the synthetic p53-responsive promoter and the Cre re
combinase gene (Axyp53RECre), and another contains two expression units; th
e first consists of E1A gene flanked by a pair of loxP sites downstream of
the constitutive CAG promoter and the second E1B19K gene under the control
of the CMV promoter (AdCALE1AL). We expected that coinfection of these two
adenoviruses into the cells with wt-p53 would lead to expression of the Cre
, which excises E1A gene and switches off E1A expression resulting in no vi
rus replication, whereas in the cells with mutant p53 E1A could be expresse
d that leads to virus replication and cell lysis. Our in vitro data demonst
rate that although infection of AdCALE1AL alone led to E1A expression, vira
l replication and cytolysis in all the thyroid cells examined irrespective
of their p53 status, the double infection did so in FRO cells (p53-null ATC
) but not in FRO cells stably expressing wt-p53 and normal thyroid cells wi
th wt-p53. These data indicate that our double infection method may have a
potential for treatment of ATC and probably also other p53-defective cancer
cells.