Abstract:

Objective To study the ability of the recombinant replication-defective adenovirus vector adv5.oriP.HRP to target the Horseradish Peroxidase (HRP) gene into EBV-positive nasopharyngeal carcinoma cells to confer sensitivity to Indole-3-Acetic Acids (IAA) to the cells, and to investigate the killing ability of HRP/IAA to nasopharyngeal carcinoma cells under oxic and anoxic conditions and the bystander effect.  Methods  C666-1, KS1 and CNE-2Z were incubated with adv5.oriP.HRP, then IAA was added. MTT assay was used to evaluate the cytotoxicity of the suicide gene therapy whether in oxic or anoxic conditions.  Results   When being infected with a recombinant adenovirus carrying the HRP gene， high expression of HRP can be seen in C666-1 cells, which were killed by IAA. However, the infected KS1 and CNE-2Z cells remained resistant to IAA and no HRP protein were found. HRP/IAA can kill EBV-positive C666-1 cells in oxic and anoxic conditions. In addition, a bystander killing effect was demonstrated against C6661 cells when only 20% of the adv5.oriP.HRP-infected cells were mixed with the uninfected cells, and the eradication of cells can almost be achieved. Conclusion  These results demonstrate that the oriP sequence can achieve high levels of gene expression specifically targeted to EBV-positive NPC cells in the context of the adv vector. HRP/IAA is a novel Prodrug/Enzyme Combination for NPC. This has now provided the tumor-specific expression system from which additional interventions can be evaluated in future treatment strategies for patients with nasopharyngeal cancer.

Key words:  HRP/IAA; Enzyme/Prodrug; Anoxic conditions; Bystander effect