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Abstract
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OBJECTIVE To detect specific cell killing effect of radiation combined with horseradish peroxidase (HRP)/indole-3-acetic (IAA) suicide gene therapy controlled by a novel radio-inducible and cancer-specific chimeric gene promoter in lung cancer.
METHODS We constructed a plasmid expressing HRP enzyme under the control of chimeric human telomerase reverse transcriptase (hTERT) promoter carrying 6 CArG elements, a plasmid expressing HRP enzyme under the control of hTERT promoter carrying single CArG element, and two control plasmids, which named pE6-hTERT-HRP, phTERT-HRP, pControl-HRP, and pControl-luc, respectively. After radiation, the proliferation inhibition and apoptosis induction effect of each type of plasmid in lung cancer cells (A549, SPC-A1) and normal lung cells (hEL) was detected by cell counting and Annexin V-FITC staining. The change of radiosensitivity of lung cancer cells with plasmid system was also detected by clonogenic assays.
RESULTS After a single dose radiation of 6 Gy,the average proliferation inhibition rates of pE6-hTERT-HRP, phTERT-HRP, pControl-HRP, and pControl-luc systems were 72. 92% ,40.60% , 51.00% and 25.19% (F= 67.31 , P< 0.01) in A549 cells ,64.63%,30.02%,48.23% and 23.16% (F=64.94, P< 0.01) in SPC-A1 cells, and 20.81%,18.05%, 44.20% and 18.32% (F=52. 19,P<0.01) in normal hEL cells, respectively. The average early apoptosis rates of these four plasmid systems were 36. 63%, 22. 30%, 24. 33% and 12. 53% (F =50. 99,P <0. 01) in A549 cells, 33.73%, 17. 37%, 22. 43% and 11.20% (F = 20. 76, P < 0. 01) in SPC-A1 cells, and 13.53 %, 12. 5%, 21.93% and 12. 16% (F = 15. 08, P < 0. 01) in normal hEL cells,respectively. The sensitizing enhancement ratios of the four plasmid systems were 3.45, 2. 29, 3.05 and 1.21 in A549 cells, while 2. 68, 2. 15, 3.05 and 1.21 in SPC-A1 cells, respectively.
CONCLUSIONS The new suicide gene system controlled by chimeric promoter may provide a novel therapeutic modality for lung cancer.
Language: zh |