ABSTRACT
<p><b>OBJECTIVE</b>To construct a modified and enhanced thymidine kinase (TK) vector regulated by human telomerase catalytic subunit promoter (hTERT) promoter and cytomegalovirus (CMV) enhancer and its killing effect on nasopharyngeal carcinoma in vitro and in vivo and its safety in vivo.</p><p><b>METHODS</b>The pGL3-basic, as basic vector template, was linked and constructed into TK vector regulated by hTERT promoter and CMV enhancer with mono-promoter vector as control. Enhanced TK expression was confirmed by fluorescent microscopy and real time fluorescent quantitative PCR. Telomerase activity was measured by stretch PCR. Tumour killing effects were examined by MTT and Boyden areola. The effects of enhanced TK on the invasiveness of tumor cell NPC 5-8F and the growth of xenograft implanted in nude mice were investigated.</p><p><b>RESULTS</b>Compared with non-enhanced vector, TK expressed by the enhanced vector significantly increased in NPC 5-8F and MCF-7 cells, telomerase activity was positive in human in NPC 5-8F cells and breast cancer MCF-7 cells and negative in control human blood vessel endothelium ECV-304 cells. After ganciclovir(GCV) treatment, NPC 5-8F cell survival rate and invasiveness decreased and tumor progress of NPC xenograft implanted in nude mice was inhibited, without obvious toxicity effects on mouse liver and kidney.</p><p><b>CONCLUSIONS</b>The enhanced TK vector regulated by hTERT promoter and CMV enhancer can obviously and specifically inhibit and kill nasopharyngeal carcinoma cells in culture and nasopharyngeal carcinoma xenograft in nude mice in vivo, without obviously toxic side effects on nude mice. The targeted and enhanced TK gene vector with high performance may be a new tumour targeted gene therapy strategy clinically to aim directly at most malignant tumours including nasopharyngeal carcinoma, with more extensive anti-cancer spectrum.</p>