533 ± 0.020 and 0.515 ± 0.025, of tumor cells NPC 5-8F and MCF-7 transfected with the plasmid pGL3-basic-hTERTp-TK- EGFP and treated with GCV, respectively. Table 2 PNPC cell survival rates measured by MTT assay Codes and Samples STAT inhibitor Survival rates A. Cells without treatment 1 B. Cells transfected with

pGL3-basic-EGFP and with GCV treatment 0.984 ± 0.009 C. Cells transfected with pGL3-basic- hTERTp-TK-EGFP-CMV and treated with GCV 0.370 ± 0.024* D. Cells transfected with pGL3-basic-hTERTp-TK-EGFP-CMV without GCV 0.982 ± 0.010 E. Cells transfected with pGL3-basic-hTERTp-TK-EGFP and treated with GCV 0.533 ± 0.020* Data are expressed as mean ± standard deviation from three experiments. * indicates p < 0.0001 compared with other groups Table 3 MCF-7 cell survival rates measured by MTT assay Codes and Samples Survival rates A. Cells without treatment 1 B. Cells transfected with pGL3-basic-EGFP and 17DMAG nmr with GCV treatment 0.987 ± 0.006 C, Cells transfected with pGL3-basic-hTERTp-TK-EGFP-CMV and treated with GCV 0.462 ± 0.049* D. Cells transfected with pGL3-basic-hTERTp-TK-EGFP-CMV without GCV 0.984 ± 0.011 E. Cells transfected with pGL3-basic-hTERTp-TK-EGFP

and treated with GCV 0.515 ± 0.025* Data are expressed as mean ± standard deviation from three experiments. * indicates p < 0.0001 compared with other groups 6. find more Injection of pGL3-basic-hTERTp-TK-EGFP-CMV/GCV inhibited tumor progress in vivo Then we explored whether injection of pGL3-basic-hTERTp-TK-EGFP -CMV/GCV could inhibit tumor progress. As showed in Figure 4 and table4, nude mice inoculated NPC 5-8F cells developed tumor with volume of 6.23 ± 0.04 cm3 and weight of 2.68 ± 0.02 g. After injection of non-enhanced plasmid and GCV, the tumor volume and weight decreased to 3.51 ± 0.02 cm3 and 1.51 ± 0.01 g (p = 0.000), respectively. In comparison, after injection of the enhanced plasmid and GCV, the tumor volume and weight decreased to 2.27 ± 0.02 cm3 and 1.17 ± 0.01 g, respectively, which were significantly lower than those of nude NADPH-cytochrome-c2 reductase mice injected with the non-enhanced vector (p = 0.000). The inhibition rates of tumor progress were 43.68% and 56.34% for injection of non-enhanced and enhanced plasmids, respectively. Figure

4 Tumor inhibition of pGL3-basic-hTERTp-TK-EGFP-CMV/GCV in nude mice with NPC xenograft. Shown are the NPC xenograft in nude mice without treatment (a), injected with GCV and the non-enhanced plasmid (b), injected with GCV and the enhance plasmid (c), injected with GCV(d), injected with Lipofectamine 2000 (e) and injected with the enhance plasmid without GCV (f). Table 4 Injection of pGL3-basic- hTERTp-TK- EGFP- CMV/GCV inhibited tumor development in vivo Sample Animals Tumor volume at day 39 (cm3) Tumor weight at day 39 (g) Inhibition rate Blank 5 6.23 ± 0.04 2.68 ± 0.02 / Non-enhanced group 5 3.51 ± 0.02 1.51 ± 0.01 43.68%* Enhanced group/GCV 5 2.72 ± 0.02 1.17 ± 0.01 56.34%* Enhanced group 5 5.80 ± 0.13 2.51 ± 0.05 6.48%* GCV group 5 5.98 ± 0.09 2.56 ± 0.