[Tumor targeted expression of adenovirus mediated CDglyTK gene regulated by irradiation via Egr-1 promoter].
OBJECTIVE
To construct adenoviral vecter of AdEgr-CD/TK in which CDglyTK gene was driven by Egr-1 promoter, and control the tumor targeted expression of CDglyTK gene by gamma irradiation so as to observe the effects of gene-radiotherapy of liver cancer.


METHODS
Adenoviral vector of AdEgr-CD/TK was generated through homologous recombination in bacteria. The expression of CDglyTK gene in MM45T. Li cells infected with AdEgr-CD/TK and exposed to different doses of gamma irradiation were analyzed, and the relative survival rate of the cells in presence of prodrugs 5-FC and GCV was tested. In addition, the tumor suppression effects of different treatments were investigated in 64 mice bearing liver cancer by observing the size of tumor at interval of four days.


RESULTS
In vitro experiment showed that gamma irradiation markedly and dose-dependently induced CDglyTK expression in MM45T. Li tumor cells, and significantly enhanced the sensitivity of MM45T. Li cells infected with AdEgr-CD/TK to prodrugs 5-FC or GCV resulting in cell being killed (P < 0.01). A synergetic cytotoxic effect was found when both 5-FC and GCV were added. In vivo experiment revealed that, compared with other control treatments, intratumoral injection of AdEgr-CD/TK combined with intraperitoneal injection of GCV + 5-FC and TLI obviously suppressed tumor growth (P < 0.01), with 30% of the tumor eradicated completely while without causing the increase of whole body cytotoxic effect.


CONCLUSIONS
Tumor targeted expression of CDglyTK gene under the control of irradiation represents a novel strategy for safe and effective gene therapy of cancer and might have wide application in the future.
Wei
D
D
Department of Biochemistry, Research Center for Human Gene Therapy, Shanghai Second Medical University, Shanghai 200025, China.
Dai
B
B
Chen
S
S
D000256:Adenoviridae / Q000235:genetics; D000818:Animals; D015152:Blotting, Northern; D004268:DNA-Binding Proteins / Q000235:genetics*; D004195:Disease Models, Animal; D051766:Early Growth Response Protein 1; D005260:Female; D005720:Gamma Rays; D005786:Gene Expression Regulation / Q000528:radiation effects*; D015316:Genetic Therapy; D017874:Immediate-Early Proteins; D007150:Immunohistochemistry; D051379:Mice; D008807:Mice, Inbred BALB C; D009369:Neoplasms / Q000628:therapy*; D011401:Promoter Regions, Genetic / Q000528:radiation effects*; D013937:Thymidine Kinase / Q000235:genetics / Q000378:metabolism / Q000627:therapeutic use; D014157:Transcription Factors / Q000235:genetics*
D004268:DNA-Binding Proteins; D051766:Early Growth Response Protein 1; C486109:Egr1 protein, mouse; D017874:Immediate-Early Proteins; D014157:Transcription Factors; D013937:Thymidine Kinase