Objective To detect the selective inhibitory effects of irradiation plus adenovirusmediated horseradish peroxidase ( HRP)/indole-3-acetic acid (IAA) suicide gene system using tumorspecific and radio-inducible chimeric promoter on human hepatocellular carcinoma subcutaneously xenografted in nude mouse.MethodsRecombinant replicated-deficient adenovirus vector containing HRP gene and chimeric human telomerase reverse transcriptase (hTERT) promoter carrying 6 radioinducible CArG elements was constructed.A human subcutaneous transplanting hepatocellular carcinoma (MHCC97 cell line) model was treated with -γ-ray irradiation plus intra-tumor injections of adenoviral vector and intra-peritoneal injections of prodrug IAA.The change of tumor volume and tumor growth inhibiting rate,the survival time of nude mice,as well as histopathology of xenograft tumor and normal tissues were evaluated.Results Thirty one days after the treatment,the relative tumor volumes in the negative,adenovirus therapy,irradiation,and combination groups were 49.23 ± 4.55,27.71 :± 7.74,28.53 + 10.48 and 11.58 ± 3.23,respectively.There was a significantly statistical difference among them (F = 16.288,P ＜0.01 ).The inhibition effect in the combination group was strongest as compared with that in other groups,and its inhibition ratio was 76.5%.The survival period extended to 43 d in the combination group,which showed a significantly difference with that in the control group(x2 = 18.307 ,P ＜0.01 ).The area of tumors necrosis in the combination group was larger than that in the other groups,and the normal tissues showed no treatment-related toxic effect in all groups.However,multiple hepatocellular carcinoma metastases were observed in the liver in the control group,there were a few metastases in the monotherapy groups and no metastasis in the combination group.Conclusions Adenovirus-mediated suicide gene therapy plus radiotherapy dramatically could inhibit tumor growth and prolong median survival time.It might provide a promising therapeutic modality for hepatocellular carcinoma therapy.

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.