Cancer-specific killing by the CD suicide gene using the human telomerase reverse transcriptase promoter.
Human telomerase reverse transcriptase (hTERT), the catalytic subunit of the telomerase, is transcriptionally upregulated in more than 90% of tumor cells. It may be used as a tool for driving a gene to kill tumors specifically. To test this idea, luciferase reporter gene was used and the results showed that hTERT promoter could restrict the gene expression in the telomerase-positive tumor cells. A tumor-specific expression plasmid phTERT-CD was constructed, in which the E. coli cytosine deaminase (CD) gene was controlled by the hTERT promoter. A colorectal cancer cell line (LoVo) and a normal amnion cell line (WISH) were transfected by this plasmid. It was shown that the expression of the CD gene increased the sensitivity of LoVo cells to the prodrug, 5-fluorocytosine (5FC), over 800-fold, while the sensitivity of WISH cells to 5FC was increased only 6-fold. Mixed cell experiments showed a strong "bystander effect" on CD-negative cells. Furthermore, a significant anti-tumor effect of the phTERT-CD/5FC system was observed in nude mice bearing mammalian carcinoma induced by s.c. inoculation of LoVo cells when the mice were given 250 mg/kg 5FC twice a day for 10 consecutive days. These results indicated that hTERT promoter could target the suicidal effect of CD gene to tumor cells, and therefore, may be a novel and promising targeting approach to the treatment of cancer.
Liu
Jing
J
Institute of Biochemistry and Cell Biology, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, Shanghai 200031, P.R. China.
Zou
Wei-Guo
WG
Lang
Ming-Fei
MF
Luo
Jia
J
Sun
Lan-Ying
LY
Wang
Xiao-Ning
XN
Qian
Qi-Jun
QJ
Liu
Xin-Yuan
XY
D000818:Animals; D002460:Cell Line; D043525:Cytosine Deaminase; D004268:DNA-Binding Proteins; D005437:Flucytosine / Q000493:pharmacokinetics / Q000494:pharmacology; D015316:Genetic Therapy / Q000379:methods*; D006801:Humans; D008297:Male; D051379:Mice; D008807:Mice, Inbred BALB C; D008819:Mice, Nude; D009700:Nucleoside Deaminases / Q000096:biosynthesis / Q000235:genetics* / Q000378:metabolism; D010957:Plasmids / Q000235:genetics; D011401:Promoter Regions, Genetic; D019098:Telomerase / Q000235:genetics* / Q000378:metabolism; D015533:Transcriptional Activation; D014407:Tumor Cells, Cultured; D023041:Xenograft Model Antitumor Assays
D004268:DNA-Binding Proteins; D005437:Flucytosine; D019098:Telomerase; D009700:Nucleoside Deaminases; D043525:Cytosine Deaminase