Anti-tumor effect of suicide gene therapy using chimeric promoter plus radiotherapy on cancer cell lines / 中华肿瘤杂志

<p><b>OBJECTIVE</b>To explore the synergistic anti-tumor effect of radiotherapy and horseradish peroxidase/prodrug indole-3-acetic acid (HRP/IAA) gene therapy system using chimeric hTERT promoter responsive to ionizing radiation.</p><p><b>METHODS</b>The synthetic hTERT promoters containing four tandem-repeat copies of radio-inducible CArG elements, and the chimeric promoter containing cytomegalovirus (CMV) early promoter were both constructed. The activities of the chimeric promoters in cancer cell lines (HeLa, A549, and MHCC97) and normal cell line (MRC-5) were detected using luciferase reporter gene expression analysis after a (60)Co γ-irradiation treatment at a series of doses(a single dose of 0 to 10 Gy). The anti-tumor effect of combining irradiation with HRP/IAA gene-directed enzyme prodrug therapy system controlled by the chimeric promoter was tested by colony formation assay, cell counting and apoptosis analysis.</p><p><b>RESULTS</b>The chimeric promoters were ineffective in normal human cells, even after irradiation, but the expression of luciferase gene in tumor cells was significantly higher. The activity of the chimeric promoter in MRC-5 cells was 22.3%, 12.9% and 13.6% of that in HeLa, A549 and MHCC97 cells, respectively. After irradiation, the ratios were 11.7%, 8.7% and 8.8%, respectively. Furthermore, the chimeric promoters could successfully induce the expression of luciferase gene following different doses of radiation, with maximal inducible activity seen after 6 Gy irradiation. The chimeric promoter containing four tandem-repeat copies of radio-inducible CArG elements and CMV early promoter showed the highest activity with 6 Gy irradiation. The relative luciferase activities in HeLa, A549 and MHCC97 cells were 1.7 ± 0.2, 2.3 ± 0.2 and 2.3 ± 0.1, respectively. The chimeric promoter mediated suicide gene therapy system could increase radio-sensitivity in different cancer cells. Compared with the control system, it plus irradiation showed stronger cell proliferation inhibition, 67.3% vs. 26.1% in HeLa, 69.0% vs. 28.3% in A549, 64.6% vs. 20.8% in MHCC97 cells, and also higher apoptosis-inducing effect, 39.6% vs. 14.2% in HeLa, 33.0% vs. 12.4% in A549, and 33.2% vs. 14.2% in MHCC97 cells.</p><p><b>CONCLUSIONS</b>Chimeric promoter containing hTERT promoter, CArG elements and CMV promoter preserve the tumor-specificity in telomerase-positive tumor cells, and irradiation-responsive to low dose of radiation. The suicide gene therapy using this promoter plus radiotherapy show a strong anti-tumor effect in vitro. It is expected to have a good potential for future application in gene radiotherapy.</p>

hTERT promoter enhances the radiosensitivity to gene-radiation therapy of human laryngeal carcinoma transplanted in nude mice / 中华肿瘤杂志

<p><b>OBJECTIVE</b>To explore the therapeutic efficiency of human telomerase reverse transcriptase promoter (hTERTp) mediated horseradish peroxidase (HRP) catalyzed effects of indole-3-acetic (IAA) on laryngeal squamous cell carcinoma with different radiosensitivity in vivo.</p><p><b>METHODS</b>Human laryngeal squamous cell carcinoma Hep-2 and Hep-2R cells were transplanted into nude mice. After growing to about 30 approximately 50 mm3, the tumor-bearing mice were randomly divided into eight groups: Hep-2 line: combined group (A), gene group (B), radiation group (C) and blank group (D); Hep-2R line: combined group (AR), gene group (BR), radiation group (CR) and blank group (DR). The phTERTp-HRP was delivered by intratumoral injection and the IAA by intraperitoneal injection, combined with 2 Gy daily radiation to a total dose of 30 Gy. The tumor volume was recorded. The cell apoptosis was detected by terminal deoxynucleotidyl transferase-mediated dUTP nick end-labeling (TUNEL) assay. The expression of HRP protein was detected by AP immunohistochemisty.</p><p><b>RESULTS</b>The tumor growth of combined groups was attenuated significantly and the tumor volume of Hep-2R blank group was the largest. The inhibition rate of each group was: A: 54.8%, B: 10.0%, C: 31.9%; AR: 52.7%, BR: 24.8%, CR: 17.0%. In the combined groups, necrosis and apoptosis of tumor cells were observed under the light microscope and the apoptotic index [A (16.6 +/- 1.3)% vs. AR (17.6 +/- 1.3)%] of tumor cells was highest (P < 0.05). The HRP protein expression of BR (33.3 +/- 8.9)% was higher than that of B (21.9 +/- 5.7)%, which was directly up-regulated in the tumors (45.0% vs. 54.8%, P < 0.05) after radiation.</p><p><b>CONCLUSION</b>In the Hep-2- and Hep-2R-transplantation tumors in nude mice, hTERTp can be induced by radiation and enhance the expression of horseradish peroxidase (HRP) gene according to telomerase activity. hTERTp-HRP/IAA system, which has synergistic effects with radiation and inhibits the tumor growth by induction of apoptosis and necrosis, may be a new gene-radiation strategy for the treatment of laryngeal carcinoma.</p>