The Combination of Suicide Gene Therapy and Radiation Enhances the Killing of Nasopharyngeal Carcinoma Xenographs

Abstract

Nasopharyngeal carcinoma (NPC) is very common in Southern China and Southeast Asian countries. To explore a novel and more effective approach to NPC therapy, a combined strategy of suicide genes and radiation was designed in this study. Five suicide gene expression cassettes, yeast CD, yeast CD/UPRT, and yeast CDglyTK gene controlled by CMV, and Egr-1 and a synthetic CMV-enhanced Egr-1 promoter (CE) were constructed in an expression vector p11MS. The expression of suicide genes in NPC CNE-2 cells were detected by RT-PCR and Western blot. The cytotoxicity of suicide gene therapy and radiation were analyzed by MTT assay. An animal study in which yeast CD/UPRT-expressing CNE-2 tumors in nude mice were treated with 5-FC and radiation was also developed. Our results revealed that p11MSCEyCD/UPRT and p11MSCEyCDglyTK are superior over three other constructs in the killing of NPC cells in vitro. We combined suicide gene-expressing tumors, 5-FC treatment, and radiation in vivo and found that the tumors greatly regressed, some disappeared completely in 3 nude mice in the yCD/UPRT group, and a significant difference of tumor volumes was observed between this group and the other four groups (p < 0.05). Our results indicated that suicide gene therapy and radiation have a synergic effect on NPC therapy, and the combined strategy of radiogene therapy is of great potential as a substitute for the traditional method, radiation alone, in NPC therapies.