Cisplatin‐controlled p53 gene therapy for human non‐small cell lung cancer xenografts in athymic nude mice via the CArG elements

Cisplatin, a commonly used chemotherapeutic agent, causes tumor cell death by producing DNA damage and generating reactive oxygen intermediates, which have been reported to activate the early growth response‐1 ( Egr‐1 ) promoter through specific cis ‐acting sequences, termed CArG elements. The aim of this study was to construct an adenoviral vector containing CArG elements cloned upstream of the cDNA for human wt‐p53 , and to observe the effect of this vector on human non‐small cell lung cancer (NSCLC) xenografts in athymic nude mice when combined with cisplatin treatment. The adenoviral vector AdEgr–p53 was generated by inserting CArG elements upstream of human wt‐p53 cDNA. Two human NSCLC cell lines of varying p53 gene status, A549 (containing wild‐type p53 ) and H358 (containing an internal homozygous deletion of the p53 gene) were used for in vitro and in vivo experiments. Wt‐p53 production in cultured tumor cells and xenografts treated with the combination of AdEgr–p53 and cisplatin were detected by enzyme‐linked immunosorbent assays. The antitumor responses in nude mice with the A549 or H358 xenografts following treatment with AdEgr–p53 and cisplatin were observed. We found that p53 was produced in tumor cells and xenografts treated with a combination of AdEgr–p53 and cisplatin. Furthermore, the Egr‐1 promoter is induced by cisplatin, and this induction is mediated in part through the CArG elements. There was an enhanced antitumor response without an increase in toxicity following treatment with AdEgr–p53 and cisplatin, compared with either agent alone. Cisplatin‐inducible p53 gene therapy may provide a means to control transgene expression while enhancing the effectiveness of commonly used chemotherapeutic agents. This is a novel treatment for human NSCLC. ( Cancer Sci 2005; 96: 706 – 712)